4e2b1b06b411d12accfad7ae28ef00cc28dbe95b
[linux-3.10.git] / drivers / block / ll_rw_blk.c
1 /*
2  *  linux/drivers/block/ll_rw_blk.c
3  *
4  * Copyright (C) 1991, 1992 Linus Torvalds
5  * Copyright (C) 1994,      Karl Keyte: Added support for disk statistics
6  * Elevator latency, (C) 2000  Andrea Arcangeli <andrea@suse.de> SuSE
7  * Queue request tables / lock, selectable elevator, Jens Axboe <axboe@suse.de>
8  * kernel-doc documentation started by NeilBrown <neilb@cse.unsw.edu.au> -  July2000
9  * bio rewrite, highmem i/o, etc, Jens Axboe <axboe@suse.de> - may 2001
10  */
11
12 /*
13  * This handles all read/write requests to block devices
14  */
15 #include <linux/config.h>
16 #include <linux/kernel.h>
17 #include <linux/module.h>
18 #include <linux/backing-dev.h>
19 #include <linux/bio.h>
20 #include <linux/blkdev.h>
21 #include <linux/highmem.h>
22 #include <linux/mm.h>
23 #include <linux/kernel_stat.h>
24 #include <linux/string.h>
25 #include <linux/init.h>
26 #include <linux/bootmem.h>      /* for max_pfn/max_low_pfn */
27 #include <linux/completion.h>
28 #include <linux/slab.h>
29 #include <linux/swap.h>
30 #include <linux/writeback.h>
31 #include <linux/blkdev.h>
32
33 /*
34  * for max sense size
35  */
36 #include <scsi/scsi_cmnd.h>
37
38 static void blk_unplug_work(void *data);
39 static void blk_unplug_timeout(unsigned long data);
40 static void drive_stat_acct(struct request *rq, int nr_sectors, int new_io);
41
42 /*
43  * For the allocated request tables
44  */
45 static kmem_cache_t *request_cachep;
46
47 /*
48  * For queue allocation
49  */
50 static kmem_cache_t *requestq_cachep;
51
52 /*
53  * For io context allocations
54  */
55 static kmem_cache_t *iocontext_cachep;
56
57 static wait_queue_head_t congestion_wqh[2] = {
58                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
59                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
60         };
61
62 /*
63  * Controlling structure to kblockd
64  */
65 static struct workqueue_struct *kblockd_workqueue; 
66
67 unsigned long blk_max_low_pfn, blk_max_pfn;
68
69 EXPORT_SYMBOL(blk_max_low_pfn);
70 EXPORT_SYMBOL(blk_max_pfn);
71
72 /* Amount of time in which a process may batch requests */
73 #define BLK_BATCH_TIME  (HZ/50UL)
74
75 /* Number of requests a "batching" process may submit */
76 #define BLK_BATCH_REQ   32
77
78 /*
79  * Return the threshold (number of used requests) at which the queue is
80  * considered to be congested.  It include a little hysteresis to keep the
81  * context switch rate down.
82  */
83 static inline int queue_congestion_on_threshold(struct request_queue *q)
84 {
85         return q->nr_congestion_on;
86 }
87
88 /*
89  * The threshold at which a queue is considered to be uncongested
90  */
91 static inline int queue_congestion_off_threshold(struct request_queue *q)
92 {
93         return q->nr_congestion_off;
94 }
95
96 static void blk_queue_congestion_threshold(struct request_queue *q)
97 {
98         int nr;
99
100         nr = q->nr_requests - (q->nr_requests / 8) + 1;
101         if (nr > q->nr_requests)
102                 nr = q->nr_requests;
103         q->nr_congestion_on = nr;
104
105         nr = q->nr_requests - (q->nr_requests / 8) - (q->nr_requests / 16) - 1;
106         if (nr < 1)
107                 nr = 1;
108         q->nr_congestion_off = nr;
109 }
110
111 /*
112  * A queue has just exitted congestion.  Note this in the global counter of
113  * congested queues, and wake up anyone who was waiting for requests to be
114  * put back.
115  */
116 static void clear_queue_congested(request_queue_t *q, int rw)
117 {
118         enum bdi_state bit;
119         wait_queue_head_t *wqh = &congestion_wqh[rw];
120
121         bit = (rw == WRITE) ? BDI_write_congested : BDI_read_congested;
122         clear_bit(bit, &q->backing_dev_info.state);
123         smp_mb__after_clear_bit();
124         if (waitqueue_active(wqh))
125                 wake_up(wqh);
126 }
127
128 /*
129  * A queue has just entered congestion.  Flag that in the queue's VM-visible
130  * state flags and increment the global gounter of congested queues.
131  */
132 static void set_queue_congested(request_queue_t *q, int rw)
133 {
134         enum bdi_state bit;
135
136         bit = (rw == WRITE) ? BDI_write_congested : BDI_read_congested;
137         set_bit(bit, &q->backing_dev_info.state);
138 }
139
140 /**
141  * blk_get_backing_dev_info - get the address of a queue's backing_dev_info
142  * @bdev:       device
143  *
144  * Locates the passed device's request queue and returns the address of its
145  * backing_dev_info
146  *
147  * Will return NULL if the request queue cannot be located.
148  */
149 struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev)
150 {
151         struct backing_dev_info *ret = NULL;
152         request_queue_t *q = bdev_get_queue(bdev);
153
154         if (q)
155                 ret = &q->backing_dev_info;
156         return ret;
157 }
158
159 EXPORT_SYMBOL(blk_get_backing_dev_info);
160
161 void blk_queue_activity_fn(request_queue_t *q, activity_fn *fn, void *data)
162 {
163         q->activity_fn = fn;
164         q->activity_data = data;
165 }
166
167 EXPORT_SYMBOL(blk_queue_activity_fn);
168
169 /**
170  * blk_queue_prep_rq - set a prepare_request function for queue
171  * @q:          queue
172  * @pfn:        prepare_request function
173  *
174  * It's possible for a queue to register a prepare_request callback which
175  * is invoked before the request is handed to the request_fn. The goal of
176  * the function is to prepare a request for I/O, it can be used to build a
177  * cdb from the request data for instance.
178  *
179  */
180 void blk_queue_prep_rq(request_queue_t *q, prep_rq_fn *pfn)
181 {
182         q->prep_rq_fn = pfn;
183 }
184
185 EXPORT_SYMBOL(blk_queue_prep_rq);
186
187 /**
188  * blk_queue_merge_bvec - set a merge_bvec function for queue
189  * @q:          queue
190  * @mbfn:       merge_bvec_fn
191  *
192  * Usually queues have static limitations on the max sectors or segments that
193  * we can put in a request. Stacking drivers may have some settings that
194  * are dynamic, and thus we have to query the queue whether it is ok to
195  * add a new bio_vec to a bio at a given offset or not. If the block device
196  * has such limitations, it needs to register a merge_bvec_fn to control
197  * the size of bio's sent to it. Note that a block device *must* allow a
198  * single page to be added to an empty bio. The block device driver may want
199  * to use the bio_split() function to deal with these bio's. By default
200  * no merge_bvec_fn is defined for a queue, and only the fixed limits are
201  * honored.
202  */
203 void blk_queue_merge_bvec(request_queue_t *q, merge_bvec_fn *mbfn)
204 {
205         q->merge_bvec_fn = mbfn;
206 }
207
208 EXPORT_SYMBOL(blk_queue_merge_bvec);
209
210 /**
211  * blk_queue_make_request - define an alternate make_request function for a device
212  * @q:  the request queue for the device to be affected
213  * @mfn: the alternate make_request function
214  *
215  * Description:
216  *    The normal way for &struct bios to be passed to a device
217  *    driver is for them to be collected into requests on a request
218  *    queue, and then to allow the device driver to select requests
219  *    off that queue when it is ready.  This works well for many block
220  *    devices. However some block devices (typically virtual devices
221  *    such as md or lvm) do not benefit from the processing on the
222  *    request queue, and are served best by having the requests passed
223  *    directly to them.  This can be achieved by providing a function
224  *    to blk_queue_make_request().
225  *
226  * Caveat:
227  *    The driver that does this *must* be able to deal appropriately
228  *    with buffers in "highmemory". This can be accomplished by either calling
229  *    __bio_kmap_atomic() to get a temporary kernel mapping, or by calling
230  *    blk_queue_bounce() to create a buffer in normal memory.
231  **/
232 void blk_queue_make_request(request_queue_t * q, make_request_fn * mfn)
233 {
234         /*
235          * set defaults
236          */
237         q->nr_requests = BLKDEV_MAX_RQ;
238         blk_queue_max_phys_segments(q, MAX_PHYS_SEGMENTS);
239         blk_queue_max_hw_segments(q, MAX_HW_SEGMENTS);
240         q->make_request_fn = mfn;
241         q->backing_dev_info.ra_pages = (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;
242         q->backing_dev_info.state = 0;
243         q->backing_dev_info.capabilities = BDI_CAP_MAP_COPY;
244         blk_queue_max_sectors(q, MAX_SECTORS);
245         blk_queue_hardsect_size(q, 512);
246         blk_queue_dma_alignment(q, 511);
247         blk_queue_congestion_threshold(q);
248         q->nr_batching = BLK_BATCH_REQ;
249
250         q->unplug_thresh = 4;           /* hmm */
251         q->unplug_delay = (3 * HZ) / 1000;      /* 3 milliseconds */
252         if (q->unplug_delay == 0)
253                 q->unplug_delay = 1;
254
255         INIT_WORK(&q->unplug_work, blk_unplug_work, q);
256
257         q->unplug_timer.function = blk_unplug_timeout;
258         q->unplug_timer.data = (unsigned long)q;
259
260         /*
261          * by default assume old behaviour and bounce for any highmem page
262          */
263         blk_queue_bounce_limit(q, BLK_BOUNCE_HIGH);
264
265         blk_queue_activity_fn(q, NULL, NULL);
266
267         INIT_LIST_HEAD(&q->drain_list);
268 }
269
270 EXPORT_SYMBOL(blk_queue_make_request);
271
272 static inline void rq_init(request_queue_t *q, struct request *rq)
273 {
274         INIT_LIST_HEAD(&rq->queuelist);
275
276         rq->errors = 0;
277         rq->rq_status = RQ_ACTIVE;
278         rq->bio = rq->biotail = NULL;
279         rq->ioprio = 0;
280         rq->buffer = NULL;
281         rq->ref_count = 1;
282         rq->q = q;
283         rq->waiting = NULL;
284         rq->special = NULL;
285         rq->data_len = 0;
286         rq->data = NULL;
287         rq->nr_phys_segments = 0;
288         rq->sense = NULL;
289         rq->end_io = NULL;
290         rq->end_io_data = NULL;
291 }
292
293 /**
294  * blk_queue_ordered - does this queue support ordered writes
295  * @q:     the request queue
296  * @flag:  see below
297  *
298  * Description:
299  *   For journalled file systems, doing ordered writes on a commit
300  *   block instead of explicitly doing wait_on_buffer (which is bad
301  *   for performance) can be a big win. Block drivers supporting this
302  *   feature should call this function and indicate so.
303  *
304  **/
305 void blk_queue_ordered(request_queue_t *q, int flag)
306 {
307         switch (flag) {
308                 case QUEUE_ORDERED_NONE:
309                         if (q->flush_rq)
310                                 kmem_cache_free(request_cachep, q->flush_rq);
311                         q->flush_rq = NULL;
312                         q->ordered = flag;
313                         break;
314                 case QUEUE_ORDERED_TAG:
315                         q->ordered = flag;
316                         break;
317                 case QUEUE_ORDERED_FLUSH:
318                         q->ordered = flag;
319                         if (!q->flush_rq)
320                                 q->flush_rq = kmem_cache_alloc(request_cachep,
321                                                                 GFP_KERNEL);
322                         break;
323                 default:
324                         printk("blk_queue_ordered: bad value %d\n", flag);
325                         break;
326         }
327 }
328
329 EXPORT_SYMBOL(blk_queue_ordered);
330
331 /**
332  * blk_queue_issue_flush_fn - set function for issuing a flush
333  * @q:     the request queue
334  * @iff:   the function to be called issuing the flush
335  *
336  * Description:
337  *   If a driver supports issuing a flush command, the support is notified
338  *   to the block layer by defining it through this call.
339  *
340  **/
341 void blk_queue_issue_flush_fn(request_queue_t *q, issue_flush_fn *iff)
342 {
343         q->issue_flush_fn = iff;
344 }
345
346 EXPORT_SYMBOL(blk_queue_issue_flush_fn);
347
348 /*
349  * Cache flushing for ordered writes handling
350  */
351 static void blk_pre_flush_end_io(struct request *flush_rq)
352 {
353         struct request *rq = flush_rq->end_io_data;
354         request_queue_t *q = rq->q;
355
356         rq->flags |= REQ_BAR_PREFLUSH;
357
358         if (!flush_rq->errors)
359                 elv_requeue_request(q, rq);
360         else {
361                 q->end_flush_fn(q, flush_rq);
362                 clear_bit(QUEUE_FLAG_FLUSH, &q->queue_flags);
363                 q->request_fn(q);
364         }
365 }
366
367 static void blk_post_flush_end_io(struct request *flush_rq)
368 {
369         struct request *rq = flush_rq->end_io_data;
370         request_queue_t *q = rq->q;
371
372         rq->flags |= REQ_BAR_POSTFLUSH;
373
374         q->end_flush_fn(q, flush_rq);
375         clear_bit(QUEUE_FLAG_FLUSH, &q->queue_flags);
376         q->request_fn(q);
377 }
378
379 struct request *blk_start_pre_flush(request_queue_t *q, struct request *rq)
380 {
381         struct request *flush_rq = q->flush_rq;
382
383         BUG_ON(!blk_barrier_rq(rq));
384
385         if (test_and_set_bit(QUEUE_FLAG_FLUSH, &q->queue_flags))
386                 return NULL;
387
388         rq_init(q, flush_rq);
389         flush_rq->elevator_private = NULL;
390         flush_rq->flags = REQ_BAR_FLUSH;
391         flush_rq->rq_disk = rq->rq_disk;
392         flush_rq->rl = NULL;
393
394         /*
395          * prepare_flush returns 0 if no flush is needed, just mark both
396          * pre and post flush as done in that case
397          */
398         if (!q->prepare_flush_fn(q, flush_rq)) {
399                 rq->flags |= REQ_BAR_PREFLUSH | REQ_BAR_POSTFLUSH;
400                 clear_bit(QUEUE_FLAG_FLUSH, &q->queue_flags);
401                 return rq;
402         }
403
404         /*
405          * some drivers dequeue requests right away, some only after io
406          * completion. make sure the request is dequeued.
407          */
408         if (!list_empty(&rq->queuelist))
409                 blkdev_dequeue_request(rq);
410
411         elv_deactivate_request(q, rq);
412
413         flush_rq->end_io_data = rq;
414         flush_rq->end_io = blk_pre_flush_end_io;
415
416         __elv_add_request(q, flush_rq, ELEVATOR_INSERT_FRONT, 0);
417         return flush_rq;
418 }
419
420 static void blk_start_post_flush(request_queue_t *q, struct request *rq)
421 {
422         struct request *flush_rq = q->flush_rq;
423
424         BUG_ON(!blk_barrier_rq(rq));
425
426         rq_init(q, flush_rq);
427         flush_rq->elevator_private = NULL;
428         flush_rq->flags = REQ_BAR_FLUSH;
429         flush_rq->rq_disk = rq->rq_disk;
430         flush_rq->rl = NULL;
431
432         if (q->prepare_flush_fn(q, flush_rq)) {
433                 flush_rq->end_io_data = rq;
434                 flush_rq->end_io = blk_post_flush_end_io;
435
436                 __elv_add_request(q, flush_rq, ELEVATOR_INSERT_FRONT, 0);
437                 q->request_fn(q);
438         }
439 }
440
441 static inline int blk_check_end_barrier(request_queue_t *q, struct request *rq,
442                                         int sectors)
443 {
444         if (sectors > rq->nr_sectors)
445                 sectors = rq->nr_sectors;
446
447         rq->nr_sectors -= sectors;
448         return rq->nr_sectors;
449 }
450
451 static int __blk_complete_barrier_rq(request_queue_t *q, struct request *rq,
452                                      int sectors, int queue_locked)
453 {
454         if (q->ordered != QUEUE_ORDERED_FLUSH)
455                 return 0;
456         if (!blk_fs_request(rq) || !blk_barrier_rq(rq))
457                 return 0;
458         if (blk_barrier_postflush(rq))
459                 return 0;
460
461         if (!blk_check_end_barrier(q, rq, sectors)) {
462                 unsigned long flags = 0;
463
464                 if (!queue_locked)
465                         spin_lock_irqsave(q->queue_lock, flags);
466
467                 blk_start_post_flush(q, rq);
468
469                 if (!queue_locked)
470                         spin_unlock_irqrestore(q->queue_lock, flags);
471         }
472
473         return 1;
474 }
475
476 /**
477  * blk_complete_barrier_rq - complete possible barrier request
478  * @q:  the request queue for the device
479  * @rq:  the request
480  * @sectors:  number of sectors to complete
481  *
482  * Description:
483  *   Used in driver end_io handling to determine whether to postpone
484  *   completion of a barrier request until a post flush has been done. This
485  *   is the unlocked variant, used if the caller doesn't already hold the
486  *   queue lock.
487  **/
488 int blk_complete_barrier_rq(request_queue_t *q, struct request *rq, int sectors)
489 {
490         return __blk_complete_barrier_rq(q, rq, sectors, 0);
491 }
492 EXPORT_SYMBOL(blk_complete_barrier_rq);
493
494 /**
495  * blk_complete_barrier_rq_locked - complete possible barrier request
496  * @q:  the request queue for the device
497  * @rq:  the request
498  * @sectors:  number of sectors to complete
499  *
500  * Description:
501  *   See blk_complete_barrier_rq(). This variant must be used if the caller
502  *   holds the queue lock.
503  **/
504 int blk_complete_barrier_rq_locked(request_queue_t *q, struct request *rq,
505                                    int sectors)
506 {
507         return __blk_complete_barrier_rq(q, rq, sectors, 1);
508 }
509 EXPORT_SYMBOL(blk_complete_barrier_rq_locked);
510
511 /**
512  * blk_queue_bounce_limit - set bounce buffer limit for queue
513  * @q:  the request queue for the device
514  * @dma_addr:   bus address limit
515  *
516  * Description:
517  *    Different hardware can have different requirements as to what pages
518  *    it can do I/O directly to. A low level driver can call
519  *    blk_queue_bounce_limit to have lower memory pages allocated as bounce
520  *    buffers for doing I/O to pages residing above @page. By default
521  *    the block layer sets this to the highest numbered "low" memory page.
522  **/
523 void blk_queue_bounce_limit(request_queue_t *q, u64 dma_addr)
524 {
525         unsigned long bounce_pfn = dma_addr >> PAGE_SHIFT;
526
527         /*
528          * set appropriate bounce gfp mask -- unfortunately we don't have a
529          * full 4GB zone, so we have to resort to low memory for any bounces.
530          * ISA has its own < 16MB zone.
531          */
532         if (bounce_pfn < blk_max_low_pfn) {
533                 BUG_ON(dma_addr < BLK_BOUNCE_ISA);
534                 init_emergency_isa_pool();
535                 q->bounce_gfp = GFP_NOIO | GFP_DMA;
536         } else
537                 q->bounce_gfp = GFP_NOIO;
538
539         q->bounce_pfn = bounce_pfn;
540 }
541
542 EXPORT_SYMBOL(blk_queue_bounce_limit);
543
544 /**
545  * blk_queue_max_sectors - set max sectors for a request for this queue
546  * @q:  the request queue for the device
547  * @max_sectors:  max sectors in the usual 512b unit
548  *
549  * Description:
550  *    Enables a low level driver to set an upper limit on the size of
551  *    received requests.
552  **/
553 void blk_queue_max_sectors(request_queue_t *q, unsigned short max_sectors)
554 {
555         if ((max_sectors << 9) < PAGE_CACHE_SIZE) {
556                 max_sectors = 1 << (PAGE_CACHE_SHIFT - 9);
557                 printk("%s: set to minimum %d\n", __FUNCTION__, max_sectors);
558         }
559
560         q->max_sectors = q->max_hw_sectors = max_sectors;
561 }
562
563 EXPORT_SYMBOL(blk_queue_max_sectors);
564
565 /**
566  * blk_queue_max_phys_segments - set max phys segments for a request for this queue
567  * @q:  the request queue for the device
568  * @max_segments:  max number of segments
569  *
570  * Description:
571  *    Enables a low level driver to set an upper limit on the number of
572  *    physical data segments in a request.  This would be the largest sized
573  *    scatter list the driver could handle.
574  **/
575 void blk_queue_max_phys_segments(request_queue_t *q, unsigned short max_segments)
576 {
577         if (!max_segments) {
578                 max_segments = 1;
579                 printk("%s: set to minimum %d\n", __FUNCTION__, max_segments);
580         }
581
582         q->max_phys_segments = max_segments;
583 }
584
585 EXPORT_SYMBOL(blk_queue_max_phys_segments);
586
587 /**
588  * blk_queue_max_hw_segments - set max hw segments for a request for this queue
589  * @q:  the request queue for the device
590  * @max_segments:  max number of segments
591  *
592  * Description:
593  *    Enables a low level driver to set an upper limit on the number of
594  *    hw data segments in a request.  This would be the largest number of
595  *    address/length pairs the host adapter can actually give as once
596  *    to the device.
597  **/
598 void blk_queue_max_hw_segments(request_queue_t *q, unsigned short max_segments)
599 {
600         if (!max_segments) {
601                 max_segments = 1;
602                 printk("%s: set to minimum %d\n", __FUNCTION__, max_segments);
603         }
604
605         q->max_hw_segments = max_segments;
606 }
607
608 EXPORT_SYMBOL(blk_queue_max_hw_segments);
609
610 /**
611  * blk_queue_max_segment_size - set max segment size for blk_rq_map_sg
612  * @q:  the request queue for the device
613  * @max_size:  max size of segment in bytes
614  *
615  * Description:
616  *    Enables a low level driver to set an upper limit on the size of a
617  *    coalesced segment
618  **/
619 void blk_queue_max_segment_size(request_queue_t *q, unsigned int max_size)
620 {
621         if (max_size < PAGE_CACHE_SIZE) {
622                 max_size = PAGE_CACHE_SIZE;
623                 printk("%s: set to minimum %d\n", __FUNCTION__, max_size);
624         }
625
626         q->max_segment_size = max_size;
627 }
628
629 EXPORT_SYMBOL(blk_queue_max_segment_size);
630
631 /**
632  * blk_queue_hardsect_size - set hardware sector size for the queue
633  * @q:  the request queue for the device
634  * @size:  the hardware sector size, in bytes
635  *
636  * Description:
637  *   This should typically be set to the lowest possible sector size
638  *   that the hardware can operate on (possible without reverting to
639  *   even internal read-modify-write operations). Usually the default
640  *   of 512 covers most hardware.
641  **/
642 void blk_queue_hardsect_size(request_queue_t *q, unsigned short size)
643 {
644         q->hardsect_size = size;
645 }
646
647 EXPORT_SYMBOL(blk_queue_hardsect_size);
648
649 /*
650  * Returns the minimum that is _not_ zero, unless both are zero.
651  */
652 #define min_not_zero(l, r) (l == 0) ? r : ((r == 0) ? l : min(l, r))
653
654 /**
655  * blk_queue_stack_limits - inherit underlying queue limits for stacked drivers
656  * @t:  the stacking driver (top)
657  * @b:  the underlying device (bottom)
658  **/
659 void blk_queue_stack_limits(request_queue_t *t, request_queue_t *b)
660 {
661         /* zero is "infinity" */
662         t->max_sectors = t->max_hw_sectors =
663                 min_not_zero(t->max_sectors,b->max_sectors);
664
665         t->max_phys_segments = min(t->max_phys_segments,b->max_phys_segments);
666         t->max_hw_segments = min(t->max_hw_segments,b->max_hw_segments);
667         t->max_segment_size = min(t->max_segment_size,b->max_segment_size);
668         t->hardsect_size = max(t->hardsect_size,b->hardsect_size);
669 }
670
671 EXPORT_SYMBOL(blk_queue_stack_limits);
672
673 /**
674  * blk_queue_segment_boundary - set boundary rules for segment merging
675  * @q:  the request queue for the device
676  * @mask:  the memory boundary mask
677  **/
678 void blk_queue_segment_boundary(request_queue_t *q, unsigned long mask)
679 {
680         if (mask < PAGE_CACHE_SIZE - 1) {
681                 mask = PAGE_CACHE_SIZE - 1;
682                 printk("%s: set to minimum %lx\n", __FUNCTION__, mask);
683         }
684
685         q->seg_boundary_mask = mask;
686 }
687
688 EXPORT_SYMBOL(blk_queue_segment_boundary);
689
690 /**
691  * blk_queue_dma_alignment - set dma length and memory alignment
692  * @q:     the request queue for the device
693  * @mask:  alignment mask
694  *
695  * description:
696  *    set required memory and length aligment for direct dma transactions.
697  *    this is used when buiding direct io requests for the queue.
698  *
699  **/
700 void blk_queue_dma_alignment(request_queue_t *q, int mask)
701 {
702         q->dma_alignment = mask;
703 }
704
705 EXPORT_SYMBOL(blk_queue_dma_alignment);
706
707 /**
708  * blk_queue_find_tag - find a request by its tag and queue
709  *
710  * @q:   The request queue for the device
711  * @tag: The tag of the request
712  *
713  * Notes:
714  *    Should be used when a device returns a tag and you want to match
715  *    it with a request.
716  *
717  *    no locks need be held.
718  **/
719 struct request *blk_queue_find_tag(request_queue_t *q, int tag)
720 {
721         struct blk_queue_tag *bqt = q->queue_tags;
722
723         if (unlikely(bqt == NULL || tag >= bqt->real_max_depth))
724                 return NULL;
725
726         return bqt->tag_index[tag];
727 }
728
729 EXPORT_SYMBOL(blk_queue_find_tag);
730
731 /**
732  * __blk_queue_free_tags - release tag maintenance info
733  * @q:  the request queue for the device
734  *
735  *  Notes:
736  *    blk_cleanup_queue() will take care of calling this function, if tagging
737  *    has been used. So there's no need to call this directly.
738  **/
739 static void __blk_queue_free_tags(request_queue_t *q)
740 {
741         struct blk_queue_tag *bqt = q->queue_tags;
742
743         if (!bqt)
744                 return;
745
746         if (atomic_dec_and_test(&bqt->refcnt)) {
747                 BUG_ON(bqt->busy);
748                 BUG_ON(!list_empty(&bqt->busy_list));
749
750                 kfree(bqt->tag_index);
751                 bqt->tag_index = NULL;
752
753                 kfree(bqt->tag_map);
754                 bqt->tag_map = NULL;
755
756                 kfree(bqt);
757         }
758
759         q->queue_tags = NULL;
760         q->queue_flags &= ~(1 << QUEUE_FLAG_QUEUED);
761 }
762
763 /**
764  * blk_queue_free_tags - release tag maintenance info
765  * @q:  the request queue for the device
766  *
767  *  Notes:
768  *      This is used to disabled tagged queuing to a device, yet leave
769  *      queue in function.
770  **/
771 void blk_queue_free_tags(request_queue_t *q)
772 {
773         clear_bit(QUEUE_FLAG_QUEUED, &q->queue_flags);
774 }
775
776 EXPORT_SYMBOL(blk_queue_free_tags);
777
778 static int
779 init_tag_map(request_queue_t *q, struct blk_queue_tag *tags, int depth)
780 {
781         struct request **tag_index;
782         unsigned long *tag_map;
783         int nr_ulongs;
784
785         if (depth > q->nr_requests * 2) {
786                 depth = q->nr_requests * 2;
787                 printk(KERN_ERR "%s: adjusted depth to %d\n",
788                                 __FUNCTION__, depth);
789         }
790
791         tag_index = kmalloc(depth * sizeof(struct request *), GFP_ATOMIC);
792         if (!tag_index)
793                 goto fail;
794
795         nr_ulongs = ALIGN(depth, BITS_PER_LONG) / BITS_PER_LONG;
796         tag_map = kmalloc(nr_ulongs * sizeof(unsigned long), GFP_ATOMIC);
797         if (!tag_map)
798                 goto fail;
799
800         memset(tag_index, 0, depth * sizeof(struct request *));
801         memset(tag_map, 0, nr_ulongs * sizeof(unsigned long));
802         tags->real_max_depth = depth;
803         tags->max_depth = depth;
804         tags->tag_index = tag_index;
805         tags->tag_map = tag_map;
806
807         return 0;
808 fail:
809         kfree(tag_index);
810         return -ENOMEM;
811 }
812
813 /**
814  * blk_queue_init_tags - initialize the queue tag info
815  * @q:  the request queue for the device
816  * @depth:  the maximum queue depth supported
817  * @tags: the tag to use
818  **/
819 int blk_queue_init_tags(request_queue_t *q, int depth,
820                         struct blk_queue_tag *tags)
821 {
822         int rc;
823
824         BUG_ON(tags && q->queue_tags && tags != q->queue_tags);
825
826         if (!tags && !q->queue_tags) {
827                 tags = kmalloc(sizeof(struct blk_queue_tag), GFP_ATOMIC);
828                 if (!tags)
829                         goto fail;
830
831                 if (init_tag_map(q, tags, depth))
832                         goto fail;
833
834                 INIT_LIST_HEAD(&tags->busy_list);
835                 tags->busy = 0;
836                 atomic_set(&tags->refcnt, 1);
837         } else if (q->queue_tags) {
838                 if ((rc = blk_queue_resize_tags(q, depth)))
839                         return rc;
840                 set_bit(QUEUE_FLAG_QUEUED, &q->queue_flags);
841                 return 0;
842         } else
843                 atomic_inc(&tags->refcnt);
844
845         /*
846          * assign it, all done
847          */
848         q->queue_tags = tags;
849         q->queue_flags |= (1 << QUEUE_FLAG_QUEUED);
850         return 0;
851 fail:
852         kfree(tags);
853         return -ENOMEM;
854 }
855
856 EXPORT_SYMBOL(blk_queue_init_tags);
857
858 /**
859  * blk_queue_resize_tags - change the queueing depth
860  * @q:  the request queue for the device
861  * @new_depth: the new max command queueing depth
862  *
863  *  Notes:
864  *    Must be called with the queue lock held.
865  **/
866 int blk_queue_resize_tags(request_queue_t *q, int new_depth)
867 {
868         struct blk_queue_tag *bqt = q->queue_tags;
869         struct request **tag_index;
870         unsigned long *tag_map;
871         int max_depth, nr_ulongs;
872
873         if (!bqt)
874                 return -ENXIO;
875
876         /*
877          * if we already have large enough real_max_depth.  just
878          * adjust max_depth.  *NOTE* as requests with tag value
879          * between new_depth and real_max_depth can be in-flight, tag
880          * map can not be shrunk blindly here.
881          */
882         if (new_depth <= bqt->real_max_depth) {
883                 bqt->max_depth = new_depth;
884                 return 0;
885         }
886
887         /*
888          * save the old state info, so we can copy it back
889          */
890         tag_index = bqt->tag_index;
891         tag_map = bqt->tag_map;
892         max_depth = bqt->real_max_depth;
893
894         if (init_tag_map(q, bqt, new_depth))
895                 return -ENOMEM;
896
897         memcpy(bqt->tag_index, tag_index, max_depth * sizeof(struct request *));
898         nr_ulongs = ALIGN(max_depth, BITS_PER_LONG) / BITS_PER_LONG;
899         memcpy(bqt->tag_map, tag_map, nr_ulongs * sizeof(unsigned long));
900
901         kfree(tag_index);
902         kfree(tag_map);
903         return 0;
904 }
905
906 EXPORT_SYMBOL(blk_queue_resize_tags);
907
908 /**
909  * blk_queue_end_tag - end tag operations for a request
910  * @q:  the request queue for the device
911  * @rq: the request that has completed
912  *
913  *  Description:
914  *    Typically called when end_that_request_first() returns 0, meaning
915  *    all transfers have been done for a request. It's important to call
916  *    this function before end_that_request_last(), as that will put the
917  *    request back on the free list thus corrupting the internal tag list.
918  *
919  *  Notes:
920  *   queue lock must be held.
921  **/
922 void blk_queue_end_tag(request_queue_t *q, struct request *rq)
923 {
924         struct blk_queue_tag *bqt = q->queue_tags;
925         int tag = rq->tag;
926
927         BUG_ON(tag == -1);
928
929         if (unlikely(tag >= bqt->real_max_depth))
930                 /*
931                  * This can happen after tag depth has been reduced.
932                  * FIXME: how about a warning or info message here?
933                  */
934                 return;
935
936         if (unlikely(!__test_and_clear_bit(tag, bqt->tag_map))) {
937                 printk(KERN_ERR "%s: attempt to clear non-busy tag (%d)\n",
938                        __FUNCTION__, tag);
939                 return;
940         }
941
942         list_del_init(&rq->queuelist);
943         rq->flags &= ~REQ_QUEUED;
944         rq->tag = -1;
945
946         if (unlikely(bqt->tag_index[tag] == NULL))
947                 printk(KERN_ERR "%s: tag %d is missing\n",
948                        __FUNCTION__, tag);
949
950         bqt->tag_index[tag] = NULL;
951         bqt->busy--;
952 }
953
954 EXPORT_SYMBOL(blk_queue_end_tag);
955
956 /**
957  * blk_queue_start_tag - find a free tag and assign it
958  * @q:  the request queue for the device
959  * @rq:  the block request that needs tagging
960  *
961  *  Description:
962  *    This can either be used as a stand-alone helper, or possibly be
963  *    assigned as the queue &prep_rq_fn (in which case &struct request
964  *    automagically gets a tag assigned). Note that this function
965  *    assumes that any type of request can be queued! if this is not
966  *    true for your device, you must check the request type before
967  *    calling this function.  The request will also be removed from
968  *    the request queue, so it's the drivers responsibility to readd
969  *    it if it should need to be restarted for some reason.
970  *
971  *  Notes:
972  *   queue lock must be held.
973  **/
974 int blk_queue_start_tag(request_queue_t *q, struct request *rq)
975 {
976         struct blk_queue_tag *bqt = q->queue_tags;
977         int tag;
978
979         if (unlikely((rq->flags & REQ_QUEUED))) {
980                 printk(KERN_ERR 
981                        "%s: request %p for device [%s] already tagged %d",
982                        __FUNCTION__, rq,
983                        rq->rq_disk ? rq->rq_disk->disk_name : "?", rq->tag);
984                 BUG();
985         }
986
987         tag = find_first_zero_bit(bqt->tag_map, bqt->max_depth);
988         if (tag >= bqt->max_depth)
989                 return 1;
990
991         __set_bit(tag, bqt->tag_map);
992
993         rq->flags |= REQ_QUEUED;
994         rq->tag = tag;
995         bqt->tag_index[tag] = rq;
996         blkdev_dequeue_request(rq);
997         list_add(&rq->queuelist, &bqt->busy_list);
998         bqt->busy++;
999         return 0;
1000 }
1001
1002 EXPORT_SYMBOL(blk_queue_start_tag);
1003
1004 /**
1005  * blk_queue_invalidate_tags - invalidate all pending tags
1006  * @q:  the request queue for the device
1007  *
1008  *  Description:
1009  *   Hardware conditions may dictate a need to stop all pending requests.
1010  *   In this case, we will safely clear the block side of the tag queue and
1011  *   readd all requests to the request queue in the right order.
1012  *
1013  *  Notes:
1014  *   queue lock must be held.
1015  **/
1016 void blk_queue_invalidate_tags(request_queue_t *q)
1017 {
1018         struct blk_queue_tag *bqt = q->queue_tags;
1019         struct list_head *tmp, *n;
1020         struct request *rq;
1021
1022         list_for_each_safe(tmp, n, &bqt->busy_list) {
1023                 rq = list_entry_rq(tmp);
1024
1025                 if (rq->tag == -1) {
1026                         printk(KERN_ERR
1027                                "%s: bad tag found on list\n", __FUNCTION__);
1028                         list_del_init(&rq->queuelist);
1029                         rq->flags &= ~REQ_QUEUED;
1030                 } else
1031                         blk_queue_end_tag(q, rq);
1032
1033                 rq->flags &= ~REQ_STARTED;
1034                 __elv_add_request(q, rq, ELEVATOR_INSERT_BACK, 0);
1035         }
1036 }
1037
1038 EXPORT_SYMBOL(blk_queue_invalidate_tags);
1039
1040 static char *rq_flags[] = {
1041         "REQ_RW",
1042         "REQ_FAILFAST",
1043         "REQ_SOFTBARRIER",
1044         "REQ_HARDBARRIER",
1045         "REQ_CMD",
1046         "REQ_NOMERGE",
1047         "REQ_STARTED",
1048         "REQ_DONTPREP",
1049         "REQ_QUEUED",
1050         "REQ_PC",
1051         "REQ_BLOCK_PC",
1052         "REQ_SENSE",
1053         "REQ_FAILED",
1054         "REQ_QUIET",
1055         "REQ_SPECIAL",
1056         "REQ_DRIVE_CMD",
1057         "REQ_DRIVE_TASK",
1058         "REQ_DRIVE_TASKFILE",
1059         "REQ_PREEMPT",
1060         "REQ_PM_SUSPEND",
1061         "REQ_PM_RESUME",
1062         "REQ_PM_SHUTDOWN",
1063 };
1064
1065 void blk_dump_rq_flags(struct request *rq, char *msg)
1066 {
1067         int bit;
1068
1069         printk("%s: dev %s: flags = ", msg,
1070                 rq->rq_disk ? rq->rq_disk->disk_name : "?");
1071         bit = 0;
1072         do {
1073                 if (rq->flags & (1 << bit))
1074                         printk("%s ", rq_flags[bit]);
1075                 bit++;
1076         } while (bit < __REQ_NR_BITS);
1077
1078         printk("\nsector %llu, nr/cnr %lu/%u\n", (unsigned long long)rq->sector,
1079                                                        rq->nr_sectors,
1080                                                        rq->current_nr_sectors);
1081         printk("bio %p, biotail %p, buffer %p, data %p, len %u\n", rq->bio, rq->biotail, rq->buffer, rq->data, rq->data_len);
1082
1083         if (rq->flags & (REQ_BLOCK_PC | REQ_PC)) {
1084                 printk("cdb: ");
1085                 for (bit = 0; bit < sizeof(rq->cmd); bit++)
1086                         printk("%02x ", rq->cmd[bit]);
1087                 printk("\n");
1088         }
1089 }
1090
1091 EXPORT_SYMBOL(blk_dump_rq_flags);
1092
1093 void blk_recount_segments(request_queue_t *q, struct bio *bio)
1094 {
1095         struct bio_vec *bv, *bvprv = NULL;
1096         int i, nr_phys_segs, nr_hw_segs, seg_size, hw_seg_size, cluster;
1097         int high, highprv = 1;
1098
1099         if (unlikely(!bio->bi_io_vec))
1100                 return;
1101
1102         cluster = q->queue_flags & (1 << QUEUE_FLAG_CLUSTER);
1103         hw_seg_size = seg_size = nr_phys_segs = nr_hw_segs = 0;
1104         bio_for_each_segment(bv, bio, i) {
1105                 /*
1106                  * the trick here is making sure that a high page is never
1107                  * considered part of another segment, since that might
1108                  * change with the bounce page.
1109                  */
1110                 high = page_to_pfn(bv->bv_page) >= q->bounce_pfn;
1111                 if (high || highprv)
1112                         goto new_hw_segment;
1113                 if (cluster) {
1114                         if (seg_size + bv->bv_len > q->max_segment_size)
1115                                 goto new_segment;
1116                         if (!BIOVEC_PHYS_MERGEABLE(bvprv, bv))
1117                                 goto new_segment;
1118                         if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bv))
1119                                 goto new_segment;
1120                         if (BIOVEC_VIRT_OVERSIZE(hw_seg_size + bv->bv_len))
1121                                 goto new_hw_segment;
1122
1123                         seg_size += bv->bv_len;
1124                         hw_seg_size += bv->bv_len;
1125                         bvprv = bv;
1126                         continue;
1127                 }
1128 new_segment:
1129                 if (BIOVEC_VIRT_MERGEABLE(bvprv, bv) &&
1130                     !BIOVEC_VIRT_OVERSIZE(hw_seg_size + bv->bv_len)) {
1131                         hw_seg_size += bv->bv_len;
1132                 } else {
1133 new_hw_segment:
1134                         if (hw_seg_size > bio->bi_hw_front_size)
1135                                 bio->bi_hw_front_size = hw_seg_size;
1136                         hw_seg_size = BIOVEC_VIRT_START_SIZE(bv) + bv->bv_len;
1137                         nr_hw_segs++;
1138                 }
1139
1140                 nr_phys_segs++;
1141                 bvprv = bv;
1142                 seg_size = bv->bv_len;
1143                 highprv = high;
1144         }
1145         if (hw_seg_size > bio->bi_hw_back_size)
1146                 bio->bi_hw_back_size = hw_seg_size;
1147         if (nr_hw_segs == 1 && hw_seg_size > bio->bi_hw_front_size)
1148                 bio->bi_hw_front_size = hw_seg_size;
1149         bio->bi_phys_segments = nr_phys_segs;
1150         bio->bi_hw_segments = nr_hw_segs;
1151         bio->bi_flags |= (1 << BIO_SEG_VALID);
1152 }
1153
1154
1155 static int blk_phys_contig_segment(request_queue_t *q, struct bio *bio,
1156                                    struct bio *nxt)
1157 {
1158         if (!(q->queue_flags & (1 << QUEUE_FLAG_CLUSTER)))
1159                 return 0;
1160
1161         if (!BIOVEC_PHYS_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)))
1162                 return 0;
1163         if (bio->bi_size + nxt->bi_size > q->max_segment_size)
1164                 return 0;
1165
1166         /*
1167          * bio and nxt are contigous in memory, check if the queue allows
1168          * these two to be merged into one
1169          */
1170         if (BIO_SEG_BOUNDARY(q, bio, nxt))
1171                 return 1;
1172
1173         return 0;
1174 }
1175
1176 static int blk_hw_contig_segment(request_queue_t *q, struct bio *bio,
1177                                  struct bio *nxt)
1178 {
1179         if (unlikely(!bio_flagged(bio, BIO_SEG_VALID)))
1180                 blk_recount_segments(q, bio);
1181         if (unlikely(!bio_flagged(nxt, BIO_SEG_VALID)))
1182                 blk_recount_segments(q, nxt);
1183         if (!BIOVEC_VIRT_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)) ||
1184             BIOVEC_VIRT_OVERSIZE(bio->bi_hw_front_size + bio->bi_hw_back_size))
1185                 return 0;
1186         if (bio->bi_size + nxt->bi_size > q->max_segment_size)
1187                 return 0;
1188
1189         return 1;
1190 }
1191
1192 /*
1193  * map a request to scatterlist, return number of sg entries setup. Caller
1194  * must make sure sg can hold rq->nr_phys_segments entries
1195  */
1196 int blk_rq_map_sg(request_queue_t *q, struct request *rq, struct scatterlist *sg)
1197 {
1198         struct bio_vec *bvec, *bvprv;
1199         struct bio *bio;
1200         int nsegs, i, cluster;
1201
1202         nsegs = 0;
1203         cluster = q->queue_flags & (1 << QUEUE_FLAG_CLUSTER);
1204
1205         /*
1206          * for each bio in rq
1207          */
1208         bvprv = NULL;
1209         rq_for_each_bio(bio, rq) {
1210                 /*
1211                  * for each segment in bio
1212                  */
1213                 bio_for_each_segment(bvec, bio, i) {
1214                         int nbytes = bvec->bv_len;
1215
1216                         if (bvprv && cluster) {
1217                                 if (sg[nsegs - 1].length + nbytes > q->max_segment_size)
1218                                         goto new_segment;
1219
1220                                 if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec))
1221                                         goto new_segment;
1222                                 if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec))
1223                                         goto new_segment;
1224
1225                                 sg[nsegs - 1].length += nbytes;
1226                         } else {
1227 new_segment:
1228                                 memset(&sg[nsegs],0,sizeof(struct scatterlist));
1229                                 sg[nsegs].page = bvec->bv_page;
1230                                 sg[nsegs].length = nbytes;
1231                                 sg[nsegs].offset = bvec->bv_offset;
1232
1233                                 nsegs++;
1234                         }
1235                         bvprv = bvec;
1236                 } /* segments in bio */
1237         } /* bios in rq */
1238
1239         return nsegs;
1240 }
1241
1242 EXPORT_SYMBOL(blk_rq_map_sg);
1243
1244 /*
1245  * the standard queue merge functions, can be overridden with device
1246  * specific ones if so desired
1247  */
1248
1249 static inline int ll_new_mergeable(request_queue_t *q,
1250                                    struct request *req,
1251                                    struct bio *bio)
1252 {
1253         int nr_phys_segs = bio_phys_segments(q, bio);
1254
1255         if (req->nr_phys_segments + nr_phys_segs > q->max_phys_segments) {
1256                 req->flags |= REQ_NOMERGE;
1257                 if (req == q->last_merge)
1258                         q->last_merge = NULL;
1259                 return 0;
1260         }
1261
1262         /*
1263          * A hw segment is just getting larger, bump just the phys
1264          * counter.
1265          */
1266         req->nr_phys_segments += nr_phys_segs;
1267         return 1;
1268 }
1269
1270 static inline int ll_new_hw_segment(request_queue_t *q,
1271                                     struct request *req,
1272                                     struct bio *bio)
1273 {
1274         int nr_hw_segs = bio_hw_segments(q, bio);
1275         int nr_phys_segs = bio_phys_segments(q, bio);
1276
1277         if (req->nr_hw_segments + nr_hw_segs > q->max_hw_segments
1278             || req->nr_phys_segments + nr_phys_segs > q->max_phys_segments) {
1279                 req->flags |= REQ_NOMERGE;
1280                 if (req == q->last_merge)
1281                         q->last_merge = NULL;
1282                 return 0;
1283         }
1284
1285         /*
1286          * This will form the start of a new hw segment.  Bump both
1287          * counters.
1288          */
1289         req->nr_hw_segments += nr_hw_segs;
1290         req->nr_phys_segments += nr_phys_segs;
1291         return 1;
1292 }
1293
1294 static int ll_back_merge_fn(request_queue_t *q, struct request *req, 
1295                             struct bio *bio)
1296 {
1297         int len;
1298
1299         if (req->nr_sectors + bio_sectors(bio) > q->max_sectors) {
1300                 req->flags |= REQ_NOMERGE;
1301                 if (req == q->last_merge)
1302                         q->last_merge = NULL;
1303                 return 0;
1304         }
1305         if (unlikely(!bio_flagged(req->biotail, BIO_SEG_VALID)))
1306                 blk_recount_segments(q, req->biotail);
1307         if (unlikely(!bio_flagged(bio, BIO_SEG_VALID)))
1308                 blk_recount_segments(q, bio);
1309         len = req->biotail->bi_hw_back_size + bio->bi_hw_front_size;
1310         if (BIOVEC_VIRT_MERGEABLE(__BVEC_END(req->biotail), __BVEC_START(bio)) &&
1311             !BIOVEC_VIRT_OVERSIZE(len)) {
1312                 int mergeable =  ll_new_mergeable(q, req, bio);
1313
1314                 if (mergeable) {
1315                         if (req->nr_hw_segments == 1)
1316                                 req->bio->bi_hw_front_size = len;
1317                         if (bio->bi_hw_segments == 1)
1318                                 bio->bi_hw_back_size = len;
1319                 }
1320                 return mergeable;
1321         }
1322
1323         return ll_new_hw_segment(q, req, bio);
1324 }
1325
1326 static int ll_front_merge_fn(request_queue_t *q, struct request *req, 
1327                              struct bio *bio)
1328 {
1329         int len;
1330
1331         if (req->nr_sectors + bio_sectors(bio) > q->max_sectors) {
1332                 req->flags |= REQ_NOMERGE;
1333                 if (req == q->last_merge)
1334                         q->last_merge = NULL;
1335                 return 0;
1336         }
1337         len = bio->bi_hw_back_size + req->bio->bi_hw_front_size;
1338         if (unlikely(!bio_flagged(bio, BIO_SEG_VALID)))
1339                 blk_recount_segments(q, bio);
1340         if (unlikely(!bio_flagged(req->bio, BIO_SEG_VALID)))
1341                 blk_recount_segments(q, req->bio);
1342         if (BIOVEC_VIRT_MERGEABLE(__BVEC_END(bio), __BVEC_START(req->bio)) &&
1343             !BIOVEC_VIRT_OVERSIZE(len)) {
1344                 int mergeable =  ll_new_mergeable(q, req, bio);
1345
1346                 if (mergeable) {
1347                         if (bio->bi_hw_segments == 1)
1348                                 bio->bi_hw_front_size = len;
1349                         if (req->nr_hw_segments == 1)
1350                                 req->biotail->bi_hw_back_size = len;
1351                 }
1352                 return mergeable;
1353         }
1354
1355         return ll_new_hw_segment(q, req, bio);
1356 }
1357
1358 static int ll_merge_requests_fn(request_queue_t *q, struct request *req,
1359                                 struct request *next)
1360 {
1361         int total_phys_segments;
1362         int total_hw_segments;
1363
1364         /*
1365          * First check if the either of the requests are re-queued
1366          * requests.  Can't merge them if they are.
1367          */
1368         if (req->special || next->special)
1369                 return 0;
1370
1371         /*
1372          * Will it become too large?
1373          */
1374         if ((req->nr_sectors + next->nr_sectors) > q->max_sectors)
1375                 return 0;
1376
1377         total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
1378         if (blk_phys_contig_segment(q, req->biotail, next->bio))
1379                 total_phys_segments--;
1380
1381         if (total_phys_segments > q->max_phys_segments)
1382                 return 0;
1383
1384         total_hw_segments = req->nr_hw_segments + next->nr_hw_segments;
1385         if (blk_hw_contig_segment(q, req->biotail, next->bio)) {
1386                 int len = req->biotail->bi_hw_back_size + next->bio->bi_hw_front_size;
1387                 /*
1388                  * propagate the combined length to the end of the requests
1389                  */
1390                 if (req->nr_hw_segments == 1)
1391                         req->bio->bi_hw_front_size = len;
1392                 if (next->nr_hw_segments == 1)
1393                         next->biotail->bi_hw_back_size = len;
1394                 total_hw_segments--;
1395         }
1396
1397         if (total_hw_segments > q->max_hw_segments)
1398                 return 0;
1399
1400         /* Merge is OK... */
1401         req->nr_phys_segments = total_phys_segments;
1402         req->nr_hw_segments = total_hw_segments;
1403         return 1;
1404 }
1405
1406 /*
1407  * "plug" the device if there are no outstanding requests: this will
1408  * force the transfer to start only after we have put all the requests
1409  * on the list.
1410  *
1411  * This is called with interrupts off and no requests on the queue and
1412  * with the queue lock held.
1413  */
1414 void blk_plug_device(request_queue_t *q)
1415 {
1416         WARN_ON(!irqs_disabled());
1417
1418         /*
1419          * don't plug a stopped queue, it must be paired with blk_start_queue()
1420          * which will restart the queueing
1421          */
1422         if (test_bit(QUEUE_FLAG_STOPPED, &q->queue_flags))
1423                 return;
1424
1425         if (!test_and_set_bit(QUEUE_FLAG_PLUGGED, &q->queue_flags))
1426                 mod_timer(&q->unplug_timer, jiffies + q->unplug_delay);
1427 }
1428
1429 EXPORT_SYMBOL(blk_plug_device);
1430
1431 /*
1432  * remove the queue from the plugged list, if present. called with
1433  * queue lock held and interrupts disabled.
1434  */
1435 int blk_remove_plug(request_queue_t *q)
1436 {
1437         WARN_ON(!irqs_disabled());
1438
1439         if (!test_and_clear_bit(QUEUE_FLAG_PLUGGED, &q->queue_flags))
1440                 return 0;
1441
1442         del_timer(&q->unplug_timer);
1443         return 1;
1444 }
1445
1446 EXPORT_SYMBOL(blk_remove_plug);
1447
1448 /*
1449  * remove the plug and let it rip..
1450  */
1451 void __generic_unplug_device(request_queue_t *q)
1452 {
1453         if (unlikely(test_bit(QUEUE_FLAG_STOPPED, &q->queue_flags)))
1454                 return;
1455
1456         if (!blk_remove_plug(q))
1457                 return;
1458
1459         q->request_fn(q);
1460 }
1461 EXPORT_SYMBOL(__generic_unplug_device);
1462
1463 /**
1464  * generic_unplug_device - fire a request queue
1465  * @q:    The &request_queue_t in question
1466  *
1467  * Description:
1468  *   Linux uses plugging to build bigger requests queues before letting
1469  *   the device have at them. If a queue is plugged, the I/O scheduler
1470  *   is still adding and merging requests on the queue. Once the queue
1471  *   gets unplugged, the request_fn defined for the queue is invoked and
1472  *   transfers started.
1473  **/
1474 void generic_unplug_device(request_queue_t *q)
1475 {
1476         spin_lock_irq(q->queue_lock);
1477         __generic_unplug_device(q);
1478         spin_unlock_irq(q->queue_lock);
1479 }
1480 EXPORT_SYMBOL(generic_unplug_device);
1481
1482 static void blk_backing_dev_unplug(struct backing_dev_info *bdi,
1483                                    struct page *page)
1484 {
1485         request_queue_t *q = bdi->unplug_io_data;
1486
1487         /*
1488          * devices don't necessarily have an ->unplug_fn defined
1489          */
1490         if (q->unplug_fn)
1491                 q->unplug_fn(q);
1492 }
1493
1494 static void blk_unplug_work(void *data)
1495 {
1496         request_queue_t *q = data;
1497
1498         q->unplug_fn(q);
1499 }
1500
1501 static void blk_unplug_timeout(unsigned long data)
1502 {
1503         request_queue_t *q = (request_queue_t *)data;
1504
1505         kblockd_schedule_work(&q->unplug_work);
1506 }
1507
1508 /**
1509  * blk_start_queue - restart a previously stopped queue
1510  * @q:    The &request_queue_t in question
1511  *
1512  * Description:
1513  *   blk_start_queue() will clear the stop flag on the queue, and call
1514  *   the request_fn for the queue if it was in a stopped state when
1515  *   entered. Also see blk_stop_queue(). Queue lock must be held.
1516  **/
1517 void blk_start_queue(request_queue_t *q)
1518 {
1519         clear_bit(QUEUE_FLAG_STOPPED, &q->queue_flags);
1520
1521         /*
1522          * one level of recursion is ok and is much faster than kicking
1523          * the unplug handling
1524          */
1525         if (!test_and_set_bit(QUEUE_FLAG_REENTER, &q->queue_flags)) {
1526                 q->request_fn(q);
1527                 clear_bit(QUEUE_FLAG_REENTER, &q->queue_flags);
1528         } else {
1529                 blk_plug_device(q);
1530                 kblockd_schedule_work(&q->unplug_work);
1531         }
1532 }
1533
1534 EXPORT_SYMBOL(blk_start_queue);
1535
1536 /**
1537  * blk_stop_queue - stop a queue
1538  * @q:    The &request_queue_t in question
1539  *
1540  * Description:
1541  *   The Linux block layer assumes that a block driver will consume all
1542  *   entries on the request queue when the request_fn strategy is called.
1543  *   Often this will not happen, because of hardware limitations (queue
1544  *   depth settings). If a device driver gets a 'queue full' response,
1545  *   or if it simply chooses not to queue more I/O at one point, it can
1546  *   call this function to prevent the request_fn from being called until
1547  *   the driver has signalled it's ready to go again. This happens by calling
1548  *   blk_start_queue() to restart queue operations. Queue lock must be held.
1549  **/
1550 void blk_stop_queue(request_queue_t *q)
1551 {
1552         blk_remove_plug(q);
1553         set_bit(QUEUE_FLAG_STOPPED, &q->queue_flags);
1554 }
1555 EXPORT_SYMBOL(blk_stop_queue);
1556
1557 /**
1558  * blk_sync_queue - cancel any pending callbacks on a queue
1559  * @q: the queue
1560  *
1561  * Description:
1562  *     The block layer may perform asynchronous callback activity
1563  *     on a queue, such as calling the unplug function after a timeout.
1564  *     A block device may call blk_sync_queue to ensure that any
1565  *     such activity is cancelled, thus allowing it to release resources
1566  *     the the callbacks might use. The caller must already have made sure
1567  *     that its ->make_request_fn will not re-add plugging prior to calling
1568  *     this function.
1569  *
1570  */
1571 void blk_sync_queue(struct request_queue *q)
1572 {
1573         del_timer_sync(&q->unplug_timer);
1574         kblockd_flush();
1575 }
1576 EXPORT_SYMBOL(blk_sync_queue);
1577
1578 /**
1579  * blk_run_queue - run a single device queue
1580  * @q:  The queue to run
1581  */
1582 void blk_run_queue(struct request_queue *q)
1583 {
1584         unsigned long flags;
1585
1586         spin_lock_irqsave(q->queue_lock, flags);
1587         blk_remove_plug(q);
1588         if (!elv_queue_empty(q))
1589                 q->request_fn(q);
1590         spin_unlock_irqrestore(q->queue_lock, flags);
1591 }
1592 EXPORT_SYMBOL(blk_run_queue);
1593
1594 /**
1595  * blk_cleanup_queue: - release a &request_queue_t when it is no longer needed
1596  * @q:    the request queue to be released
1597  *
1598  * Description:
1599  *     blk_cleanup_queue is the pair to blk_init_queue() or
1600  *     blk_queue_make_request().  It should be called when a request queue is
1601  *     being released; typically when a block device is being de-registered.
1602  *     Currently, its primary task it to free all the &struct request
1603  *     structures that were allocated to the queue and the queue itself.
1604  *
1605  * Caveat:
1606  *     Hopefully the low level driver will have finished any
1607  *     outstanding requests first...
1608  **/
1609 void blk_cleanup_queue(request_queue_t * q)
1610 {
1611         struct request_list *rl = &q->rq;
1612
1613         if (!atomic_dec_and_test(&q->refcnt))
1614                 return;
1615
1616         if (q->elevator)
1617                 elevator_exit(q->elevator);
1618
1619         blk_sync_queue(q);
1620
1621         if (rl->rq_pool)
1622                 mempool_destroy(rl->rq_pool);
1623
1624         if (q->queue_tags)
1625                 __blk_queue_free_tags(q);
1626
1627         blk_queue_ordered(q, QUEUE_ORDERED_NONE);
1628
1629         kmem_cache_free(requestq_cachep, q);
1630 }
1631
1632 EXPORT_SYMBOL(blk_cleanup_queue);
1633
1634 static int blk_init_free_list(request_queue_t *q)
1635 {
1636         struct request_list *rl = &q->rq;
1637
1638         rl->count[READ] = rl->count[WRITE] = 0;
1639         rl->starved[READ] = rl->starved[WRITE] = 0;
1640         init_waitqueue_head(&rl->wait[READ]);
1641         init_waitqueue_head(&rl->wait[WRITE]);
1642         init_waitqueue_head(&rl->drain);
1643
1644         rl->rq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab,
1645                                 mempool_free_slab, request_cachep, q->node);
1646
1647         if (!rl->rq_pool)
1648                 return -ENOMEM;
1649
1650         return 0;
1651 }
1652
1653 static int __make_request(request_queue_t *, struct bio *);
1654
1655 request_queue_t *blk_alloc_queue(int gfp_mask)
1656 {
1657         return blk_alloc_queue_node(gfp_mask, -1);
1658 }
1659 EXPORT_SYMBOL(blk_alloc_queue);
1660
1661 request_queue_t *blk_alloc_queue_node(int gfp_mask, int node_id)
1662 {
1663         request_queue_t *q;
1664
1665         q = kmem_cache_alloc_node(requestq_cachep, gfp_mask, node_id);
1666         if (!q)
1667                 return NULL;
1668
1669         memset(q, 0, sizeof(*q));
1670         init_timer(&q->unplug_timer);
1671         atomic_set(&q->refcnt, 1);
1672
1673         q->backing_dev_info.unplug_io_fn = blk_backing_dev_unplug;
1674         q->backing_dev_info.unplug_io_data = q;
1675
1676         return q;
1677 }
1678 EXPORT_SYMBOL(blk_alloc_queue_node);
1679
1680 /**
1681  * blk_init_queue  - prepare a request queue for use with a block device
1682  * @rfn:  The function to be called to process requests that have been
1683  *        placed on the queue.
1684  * @lock: Request queue spin lock
1685  *
1686  * Description:
1687  *    If a block device wishes to use the standard request handling procedures,
1688  *    which sorts requests and coalesces adjacent requests, then it must
1689  *    call blk_init_queue().  The function @rfn will be called when there
1690  *    are requests on the queue that need to be processed.  If the device
1691  *    supports plugging, then @rfn may not be called immediately when requests
1692  *    are available on the queue, but may be called at some time later instead.
1693  *    Plugged queues are generally unplugged when a buffer belonging to one
1694  *    of the requests on the queue is needed, or due to memory pressure.
1695  *
1696  *    @rfn is not required, or even expected, to remove all requests off the
1697  *    queue, but only as many as it can handle at a time.  If it does leave
1698  *    requests on the queue, it is responsible for arranging that the requests
1699  *    get dealt with eventually.
1700  *
1701  *    The queue spin lock must be held while manipulating the requests on the
1702  *    request queue.
1703  *
1704  *    Function returns a pointer to the initialized request queue, or NULL if
1705  *    it didn't succeed.
1706  *
1707  * Note:
1708  *    blk_init_queue() must be paired with a blk_cleanup_queue() call
1709  *    when the block device is deactivated (such as at module unload).
1710  **/
1711
1712 request_queue_t *blk_init_queue(request_fn_proc *rfn, spinlock_t *lock)
1713 {
1714         return blk_init_queue_node(rfn, lock, -1);
1715 }
1716 EXPORT_SYMBOL(blk_init_queue);
1717
1718 request_queue_t *
1719 blk_init_queue_node(request_fn_proc *rfn, spinlock_t *lock, int node_id)
1720 {
1721         request_queue_t *q = blk_alloc_queue_node(GFP_KERNEL, node_id);
1722
1723         if (!q)
1724                 return NULL;
1725
1726         q->node = node_id;
1727         if (blk_init_free_list(q))
1728                 goto out_init;
1729
1730         /*
1731          * if caller didn't supply a lock, they get per-queue locking with
1732          * our embedded lock
1733          */
1734         if (!lock) {
1735                 spin_lock_init(&q->__queue_lock);
1736                 lock = &q->__queue_lock;
1737         }
1738
1739         q->request_fn           = rfn;
1740         q->back_merge_fn        = ll_back_merge_fn;
1741         q->front_merge_fn       = ll_front_merge_fn;
1742         q->merge_requests_fn    = ll_merge_requests_fn;
1743         q->prep_rq_fn           = NULL;
1744         q->unplug_fn            = generic_unplug_device;
1745         q->queue_flags          = (1 << QUEUE_FLAG_CLUSTER);
1746         q->queue_lock           = lock;
1747
1748         blk_queue_segment_boundary(q, 0xffffffff);
1749
1750         blk_queue_make_request(q, __make_request);
1751         blk_queue_max_segment_size(q, MAX_SEGMENT_SIZE);
1752
1753         blk_queue_max_hw_segments(q, MAX_HW_SEGMENTS);
1754         blk_queue_max_phys_segments(q, MAX_PHYS_SEGMENTS);
1755
1756         /*
1757          * all done
1758          */
1759         if (!elevator_init(q, NULL)) {
1760                 blk_queue_congestion_threshold(q);
1761                 return q;
1762         }
1763
1764         blk_cleanup_queue(q);
1765 out_init:
1766         kmem_cache_free(requestq_cachep, q);
1767         return NULL;
1768 }
1769 EXPORT_SYMBOL(blk_init_queue_node);
1770
1771 int blk_get_queue(request_queue_t *q)
1772 {
1773         if (likely(!test_bit(QUEUE_FLAG_DEAD, &q->queue_flags))) {
1774                 atomic_inc(&q->refcnt);
1775                 return 0;
1776         }
1777
1778         return 1;
1779 }
1780
1781 EXPORT_SYMBOL(blk_get_queue);
1782
1783 static inline void blk_free_request(request_queue_t *q, struct request *rq)
1784 {
1785         elv_put_request(q, rq);
1786         mempool_free(rq, q->rq.rq_pool);
1787 }
1788
1789 static inline struct request *
1790 blk_alloc_request(request_queue_t *q, int rw, struct bio *bio, int gfp_mask)
1791 {
1792         struct request *rq = mempool_alloc(q->rq.rq_pool, gfp_mask);
1793
1794         if (!rq)
1795                 return NULL;
1796
1797         /*
1798          * first three bits are identical in rq->flags and bio->bi_rw,
1799          * see bio.h and blkdev.h
1800          */
1801         rq->flags = rw;
1802
1803         if (!elv_set_request(q, rq, bio, gfp_mask))
1804                 return rq;
1805
1806         mempool_free(rq, q->rq.rq_pool);
1807         return NULL;
1808 }
1809
1810 /*
1811  * ioc_batching returns true if the ioc is a valid batching request and
1812  * should be given priority access to a request.
1813  */
1814 static inline int ioc_batching(request_queue_t *q, struct io_context *ioc)
1815 {
1816         if (!ioc)
1817                 return 0;
1818
1819         /*
1820          * Make sure the process is able to allocate at least 1 request
1821          * even if the batch times out, otherwise we could theoretically
1822          * lose wakeups.
1823          */
1824         return ioc->nr_batch_requests == q->nr_batching ||
1825                 (ioc->nr_batch_requests > 0
1826                 && time_before(jiffies, ioc->last_waited + BLK_BATCH_TIME));
1827 }
1828
1829 /*
1830  * ioc_set_batching sets ioc to be a new "batcher" if it is not one. This
1831  * will cause the process to be a "batcher" on all queues in the system. This
1832  * is the behaviour we want though - once it gets a wakeup it should be given
1833  * a nice run.
1834  */
1835 static void ioc_set_batching(request_queue_t *q, struct io_context *ioc)
1836 {
1837         if (!ioc || ioc_batching(q, ioc))
1838                 return;
1839
1840         ioc->nr_batch_requests = q->nr_batching;
1841         ioc->last_waited = jiffies;
1842 }
1843
1844 static void __freed_request(request_queue_t *q, int rw)
1845 {
1846         struct request_list *rl = &q->rq;
1847
1848         if (rl->count[rw] < queue_congestion_off_threshold(q))
1849                 clear_queue_congested(q, rw);
1850
1851         if (rl->count[rw] + 1 <= q->nr_requests) {
1852                 if (waitqueue_active(&rl->wait[rw]))
1853                         wake_up(&rl->wait[rw]);
1854
1855                 blk_clear_queue_full(q, rw);
1856         }
1857 }
1858
1859 /*
1860  * A request has just been released.  Account for it, update the full and
1861  * congestion status, wake up any waiters.   Called under q->queue_lock.
1862  */
1863 static void freed_request(request_queue_t *q, int rw)
1864 {
1865         struct request_list *rl = &q->rq;
1866
1867         rl->count[rw]--;
1868
1869         __freed_request(q, rw);
1870
1871         if (unlikely(rl->starved[rw ^ 1]))
1872                 __freed_request(q, rw ^ 1);
1873
1874         if (!rl->count[READ] && !rl->count[WRITE]) {
1875                 smp_mb();
1876                 if (unlikely(waitqueue_active(&rl->drain)))
1877                         wake_up(&rl->drain);
1878         }
1879 }
1880
1881 #define blkdev_free_rq(list) list_entry((list)->next, struct request, queuelist)
1882 /*
1883  * Get a free request, queue_lock must be held.
1884  * Returns NULL on failure, with queue_lock held.
1885  * Returns !NULL on success, with queue_lock *not held*.
1886  */
1887 static struct request *get_request(request_queue_t *q, int rw, struct bio *bio,
1888                                    int gfp_mask)
1889 {
1890         struct request *rq = NULL;
1891         struct request_list *rl = &q->rq;
1892         struct io_context *ioc = current_io_context(GFP_ATOMIC);
1893
1894         if (unlikely(test_bit(QUEUE_FLAG_DRAIN, &q->queue_flags)))
1895                 goto out;
1896
1897         if (rl->count[rw]+1 >= q->nr_requests) {
1898                 /*
1899                  * The queue will fill after this allocation, so set it as
1900                  * full, and mark this process as "batching". This process
1901                  * will be allowed to complete a batch of requests, others
1902                  * will be blocked.
1903                  */
1904                 if (!blk_queue_full(q, rw)) {
1905                         ioc_set_batching(q, ioc);
1906                         blk_set_queue_full(q, rw);
1907                 }
1908         }
1909
1910         switch (elv_may_queue(q, rw, bio)) {
1911                 case ELV_MQUEUE_NO:
1912                         goto rq_starved;
1913                 case ELV_MQUEUE_MAY:
1914                         break;
1915                 case ELV_MQUEUE_MUST:
1916                         goto get_rq;
1917         }
1918
1919         if (blk_queue_full(q, rw) && !ioc_batching(q, ioc)) {
1920                 /*
1921                  * The queue is full and the allocating process is not a
1922                  * "batcher", and not exempted by the IO scheduler
1923                  */
1924                 goto out;
1925         }
1926
1927 get_rq:
1928         /*
1929          * Only allow batching queuers to allocate up to 50% over the defined
1930          * limit of requests, otherwise we could have thousands of requests
1931          * allocated with any setting of ->nr_requests
1932          */
1933         if (rl->count[rw] >= (3 * q->nr_requests / 2))
1934                 goto out;
1935
1936         rl->count[rw]++;
1937         rl->starved[rw] = 0;
1938         if (rl->count[rw] >= queue_congestion_on_threshold(q))
1939                 set_queue_congested(q, rw);
1940         spin_unlock_irq(q->queue_lock);
1941
1942         rq = blk_alloc_request(q, rw, bio, gfp_mask);
1943         if (!rq) {
1944                 /*
1945                  * Allocation failed presumably due to memory. Undo anything
1946                  * we might have messed up.
1947                  *
1948                  * Allocating task should really be put onto the front of the
1949                  * wait queue, but this is pretty rare.
1950                  */
1951                 spin_lock_irq(q->queue_lock);
1952                 freed_request(q, rw);
1953
1954                 /*
1955                  * in the very unlikely event that allocation failed and no
1956                  * requests for this direction was pending, mark us starved
1957                  * so that freeing of a request in the other direction will
1958                  * notice us. another possible fix would be to split the
1959                  * rq mempool into READ and WRITE
1960                  */
1961 rq_starved:
1962                 if (unlikely(rl->count[rw] == 0))
1963                         rl->starved[rw] = 1;
1964
1965                 goto out;
1966         }
1967
1968         if (ioc_batching(q, ioc))
1969                 ioc->nr_batch_requests--;
1970         
1971         rq_init(q, rq);
1972         rq->rl = rl;
1973 out:
1974         return rq;
1975 }
1976
1977 /*
1978  * No available requests for this queue, unplug the device and wait for some
1979  * requests to become available.
1980  *
1981  * Called with q->queue_lock held, and returns with it unlocked.
1982  */
1983 static struct request *get_request_wait(request_queue_t *q, int rw,
1984                                         struct bio *bio)
1985 {
1986         struct request *rq;
1987
1988         rq = get_request(q, rw, bio, GFP_NOIO);
1989         while (!rq) {
1990                 DEFINE_WAIT(wait);
1991                 struct request_list *rl = &q->rq;
1992
1993                 prepare_to_wait_exclusive(&rl->wait[rw], &wait,
1994                                 TASK_UNINTERRUPTIBLE);
1995
1996                 rq = get_request(q, rw, bio, GFP_NOIO);
1997
1998                 if (!rq) {
1999                         struct io_context *ioc;
2000
2001                         __generic_unplug_device(q);
2002                         spin_unlock_irq(q->queue_lock);
2003                         io_schedule();
2004
2005                         /*
2006                          * After sleeping, we become a "batching" process and
2007                          * will be able to allocate at least one request, and
2008                          * up to a big batch of them for a small period time.
2009                          * See ioc_batching, ioc_set_batching
2010                          */
2011                         ioc = current_io_context(GFP_NOIO);
2012                         ioc_set_batching(q, ioc);
2013
2014                         spin_lock_irq(q->queue_lock);
2015                 }
2016                 finish_wait(&rl->wait[rw], &wait);
2017         }
2018
2019         return rq;
2020 }
2021
2022 struct request *blk_get_request(request_queue_t *q, int rw, int gfp_mask)
2023 {
2024         struct request *rq;
2025
2026         BUG_ON(rw != READ && rw != WRITE);
2027
2028         spin_lock_irq(q->queue_lock);
2029         if (gfp_mask & __GFP_WAIT) {
2030                 rq = get_request_wait(q, rw, NULL);
2031         } else {
2032                 rq = get_request(q, rw, NULL, gfp_mask);
2033                 if (!rq)
2034                         spin_unlock_irq(q->queue_lock);
2035         }
2036         /* q->queue_lock is unlocked at this point */
2037
2038         return rq;
2039 }
2040 EXPORT_SYMBOL(blk_get_request);
2041
2042 /**
2043  * blk_requeue_request - put a request back on queue
2044  * @q:          request queue where request should be inserted
2045  * @rq:         request to be inserted
2046  *
2047  * Description:
2048  *    Drivers often keep queueing requests until the hardware cannot accept
2049  *    more, when that condition happens we need to put the request back
2050  *    on the queue. Must be called with queue lock held.
2051  */
2052 void blk_requeue_request(request_queue_t *q, struct request *rq)
2053 {
2054         if (blk_rq_tagged(rq))
2055                 blk_queue_end_tag(q, rq);
2056
2057         elv_requeue_request(q, rq);
2058 }
2059
2060 EXPORT_SYMBOL(blk_requeue_request);
2061
2062 /**
2063  * blk_insert_request - insert a special request in to a request queue
2064  * @q:          request queue where request should be inserted
2065  * @rq:         request to be inserted
2066  * @at_head:    insert request at head or tail of queue
2067  * @data:       private data
2068  *
2069  * Description:
2070  *    Many block devices need to execute commands asynchronously, so they don't
2071  *    block the whole kernel from preemption during request execution.  This is
2072  *    accomplished normally by inserting aritficial requests tagged as
2073  *    REQ_SPECIAL in to the corresponding request queue, and letting them be
2074  *    scheduled for actual execution by the request queue.
2075  *
2076  *    We have the option of inserting the head or the tail of the queue.
2077  *    Typically we use the tail for new ioctls and so forth.  We use the head
2078  *    of the queue for things like a QUEUE_FULL message from a device, or a
2079  *    host that is unable to accept a particular command.
2080  */
2081 void blk_insert_request(request_queue_t *q, struct request *rq,
2082                         int at_head, void *data)
2083 {
2084         int where = at_head ? ELEVATOR_INSERT_FRONT : ELEVATOR_INSERT_BACK;
2085         unsigned long flags;
2086
2087         /*
2088          * tell I/O scheduler that this isn't a regular read/write (ie it
2089          * must not attempt merges on this) and that it acts as a soft
2090          * barrier
2091          */
2092         rq->flags |= REQ_SPECIAL | REQ_SOFTBARRIER;
2093
2094         rq->special = data;
2095
2096         spin_lock_irqsave(q->queue_lock, flags);
2097
2098         /*
2099          * If command is tagged, release the tag
2100          */
2101         if (blk_rq_tagged(rq))
2102                 blk_queue_end_tag(q, rq);
2103
2104         drive_stat_acct(rq, rq->nr_sectors, 1);
2105         __elv_add_request(q, rq, where, 0);
2106
2107         if (blk_queue_plugged(q))
2108                 __generic_unplug_device(q);
2109         else
2110                 q->request_fn(q);
2111         spin_unlock_irqrestore(q->queue_lock, flags);
2112 }
2113
2114 EXPORT_SYMBOL(blk_insert_request);
2115
2116 /**
2117  * blk_rq_map_user - map user data to a request, for REQ_BLOCK_PC usage
2118  * @q:          request queue where request should be inserted
2119  * @rq:         request structure to fill
2120  * @ubuf:       the user buffer
2121  * @len:        length of user data
2122  *
2123  * Description:
2124  *    Data will be mapped directly for zero copy io, if possible. Otherwise
2125  *    a kernel bounce buffer is used.
2126  *
2127  *    A matching blk_rq_unmap_user() must be issued at the end of io, while
2128  *    still in process context.
2129  *
2130  *    Note: The mapped bio may need to be bounced through blk_queue_bounce()
2131  *    before being submitted to the device, as pages mapped may be out of
2132  *    reach. It's the callers responsibility to make sure this happens. The
2133  *    original bio must be passed back in to blk_rq_unmap_user() for proper
2134  *    unmapping.
2135  */
2136 int blk_rq_map_user(request_queue_t *q, struct request *rq, void __user *ubuf,
2137                     unsigned int len)
2138 {
2139         unsigned long uaddr;
2140         struct bio *bio;
2141         int reading;
2142
2143         if (len > (q->max_sectors << 9))
2144                 return -EINVAL;
2145         if (!len || !ubuf)
2146                 return -EINVAL;
2147
2148         reading = rq_data_dir(rq) == READ;
2149
2150         /*
2151          * if alignment requirement is satisfied, map in user pages for
2152          * direct dma. else, set up kernel bounce buffers
2153          */
2154         uaddr = (unsigned long) ubuf;
2155         if (!(uaddr & queue_dma_alignment(q)) && !(len & queue_dma_alignment(q)))
2156                 bio = bio_map_user(q, NULL, uaddr, len, reading);
2157         else
2158                 bio = bio_copy_user(q, uaddr, len, reading);
2159
2160         if (!IS_ERR(bio)) {
2161                 rq->bio = rq->biotail = bio;
2162                 blk_rq_bio_prep(q, rq, bio);
2163
2164                 rq->buffer = rq->data = NULL;
2165                 rq->data_len = len;
2166                 return 0;
2167         }
2168
2169         /*
2170          * bio is the err-ptr
2171          */
2172         return PTR_ERR(bio);
2173 }
2174
2175 EXPORT_SYMBOL(blk_rq_map_user);
2176
2177 /**
2178  * blk_rq_map_user_iov - map user data to a request, for REQ_BLOCK_PC usage
2179  * @q:          request queue where request should be inserted
2180  * @rq:         request to map data to
2181  * @iov:        pointer to the iovec
2182  * @iov_count:  number of elements in the iovec
2183  *
2184  * Description:
2185  *    Data will be mapped directly for zero copy io, if possible. Otherwise
2186  *    a kernel bounce buffer is used.
2187  *
2188  *    A matching blk_rq_unmap_user() must be issued at the end of io, while
2189  *    still in process context.
2190  *
2191  *    Note: The mapped bio may need to be bounced through blk_queue_bounce()
2192  *    before being submitted to the device, as pages mapped may be out of
2193  *    reach. It's the callers responsibility to make sure this happens. The
2194  *    original bio must be passed back in to blk_rq_unmap_user() for proper
2195  *    unmapping.
2196  */
2197 int blk_rq_map_user_iov(request_queue_t *q, struct request *rq,
2198                         struct sg_iovec *iov, int iov_count)
2199 {
2200         struct bio *bio;
2201
2202         if (!iov || iov_count <= 0)
2203                 return -EINVAL;
2204
2205         /* we don't allow misaligned data like bio_map_user() does.  If the
2206          * user is using sg, they're expected to know the alignment constraints
2207          * and respect them accordingly */
2208         bio = bio_map_user_iov(q, NULL, iov, iov_count, rq_data_dir(rq)== READ);
2209         if (IS_ERR(bio))
2210                 return PTR_ERR(bio);
2211
2212         rq->bio = rq->biotail = bio;
2213         blk_rq_bio_prep(q, rq, bio);
2214         rq->buffer = rq->data = NULL;
2215         rq->data_len = bio->bi_size;
2216         return 0;
2217 }
2218
2219 EXPORT_SYMBOL(blk_rq_map_user_iov);
2220
2221 /**
2222  * blk_rq_unmap_user - unmap a request with user data
2223  * @bio:        bio to be unmapped
2224  * @ulen:       length of user buffer
2225  *
2226  * Description:
2227  *    Unmap a bio previously mapped by blk_rq_map_user().
2228  */
2229 int blk_rq_unmap_user(struct bio *bio, unsigned int ulen)
2230 {
2231         int ret = 0;
2232
2233         if (bio) {
2234                 if (bio_flagged(bio, BIO_USER_MAPPED))
2235                         bio_unmap_user(bio);
2236                 else
2237                         ret = bio_uncopy_user(bio);
2238         }
2239
2240         return 0;
2241 }
2242
2243 EXPORT_SYMBOL(blk_rq_unmap_user);
2244
2245 /**
2246  * blk_rq_map_kern - map kernel data to a request, for REQ_BLOCK_PC usage
2247  * @q:          request queue where request should be inserted
2248  * @rq:         request to fill
2249  * @kbuf:       the kernel buffer
2250  * @len:        length of user data
2251  * @gfp_mask:   memory allocation flags
2252  */
2253 int blk_rq_map_kern(request_queue_t *q, struct request *rq, void *kbuf,
2254                     unsigned int len, unsigned int gfp_mask)
2255 {
2256         struct bio *bio;
2257
2258         if (len > (q->max_sectors << 9))
2259                 return -EINVAL;
2260         if (!len || !kbuf)
2261                 return -EINVAL;
2262
2263         bio = bio_map_kern(q, kbuf, len, gfp_mask);
2264         if (IS_ERR(bio))
2265                 return PTR_ERR(bio);
2266
2267         if (rq_data_dir(rq) == WRITE)
2268                 bio->bi_rw |= (1 << BIO_RW);
2269
2270         rq->bio = rq->biotail = bio;
2271         blk_rq_bio_prep(q, rq, bio);
2272
2273         rq->buffer = rq->data = NULL;
2274         rq->data_len = len;
2275         return 0;
2276 }
2277
2278 EXPORT_SYMBOL(blk_rq_map_kern);
2279
2280 /**
2281  * blk_execute_rq_nowait - insert a request into queue for execution
2282  * @q:          queue to insert the request in
2283  * @bd_disk:    matching gendisk
2284  * @rq:         request to insert
2285  * @at_head:    insert request at head or tail of queue
2286  * @done:       I/O completion handler
2287  *
2288  * Description:
2289  *    Insert a fully prepared request at the back of the io scheduler queue
2290  *    for execution.  Don't wait for completion.
2291  */
2292 void blk_execute_rq_nowait(request_queue_t *q, struct gendisk *bd_disk,
2293                            struct request *rq, int at_head,
2294                            void (*done)(struct request *))
2295 {
2296         int where = at_head ? ELEVATOR_INSERT_FRONT : ELEVATOR_INSERT_BACK;
2297
2298         rq->rq_disk = bd_disk;
2299         rq->flags |= REQ_NOMERGE;
2300         rq->end_io = done;
2301         elv_add_request(q, rq, where, 1);
2302         generic_unplug_device(q);
2303 }
2304
2305 /**
2306  * blk_execute_rq - insert a request into queue for execution
2307  * @q:          queue to insert the request in
2308  * @bd_disk:    matching gendisk
2309  * @rq:         request to insert
2310  * @at_head:    insert request at head or tail of queue
2311  *
2312  * Description:
2313  *    Insert a fully prepared request at the back of the io scheduler queue
2314  *    for execution and wait for completion.
2315  */
2316 int blk_execute_rq(request_queue_t *q, struct gendisk *bd_disk,
2317                    struct request *rq, int at_head)
2318 {
2319         DECLARE_COMPLETION(wait);
2320         char sense[SCSI_SENSE_BUFFERSIZE];
2321         int err = 0;
2322
2323         /*
2324          * we need an extra reference to the request, so we can look at
2325          * it after io completion
2326          */
2327         rq->ref_count++;
2328
2329         if (!rq->sense) {
2330                 memset(sense, 0, sizeof(sense));
2331                 rq->sense = sense;
2332                 rq->sense_len = 0;
2333         }
2334
2335         rq->waiting = &wait;
2336         blk_execute_rq_nowait(q, bd_disk, rq, at_head, blk_end_sync_rq);
2337         wait_for_completion(&wait);
2338         rq->waiting = NULL;
2339
2340         if (rq->errors)
2341                 err = -EIO;
2342
2343         return err;
2344 }
2345
2346 EXPORT_SYMBOL(blk_execute_rq);
2347
2348 /**
2349  * blkdev_issue_flush - queue a flush
2350  * @bdev:       blockdev to issue flush for
2351  * @error_sector:       error sector
2352  *
2353  * Description:
2354  *    Issue a flush for the block device in question. Caller can supply
2355  *    room for storing the error offset in case of a flush error, if they
2356  *    wish to.  Caller must run wait_for_completion() on its own.
2357  */
2358 int blkdev_issue_flush(struct block_device *bdev, sector_t *error_sector)
2359 {
2360         request_queue_t *q;
2361
2362         if (bdev->bd_disk == NULL)
2363                 return -ENXIO;
2364
2365         q = bdev_get_queue(bdev);
2366         if (!q)
2367                 return -ENXIO;
2368         if (!q->issue_flush_fn)
2369                 return -EOPNOTSUPP;
2370
2371         return q->issue_flush_fn(q, bdev->bd_disk, error_sector);
2372 }
2373
2374 EXPORT_SYMBOL(blkdev_issue_flush);
2375
2376 static void drive_stat_acct(struct request *rq, int nr_sectors, int new_io)
2377 {
2378         int rw = rq_data_dir(rq);
2379
2380         if (!blk_fs_request(rq) || !rq->rq_disk)
2381                 return;
2382
2383         if (rw == READ) {
2384                 __disk_stat_add(rq->rq_disk, read_sectors, nr_sectors);
2385                 if (!new_io)
2386                         __disk_stat_inc(rq->rq_disk, read_merges);
2387         } else if (rw == WRITE) {
2388                 __disk_stat_add(rq->rq_disk, write_sectors, nr_sectors);
2389                 if (!new_io)
2390                         __disk_stat_inc(rq->rq_disk, write_merges);
2391         }
2392         if (new_io) {
2393                 disk_round_stats(rq->rq_disk);
2394                 rq->rq_disk->in_flight++;
2395         }
2396 }
2397
2398 /*
2399  * add-request adds a request to the linked list.
2400  * queue lock is held and interrupts disabled, as we muck with the
2401  * request queue list.
2402  */
2403 static inline void add_request(request_queue_t * q, struct request * req)
2404 {
2405         drive_stat_acct(req, req->nr_sectors, 1);
2406
2407         if (q->activity_fn)
2408                 q->activity_fn(q->activity_data, rq_data_dir(req));
2409
2410         /*
2411          * elevator indicated where it wants this request to be
2412          * inserted at elevator_merge time
2413          */
2414         __elv_add_request(q, req, ELEVATOR_INSERT_SORT, 0);
2415 }
2416  
2417 /*
2418  * disk_round_stats()   - Round off the performance stats on a struct
2419  * disk_stats.
2420  *
2421  * The average IO queue length and utilisation statistics are maintained
2422  * by observing the current state of the queue length and the amount of
2423  * time it has been in this state for.
2424  *
2425  * Normally, that accounting is done on IO completion, but that can result
2426  * in more than a second's worth of IO being accounted for within any one
2427  * second, leading to >100% utilisation.  To deal with that, we call this
2428  * function to do a round-off before returning the results when reading
2429  * /proc/diskstats.  This accounts immediately for all queue usage up to
2430  * the current jiffies and restarts the counters again.
2431  */
2432 void disk_round_stats(struct gendisk *disk)
2433 {
2434         unsigned long now = jiffies;
2435
2436         if (now == disk->stamp)
2437                 return;
2438
2439         if (disk->in_flight) {
2440                 __disk_stat_add(disk, time_in_queue,
2441                                 disk->in_flight * (now - disk->stamp));
2442                 __disk_stat_add(disk, io_ticks, (now - disk->stamp));
2443         }
2444         disk->stamp = now;
2445 }
2446
2447 /*
2448  * queue lock must be held
2449  */
2450 static void __blk_put_request(request_queue_t *q, struct request *req)
2451 {
2452         struct request_list *rl = req->rl;
2453
2454         if (unlikely(!q))
2455                 return;
2456         if (unlikely(--req->ref_count))
2457                 return;
2458
2459         req->rq_status = RQ_INACTIVE;
2460         req->rl = NULL;
2461
2462         /*
2463          * Request may not have originated from ll_rw_blk. if not,
2464          * it didn't come out of our reserved rq pools
2465          */
2466         if (rl) {
2467                 int rw = rq_data_dir(req);
2468
2469                 elv_completed_request(q, req);
2470
2471                 BUG_ON(!list_empty(&req->queuelist));
2472
2473                 blk_free_request(q, req);
2474                 freed_request(q, rw);
2475         }
2476 }
2477
2478 void blk_put_request(struct request *req)
2479 {
2480         /*
2481          * if req->rl isn't set, this request didnt originate from the
2482          * block layer, so it's safe to just disregard it
2483          */
2484         if (req->rl) {
2485                 unsigned long flags;
2486                 request_queue_t *q = req->q;
2487
2488                 spin_lock_irqsave(q->queue_lock, flags);
2489                 __blk_put_request(q, req);
2490                 spin_unlock_irqrestore(q->queue_lock, flags);
2491         }
2492 }
2493
2494 EXPORT_SYMBOL(blk_put_request);
2495
2496 /**
2497  * blk_end_sync_rq - executes a completion event on a request
2498  * @rq: request to complete
2499  */
2500 void blk_end_sync_rq(struct request *rq)
2501 {
2502         struct completion *waiting = rq->waiting;
2503
2504         rq->waiting = NULL;
2505         __blk_put_request(rq->q, rq);
2506
2507         /*
2508          * complete last, if this is a stack request the process (and thus
2509          * the rq pointer) could be invalid right after this complete()
2510          */
2511         complete(waiting);
2512 }
2513 EXPORT_SYMBOL(blk_end_sync_rq);
2514
2515 /**
2516  * blk_congestion_wait - wait for a queue to become uncongested
2517  * @rw: READ or WRITE
2518  * @timeout: timeout in jiffies
2519  *
2520  * Waits for up to @timeout jiffies for a queue (any queue) to exit congestion.
2521  * If no queues are congested then just wait for the next request to be
2522  * returned.
2523  */
2524 long blk_congestion_wait(int rw, long timeout)
2525 {
2526         long ret;
2527         DEFINE_WAIT(wait);
2528         wait_queue_head_t *wqh = &congestion_wqh[rw];
2529
2530         prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
2531         ret = io_schedule_timeout(timeout);
2532         finish_wait(wqh, &wait);
2533         return ret;
2534 }
2535
2536 EXPORT_SYMBOL(blk_congestion_wait);
2537
2538 /*
2539  * Has to be called with the request spinlock acquired
2540  */
2541 static int attempt_merge(request_queue_t *q, struct request *req,
2542                           struct request *next)
2543 {
2544         if (!rq_mergeable(req) || !rq_mergeable(next))
2545                 return 0;
2546
2547         /*
2548          * not contigious
2549          */
2550         if (req->sector + req->nr_sectors != next->sector)
2551                 return 0;
2552
2553         if (rq_data_dir(req) != rq_data_dir(next)
2554             || req->rq_disk != next->rq_disk
2555             || next->waiting || next->special)
2556                 return 0;
2557
2558         /*
2559          * If we are allowed to merge, then append bio list
2560          * from next to rq and release next. merge_requests_fn
2561          * will have updated segment counts, update sector
2562          * counts here.
2563          */
2564         if (!q->merge_requests_fn(q, req, next))
2565                 return 0;
2566
2567         /*
2568          * At this point we have either done a back merge
2569          * or front merge. We need the smaller start_time of
2570          * the merged requests to be the current request
2571          * for accounting purposes.
2572          */
2573         if (time_after(req->start_time, next->start_time))
2574                 req->start_time = next->start_time;
2575
2576         req->biotail->bi_next = next->bio;
2577         req->biotail = next->biotail;
2578
2579         req->nr_sectors = req->hard_nr_sectors += next->hard_nr_sectors;
2580
2581         elv_merge_requests(q, req, next);
2582
2583         if (req->rq_disk) {
2584                 disk_round_stats(req->rq_disk);
2585                 req->rq_disk->in_flight--;
2586         }
2587
2588         req->ioprio = ioprio_best(req->ioprio, next->ioprio);
2589
2590         __blk_put_request(q, next);
2591         return 1;
2592 }
2593
2594 static inline int attempt_back_merge(request_queue_t *q, struct request *rq)
2595 {
2596         struct request *next = elv_latter_request(q, rq);
2597
2598         if (next)
2599                 return attempt_merge(q, rq, next);
2600
2601         return 0;
2602 }
2603
2604 static inline int attempt_front_merge(request_queue_t *q, struct request *rq)
2605 {
2606         struct request *prev = elv_former_request(q, rq);
2607
2608         if (prev)
2609                 return attempt_merge(q, prev, rq);
2610
2611         return 0;
2612 }
2613
2614 /**
2615  * blk_attempt_remerge  - attempt to remerge active head with next request
2616  * @q:    The &request_queue_t belonging to the device
2617  * @rq:   The head request (usually)
2618  *
2619  * Description:
2620  *    For head-active devices, the queue can easily be unplugged so quickly
2621  *    that proper merging is not done on the front request. This may hurt
2622  *    performance greatly for some devices. The block layer cannot safely
2623  *    do merging on that first request for these queues, but the driver can
2624  *    call this function and make it happen any way. Only the driver knows
2625  *    when it is safe to do so.
2626  **/
2627 void blk_attempt_remerge(request_queue_t *q, struct request *rq)
2628 {
2629         unsigned long flags;
2630
2631         spin_lock_irqsave(q->queue_lock, flags);
2632         attempt_back_merge(q, rq);
2633         spin_unlock_irqrestore(q->queue_lock, flags);
2634 }
2635
2636 EXPORT_SYMBOL(blk_attempt_remerge);
2637
2638 static int __make_request(request_queue_t *q, struct bio *bio)
2639 {
2640         struct request *req;
2641         int el_ret, rw, nr_sectors, cur_nr_sectors, barrier, err, sync;
2642         unsigned short prio;
2643         sector_t sector;
2644
2645         sector = bio->bi_sector;
2646         nr_sectors = bio_sectors(bio);
2647         cur_nr_sectors = bio_cur_sectors(bio);
2648         prio = bio_prio(bio);
2649
2650         rw = bio_data_dir(bio);
2651         sync = bio_sync(bio);
2652
2653         /*
2654          * low level driver can indicate that it wants pages above a
2655          * certain limit bounced to low memory (ie for highmem, or even
2656          * ISA dma in theory)
2657          */
2658         blk_queue_bounce(q, &bio);
2659
2660         spin_lock_prefetch(q->queue_lock);
2661
2662         barrier = bio_barrier(bio);
2663         if (unlikely(barrier) && (q->ordered == QUEUE_ORDERED_NONE)) {
2664                 err = -EOPNOTSUPP;
2665                 goto end_io;
2666         }
2667
2668         spin_lock_irq(q->queue_lock);
2669
2670         if (unlikely(barrier) || elv_queue_empty(q))
2671                 goto get_rq;
2672
2673         el_ret = elv_merge(q, &req, bio);
2674         switch (el_ret) {
2675                 case ELEVATOR_BACK_MERGE:
2676                         BUG_ON(!rq_mergeable(req));
2677
2678                         if (!q->back_merge_fn(q, req, bio))
2679                                 break;
2680
2681                         req->biotail->bi_next = bio;
2682                         req->biotail = bio;
2683                         req->nr_sectors = req->hard_nr_sectors += nr_sectors;
2684                         req->ioprio = ioprio_best(req->ioprio, prio);
2685                         drive_stat_acct(req, nr_sectors, 0);
2686                         if (!attempt_back_merge(q, req))
2687                                 elv_merged_request(q, req);
2688                         goto out;
2689
2690                 case ELEVATOR_FRONT_MERGE:
2691                         BUG_ON(!rq_mergeable(req));
2692
2693                         if (!q->front_merge_fn(q, req, bio))
2694                                 break;
2695
2696                         bio->bi_next = req->bio;
2697                         req->bio = bio;
2698
2699                         /*
2700                          * may not be valid. if the low level driver said
2701                          * it didn't need a bounce buffer then it better
2702                          * not touch req->buffer either...
2703                          */
2704                         req->buffer = bio_data(bio);
2705                         req->current_nr_sectors = cur_nr_sectors;
2706                         req->hard_cur_sectors = cur_nr_sectors;
2707                         req->sector = req->hard_sector = sector;
2708                         req->nr_sectors = req->hard_nr_sectors += nr_sectors;
2709                         req->ioprio = ioprio_best(req->ioprio, prio);
2710                         drive_stat_acct(req, nr_sectors, 0);
2711                         if (!attempt_front_merge(q, req))
2712                                 elv_merged_request(q, req);
2713                         goto out;
2714
2715                 /* ELV_NO_MERGE: elevator says don't/can't merge. */
2716                 default:
2717                         ;
2718         }
2719
2720 get_rq:
2721         /*
2722          * Grab a free request. This is might sleep but can not fail.
2723          * Returns with the queue unlocked.
2724          */
2725         req = get_request_wait(q, rw, bio);
2726
2727         /*
2728          * After dropping the lock and possibly sleeping here, our request
2729          * may now be mergeable after it had proven unmergeable (above).
2730          * We don't worry about that case for efficiency. It won't happen
2731          * often, and the elevators are able to handle it.
2732          */
2733
2734         req->flags |= REQ_CMD;
2735
2736         /*
2737          * inherit FAILFAST from bio (for read-ahead, and explicit FAILFAST)
2738          */
2739         if (bio_rw_ahead(bio) || bio_failfast(bio))
2740                 req->flags |= REQ_FAILFAST;
2741
2742         /*
2743          * REQ_BARRIER implies no merging, but lets make it explicit
2744          */
2745         if (unlikely(barrier))
2746                 req->flags |= (REQ_HARDBARRIER | REQ_NOMERGE);
2747
2748         req->errors = 0;
2749         req->hard_sector = req->sector = sector;
2750         req->hard_nr_sectors = req->nr_sectors = nr_sectors;
2751         req->current_nr_sectors = req->hard_cur_sectors = cur_nr_sectors;
2752         req->nr_phys_segments = bio_phys_segments(q, bio);
2753         req->nr_hw_segments = bio_hw_segments(q, bio);
2754         req->buffer = bio_data(bio);    /* see ->buffer comment above */
2755         req->waiting = NULL;
2756         req->bio = req->biotail = bio;
2757         req->ioprio = prio;
2758         req->rq_disk = bio->bi_bdev->bd_disk;
2759         req->start_time = jiffies;
2760
2761         spin_lock_irq(q->queue_lock);
2762         if (elv_queue_empty(q))
2763                 blk_plug_device(q);
2764         add_request(q, req);
2765 out:
2766         if (sync)
2767                 __generic_unplug_device(q);
2768
2769         spin_unlock_irq(q->queue_lock);
2770         return 0;
2771
2772 end_io:
2773         bio_endio(bio, nr_sectors << 9, err);
2774         return 0;
2775 }
2776
2777 /*
2778  * If bio->bi_dev is a partition, remap the location
2779  */
2780 static inline void blk_partition_remap(struct bio *bio)
2781 {
2782         struct block_device *bdev = bio->bi_bdev;
2783
2784         if (bdev != bdev->bd_contains) {
2785                 struct hd_struct *p = bdev->bd_part;
2786
2787                 switch (bio_data_dir(bio)) {
2788                 case READ:
2789                         p->read_sectors += bio_sectors(bio);
2790                         p->reads++;
2791                         break;
2792                 case WRITE:
2793                         p->write_sectors += bio_sectors(bio);
2794                         p->writes++;
2795                         break;
2796                 }
2797                 bio->bi_sector += p->start_sect;
2798                 bio->bi_bdev = bdev->bd_contains;
2799         }
2800 }
2801
2802 void blk_finish_queue_drain(request_queue_t *q)
2803 {
2804         struct request_list *rl = &q->rq;
2805         struct request *rq;
2806         int requeued = 0;
2807
2808         spin_lock_irq(q->queue_lock);
2809         clear_bit(QUEUE_FLAG_DRAIN, &q->queue_flags);
2810
2811         while (!list_empty(&q->drain_list)) {
2812                 rq = list_entry_rq(q->drain_list.next);
2813
2814                 list_del_init(&rq->queuelist);
2815                 elv_requeue_request(q, rq);
2816                 requeued++;
2817         }
2818
2819         if (requeued)
2820                 q->request_fn(q);
2821
2822         spin_unlock_irq(q->queue_lock);
2823
2824         wake_up(&rl->wait[0]);
2825         wake_up(&rl->wait[1]);
2826         wake_up(&rl->drain);
2827 }
2828
2829 static int wait_drain(request_queue_t *q, struct request_list *rl, int dispatch)
2830 {
2831         int wait = rl->count[READ] + rl->count[WRITE];
2832
2833         if (dispatch)
2834                 wait += !list_empty(&q->queue_head);
2835
2836         return wait;
2837 }
2838
2839 /*
2840  * We rely on the fact that only requests allocated through blk_alloc_request()
2841  * have io scheduler private data structures associated with them. Any other
2842  * type of request (allocated on stack or through kmalloc()) should not go
2843  * to the io scheduler core, but be attached to the queue head instead.
2844  */
2845 void blk_wait_queue_drained(request_queue_t *q, int wait_dispatch)
2846 {
2847         struct request_list *rl = &q->rq;
2848         DEFINE_WAIT(wait);
2849
2850         spin_lock_irq(q->queue_lock);
2851         set_bit(QUEUE_FLAG_DRAIN, &q->queue_flags);
2852
2853         while (wait_drain(q, rl, wait_dispatch)) {
2854                 prepare_to_wait(&rl->drain, &wait, TASK_UNINTERRUPTIBLE);
2855
2856                 if (wait_drain(q, rl, wait_dispatch)) {
2857                         __generic_unplug_device(q);
2858                         spin_unlock_irq(q->queue_lock);
2859                         io_schedule();
2860                         spin_lock_irq(q->queue_lock);
2861                 }
2862
2863                 finish_wait(&rl->drain, &wait);
2864         }
2865
2866         spin_unlock_irq(q->queue_lock);
2867 }
2868
2869 /*
2870  * block waiting for the io scheduler being started again.
2871  */
2872 static inline void block_wait_queue_running(request_queue_t *q)
2873 {
2874         DEFINE_WAIT(wait);
2875
2876         while (unlikely(test_bit(QUEUE_FLAG_DRAIN, &q->queue_flags))) {
2877                 struct request_list *rl = &q->rq;
2878
2879                 prepare_to_wait_exclusive(&rl->drain, &wait,
2880                                 TASK_UNINTERRUPTIBLE);
2881
2882                 /*
2883                  * re-check the condition. avoids using prepare_to_wait()
2884                  * in the fast path (queue is running)
2885                  */
2886                 if (test_bit(QUEUE_FLAG_DRAIN, &q->queue_flags))
2887                         io_schedule();
2888
2889                 finish_wait(&rl->drain, &wait);
2890         }
2891 }
2892
2893 static void handle_bad_sector(struct bio *bio)
2894 {
2895         char b[BDEVNAME_SIZE];
2896
2897         printk(KERN_INFO "attempt to access beyond end of device\n");
2898         printk(KERN_INFO "%s: rw=%ld, want=%Lu, limit=%Lu\n",
2899                         bdevname(bio->bi_bdev, b),
2900                         bio->bi_rw,
2901                         (unsigned long long)bio->bi_sector + bio_sectors(bio),
2902                         (long long)(bio->bi_bdev->bd_inode->i_size >> 9));
2903
2904         set_bit(BIO_EOF, &bio->bi_flags);
2905 }
2906
2907 /**
2908  * generic_make_request: hand a buffer to its device driver for I/O
2909  * @bio:  The bio describing the location in memory and on the device.
2910  *
2911  * generic_make_request() is used to make I/O requests of block
2912  * devices. It is passed a &struct bio, which describes the I/O that needs
2913  * to be done.
2914  *
2915  * generic_make_request() does not return any status.  The
2916  * success/failure status of the request, along with notification of
2917  * completion, is delivered asynchronously through the bio->bi_end_io
2918  * function described (one day) else where.
2919  *
2920  * The caller of generic_make_request must make sure that bi_io_vec
2921  * are set to describe the memory buffer, and that bi_dev and bi_sector are
2922  * set to describe the device address, and the
2923  * bi_end_io and optionally bi_private are set to describe how
2924  * completion notification should be signaled.
2925  *
2926  * generic_make_request and the drivers it calls may use bi_next if this
2927  * bio happens to be merged with someone else, and may change bi_dev and
2928  * bi_sector for remaps as it sees fit.  So the values of these fields
2929  * should NOT be depended on after the call to generic_make_request.
2930  */
2931 void generic_make_request(struct bio *bio)
2932 {
2933         request_queue_t *q;
2934         sector_t maxsector;
2935         int ret, nr_sectors = bio_sectors(bio);
2936
2937         might_sleep();
2938         /* Test device or partition size, when known. */
2939         maxsector = bio->bi_bdev->bd_inode->i_size >> 9;
2940         if (maxsector) {
2941                 sector_t sector = bio->bi_sector;
2942
2943                 if (maxsector < nr_sectors || maxsector - nr_sectors < sector) {
2944                         /*
2945                          * This may well happen - the kernel calls bread()
2946                          * without checking the size of the device, e.g., when
2947                          * mounting a device.
2948                          */
2949                         handle_bad_sector(bio);
2950                         goto end_io;
2951                 }
2952         }
2953
2954         /*
2955          * Resolve the mapping until finished. (drivers are
2956          * still free to implement/resolve their own stacking
2957          * by explicitly returning 0)
2958          *
2959          * NOTE: we don't repeat the blk_size check for each new device.
2960          * Stacking drivers are expected to know what they are doing.
2961          */
2962         do {
2963                 char b[BDEVNAME_SIZE];
2964
2965                 q = bdev_get_queue(bio->bi_bdev);
2966                 if (!q) {
2967                         printk(KERN_ERR
2968                                "generic_make_request: Trying to access "
2969                                 "nonexistent block-device %s (%Lu)\n",
2970                                 bdevname(bio->bi_bdev, b),
2971                                 (long long) bio->bi_sector);
2972 end_io:
2973                         bio_endio(bio, bio->bi_size, -EIO);
2974                         break;
2975                 }
2976
2977                 if (unlikely(bio_sectors(bio) > q->max_hw_sectors)) {
2978                         printk("bio too big device %s (%u > %u)\n", 
2979                                 bdevname(bio->bi_bdev, b),
2980                                 bio_sectors(bio),
2981                                 q->max_hw_sectors);
2982                         goto end_io;
2983                 }
2984
2985                 if (unlikely(test_bit(QUEUE_FLAG_DEAD, &q->queue_flags)))
2986                         goto end_io;
2987
2988                 block_wait_queue_running(q);
2989
2990                 /*
2991                  * If this device has partitions, remap block n
2992                  * of partition p to block n+start(p) of the disk.
2993                  */
2994                 blk_partition_remap(bio);
2995
2996                 ret = q->make_request_fn(q, bio);
2997         } while (ret);
2998 }
2999
3000 EXPORT_SYMBOL(generic_make_request);
3001
3002 /**
3003  * submit_bio: submit a bio to the block device layer for I/O
3004  * @rw: whether to %READ or %WRITE, or maybe to %READA (read ahead)
3005  * @bio: The &struct bio which describes the I/O
3006  *
3007  * submit_bio() is very similar in purpose to generic_make_request(), and
3008  * uses that function to do most of the work. Both are fairly rough
3009  * interfaces, @bio must be presetup and ready for I/O.
3010  *
3011  */
3012 void submit_bio(int rw, struct bio *bio)
3013 {
3014         int count = bio_sectors(bio);
3015
3016         BIO_BUG_ON(!bio->bi_size);
3017         BIO_BUG_ON(!bio->bi_io_vec);
3018         bio->bi_rw |= rw;
3019         if (rw & WRITE)
3020                 mod_page_state(pgpgout, count);
3021         else
3022                 mod_page_state(pgpgin, count);
3023
3024         if (unlikely(block_dump)) {
3025                 char b[BDEVNAME_SIZE];
3026                 printk(KERN_DEBUG "%s(%d): %s block %Lu on %s\n",
3027                         current->comm, current->pid,
3028                         (rw & WRITE) ? "WRITE" : "READ",
3029                         (unsigned long long)bio->bi_sector,
3030                         bdevname(bio->bi_bdev,b));
3031         }
3032
3033         generic_make_request(bio);
3034 }
3035
3036 EXPORT_SYMBOL(submit_bio);
3037
3038 static void blk_recalc_rq_segments(struct request *rq)
3039 {
3040         struct bio *bio, *prevbio = NULL;
3041         int nr_phys_segs, nr_hw_segs;
3042         unsigned int phys_size, hw_size;
3043         request_queue_t *q = rq->q;
3044
3045         if (!rq->bio)
3046                 return;
3047
3048         phys_size = hw_size = nr_phys_segs = nr_hw_segs = 0;
3049         rq_for_each_bio(bio, rq) {
3050                 /* Force bio hw/phys segs to be recalculated. */
3051                 bio->bi_flags &= ~(1 << BIO_SEG_VALID);
3052
3053                 nr_phys_segs += bio_phys_segments(q, bio);
3054                 nr_hw_segs += bio_hw_segments(q, bio);
3055                 if (prevbio) {
3056                         int pseg = phys_size + prevbio->bi_size + bio->bi_size;
3057                         int hseg = hw_size + prevbio->bi_size + bio->bi_size;
3058
3059                         if (blk_phys_contig_segment(q, prevbio, bio) &&
3060                             pseg <= q->max_segment_size) {
3061                                 nr_phys_segs--;
3062                                 phys_size += prevbio->bi_size + bio->bi_size;
3063                         } else
3064                                 phys_size = 0;
3065
3066                         if (blk_hw_contig_segment(q, prevbio, bio) &&
3067                             hseg <= q->max_segment_size) {
3068                                 nr_hw_segs--;
3069                                 hw_size += prevbio->bi_size + bio->bi_size;
3070                         } else
3071                                 hw_size = 0;
3072                 }
3073                 prevbio = bio;
3074         }
3075
3076         rq->nr_phys_segments = nr_phys_segs;
3077         rq->nr_hw_segments = nr_hw_segs;
3078 }
3079
3080 static void blk_recalc_rq_sectors(struct request *rq, int nsect)
3081 {
3082         if (blk_fs_request(rq)) {
3083                 rq->hard_sector += nsect;
3084                 rq->hard_nr_sectors -= nsect;
3085
3086                 /*
3087                  * Move the I/O submission pointers ahead if required.
3088                  */
3089                 if ((rq->nr_sectors >= rq->hard_nr_sectors) &&
3090                     (rq->sector <= rq->hard_sector)) {
3091                         rq->sector = rq->hard_sector;
3092                         rq->nr_sectors = rq->hard_nr_sectors;
3093                         rq->hard_cur_sectors = bio_cur_sectors(rq->bio);
3094                         rq->current_nr_sectors = rq->hard_cur_sectors;
3095                         rq->buffer = bio_data(rq->bio);
3096                 }
3097
3098                 /*
3099                  * if total number of sectors is less than the first segment
3100                  * size, something has gone terribly wrong
3101                  */
3102                 if (rq->nr_sectors < rq->current_nr_sectors) {
3103                         printk("blk: request botched\n");
3104                         rq->nr_sectors = rq->current_nr_sectors;
3105                 }
3106         }
3107 }
3108
3109 static int __end_that_request_first(struct request *req, int uptodate,
3110                                     int nr_bytes)
3111 {
3112         int total_bytes, bio_nbytes, error, next_idx = 0;
3113         struct bio *bio;
3114
3115         /*
3116          * extend uptodate bool to allow < 0 value to be direct io error
3117          */
3118         error = 0;
3119         if (end_io_error(uptodate))
3120                 error = !uptodate ? -EIO : uptodate;
3121
3122         /*
3123          * for a REQ_BLOCK_PC request, we want to carry any eventual
3124          * sense key with us all the way through
3125          */
3126         if (!blk_pc_request(req))
3127                 req->errors = 0;
3128
3129         if (!uptodate) {
3130                 if (blk_fs_request(req) && !(req->flags & REQ_QUIET))
3131                         printk("end_request: I/O error, dev %s, sector %llu\n",
3132                                 req->rq_disk ? req->rq_disk->disk_name : "?",
3133                                 (unsigned long long)req->sector);
3134         }
3135
3136         total_bytes = bio_nbytes = 0;
3137         while ((bio = req->bio) != NULL) {
3138                 int nbytes;
3139
3140                 if (nr_bytes >= bio->bi_size) {
3141                         req->bio = bio->bi_next;
3142                         nbytes = bio->bi_size;
3143                         bio_endio(bio, nbytes, error);
3144                         next_idx = 0;
3145                         bio_nbytes = 0;
3146                 } else {
3147                         int idx = bio->bi_idx + next_idx;
3148
3149                         if (unlikely(bio->bi_idx >= bio->bi_vcnt)) {
3150                                 blk_dump_rq_flags(req, "__end_that");
3151                                 printk("%s: bio idx %d >= vcnt %d\n",
3152                                                 __FUNCTION__,
3153                                                 bio->bi_idx, bio->bi_vcnt);
3154                                 break;
3155                         }
3156
3157                         nbytes = bio_iovec_idx(bio, idx)->bv_len;
3158                         BIO_BUG_ON(nbytes > bio->bi_size);
3159
3160                         /*
3161                          * not a complete bvec done
3162                          */
3163                         if (unlikely(nbytes > nr_bytes)) {
3164                                 bio_nbytes += nr_bytes;
3165                                 total_bytes += nr_bytes;
3166                                 break;
3167                         }
3168
3169                         /*
3170                          * advance to the next vector
3171                          */
3172                         next_idx++;
3173                         bio_nbytes += nbytes;
3174                 }
3175
3176                 total_bytes += nbytes;
3177                 nr_bytes -= nbytes;
3178
3179                 if ((bio = req->bio)) {
3180                         /*
3181                          * end more in this run, or just return 'not-done'
3182                          */
3183                         if (unlikely(nr_bytes <= 0))
3184                                 break;
3185                 }
3186         }
3187
3188         /*
3189          * completely done
3190          */
3191         if (!req->bio)
3192                 return 0;
3193
3194         /*
3195          * if the request wasn't completed, update state
3196          */
3197         if (bio_nbytes) {
3198                 bio_endio(bio, bio_nbytes, error);
3199                 bio->bi_idx += next_idx;
3200                 bio_iovec(bio)->bv_offset += nr_bytes;
3201                 bio_iovec(bio)->bv_len -= nr_bytes;
3202         }
3203
3204         blk_recalc_rq_sectors(req, total_bytes >> 9);
3205         blk_recalc_rq_segments(req);
3206         return 1;
3207 }
3208
3209 /**
3210  * end_that_request_first - end I/O on a request
3211  * @req:      the request being processed
3212  * @uptodate: 1 for success, 0 for I/O error, < 0 for specific error
3213  * @nr_sectors: number of sectors to end I/O on
3214  *
3215  * Description:
3216  *     Ends I/O on a number of sectors attached to @req, and sets it up
3217  *     for the next range of segments (if any) in the cluster.
3218  *
3219  * Return:
3220  *     0 - we are done with this request, call end_that_request_last()
3221  *     1 - still buffers pending for this request
3222  **/
3223 int end_that_request_first(struct request *req, int uptodate, int nr_sectors)
3224 {
3225         return __end_that_request_first(req, uptodate, nr_sectors << 9);
3226 }
3227
3228 EXPORT_SYMBOL(end_that_request_first);
3229
3230 /**
3231  * end_that_request_chunk - end I/O on a request
3232  * @req:      the request being processed
3233  * @uptodate: 1 for success, 0 for I/O error, < 0 for specific error
3234  * @nr_bytes: number of bytes to complete
3235  *
3236  * Description:
3237  *     Ends I/O on a number of bytes attached to @req, and sets it up
3238  *     for the next range of segments (if any). Like end_that_request_first(),
3239  *     but deals with bytes instead of sectors.
3240  *
3241  * Return:
3242  *     0 - we are done with this request, call end_that_request_last()
3243  *     1 - still buffers pending for this request
3244  **/
3245 int end_that_request_chunk(struct request *req, int uptodate, int nr_bytes)
3246 {
3247         return __end_that_request_first(req, uptodate, nr_bytes);
3248 }
3249
3250 EXPORT_SYMBOL(end_that_request_chunk);
3251
3252 /*
3253  * queue lock must be held
3254  */
3255 void end_that_request_last(struct request *req)
3256 {
3257         struct gendisk *disk = req->rq_disk;
3258
3259         if (unlikely(laptop_mode) && blk_fs_request(req))
3260                 laptop_io_completion();
3261
3262         if (disk && blk_fs_request(req)) {
3263                 unsigned long duration = jiffies - req->start_time;
3264                 switch (rq_data_dir(req)) {
3265                     case WRITE:
3266                         __disk_stat_inc(disk, writes);
3267                         __disk_stat_add(disk, write_ticks, duration);
3268                         break;
3269                     case READ:
3270                         __disk_stat_inc(disk, reads);
3271                         __disk_stat_add(disk, read_ticks, duration);
3272                         break;
3273                 }
3274                 disk_round_stats(disk);
3275                 disk->in_flight--;
3276         }
3277         if (req->end_io)
3278                 req->end_io(req);
3279         else
3280                 __blk_put_request(req->q, req);
3281 }
3282
3283 EXPORT_SYMBOL(end_that_request_last);
3284
3285 void end_request(struct request *req, int uptodate)
3286 {
3287         if (!end_that_request_first(req, uptodate, req->hard_cur_sectors)) {
3288                 add_disk_randomness(req->rq_disk);
3289                 blkdev_dequeue_request(req);
3290                 end_that_request_last(req);
3291         }
3292 }
3293
3294 EXPORT_SYMBOL(end_request);
3295
3296 void blk_rq_bio_prep(request_queue_t *q, struct request *rq, struct bio *bio)
3297 {
3298         /* first three bits are identical in rq->flags and bio->bi_rw */
3299         rq->flags |= (bio->bi_rw & 7);
3300
3301         rq->nr_phys_segments = bio_phys_segments(q, bio);
3302         rq->nr_hw_segments = bio_hw_segments(q, bio);
3303         rq->current_nr_sectors = bio_cur_sectors(bio);
3304         rq->hard_cur_sectors = rq->current_nr_sectors;
3305         rq->hard_nr_sectors = rq->nr_sectors = bio_sectors(bio);
3306         rq->buffer = bio_data(bio);
3307
3308         rq->bio = rq->biotail = bio;
3309 }
3310
3311 EXPORT_SYMBOL(blk_rq_bio_prep);
3312
3313 int kblockd_schedule_work(struct work_struct *work)
3314 {
3315         return queue_work(kblockd_workqueue, work);
3316 }
3317
3318 EXPORT_SYMBOL(kblockd_schedule_work);
3319
3320 void kblockd_flush(void)
3321 {
3322         flush_workqueue(kblockd_workqueue);
3323 }
3324 EXPORT_SYMBOL(kblockd_flush);
3325
3326 int __init blk_dev_init(void)
3327 {
3328         kblockd_workqueue = create_workqueue("kblockd");
3329         if (!kblockd_workqueue)
3330                 panic("Failed to create kblockd\n");
3331
3332         request_cachep = kmem_cache_create("blkdev_requests",
3333                         sizeof(struct request), 0, SLAB_PANIC, NULL, NULL);
3334
3335         requestq_cachep = kmem_cache_create("blkdev_queue",
3336                         sizeof(request_queue_t), 0, SLAB_PANIC, NULL, NULL);
3337
3338         iocontext_cachep = kmem_cache_create("blkdev_ioc",
3339                         sizeof(struct io_context), 0, SLAB_PANIC, NULL, NULL);
3340
3341         blk_max_low_pfn = max_low_pfn;
3342         blk_max_pfn = max_pfn;
3343
3344         return 0;
3345 }
3346
3347 /*
3348  * IO Context helper functions
3349  */
3350 void put_io_context(struct io_context *ioc)
3351 {
3352         if (ioc == NULL)
3353                 return;
3354
3355         BUG_ON(atomic_read(&ioc->refcount) == 0);
3356
3357         if (atomic_dec_and_test(&ioc->refcount)) {
3358                 if (ioc->aic && ioc->aic->dtor)
3359                         ioc->aic->dtor(ioc->aic);
3360                 if (ioc->cic && ioc->cic->dtor)
3361                         ioc->cic->dtor(ioc->cic);
3362
3363                 kmem_cache_free(iocontext_cachep, ioc);
3364         }
3365 }
3366 EXPORT_SYMBOL(put_io_context);
3367
3368 /* Called by the exitting task */
3369 void exit_io_context(void)
3370 {
3371         unsigned long flags;
3372         struct io_context *ioc;
3373
3374         local_irq_save(flags);
3375         task_lock(current);
3376         ioc = current->io_context;
3377         current->io_context = NULL;
3378         ioc->task = NULL;
3379         task_unlock(current);
3380         local_irq_restore(flags);
3381
3382         if (ioc->aic && ioc->aic->exit)
3383                 ioc->aic->exit(ioc->aic);
3384         if (ioc->cic && ioc->cic->exit)
3385                 ioc->cic->exit(ioc->cic);
3386
3387         put_io_context(ioc);
3388 }
3389
3390 /*
3391  * If the current task has no IO context then create one and initialise it.
3392  * Otherwise, return its existing IO context.
3393  *
3394  * This returned IO context doesn't have a specifically elevated refcount,
3395  * but since the current task itself holds a reference, the context can be
3396  * used in general code, so long as it stays within `current` context.
3397  */
3398 struct io_context *current_io_context(int gfp_flags)
3399 {
3400         struct task_struct *tsk = current;
3401         struct io_context *ret;
3402
3403         ret = tsk->io_context;
3404         if (likely(ret))
3405                 return ret;
3406
3407         ret = kmem_cache_alloc(iocontext_cachep, gfp_flags);
3408         if (ret) {
3409                 atomic_set(&ret->refcount, 1);
3410                 ret->task = current;
3411                 ret->set_ioprio = NULL;
3412                 ret->last_waited = jiffies; /* doesn't matter... */
3413                 ret->nr_batch_requests = 0; /* because this is 0 */
3414                 ret->aic = NULL;
3415                 ret->cic = NULL;
3416                 tsk->io_context = ret;
3417         }
3418
3419         return ret;
3420 }
3421 EXPORT_SYMBOL(current_io_context);
3422
3423 /*
3424  * If the current task has no IO context then create one and initialise it.
3425  * If it does have a context, take a ref on it.
3426  *
3427  * This is always called in the context of the task which submitted the I/O.
3428  */
3429 struct io_context *get_io_context(int gfp_flags)
3430 {
3431         struct io_context *ret;
3432         ret = current_io_context(gfp_flags);
3433         if (likely(ret))
3434                 atomic_inc(&ret->refcount);
3435         return ret;
3436 }
3437 EXPORT_SYMBOL(get_io_context);
3438
3439 void copy_io_context(struct io_context **pdst, struct io_context **psrc)
3440 {
3441         struct io_context *src = *psrc;
3442         struct io_context *dst = *pdst;
3443
3444         if (src) {
3445                 BUG_ON(atomic_read(&src->refcount) == 0);
3446                 atomic_inc(&src->refcount);
3447                 put_io_context(dst);
3448                 *pdst = src;
3449         }
3450 }
3451 EXPORT_SYMBOL(copy_io_context);
3452
3453 void swap_io_context(struct io_context **ioc1, struct io_context **ioc2)
3454 {
3455         struct io_context *temp;
3456         temp = *ioc1;
3457         *ioc1 = *ioc2;
3458         *ioc2 = temp;
3459 }
3460 EXPORT_SYMBOL(swap_io_context);
3461
3462 /*
3463  * sysfs parts below
3464  */
3465 struct queue_sysfs_entry {
3466         struct attribute attr;
3467         ssize_t (*show)(struct request_queue *, char *);
3468         ssize_t (*store)(struct request_queue *, const char *, size_t);
3469 };
3470
3471 static ssize_t
3472 queue_var_show(unsigned int var, char *page)
3473 {
3474         return sprintf(page, "%d\n", var);
3475 }
3476
3477 static ssize_t
3478 queue_var_store(unsigned long *var, const char *page, size_t count)
3479 {
3480         char *p = (char *) page;
3481
3482         *var = simple_strtoul(p, &p, 10);
3483         return count;
3484 }
3485
3486 static ssize_t queue_requests_show(struct request_queue *q, char *page)
3487 {
3488         return queue_var_show(q->nr_requests, (page));
3489 }
3490
3491 static ssize_t
3492 queue_requests_store(struct request_queue *q, const char *page, size_t count)
3493 {
3494         struct request_list *rl = &q->rq;
3495
3496         int ret = queue_var_store(&q->nr_requests, page, count);
3497         if (q->nr_requests < BLKDEV_MIN_RQ)
3498                 q->nr_requests = BLKDEV_MIN_RQ;
3499         blk_queue_congestion_threshold(q);
3500
3501         if (rl->count[READ] >= queue_congestion_on_threshold(q))
3502                 set_queue_congested(q, READ);
3503         else if (rl->count[READ] < queue_congestion_off_threshold(q))
3504                 clear_queue_congested(q, READ);
3505
3506         if (rl->count[WRITE] >= queue_congestion_on_threshold(q))
3507                 set_queue_congested(q, WRITE);
3508         else if (rl->count[WRITE] < queue_congestion_off_threshold(q))
3509                 clear_queue_congested(q, WRITE);
3510
3511         if (rl->count[READ] >= q->nr_requests) {
3512                 blk_set_queue_full(q, READ);
3513         } else if (rl->count[READ]+1 <= q->nr_requests) {
3514                 blk_clear_queue_full(q, READ);
3515                 wake_up(&rl->wait[READ]);
3516         }
3517
3518         if (rl->count[WRITE] >= q->nr_requests) {
3519                 blk_set_queue_full(q, WRITE);
3520         } else if (rl->count[WRITE]+1 <= q->nr_requests) {
3521                 blk_clear_queue_full(q, WRITE);
3522                 wake_up(&rl->wait[WRITE]);
3523         }
3524         return ret;
3525 }
3526
3527 static ssize_t queue_ra_show(struct request_queue *q, char *page)
3528 {
3529         int ra_kb = q->backing_dev_info.ra_pages << (PAGE_CACHE_SHIFT - 10);
3530
3531         return queue_var_show(ra_kb, (page));
3532 }
3533
3534 static ssize_t
3535 queue_ra_store(struct request_queue *q, const char *page, size_t count)
3536 {
3537         unsigned long ra_kb;
3538         ssize_t ret = queue_var_store(&ra_kb, page, count);
3539
3540         spin_lock_irq(q->queue_lock);
3541         if (ra_kb > (q->max_sectors >> 1))
3542                 ra_kb = (q->max_sectors >> 1);
3543
3544         q->backing_dev_info.ra_pages = ra_kb >> (PAGE_CACHE_SHIFT - 10);
3545         spin_unlock_irq(q->queue_lock);
3546
3547         return ret;
3548 }
3549
3550 static ssize_t queue_max_sectors_show(struct request_queue *q, char *page)
3551 {
3552         int max_sectors_kb = q->max_sectors >> 1;
3553
3554         return queue_var_show(max_sectors_kb, (page));
3555 }
3556
3557 static ssize_t
3558 queue_max_sectors_store(struct request_queue *q, const char *page, size_t count)
3559 {
3560         unsigned long max_sectors_kb,
3561                         max_hw_sectors_kb = q->max_hw_sectors >> 1,
3562                         page_kb = 1 << (PAGE_CACHE_SHIFT - 10);
3563         ssize_t ret = queue_var_store(&max_sectors_kb, page, count);
3564         int ra_kb;
3565
3566         if (max_sectors_kb > max_hw_sectors_kb || max_sectors_kb < page_kb)
3567                 return -EINVAL;
3568         /*
3569          * Take the queue lock to update the readahead and max_sectors
3570          * values synchronously:
3571          */
3572         spin_lock_irq(q->queue_lock);
3573         /*
3574          * Trim readahead window as well, if necessary:
3575          */
3576         ra_kb = q->backing_dev_info.ra_pages << (PAGE_CACHE_SHIFT - 10);
3577         if (ra_kb > max_sectors_kb)
3578                 q->backing_dev_info.ra_pages =
3579                                 max_sectors_kb >> (PAGE_CACHE_SHIFT - 10);
3580
3581         q->max_sectors = max_sectors_kb << 1;
3582         spin_unlock_irq(q->queue_lock);
3583
3584         return ret;
3585 }
3586
3587 static ssize_t queue_max_hw_sectors_show(struct request_queue *q, char *page)
3588 {
3589         int max_hw_sectors_kb = q->max_hw_sectors >> 1;
3590
3591         return queue_var_show(max_hw_sectors_kb, (page));
3592 }
3593
3594
3595 static struct queue_sysfs_entry queue_requests_entry = {
3596         .attr = {.name = "nr_requests", .mode = S_IRUGO | S_IWUSR },
3597         .show = queue_requests_show,
3598         .store = queue_requests_store,
3599 };
3600
3601 static struct queue_sysfs_entry queue_ra_entry = {
3602         .attr = {.name = "read_ahead_kb", .mode = S_IRUGO | S_IWUSR },
3603         .show = queue_ra_show,
3604         .store = queue_ra_store,
3605 };
3606
3607 static struct queue_sysfs_entry queue_max_sectors_entry = {
3608         .attr = {.name = "max_sectors_kb", .mode = S_IRUGO | S_IWUSR },
3609         .show = queue_max_sectors_show,
3610         .store = queue_max_sectors_store,
3611 };
3612
3613 static struct queue_sysfs_entry queue_max_hw_sectors_entry = {
3614         .attr = {.name = "max_hw_sectors_kb", .mode = S_IRUGO },
3615         .show = queue_max_hw_sectors_show,
3616 };
3617
3618 static struct queue_sysfs_entry queue_iosched_entry = {
3619         .attr = {.name = "scheduler", .mode = S_IRUGO | S_IWUSR },
3620         .show = elv_iosched_show,
3621         .store = elv_iosched_store,
3622 };
3623
3624 static struct attribute *default_attrs[] = {
3625         &queue_requests_entry.attr,
3626         &queue_ra_entry.attr,
3627         &queue_max_hw_sectors_entry.attr,
3628         &queue_max_sectors_entry.attr,
3629         &queue_iosched_entry.attr,
3630         NULL,
3631 };
3632
3633 #define to_queue(atr) container_of((atr), struct queue_sysfs_entry, attr)
3634
3635 static ssize_t
3636 queue_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
3637 {
3638         struct queue_sysfs_entry *entry = to_queue(attr);
3639         struct request_queue *q;
3640
3641         q = container_of(kobj, struct request_queue, kobj);
3642         if (!entry->show)
3643                 return -EIO;
3644
3645         return entry->show(q, page);
3646 }
3647
3648 static ssize_t
3649 queue_attr_store(struct kobject *kobj, struct attribute *attr,
3650                     const char *page, size_t length)
3651 {
3652         struct queue_sysfs_entry *entry = to_queue(attr);
3653         struct request_queue *q;
3654
3655         q = container_of(kobj, struct request_queue, kobj);
3656         if (!entry->store)
3657                 return -EIO;
3658
3659         return entry->store(q, page, length);
3660 }
3661
3662 static struct sysfs_ops queue_sysfs_ops = {
3663         .show   = queue_attr_show,
3664         .store  = queue_attr_store,
3665 };
3666
3667 static struct kobj_type queue_ktype = {
3668         .sysfs_ops      = &queue_sysfs_ops,
3669         .default_attrs  = default_attrs,
3670 };
3671
3672 int blk_register_queue(struct gendisk *disk)
3673 {
3674         int ret;
3675
3676         request_queue_t *q = disk->queue;
3677
3678         if (!q || !q->request_fn)
3679                 return -ENXIO;
3680
3681         q->kobj.parent = kobject_get(&disk->kobj);
3682         if (!q->kobj.parent)
3683                 return -EBUSY;
3684
3685         snprintf(q->kobj.name, KOBJ_NAME_LEN, "%s", "queue");
3686         q->kobj.ktype = &queue_ktype;
3687
3688         ret = kobject_register(&q->kobj);
3689         if (ret < 0)
3690                 return ret;
3691
3692         ret = elv_register_queue(q);
3693         if (ret) {
3694                 kobject_unregister(&q->kobj);
3695                 return ret;
3696         }
3697
3698         return 0;
3699 }
3700
3701 void blk_unregister_queue(struct gendisk *disk)
3702 {
3703         request_queue_t *q = disk->queue;
3704
3705         if (q && q->request_fn) {
3706                 elv_unregister_queue(q);
3707
3708                 kobject_unregister(&q->kobj);
3709                 kobject_put(&disk->kobj);
3710         }
3711 }