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[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
32 /*
33  * for max sense size
34  */
35 #include <scsi/scsi_cmnd.h>
36
37 static void blk_unplug_work(void *data);
38 static void blk_unplug_timeout(unsigned long data);
39
40 /*
41  * For the allocated request tables
42  */
43 static kmem_cache_t *request_cachep;
44
45 /*
46  * For queue allocation
47  */
48 static kmem_cache_t *requestq_cachep;
49
50 /*
51  * For io context allocations
52  */
53 static kmem_cache_t *iocontext_cachep;
54
55 static wait_queue_head_t congestion_wqh[2] = {
56                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
57                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
58         };
59
60 /*
61  * Controlling structure to kblockd
62  */
63 static struct workqueue_struct *kblockd_workqueue; 
64
65 unsigned long blk_max_low_pfn, blk_max_pfn;
66
67 EXPORT_SYMBOL(blk_max_low_pfn);
68 EXPORT_SYMBOL(blk_max_pfn);
69
70 /* Amount of time in which a process may batch requests */
71 #define BLK_BATCH_TIME  (HZ/50UL)
72
73 /* Number of requests a "batching" process may submit */
74 #define BLK_BATCH_REQ   32
75
76 /*
77  * Return the threshold (number of used requests) at which the queue is
78  * considered to be congested.  It include a little hysteresis to keep the
79  * context switch rate down.
80  */
81 static inline int queue_congestion_on_threshold(struct request_queue *q)
82 {
83         return q->nr_congestion_on;
84 }
85
86 /*
87  * The threshold at which a queue is considered to be uncongested
88  */
89 static inline int queue_congestion_off_threshold(struct request_queue *q)
90 {
91         return q->nr_congestion_off;
92 }
93
94 static void blk_queue_congestion_threshold(struct request_queue *q)
95 {
96         int nr;
97
98         nr = q->nr_requests - (q->nr_requests / 8) + 1;
99         if (nr > q->nr_requests)
100                 nr = q->nr_requests;
101         q->nr_congestion_on = nr;
102
103         nr = q->nr_requests - (q->nr_requests / 8) - (q->nr_requests / 16) - 1;
104         if (nr < 1)
105                 nr = 1;
106         q->nr_congestion_off = nr;
107 }
108
109 /*
110  * A queue has just exitted congestion.  Note this in the global counter of
111  * congested queues, and wake up anyone who was waiting for requests to be
112  * put back.
113  */
114 static void clear_queue_congested(request_queue_t *q, int rw)
115 {
116         enum bdi_state bit;
117         wait_queue_head_t *wqh = &congestion_wqh[rw];
118
119         bit = (rw == WRITE) ? BDI_write_congested : BDI_read_congested;
120         clear_bit(bit, &q->backing_dev_info.state);
121         smp_mb__after_clear_bit();
122         if (waitqueue_active(wqh))
123                 wake_up(wqh);
124 }
125
126 /*
127  * A queue has just entered congestion.  Flag that in the queue's VM-visible
128  * state flags and increment the global gounter of congested queues.
129  */
130 static void set_queue_congested(request_queue_t *q, int rw)
131 {
132         enum bdi_state bit;
133
134         bit = (rw == WRITE) ? BDI_write_congested : BDI_read_congested;
135         set_bit(bit, &q->backing_dev_info.state);
136 }
137
138 /**
139  * blk_get_backing_dev_info - get the address of a queue's backing_dev_info
140  * @bdev:       device
141  *
142  * Locates the passed device's request queue and returns the address of its
143  * backing_dev_info
144  *
145  * Will return NULL if the request queue cannot be located.
146  */
147 struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev)
148 {
149         struct backing_dev_info *ret = NULL;
150         request_queue_t *q = bdev_get_queue(bdev);
151
152         if (q)
153                 ret = &q->backing_dev_info;
154         return ret;
155 }
156
157 EXPORT_SYMBOL(blk_get_backing_dev_info);
158
159 void blk_queue_activity_fn(request_queue_t *q, activity_fn *fn, void *data)
160 {
161         q->activity_fn = fn;
162         q->activity_data = data;
163 }
164
165 EXPORT_SYMBOL(blk_queue_activity_fn);
166
167 /**
168  * blk_queue_prep_rq - set a prepare_request function for queue
169  * @q:          queue
170  * @pfn:        prepare_request function
171  *
172  * It's possible for a queue to register a prepare_request callback which
173  * is invoked before the request is handed to the request_fn. The goal of
174  * the function is to prepare a request for I/O, it can be used to build a
175  * cdb from the request data for instance.
176  *
177  */
178 void blk_queue_prep_rq(request_queue_t *q, prep_rq_fn *pfn)
179 {
180         q->prep_rq_fn = pfn;
181 }
182
183 EXPORT_SYMBOL(blk_queue_prep_rq);
184
185 /**
186  * blk_queue_merge_bvec - set a merge_bvec function for queue
187  * @q:          queue
188  * @mbfn:       merge_bvec_fn
189  *
190  * Usually queues have static limitations on the max sectors or segments that
191  * we can put in a request. Stacking drivers may have some settings that
192  * are dynamic, and thus we have to query the queue whether it is ok to
193  * add a new bio_vec to a bio at a given offset or not. If the block device
194  * has such limitations, it needs to register a merge_bvec_fn to control
195  * the size of bio's sent to it. Note that a block device *must* allow a
196  * single page to be added to an empty bio. The block device driver may want
197  * to use the bio_split() function to deal with these bio's. By default
198  * no merge_bvec_fn is defined for a queue, and only the fixed limits are
199  * honored.
200  */
201 void blk_queue_merge_bvec(request_queue_t *q, merge_bvec_fn *mbfn)
202 {
203         q->merge_bvec_fn = mbfn;
204 }
205
206 EXPORT_SYMBOL(blk_queue_merge_bvec);
207
208 /**
209  * blk_queue_make_request - define an alternate make_request function for a device
210  * @q:  the request queue for the device to be affected
211  * @mfn: the alternate make_request function
212  *
213  * Description:
214  *    The normal way for &struct bios to be passed to a device
215  *    driver is for them to be collected into requests on a request
216  *    queue, and then to allow the device driver to select requests
217  *    off that queue when it is ready.  This works well for many block
218  *    devices. However some block devices (typically virtual devices
219  *    such as md or lvm) do not benefit from the processing on the
220  *    request queue, and are served best by having the requests passed
221  *    directly to them.  This can be achieved by providing a function
222  *    to blk_queue_make_request().
223  *
224  * Caveat:
225  *    The driver that does this *must* be able to deal appropriately
226  *    with buffers in "highmemory". This can be accomplished by either calling
227  *    __bio_kmap_atomic() to get a temporary kernel mapping, or by calling
228  *    blk_queue_bounce() to create a buffer in normal memory.
229  **/
230 void blk_queue_make_request(request_queue_t * q, make_request_fn * mfn)
231 {
232         /*
233          * set defaults
234          */
235         q->nr_requests = BLKDEV_MAX_RQ;
236         q->max_phys_segments = MAX_PHYS_SEGMENTS;
237         q->max_hw_segments = MAX_HW_SEGMENTS;
238         q->make_request_fn = mfn;
239         q->backing_dev_info.ra_pages = (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;
240         q->backing_dev_info.state = 0;
241         q->backing_dev_info.capabilities = BDI_CAP_MAP_COPY;
242         blk_queue_max_sectors(q, MAX_SECTORS);
243         blk_queue_hardsect_size(q, 512);
244         blk_queue_dma_alignment(q, 511);
245         blk_queue_congestion_threshold(q);
246         q->nr_batching = BLK_BATCH_REQ;
247
248         q->unplug_thresh = 4;           /* hmm */
249         q->unplug_delay = (3 * HZ) / 1000;      /* 3 milliseconds */
250         if (q->unplug_delay == 0)
251                 q->unplug_delay = 1;
252
253         INIT_WORK(&q->unplug_work, blk_unplug_work, q);
254
255         q->unplug_timer.function = blk_unplug_timeout;
256         q->unplug_timer.data = (unsigned long)q;
257
258         /*
259          * by default assume old behaviour and bounce for any highmem page
260          */
261         blk_queue_bounce_limit(q, BLK_BOUNCE_HIGH);
262
263         blk_queue_activity_fn(q, NULL, NULL);
264
265         INIT_LIST_HEAD(&q->drain_list);
266 }
267
268 EXPORT_SYMBOL(blk_queue_make_request);
269
270 static inline void rq_init(request_queue_t *q, struct request *rq)
271 {
272         INIT_LIST_HEAD(&rq->queuelist);
273
274         rq->errors = 0;
275         rq->rq_status = RQ_ACTIVE;
276         rq->bio = rq->biotail = NULL;
277         rq->buffer = NULL;
278         rq->ref_count = 1;
279         rq->q = q;
280         rq->waiting = NULL;
281         rq->special = NULL;
282         rq->data_len = 0;
283         rq->data = NULL;
284         rq->sense = NULL;
285         rq->end_io = NULL;
286         rq->end_io_data = NULL;
287 }
288
289 /**
290  * blk_queue_ordered - does this queue support ordered writes
291  * @q:     the request queue
292  * @flag:  see below
293  *
294  * Description:
295  *   For journalled file systems, doing ordered writes on a commit
296  *   block instead of explicitly doing wait_on_buffer (which is bad
297  *   for performance) can be a big win. Block drivers supporting this
298  *   feature should call this function and indicate so.
299  *
300  **/
301 void blk_queue_ordered(request_queue_t *q, int flag)
302 {
303         switch (flag) {
304                 case QUEUE_ORDERED_NONE:
305                         if (q->flush_rq)
306                                 kmem_cache_free(request_cachep, q->flush_rq);
307                         q->flush_rq = NULL;
308                         q->ordered = flag;
309                         break;
310                 case QUEUE_ORDERED_TAG:
311                         q->ordered = flag;
312                         break;
313                 case QUEUE_ORDERED_FLUSH:
314                         q->ordered = flag;
315                         if (!q->flush_rq)
316                                 q->flush_rq = kmem_cache_alloc(request_cachep,
317                                                                 GFP_KERNEL);
318                         break;
319                 default:
320                         printk("blk_queue_ordered: bad value %d\n", flag);
321                         break;
322         }
323 }
324
325 EXPORT_SYMBOL(blk_queue_ordered);
326
327 /**
328  * blk_queue_issue_flush_fn - set function for issuing a flush
329  * @q:     the request queue
330  * @iff:   the function to be called issuing the flush
331  *
332  * Description:
333  *   If a driver supports issuing a flush command, the support is notified
334  *   to the block layer by defining it through this call.
335  *
336  **/
337 void blk_queue_issue_flush_fn(request_queue_t *q, issue_flush_fn *iff)
338 {
339         q->issue_flush_fn = iff;
340 }
341
342 EXPORT_SYMBOL(blk_queue_issue_flush_fn);
343
344 /*
345  * Cache flushing for ordered writes handling
346  */
347 static void blk_pre_flush_end_io(struct request *flush_rq)
348 {
349         struct request *rq = flush_rq->end_io_data;
350         request_queue_t *q = rq->q;
351
352         rq->flags |= REQ_BAR_PREFLUSH;
353
354         if (!flush_rq->errors)
355                 elv_requeue_request(q, rq);
356         else {
357                 q->end_flush_fn(q, flush_rq);
358                 clear_bit(QUEUE_FLAG_FLUSH, &q->queue_flags);
359                 q->request_fn(q);
360         }
361 }
362
363 static void blk_post_flush_end_io(struct request *flush_rq)
364 {
365         struct request *rq = flush_rq->end_io_data;
366         request_queue_t *q = rq->q;
367
368         rq->flags |= REQ_BAR_POSTFLUSH;
369
370         q->end_flush_fn(q, flush_rq);
371         clear_bit(QUEUE_FLAG_FLUSH, &q->queue_flags);
372         q->request_fn(q);
373 }
374
375 struct request *blk_start_pre_flush(request_queue_t *q, struct request *rq)
376 {
377         struct request *flush_rq = q->flush_rq;
378
379         BUG_ON(!blk_barrier_rq(rq));
380
381         if (test_and_set_bit(QUEUE_FLAG_FLUSH, &q->queue_flags))
382                 return NULL;
383
384         rq_init(q, flush_rq);
385         flush_rq->elevator_private = NULL;
386         flush_rq->flags = REQ_BAR_FLUSH;
387         flush_rq->rq_disk = rq->rq_disk;
388         flush_rq->rl = NULL;
389
390         /*
391          * prepare_flush returns 0 if no flush is needed, just mark both
392          * pre and post flush as done in that case
393          */
394         if (!q->prepare_flush_fn(q, flush_rq)) {
395                 rq->flags |= REQ_BAR_PREFLUSH | REQ_BAR_POSTFLUSH;
396                 clear_bit(QUEUE_FLAG_FLUSH, &q->queue_flags);
397                 return rq;
398         }
399
400         /*
401          * some drivers dequeue requests right away, some only after io
402          * completion. make sure the request is dequeued.
403          */
404         if (!list_empty(&rq->queuelist))
405                 blkdev_dequeue_request(rq);
406
407         elv_deactivate_request(q, rq);
408
409         flush_rq->end_io_data = rq;
410         flush_rq->end_io = blk_pre_flush_end_io;
411
412         __elv_add_request(q, flush_rq, ELEVATOR_INSERT_FRONT, 0);
413         return flush_rq;
414 }
415
416 static void blk_start_post_flush(request_queue_t *q, struct request *rq)
417 {
418         struct request *flush_rq = q->flush_rq;
419
420         BUG_ON(!blk_barrier_rq(rq));
421
422         rq_init(q, flush_rq);
423         flush_rq->elevator_private = NULL;
424         flush_rq->flags = REQ_BAR_FLUSH;
425         flush_rq->rq_disk = rq->rq_disk;
426         flush_rq->rl = NULL;
427
428         if (q->prepare_flush_fn(q, flush_rq)) {
429                 flush_rq->end_io_data = rq;
430                 flush_rq->end_io = blk_post_flush_end_io;
431
432                 __elv_add_request(q, flush_rq, ELEVATOR_INSERT_FRONT, 0);
433                 q->request_fn(q);
434         }
435 }
436
437 static inline int blk_check_end_barrier(request_queue_t *q, struct request *rq,
438                                         int sectors)
439 {
440         if (sectors > rq->nr_sectors)
441                 sectors = rq->nr_sectors;
442
443         rq->nr_sectors -= sectors;
444         return rq->nr_sectors;
445 }
446
447 static int __blk_complete_barrier_rq(request_queue_t *q, struct request *rq,
448                                      int sectors, int queue_locked)
449 {
450         if (q->ordered != QUEUE_ORDERED_FLUSH)
451                 return 0;
452         if (!blk_fs_request(rq) || !blk_barrier_rq(rq))
453                 return 0;
454         if (blk_barrier_postflush(rq))
455                 return 0;
456
457         if (!blk_check_end_barrier(q, rq, sectors)) {
458                 unsigned long flags = 0;
459
460                 if (!queue_locked)
461                         spin_lock_irqsave(q->queue_lock, flags);
462
463                 blk_start_post_flush(q, rq);
464
465                 if (!queue_locked)
466                         spin_unlock_irqrestore(q->queue_lock, flags);
467         }
468
469         return 1;
470 }
471
472 /**
473  * blk_complete_barrier_rq - complete possible barrier request
474  * @q:  the request queue for the device
475  * @rq:  the request
476  * @sectors:  number of sectors to complete
477  *
478  * Description:
479  *   Used in driver end_io handling to determine whether to postpone
480  *   completion of a barrier request until a post flush has been done. This
481  *   is the unlocked variant, used if the caller doesn't already hold the
482  *   queue lock.
483  **/
484 int blk_complete_barrier_rq(request_queue_t *q, struct request *rq, int sectors)
485 {
486         return __blk_complete_barrier_rq(q, rq, sectors, 0);
487 }
488 EXPORT_SYMBOL(blk_complete_barrier_rq);
489
490 /**
491  * blk_complete_barrier_rq_locked - complete possible barrier request
492  * @q:  the request queue for the device
493  * @rq:  the request
494  * @sectors:  number of sectors to complete
495  *
496  * Description:
497  *   See blk_complete_barrier_rq(). This variant must be used if the caller
498  *   holds the queue lock.
499  **/
500 int blk_complete_barrier_rq_locked(request_queue_t *q, struct request *rq,
501                                    int sectors)
502 {
503         return __blk_complete_barrier_rq(q, rq, sectors, 1);
504 }
505 EXPORT_SYMBOL(blk_complete_barrier_rq_locked);
506
507 /**
508  * blk_queue_bounce_limit - set bounce buffer limit for queue
509  * @q:  the request queue for the device
510  * @dma_addr:   bus address limit
511  *
512  * Description:
513  *    Different hardware can have different requirements as to what pages
514  *    it can do I/O directly to. A low level driver can call
515  *    blk_queue_bounce_limit to have lower memory pages allocated as bounce
516  *    buffers for doing I/O to pages residing above @page. By default
517  *    the block layer sets this to the highest numbered "low" memory page.
518  **/
519 void blk_queue_bounce_limit(request_queue_t *q, u64 dma_addr)
520 {
521         unsigned long bounce_pfn = dma_addr >> PAGE_SHIFT;
522
523         /*
524          * set appropriate bounce gfp mask -- unfortunately we don't have a
525          * full 4GB zone, so we have to resort to low memory for any bounces.
526          * ISA has its own < 16MB zone.
527          */
528         if (bounce_pfn < blk_max_low_pfn) {
529                 BUG_ON(dma_addr < BLK_BOUNCE_ISA);
530                 init_emergency_isa_pool();
531                 q->bounce_gfp = GFP_NOIO | GFP_DMA;
532         } else
533                 q->bounce_gfp = GFP_NOIO;
534
535         q->bounce_pfn = bounce_pfn;
536 }
537
538 EXPORT_SYMBOL(blk_queue_bounce_limit);
539
540 /**
541  * blk_queue_max_sectors - set max sectors for a request for this queue
542  * @q:  the request queue for the device
543  * @max_sectors:  max sectors in the usual 512b unit
544  *
545  * Description:
546  *    Enables a low level driver to set an upper limit on the size of
547  *    received requests.
548  **/
549 void blk_queue_max_sectors(request_queue_t *q, unsigned short max_sectors)
550 {
551         if ((max_sectors << 9) < PAGE_CACHE_SIZE) {
552                 max_sectors = 1 << (PAGE_CACHE_SHIFT - 9);
553                 printk("%s: set to minimum %d\n", __FUNCTION__, max_sectors);
554         }
555
556         q->max_sectors = q->max_hw_sectors = max_sectors;
557 }
558
559 EXPORT_SYMBOL(blk_queue_max_sectors);
560
561 /**
562  * blk_queue_max_phys_segments - set max phys segments for a request for this queue
563  * @q:  the request queue for the device
564  * @max_segments:  max number of segments
565  *
566  * Description:
567  *    Enables a low level driver to set an upper limit on the number of
568  *    physical data segments in a request.  This would be the largest sized
569  *    scatter list the driver could handle.
570  **/
571 void blk_queue_max_phys_segments(request_queue_t *q, unsigned short max_segments)
572 {
573         if (!max_segments) {
574                 max_segments = 1;
575                 printk("%s: set to minimum %d\n", __FUNCTION__, max_segments);
576         }
577
578         q->max_phys_segments = max_segments;
579 }
580
581 EXPORT_SYMBOL(blk_queue_max_phys_segments);
582
583 /**
584  * blk_queue_max_hw_segments - set max hw segments for a request for this queue
585  * @q:  the request queue for the device
586  * @max_segments:  max number of segments
587  *
588  * Description:
589  *    Enables a low level driver to set an upper limit on the number of
590  *    hw data segments in a request.  This would be the largest number of
591  *    address/length pairs the host adapter can actually give as once
592  *    to the device.
593  **/
594 void blk_queue_max_hw_segments(request_queue_t *q, unsigned short max_segments)
595 {
596         if (!max_segments) {
597                 max_segments = 1;
598                 printk("%s: set to minimum %d\n", __FUNCTION__, max_segments);
599         }
600
601         q->max_hw_segments = max_segments;
602 }
603
604 EXPORT_SYMBOL(blk_queue_max_hw_segments);
605
606 /**
607  * blk_queue_max_segment_size - set max segment size for blk_rq_map_sg
608  * @q:  the request queue for the device
609  * @max_size:  max size of segment in bytes
610  *
611  * Description:
612  *    Enables a low level driver to set an upper limit on the size of a
613  *    coalesced segment
614  **/
615 void blk_queue_max_segment_size(request_queue_t *q, unsigned int max_size)
616 {
617         if (max_size < PAGE_CACHE_SIZE) {
618                 max_size = PAGE_CACHE_SIZE;
619                 printk("%s: set to minimum %d\n", __FUNCTION__, max_size);
620         }
621
622         q->max_segment_size = max_size;
623 }
624
625 EXPORT_SYMBOL(blk_queue_max_segment_size);
626
627 /**
628  * blk_queue_hardsect_size - set hardware sector size for the queue
629  * @q:  the request queue for the device
630  * @size:  the hardware sector size, in bytes
631  *
632  * Description:
633  *   This should typically be set to the lowest possible sector size
634  *   that the hardware can operate on (possible without reverting to
635  *   even internal read-modify-write operations). Usually the default
636  *   of 512 covers most hardware.
637  **/
638 void blk_queue_hardsect_size(request_queue_t *q, unsigned short size)
639 {
640         q->hardsect_size = size;
641 }
642
643 EXPORT_SYMBOL(blk_queue_hardsect_size);
644
645 /*
646  * Returns the minimum that is _not_ zero, unless both are zero.
647  */
648 #define min_not_zero(l, r) (l == 0) ? r : ((r == 0) ? l : min(l, r))
649
650 /**
651  * blk_queue_stack_limits - inherit underlying queue limits for stacked drivers
652  * @t:  the stacking driver (top)
653  * @b:  the underlying device (bottom)
654  **/
655 void blk_queue_stack_limits(request_queue_t *t, request_queue_t *b)
656 {
657         /* zero is "infinity" */
658         t->max_sectors = t->max_hw_sectors =
659                 min_not_zero(t->max_sectors,b->max_sectors);
660
661         t->max_phys_segments = min(t->max_phys_segments,b->max_phys_segments);
662         t->max_hw_segments = min(t->max_hw_segments,b->max_hw_segments);
663         t->max_segment_size = min(t->max_segment_size,b->max_segment_size);
664         t->hardsect_size = max(t->hardsect_size,b->hardsect_size);
665 }
666
667 EXPORT_SYMBOL(blk_queue_stack_limits);
668
669 /**
670  * blk_queue_segment_boundary - set boundary rules for segment merging
671  * @q:  the request queue for the device
672  * @mask:  the memory boundary mask
673  **/
674 void blk_queue_segment_boundary(request_queue_t *q, unsigned long mask)
675 {
676         if (mask < PAGE_CACHE_SIZE - 1) {
677                 mask = PAGE_CACHE_SIZE - 1;
678                 printk("%s: set to minimum %lx\n", __FUNCTION__, mask);
679         }
680
681         q->seg_boundary_mask = mask;
682 }
683
684 EXPORT_SYMBOL(blk_queue_segment_boundary);
685
686 /**
687  * blk_queue_dma_alignment - set dma length and memory alignment
688  * @q:     the request queue for the device
689  * @mask:  alignment mask
690  *
691  * description:
692  *    set required memory and length aligment for direct dma transactions.
693  *    this is used when buiding direct io requests for the queue.
694  *
695  **/
696 void blk_queue_dma_alignment(request_queue_t *q, int mask)
697 {
698         q->dma_alignment = mask;
699 }
700
701 EXPORT_SYMBOL(blk_queue_dma_alignment);
702
703 /**
704  * blk_queue_find_tag - find a request by its tag and queue
705  *
706  * @q:   The request queue for the device
707  * @tag: The tag of the request
708  *
709  * Notes:
710  *    Should be used when a device returns a tag and you want to match
711  *    it with a request.
712  *
713  *    no locks need be held.
714  **/
715 struct request *blk_queue_find_tag(request_queue_t *q, int tag)
716 {
717         struct blk_queue_tag *bqt = q->queue_tags;
718
719         if (unlikely(bqt == NULL || tag >= bqt->real_max_depth))
720                 return NULL;
721
722         return bqt->tag_index[tag];
723 }
724
725 EXPORT_SYMBOL(blk_queue_find_tag);
726
727 /**
728  * __blk_queue_free_tags - release tag maintenance info
729  * @q:  the request queue for the device
730  *
731  *  Notes:
732  *    blk_cleanup_queue() will take care of calling this function, if tagging
733  *    has been used. So there's no need to call this directly.
734  **/
735 static void __blk_queue_free_tags(request_queue_t *q)
736 {
737         struct blk_queue_tag *bqt = q->queue_tags;
738
739         if (!bqt)
740                 return;
741
742         if (atomic_dec_and_test(&bqt->refcnt)) {
743                 BUG_ON(bqt->busy);
744                 BUG_ON(!list_empty(&bqt->busy_list));
745
746                 kfree(bqt->tag_index);
747                 bqt->tag_index = NULL;
748
749                 kfree(bqt->tag_map);
750                 bqt->tag_map = NULL;
751
752                 kfree(bqt);
753         }
754
755         q->queue_tags = NULL;
756         q->queue_flags &= ~(1 << QUEUE_FLAG_QUEUED);
757 }
758
759 /**
760  * blk_queue_free_tags - release tag maintenance info
761  * @q:  the request queue for the device
762  *
763  *  Notes:
764  *      This is used to disabled tagged queuing to a device, yet leave
765  *      queue in function.
766  **/
767 void blk_queue_free_tags(request_queue_t *q)
768 {
769         clear_bit(QUEUE_FLAG_QUEUED, &q->queue_flags);
770 }
771
772 EXPORT_SYMBOL(blk_queue_free_tags);
773
774 static int
775 init_tag_map(request_queue_t *q, struct blk_queue_tag *tags, int depth)
776 {
777         int bits, i;
778         struct request **tag_index;
779         unsigned long *tag_map;
780
781         if (depth > q->nr_requests * 2) {
782                 depth = q->nr_requests * 2;
783                 printk(KERN_ERR "%s: adjusted depth to %d\n",
784                                 __FUNCTION__, depth);
785         }
786
787         tag_index = kmalloc(depth * sizeof(struct request *), GFP_ATOMIC);
788         if (!tag_index)
789                 goto fail;
790
791         bits = (depth / BLK_TAGS_PER_LONG) + 1;
792         tag_map = kmalloc(bits * sizeof(unsigned long), GFP_ATOMIC);
793         if (!tag_map)
794                 goto fail;
795
796         memset(tag_index, 0, depth * sizeof(struct request *));
797         memset(tag_map, 0, bits * sizeof(unsigned long));
798         tags->max_depth = depth;
799         tags->real_max_depth = bits * BITS_PER_LONG;
800         tags->tag_index = tag_index;
801         tags->tag_map = tag_map;
802
803         /*
804          * set the upper bits if the depth isn't a multiple of the word size
805          */
806         for (i = depth; i < bits * BLK_TAGS_PER_LONG; i++)
807                 __set_bit(i, tag_map);
808
809         return 0;
810 fail:
811         kfree(tag_index);
812         return -ENOMEM;
813 }
814
815 /**
816  * blk_queue_init_tags - initialize the queue tag info
817  * @q:  the request queue for the device
818  * @depth:  the maximum queue depth supported
819  * @tags: the tag to use
820  **/
821 int blk_queue_init_tags(request_queue_t *q, int depth,
822                         struct blk_queue_tag *tags)
823 {
824         int rc;
825
826         BUG_ON(tags && q->queue_tags && tags != q->queue_tags);
827
828         if (!tags && !q->queue_tags) {
829                 tags = kmalloc(sizeof(struct blk_queue_tag), GFP_ATOMIC);
830                 if (!tags)
831                         goto fail;
832
833                 if (init_tag_map(q, tags, depth))
834                         goto fail;
835
836                 INIT_LIST_HEAD(&tags->busy_list);
837                 tags->busy = 0;
838                 atomic_set(&tags->refcnt, 1);
839         } else if (q->queue_tags) {
840                 if ((rc = blk_queue_resize_tags(q, depth)))
841                         return rc;
842                 set_bit(QUEUE_FLAG_QUEUED, &q->queue_flags);
843                 return 0;
844         } else
845                 atomic_inc(&tags->refcnt);
846
847         /*
848          * assign it, all done
849          */
850         q->queue_tags = tags;
851         q->queue_flags |= (1 << QUEUE_FLAG_QUEUED);
852         return 0;
853 fail:
854         kfree(tags);
855         return -ENOMEM;
856 }
857
858 EXPORT_SYMBOL(blk_queue_init_tags);
859
860 /**
861  * blk_queue_resize_tags - change the queueing depth
862  * @q:  the request queue for the device
863  * @new_depth: the new max command queueing depth
864  *
865  *  Notes:
866  *    Must be called with the queue lock held.
867  **/
868 int blk_queue_resize_tags(request_queue_t *q, int new_depth)
869 {
870         struct blk_queue_tag *bqt = q->queue_tags;
871         struct request **tag_index;
872         unsigned long *tag_map;
873         int bits, max_depth;
874
875         if (!bqt)
876                 return -ENXIO;
877
878         /*
879          * don't bother sizing down
880          */
881         if (new_depth <= bqt->real_max_depth) {
882                 bqt->max_depth = new_depth;
883                 return 0;
884         }
885
886         /*
887          * save the old state info, so we can copy it back
888          */
889         tag_index = bqt->tag_index;
890         tag_map = bqt->tag_map;
891         max_depth = bqt->real_max_depth;
892
893         if (init_tag_map(q, bqt, new_depth))
894                 return -ENOMEM;
895
896         memcpy(bqt->tag_index, tag_index, max_depth * sizeof(struct request *));
897         bits = max_depth / BLK_TAGS_PER_LONG;
898         memcpy(bqt->tag_map, tag_map, bits * sizeof(unsigned long));
899
900         kfree(tag_index);
901         kfree(tag_map);
902         return 0;
903 }
904
905 EXPORT_SYMBOL(blk_queue_resize_tags);
906
907 /**
908  * blk_queue_end_tag - end tag operations for a request
909  * @q:  the request queue for the device
910  * @rq: the request that has completed
911  *
912  *  Description:
913  *    Typically called when end_that_request_first() returns 0, meaning
914  *    all transfers have been done for a request. It's important to call
915  *    this function before end_that_request_last(), as that will put the
916  *    request back on the free list thus corrupting the internal tag list.
917  *
918  *  Notes:
919  *   queue lock must be held.
920  **/
921 void blk_queue_end_tag(request_queue_t *q, struct request *rq)
922 {
923         struct blk_queue_tag *bqt = q->queue_tags;
924         int tag = rq->tag;
925
926         BUG_ON(tag == -1);
927
928         if (unlikely(tag >= bqt->real_max_depth))
929                 return;
930
931         if (unlikely(!__test_and_clear_bit(tag, bqt->tag_map))) {
932                 printk("attempt to clear non-busy tag (%d)\n", tag);
933                 return;
934         }
935
936         list_del_init(&rq->queuelist);
937         rq->flags &= ~REQ_QUEUED;
938         rq->tag = -1;
939
940         if (unlikely(bqt->tag_index[tag] == NULL))
941                 printk("tag %d is missing\n", tag);
942
943         bqt->tag_index[tag] = NULL;
944         bqt->busy--;
945 }
946
947 EXPORT_SYMBOL(blk_queue_end_tag);
948
949 /**
950  * blk_queue_start_tag - find a free tag and assign it
951  * @q:  the request queue for the device
952  * @rq:  the block request that needs tagging
953  *
954  *  Description:
955  *    This can either be used as a stand-alone helper, or possibly be
956  *    assigned as the queue &prep_rq_fn (in which case &struct request
957  *    automagically gets a tag assigned). Note that this function
958  *    assumes that any type of request can be queued! if this is not
959  *    true for your device, you must check the request type before
960  *    calling this function.  The request will also be removed from
961  *    the request queue, so it's the drivers responsibility to readd
962  *    it if it should need to be restarted for some reason.
963  *
964  *  Notes:
965  *   queue lock must be held.
966  **/
967 int blk_queue_start_tag(request_queue_t *q, struct request *rq)
968 {
969         struct blk_queue_tag *bqt = q->queue_tags;
970         unsigned long *map = bqt->tag_map;
971         int tag = 0;
972
973         if (unlikely((rq->flags & REQ_QUEUED))) {
974                 printk(KERN_ERR 
975                        "request %p for device [%s] already tagged %d",
976                        rq, rq->rq_disk ? rq->rq_disk->disk_name : "?", rq->tag);
977                 BUG();
978         }
979
980         for (map = bqt->tag_map; *map == -1UL; map++) {
981                 tag += BLK_TAGS_PER_LONG;
982
983                 if (tag >= bqt->max_depth)
984                         return 1;
985         }
986
987         tag += ffz(*map);
988         __set_bit(tag, bqt->tag_map);
989
990         rq->flags |= REQ_QUEUED;
991         rq->tag = tag;
992         bqt->tag_index[tag] = rq;
993         blkdev_dequeue_request(rq);
994         list_add(&rq->queuelist, &bqt->busy_list);
995         bqt->busy++;
996         return 0;
997 }
998
999 EXPORT_SYMBOL(blk_queue_start_tag);
1000
1001 /**
1002  * blk_queue_invalidate_tags - invalidate all pending tags
1003  * @q:  the request queue for the device
1004  *
1005  *  Description:
1006  *   Hardware conditions may dictate a need to stop all pending requests.
1007  *   In this case, we will safely clear the block side of the tag queue and
1008  *   readd all requests to the request queue in the right order.
1009  *
1010  *  Notes:
1011  *   queue lock must be held.
1012  **/
1013 void blk_queue_invalidate_tags(request_queue_t *q)
1014 {
1015         struct blk_queue_tag *bqt = q->queue_tags;
1016         struct list_head *tmp, *n;
1017         struct request *rq;
1018
1019         list_for_each_safe(tmp, n, &bqt->busy_list) {
1020                 rq = list_entry_rq(tmp);
1021
1022                 if (rq->tag == -1) {
1023                         printk("bad tag found on list\n");
1024                         list_del_init(&rq->queuelist);
1025                         rq->flags &= ~REQ_QUEUED;
1026                 } else
1027                         blk_queue_end_tag(q, rq);
1028
1029                 rq->flags &= ~REQ_STARTED;
1030                 __elv_add_request(q, rq, ELEVATOR_INSERT_BACK, 0);
1031         }
1032 }
1033
1034 EXPORT_SYMBOL(blk_queue_invalidate_tags);
1035
1036 static char *rq_flags[] = {
1037         "REQ_RW",
1038         "REQ_FAILFAST",
1039         "REQ_SOFTBARRIER",
1040         "REQ_HARDBARRIER",
1041         "REQ_CMD",
1042         "REQ_NOMERGE",
1043         "REQ_STARTED",
1044         "REQ_DONTPREP",
1045         "REQ_QUEUED",
1046         "REQ_PC",
1047         "REQ_BLOCK_PC",
1048         "REQ_SENSE",
1049         "REQ_FAILED",
1050         "REQ_QUIET",
1051         "REQ_SPECIAL",
1052         "REQ_DRIVE_CMD",
1053         "REQ_DRIVE_TASK",
1054         "REQ_DRIVE_TASKFILE",
1055         "REQ_PREEMPT",
1056         "REQ_PM_SUSPEND",
1057         "REQ_PM_RESUME",
1058         "REQ_PM_SHUTDOWN",
1059 };
1060
1061 void blk_dump_rq_flags(struct request *rq, char *msg)
1062 {
1063         int bit;
1064
1065         printk("%s: dev %s: flags = ", msg,
1066                 rq->rq_disk ? rq->rq_disk->disk_name : "?");
1067         bit = 0;
1068         do {
1069                 if (rq->flags & (1 << bit))
1070                         printk("%s ", rq_flags[bit]);
1071                 bit++;
1072         } while (bit < __REQ_NR_BITS);
1073
1074         printk("\nsector %llu, nr/cnr %lu/%u\n", (unsigned long long)rq->sector,
1075                                                        rq->nr_sectors,
1076                                                        rq->current_nr_sectors);
1077         printk("bio %p, biotail %p, buffer %p, data %p, len %u\n", rq->bio, rq->biotail, rq->buffer, rq->data, rq->data_len);
1078
1079         if (rq->flags & (REQ_BLOCK_PC | REQ_PC)) {
1080                 printk("cdb: ");
1081                 for (bit = 0; bit < sizeof(rq->cmd); bit++)
1082                         printk("%02x ", rq->cmd[bit]);
1083                 printk("\n");
1084         }
1085 }
1086
1087 EXPORT_SYMBOL(blk_dump_rq_flags);
1088
1089 void blk_recount_segments(request_queue_t *q, struct bio *bio)
1090 {
1091         struct bio_vec *bv, *bvprv = NULL;
1092         int i, nr_phys_segs, nr_hw_segs, seg_size, hw_seg_size, cluster;
1093         int high, highprv = 1;
1094
1095         if (unlikely(!bio->bi_io_vec))
1096                 return;
1097
1098         cluster = q->queue_flags & (1 << QUEUE_FLAG_CLUSTER);
1099         hw_seg_size = seg_size = nr_phys_segs = nr_hw_segs = 0;
1100         bio_for_each_segment(bv, bio, i) {
1101                 /*
1102                  * the trick here is making sure that a high page is never
1103                  * considered part of another segment, since that might
1104                  * change with the bounce page.
1105                  */
1106                 high = page_to_pfn(bv->bv_page) >= q->bounce_pfn;
1107                 if (high || highprv)
1108                         goto new_hw_segment;
1109                 if (cluster) {
1110                         if (seg_size + bv->bv_len > q->max_segment_size)
1111                                 goto new_segment;
1112                         if (!BIOVEC_PHYS_MERGEABLE(bvprv, bv))
1113                                 goto new_segment;
1114                         if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bv))
1115                                 goto new_segment;
1116                         if (BIOVEC_VIRT_OVERSIZE(hw_seg_size + bv->bv_len))
1117                                 goto new_hw_segment;
1118
1119                         seg_size += bv->bv_len;
1120                         hw_seg_size += bv->bv_len;
1121                         bvprv = bv;
1122                         continue;
1123                 }
1124 new_segment:
1125                 if (BIOVEC_VIRT_MERGEABLE(bvprv, bv) &&
1126                     !BIOVEC_VIRT_OVERSIZE(hw_seg_size + bv->bv_len)) {
1127                         hw_seg_size += bv->bv_len;
1128                 } else {
1129 new_hw_segment:
1130                         if (hw_seg_size > bio->bi_hw_front_size)
1131                                 bio->bi_hw_front_size = hw_seg_size;
1132                         hw_seg_size = BIOVEC_VIRT_START_SIZE(bv) + bv->bv_len;
1133                         nr_hw_segs++;
1134                 }
1135
1136                 nr_phys_segs++;
1137                 bvprv = bv;
1138                 seg_size = bv->bv_len;
1139                 highprv = high;
1140         }
1141         if (hw_seg_size > bio->bi_hw_back_size)
1142                 bio->bi_hw_back_size = hw_seg_size;
1143         if (nr_hw_segs == 1 && hw_seg_size > bio->bi_hw_front_size)
1144                 bio->bi_hw_front_size = hw_seg_size;
1145         bio->bi_phys_segments = nr_phys_segs;
1146         bio->bi_hw_segments = nr_hw_segs;
1147         bio->bi_flags |= (1 << BIO_SEG_VALID);
1148 }
1149
1150
1151 int blk_phys_contig_segment(request_queue_t *q, struct bio *bio,
1152                                    struct bio *nxt)
1153 {
1154         if (!(q->queue_flags & (1 << QUEUE_FLAG_CLUSTER)))
1155                 return 0;
1156
1157         if (!BIOVEC_PHYS_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)))
1158                 return 0;
1159         if (bio->bi_size + nxt->bi_size > q->max_segment_size)
1160                 return 0;
1161
1162         /*
1163          * bio and nxt are contigous in memory, check if the queue allows
1164          * these two to be merged into one
1165          */
1166         if (BIO_SEG_BOUNDARY(q, bio, nxt))
1167                 return 1;
1168
1169         return 0;
1170 }
1171
1172 EXPORT_SYMBOL(blk_phys_contig_segment);
1173
1174 int blk_hw_contig_segment(request_queue_t *q, struct bio *bio,
1175                                  struct bio *nxt)
1176 {
1177         if (unlikely(!bio_flagged(bio, BIO_SEG_VALID)))
1178                 blk_recount_segments(q, bio);
1179         if (unlikely(!bio_flagged(nxt, BIO_SEG_VALID)))
1180                 blk_recount_segments(q, nxt);
1181         if (!BIOVEC_VIRT_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)) ||
1182             BIOVEC_VIRT_OVERSIZE(bio->bi_hw_front_size + bio->bi_hw_back_size))
1183                 return 0;
1184         if (bio->bi_size + nxt->bi_size > q->max_segment_size)
1185                 return 0;
1186
1187         return 1;
1188 }
1189
1190 EXPORT_SYMBOL(blk_hw_contig_segment);
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 = req->nr_phys_segments +next->nr_phys_segments;
1362         int total_hw_segments = req->nr_hw_segments + next->nr_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 to 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 (test_bit(QUEUE_FLAG_STOPPED, &q->queue_flags))
1454                 return;
1455
1456         if (!blk_remove_plug(q))
1457                 return;
1458
1459         /*
1460          * was plugged, fire request_fn if queue has stuff to do
1461          */
1462         if (elv_next_request(q))
1463                 q->request_fn(q);
1464 }
1465 EXPORT_SYMBOL(__generic_unplug_device);
1466
1467 /**
1468  * generic_unplug_device - fire a request queue
1469  * @q:    The &request_queue_t in question
1470  *
1471  * Description:
1472  *   Linux uses plugging to build bigger requests queues before letting
1473  *   the device have at them. If a queue is plugged, the I/O scheduler
1474  *   is still adding and merging requests on the queue. Once the queue
1475  *   gets unplugged, the request_fn defined for the queue is invoked and
1476  *   transfers started.
1477  **/
1478 void generic_unplug_device(request_queue_t *q)
1479 {
1480         spin_lock_irq(q->queue_lock);
1481         __generic_unplug_device(q);
1482         spin_unlock_irq(q->queue_lock);
1483 }
1484 EXPORT_SYMBOL(generic_unplug_device);
1485
1486 static void blk_backing_dev_unplug(struct backing_dev_info *bdi,
1487                                    struct page *page)
1488 {
1489         request_queue_t *q = bdi->unplug_io_data;
1490
1491         /*
1492          * devices don't necessarily have an ->unplug_fn defined
1493          */
1494         if (q->unplug_fn)
1495                 q->unplug_fn(q);
1496 }
1497
1498 static void blk_unplug_work(void *data)
1499 {
1500         request_queue_t *q = data;
1501
1502         q->unplug_fn(q);
1503 }
1504
1505 static void blk_unplug_timeout(unsigned long data)
1506 {
1507         request_queue_t *q = (request_queue_t *)data;
1508
1509         kblockd_schedule_work(&q->unplug_work);
1510 }
1511
1512 /**
1513  * blk_start_queue - restart a previously stopped queue
1514  * @q:    The &request_queue_t in question
1515  *
1516  * Description:
1517  *   blk_start_queue() will clear the stop flag on the queue, and call
1518  *   the request_fn for the queue if it was in a stopped state when
1519  *   entered. Also see blk_stop_queue(). Queue lock must be held.
1520  **/
1521 void blk_start_queue(request_queue_t *q)
1522 {
1523         clear_bit(QUEUE_FLAG_STOPPED, &q->queue_flags);
1524
1525         /*
1526          * one level of recursion is ok and is much faster than kicking
1527          * the unplug handling
1528          */
1529         if (!test_and_set_bit(QUEUE_FLAG_REENTER, &q->queue_flags)) {
1530                 q->request_fn(q);
1531                 clear_bit(QUEUE_FLAG_REENTER, &q->queue_flags);
1532         } else {
1533                 blk_plug_device(q);
1534                 kblockd_schedule_work(&q->unplug_work);
1535         }
1536 }
1537
1538 EXPORT_SYMBOL(blk_start_queue);
1539
1540 /**
1541  * blk_stop_queue - stop a queue
1542  * @q:    The &request_queue_t in question
1543  *
1544  * Description:
1545  *   The Linux block layer assumes that a block driver will consume all
1546  *   entries on the request queue when the request_fn strategy is called.
1547  *   Often this will not happen, because of hardware limitations (queue
1548  *   depth settings). If a device driver gets a 'queue full' response,
1549  *   or if it simply chooses not to queue more I/O at one point, it can
1550  *   call this function to prevent the request_fn from being called until
1551  *   the driver has signalled it's ready to go again. This happens by calling
1552  *   blk_start_queue() to restart queue operations. Queue lock must be held.
1553  **/
1554 void blk_stop_queue(request_queue_t *q)
1555 {
1556         blk_remove_plug(q);
1557         set_bit(QUEUE_FLAG_STOPPED, &q->queue_flags);
1558 }
1559 EXPORT_SYMBOL(blk_stop_queue);
1560
1561 /**
1562  * blk_sync_queue - cancel any pending callbacks on a queue
1563  * @q: the queue
1564  *
1565  * Description:
1566  *     The block layer may perform asynchronous callback activity
1567  *     on a queue, such as calling the unplug function after a timeout.
1568  *     A block device may call blk_sync_queue to ensure that any
1569  *     such activity is cancelled, thus allowing it to release resources
1570  *     the the callbacks might use. The caller must already have made sure
1571  *     that its ->make_request_fn will not re-add plugging prior to calling
1572  *     this function.
1573  *
1574  */
1575 void blk_sync_queue(struct request_queue *q)
1576 {
1577         del_timer_sync(&q->unplug_timer);
1578         kblockd_flush();
1579 }
1580 EXPORT_SYMBOL(blk_sync_queue);
1581
1582 /**
1583  * blk_run_queue - run a single device queue
1584  * @q:  The queue to run
1585  */
1586 void blk_run_queue(struct request_queue *q)
1587 {
1588         unsigned long flags;
1589
1590         spin_lock_irqsave(q->queue_lock, flags);
1591         blk_remove_plug(q);
1592         q->request_fn(q);
1593         spin_unlock_irqrestore(q->queue_lock, flags);
1594 }
1595 EXPORT_SYMBOL(blk_run_queue);
1596
1597 /**
1598  * blk_cleanup_queue: - release a &request_queue_t when it is no longer needed
1599  * @q:    the request queue to be released
1600  *
1601  * Description:
1602  *     blk_cleanup_queue is the pair to blk_init_queue() or
1603  *     blk_queue_make_request().  It should be called when a request queue is
1604  *     being released; typically when a block device is being de-registered.
1605  *     Currently, its primary task it to free all the &struct request
1606  *     structures that were allocated to the queue and the queue itself.
1607  *
1608  * Caveat:
1609  *     Hopefully the low level driver will have finished any
1610  *     outstanding requests first...
1611  **/
1612 void blk_cleanup_queue(request_queue_t * q)
1613 {
1614         struct request_list *rl = &q->rq;
1615
1616         if (!atomic_dec_and_test(&q->refcnt))
1617                 return;
1618
1619         if (q->elevator)
1620                 elevator_exit(q->elevator);
1621
1622         blk_sync_queue(q);
1623
1624         if (rl->rq_pool)
1625                 mempool_destroy(rl->rq_pool);
1626
1627         if (q->queue_tags)
1628                 __blk_queue_free_tags(q);
1629
1630         blk_queue_ordered(q, QUEUE_ORDERED_NONE);
1631
1632         kmem_cache_free(requestq_cachep, q);
1633 }
1634
1635 EXPORT_SYMBOL(blk_cleanup_queue);
1636
1637 static int blk_init_free_list(request_queue_t *q)
1638 {
1639         struct request_list *rl = &q->rq;
1640
1641         rl->count[READ] = rl->count[WRITE] = 0;
1642         rl->starved[READ] = rl->starved[WRITE] = 0;
1643         init_waitqueue_head(&rl->wait[READ]);
1644         init_waitqueue_head(&rl->wait[WRITE]);
1645         init_waitqueue_head(&rl->drain);
1646
1647         rl->rq_pool = mempool_create(BLKDEV_MIN_RQ, mempool_alloc_slab, mempool_free_slab, request_cachep);
1648
1649         if (!rl->rq_pool)
1650                 return -ENOMEM;
1651
1652         return 0;
1653 }
1654
1655 static int __make_request(request_queue_t *, struct bio *);
1656
1657 request_queue_t *blk_alloc_queue(int gfp_mask)
1658 {
1659         request_queue_t *q = kmem_cache_alloc(requestq_cachep, gfp_mask);
1660
1661         if (!q)
1662                 return NULL;
1663
1664         memset(q, 0, sizeof(*q));
1665         init_timer(&q->unplug_timer);
1666         atomic_set(&q->refcnt, 1);
1667
1668         q->backing_dev_info.unplug_io_fn = blk_backing_dev_unplug;
1669         q->backing_dev_info.unplug_io_data = q;
1670
1671         return q;
1672 }
1673
1674 EXPORT_SYMBOL(blk_alloc_queue);
1675
1676 /**
1677  * blk_init_queue  - prepare a request queue for use with a block device
1678  * @rfn:  The function to be called to process requests that have been
1679  *        placed on the queue.
1680  * @lock: Request queue spin lock
1681  *
1682  * Description:
1683  *    If a block device wishes to use the standard request handling procedures,
1684  *    which sorts requests and coalesces adjacent requests, then it must
1685  *    call blk_init_queue().  The function @rfn will be called when there
1686  *    are requests on the queue that need to be processed.  If the device
1687  *    supports plugging, then @rfn may not be called immediately when requests
1688  *    are available on the queue, but may be called at some time later instead.
1689  *    Plugged queues are generally unplugged when a buffer belonging to one
1690  *    of the requests on the queue is needed, or due to memory pressure.
1691  *
1692  *    @rfn is not required, or even expected, to remove all requests off the
1693  *    queue, but only as many as it can handle at a time.  If it does leave
1694  *    requests on the queue, it is responsible for arranging that the requests
1695  *    get dealt with eventually.
1696  *
1697  *    The queue spin lock must be held while manipulating the requests on the
1698  *    request queue.
1699  *
1700  *    Function returns a pointer to the initialized request queue, or NULL if
1701  *    it didn't succeed.
1702  *
1703  * Note:
1704  *    blk_init_queue() must be paired with a blk_cleanup_queue() call
1705  *    when the block device is deactivated (such as at module unload).
1706  **/
1707 request_queue_t *blk_init_queue(request_fn_proc *rfn, spinlock_t *lock)
1708 {
1709         request_queue_t *q = blk_alloc_queue(GFP_KERNEL);
1710
1711         if (!q)
1712                 return NULL;
1713
1714         if (blk_init_free_list(q))
1715                 goto out_init;
1716
1717         q->request_fn           = rfn;
1718         q->back_merge_fn        = ll_back_merge_fn;
1719         q->front_merge_fn       = ll_front_merge_fn;
1720         q->merge_requests_fn    = ll_merge_requests_fn;
1721         q->prep_rq_fn           = NULL;
1722         q->unplug_fn            = generic_unplug_device;
1723         q->queue_flags          = (1 << QUEUE_FLAG_CLUSTER);
1724         q->queue_lock           = lock;
1725
1726         blk_queue_segment_boundary(q, 0xffffffff);
1727
1728         blk_queue_make_request(q, __make_request);
1729         blk_queue_max_segment_size(q, MAX_SEGMENT_SIZE);
1730
1731         blk_queue_max_hw_segments(q, MAX_HW_SEGMENTS);
1732         blk_queue_max_phys_segments(q, MAX_PHYS_SEGMENTS);
1733
1734         /*
1735          * all done
1736          */
1737         if (!elevator_init(q, NULL)) {
1738                 blk_queue_congestion_threshold(q);
1739                 return q;
1740         }
1741
1742         blk_cleanup_queue(q);
1743 out_init:
1744         kmem_cache_free(requestq_cachep, q);
1745         return NULL;
1746 }
1747
1748 EXPORT_SYMBOL(blk_init_queue);
1749
1750 int blk_get_queue(request_queue_t *q)
1751 {
1752         if (!test_bit(QUEUE_FLAG_DEAD, &q->queue_flags)) {
1753                 atomic_inc(&q->refcnt);
1754                 return 0;
1755         }
1756
1757         return 1;
1758 }
1759
1760 EXPORT_SYMBOL(blk_get_queue);
1761
1762 static inline void blk_free_request(request_queue_t *q, struct request *rq)
1763 {
1764         elv_put_request(q, rq);
1765         mempool_free(rq, q->rq.rq_pool);
1766 }
1767
1768 static inline struct request *blk_alloc_request(request_queue_t *q, int rw,
1769                                                 int gfp_mask)
1770 {
1771         struct request *rq = mempool_alloc(q->rq.rq_pool, gfp_mask);
1772
1773         if (!rq)
1774                 return NULL;
1775
1776         /*
1777          * first three bits are identical in rq->flags and bio->bi_rw,
1778          * see bio.h and blkdev.h
1779          */
1780         rq->flags = rw;
1781
1782         if (!elv_set_request(q, rq, gfp_mask))
1783                 return rq;
1784
1785         mempool_free(rq, q->rq.rq_pool);
1786         return NULL;
1787 }
1788
1789 /*
1790  * ioc_batching returns true if the ioc is a valid batching request and
1791  * should be given priority access to a request.
1792  */
1793 static inline int ioc_batching(request_queue_t *q, struct io_context *ioc)
1794 {
1795         if (!ioc)
1796                 return 0;
1797
1798         /*
1799          * Make sure the process is able to allocate at least 1 request
1800          * even if the batch times out, otherwise we could theoretically
1801          * lose wakeups.
1802          */
1803         return ioc->nr_batch_requests == q->nr_batching ||
1804                 (ioc->nr_batch_requests > 0
1805                 && time_before(jiffies, ioc->last_waited + BLK_BATCH_TIME));
1806 }
1807
1808 /*
1809  * ioc_set_batching sets ioc to be a new "batcher" if it is not one. This
1810  * will cause the process to be a "batcher" on all queues in the system. This
1811  * is the behaviour we want though - once it gets a wakeup it should be given
1812  * a nice run.
1813  */
1814 void ioc_set_batching(request_queue_t *q, struct io_context *ioc)
1815 {
1816         if (!ioc || ioc_batching(q, ioc))
1817                 return;
1818
1819         ioc->nr_batch_requests = q->nr_batching;
1820         ioc->last_waited = jiffies;
1821 }
1822
1823 static void __freed_request(request_queue_t *q, int rw)
1824 {
1825         struct request_list *rl = &q->rq;
1826
1827         if (rl->count[rw] < queue_congestion_off_threshold(q))
1828                 clear_queue_congested(q, rw);
1829
1830         if (rl->count[rw] + 1 <= q->nr_requests) {
1831                 smp_mb();
1832                 if (waitqueue_active(&rl->wait[rw]))
1833                         wake_up(&rl->wait[rw]);
1834
1835                 blk_clear_queue_full(q, rw);
1836         }
1837 }
1838
1839 /*
1840  * A request has just been released.  Account for it, update the full and
1841  * congestion status, wake up any waiters.   Called under q->queue_lock.
1842  */
1843 static void freed_request(request_queue_t *q, int rw)
1844 {
1845         struct request_list *rl = &q->rq;
1846
1847         rl->count[rw]--;
1848
1849         __freed_request(q, rw);
1850
1851         if (unlikely(rl->starved[rw ^ 1]))
1852                 __freed_request(q, rw ^ 1);
1853
1854         if (!rl->count[READ] && !rl->count[WRITE]) {
1855                 smp_mb();
1856                 if (unlikely(waitqueue_active(&rl->drain)))
1857                         wake_up(&rl->drain);
1858         }
1859 }
1860
1861 #define blkdev_free_rq(list) list_entry((list)->next, struct request, queuelist)
1862 /*
1863  * Get a free request, queue_lock must not be held
1864  */
1865 static struct request *get_request(request_queue_t *q, int rw, int gfp_mask)
1866 {
1867         struct request *rq = NULL;
1868         struct request_list *rl = &q->rq;
1869         struct io_context *ioc = get_io_context(gfp_mask);
1870
1871         if (unlikely(test_bit(QUEUE_FLAG_DRAIN, &q->queue_flags)))
1872                 goto out;
1873
1874         spin_lock_irq(q->queue_lock);
1875         if (rl->count[rw]+1 >= q->nr_requests) {
1876                 /*
1877                  * The queue will fill after this allocation, so set it as
1878                  * full, and mark this process as "batching". This process
1879                  * will be allowed to complete a batch of requests, others
1880                  * will be blocked.
1881                  */
1882                 if (!blk_queue_full(q, rw)) {
1883                         ioc_set_batching(q, ioc);
1884                         blk_set_queue_full(q, rw);
1885                 }
1886         }
1887
1888         switch (elv_may_queue(q, rw)) {
1889                 case ELV_MQUEUE_NO:
1890                         goto rq_starved;
1891                 case ELV_MQUEUE_MAY:
1892                         break;
1893                 case ELV_MQUEUE_MUST:
1894                         goto get_rq;
1895         }
1896
1897         if (blk_queue_full(q, rw) && !ioc_batching(q, ioc)) {
1898                 /*
1899                  * The queue is full and the allocating process is not a
1900                  * "batcher", and not exempted by the IO scheduler
1901                  */
1902                 spin_unlock_irq(q->queue_lock);
1903                 goto out;
1904         }
1905
1906 get_rq:
1907         rl->count[rw]++;
1908         rl->starved[rw] = 0;
1909         if (rl->count[rw] >= queue_congestion_on_threshold(q))
1910                 set_queue_congested(q, rw);
1911         spin_unlock_irq(q->queue_lock);
1912
1913         rq = blk_alloc_request(q, rw, gfp_mask);
1914         if (!rq) {
1915                 /*
1916                  * Allocation failed presumably due to memory. Undo anything
1917                  * we might have messed up.
1918                  *
1919                  * Allocating task should really be put onto the front of the
1920                  * wait queue, but this is pretty rare.
1921                  */
1922                 spin_lock_irq(q->queue_lock);
1923                 freed_request(q, rw);
1924
1925                 /*
1926                  * in the very unlikely event that allocation failed and no
1927                  * requests for this direction was pending, mark us starved
1928                  * so that freeing of a request in the other direction will
1929                  * notice us. another possible fix would be to split the
1930                  * rq mempool into READ and WRITE
1931                  */
1932 rq_starved:
1933                 if (unlikely(rl->count[rw] == 0))
1934                         rl->starved[rw] = 1;
1935
1936                 spin_unlock_irq(q->queue_lock);
1937                 goto out;
1938         }
1939
1940         if (ioc_batching(q, ioc))
1941                 ioc->nr_batch_requests--;
1942         
1943         rq_init(q, rq);
1944         rq->rl = rl;
1945 out:
1946         put_io_context(ioc);
1947         return rq;
1948 }
1949
1950 /*
1951  * No available requests for this queue, unplug the device and wait for some
1952  * requests to become available.
1953  */
1954 static struct request *get_request_wait(request_queue_t *q, int rw)
1955 {
1956         DEFINE_WAIT(wait);
1957         struct request *rq;
1958
1959         generic_unplug_device(q);
1960         do {
1961                 struct request_list *rl = &q->rq;
1962
1963                 prepare_to_wait_exclusive(&rl->wait[rw], &wait,
1964                                 TASK_UNINTERRUPTIBLE);
1965
1966                 rq = get_request(q, rw, GFP_NOIO);
1967
1968                 if (!rq) {
1969                         struct io_context *ioc;
1970
1971                         io_schedule();
1972
1973                         /*
1974                          * After sleeping, we become a "batching" process and
1975                          * will be able to allocate at least one request, and
1976                          * up to a big batch of them for a small period time.
1977                          * See ioc_batching, ioc_set_batching
1978                          */
1979                         ioc = get_io_context(GFP_NOIO);
1980                         ioc_set_batching(q, ioc);
1981                         put_io_context(ioc);
1982                 }
1983                 finish_wait(&rl->wait[rw], &wait);
1984         } while (!rq);
1985
1986         return rq;
1987 }
1988
1989 struct request *blk_get_request(request_queue_t *q, int rw, int gfp_mask)
1990 {
1991         struct request *rq;
1992
1993         BUG_ON(rw != READ && rw != WRITE);
1994
1995         if (gfp_mask & __GFP_WAIT)
1996                 rq = get_request_wait(q, rw);
1997         else
1998                 rq = get_request(q, rw, gfp_mask);
1999
2000         return rq;
2001 }
2002
2003 EXPORT_SYMBOL(blk_get_request);
2004
2005 /**
2006  * blk_requeue_request - put a request back on queue
2007  * @q:          request queue where request should be inserted
2008  * @rq:         request to be inserted
2009  *
2010  * Description:
2011  *    Drivers often keep queueing requests until the hardware cannot accept
2012  *    more, when that condition happens we need to put the request back
2013  *    on the queue. Must be called with queue lock held.
2014  */
2015 void blk_requeue_request(request_queue_t *q, struct request *rq)
2016 {
2017         if (blk_rq_tagged(rq))
2018                 blk_queue_end_tag(q, rq);
2019
2020         elv_requeue_request(q, rq);
2021 }
2022
2023 EXPORT_SYMBOL(blk_requeue_request);
2024
2025 /**
2026  * blk_insert_request - insert a special request in to a request queue
2027  * @q:          request queue where request should be inserted
2028  * @rq:         request to be inserted
2029  * @at_head:    insert request at head or tail of queue
2030  * @data:       private data
2031  * @reinsert:   true if request it a reinsertion of previously processed one
2032  *
2033  * Description:
2034  *    Many block devices need to execute commands asynchronously, so they don't
2035  *    block the whole kernel from preemption during request execution.  This is
2036  *    accomplished normally by inserting aritficial requests tagged as
2037  *    REQ_SPECIAL in to the corresponding request queue, and letting them be
2038  *    scheduled for actual execution by the request queue.
2039  *
2040  *    We have the option of inserting the head or the tail of the queue.
2041  *    Typically we use the tail for new ioctls and so forth.  We use the head
2042  *    of the queue for things like a QUEUE_FULL message from a device, or a
2043  *    host that is unable to accept a particular command.
2044  */
2045 void blk_insert_request(request_queue_t *q, struct request *rq,
2046                         int at_head, void *data, int reinsert)
2047 {
2048         unsigned long flags;
2049
2050         /*
2051          * tell I/O scheduler that this isn't a regular read/write (ie it
2052          * must not attempt merges on this) and that it acts as a soft
2053          * barrier
2054          */
2055         rq->flags |= REQ_SPECIAL | REQ_SOFTBARRIER;
2056
2057         rq->special = data;
2058
2059         spin_lock_irqsave(q->queue_lock, flags);
2060
2061         /*
2062          * If command is tagged, release the tag
2063          */
2064         if (reinsert)
2065                 blk_requeue_request(q, rq);
2066         else {
2067                 int where = ELEVATOR_INSERT_BACK;
2068
2069                 if (at_head)
2070                         where = ELEVATOR_INSERT_FRONT;
2071
2072                 if (blk_rq_tagged(rq))
2073                         blk_queue_end_tag(q, rq);
2074
2075                 drive_stat_acct(rq, rq->nr_sectors, 1);
2076                 __elv_add_request(q, rq, where, 0);
2077         }
2078         if (blk_queue_plugged(q))
2079                 __generic_unplug_device(q);
2080         else
2081                 q->request_fn(q);
2082         spin_unlock_irqrestore(q->queue_lock, flags);
2083 }
2084
2085 EXPORT_SYMBOL(blk_insert_request);
2086
2087 /**
2088  * blk_rq_map_user - map user data to a request, for REQ_BLOCK_PC usage
2089  * @q:          request queue where request should be inserted
2090  * @rw:         READ or WRITE data
2091  * @ubuf:       the user buffer
2092  * @len:        length of user data
2093  *
2094  * Description:
2095  *    Data will be mapped directly for zero copy io, if possible. Otherwise
2096  *    a kernel bounce buffer is used.
2097  *
2098  *    A matching blk_rq_unmap_user() must be issued at the end of io, while
2099  *    still in process context.
2100  *
2101  *    Note: The mapped bio may need to be bounced through blk_queue_bounce()
2102  *    before being submitted to the device, as pages mapped may be out of
2103  *    reach. It's the callers responsibility to make sure this happens. The
2104  *    original bio must be passed back in to blk_rq_unmap_user() for proper
2105  *    unmapping.
2106  */
2107 struct request *blk_rq_map_user(request_queue_t *q, int rw, void __user *ubuf,
2108                                 unsigned int len)
2109 {
2110         unsigned long uaddr;
2111         struct request *rq;
2112         struct bio *bio;
2113
2114         if (len > (q->max_sectors << 9))
2115                 return ERR_PTR(-EINVAL);
2116         if ((!len && ubuf) || (len && !ubuf))
2117                 return ERR_PTR(-EINVAL);
2118
2119         rq = blk_get_request(q, rw, __GFP_WAIT);
2120         if (!rq)
2121                 return ERR_PTR(-ENOMEM);
2122
2123         /*
2124          * if alignment requirement is satisfied, map in user pages for
2125          * direct dma. else, set up kernel bounce buffers
2126          */
2127         uaddr = (unsigned long) ubuf;
2128         if (!(uaddr & queue_dma_alignment(q)) && !(len & queue_dma_alignment(q)))
2129                 bio = bio_map_user(q, NULL, uaddr, len, rw == READ);
2130         else
2131                 bio = bio_copy_user(q, uaddr, len, rw == READ);
2132
2133         if (!IS_ERR(bio)) {
2134                 rq->bio = rq->biotail = bio;
2135                 blk_rq_bio_prep(q, rq, bio);
2136
2137                 rq->buffer = rq->data = NULL;
2138                 rq->data_len = len;
2139                 return rq;
2140         }
2141
2142         /*
2143          * bio is the err-ptr
2144          */
2145         blk_put_request(rq);
2146         return (struct request *) bio;
2147 }
2148
2149 EXPORT_SYMBOL(blk_rq_map_user);
2150
2151 /**
2152  * blk_rq_unmap_user - unmap a request with user data
2153  * @rq:         request to be unmapped
2154  * @bio:        bio for the request
2155  * @ulen:       length of user buffer
2156  *
2157  * Description:
2158  *    Unmap a request previously mapped by blk_rq_map_user().
2159  */
2160 int blk_rq_unmap_user(struct request *rq, struct bio *bio, unsigned int ulen)
2161 {
2162         int ret = 0;
2163
2164         if (bio) {
2165                 if (bio_flagged(bio, BIO_USER_MAPPED))
2166                         bio_unmap_user(bio);
2167                 else
2168                         ret = bio_uncopy_user(bio);
2169         }
2170
2171         blk_put_request(rq);
2172         return ret;
2173 }
2174
2175 EXPORT_SYMBOL(blk_rq_unmap_user);
2176
2177 /**
2178  * blk_execute_rq - insert a request into queue for execution
2179  * @q:          queue to insert the request in
2180  * @bd_disk:    matching gendisk
2181  * @rq:         request to insert
2182  *
2183  * Description:
2184  *    Insert a fully prepared request at the back of the io scheduler queue
2185  *    for execution.
2186  */
2187 int blk_execute_rq(request_queue_t *q, struct gendisk *bd_disk,
2188                    struct request *rq)
2189 {
2190         DECLARE_COMPLETION(wait);
2191         char sense[SCSI_SENSE_BUFFERSIZE];
2192         int err = 0;
2193
2194         rq->rq_disk = bd_disk;
2195
2196         /*
2197          * we need an extra reference to the request, so we can look at
2198          * it after io completion
2199          */
2200         rq->ref_count++;
2201
2202         if (!rq->sense) {
2203                 memset(sense, 0, sizeof(sense));
2204                 rq->sense = sense;
2205                 rq->sense_len = 0;
2206         }
2207
2208         rq->flags |= REQ_NOMERGE;
2209         rq->waiting = &wait;
2210         rq->end_io = blk_end_sync_rq;
2211         elv_add_request(q, rq, ELEVATOR_INSERT_BACK, 1);
2212         generic_unplug_device(q);
2213         wait_for_completion(&wait);
2214         rq->waiting = NULL;
2215
2216         if (rq->errors)
2217                 err = -EIO;
2218
2219         return err;
2220 }
2221
2222 EXPORT_SYMBOL(blk_execute_rq);
2223
2224 /**
2225  * blkdev_issue_flush - queue a flush
2226  * @bdev:       blockdev to issue flush for
2227  * @error_sector:       error sector
2228  *
2229  * Description:
2230  *    Issue a flush for the block device in question. Caller can supply
2231  *    room for storing the error offset in case of a flush error, if they
2232  *    wish to.  Caller must run wait_for_completion() on its own.
2233  */
2234 int blkdev_issue_flush(struct block_device *bdev, sector_t *error_sector)
2235 {
2236         request_queue_t *q;
2237
2238         if (bdev->bd_disk == NULL)
2239                 return -ENXIO;
2240
2241         q = bdev_get_queue(bdev);
2242         if (!q)
2243                 return -ENXIO;
2244         if (!q->issue_flush_fn)
2245                 return -EOPNOTSUPP;
2246
2247         return q->issue_flush_fn(q, bdev->bd_disk, error_sector);
2248 }
2249
2250 EXPORT_SYMBOL(blkdev_issue_flush);
2251
2252 /**
2253  * blkdev_scsi_issue_flush_fn - issue flush for SCSI devices
2254  * @q:          device queue
2255  * @disk:       gendisk
2256  * @error_sector:       error offset
2257  *
2258  * Description:
2259  *    Devices understanding the SCSI command set, can use this function as
2260  *    a helper for issuing a cache flush. Note: driver is required to store
2261  *    the error offset (in case of error flushing) in ->sector of struct
2262  *    request.
2263  */
2264 int blkdev_scsi_issue_flush_fn(request_queue_t *q, struct gendisk *disk,
2265                                sector_t *error_sector)
2266 {
2267         struct request *rq = blk_get_request(q, WRITE, __GFP_WAIT);
2268         int ret;
2269
2270         rq->flags |= REQ_BLOCK_PC | REQ_SOFTBARRIER;
2271         rq->sector = 0;
2272         memset(rq->cmd, 0, sizeof(rq->cmd));
2273         rq->cmd[0] = 0x35;
2274         rq->cmd_len = 12;
2275         rq->data = NULL;
2276         rq->data_len = 0;
2277         rq->timeout = 60 * HZ;
2278
2279         ret = blk_execute_rq(q, disk, rq);
2280
2281         if (ret && error_sector)
2282                 *error_sector = rq->sector;
2283
2284         blk_put_request(rq);
2285         return ret;
2286 }
2287
2288 EXPORT_SYMBOL(blkdev_scsi_issue_flush_fn);
2289
2290 void drive_stat_acct(struct request *rq, int nr_sectors, int new_io)
2291 {
2292         int rw = rq_data_dir(rq);
2293
2294         if (!blk_fs_request(rq) || !rq->rq_disk)
2295                 return;
2296
2297         if (rw == READ) {
2298                 __disk_stat_add(rq->rq_disk, read_sectors, nr_sectors);
2299                 if (!new_io)
2300                         __disk_stat_inc(rq->rq_disk, read_merges);
2301         } else if (rw == WRITE) {
2302                 __disk_stat_add(rq->rq_disk, write_sectors, nr_sectors);
2303                 if (!new_io)
2304                         __disk_stat_inc(rq->rq_disk, write_merges);
2305         }
2306         if (new_io) {
2307                 disk_round_stats(rq->rq_disk);
2308                 rq->rq_disk->in_flight++;
2309         }
2310 }
2311
2312 /*
2313  * add-request adds a request to the linked list.
2314  * queue lock is held and interrupts disabled, as we muck with the
2315  * request queue list.
2316  */
2317 static inline void add_request(request_queue_t * q, struct request * req)
2318 {
2319         drive_stat_acct(req, req->nr_sectors, 1);
2320
2321         if (q->activity_fn)
2322                 q->activity_fn(q->activity_data, rq_data_dir(req));
2323
2324         /*
2325          * elevator indicated where it wants this request to be
2326          * inserted at elevator_merge time
2327          */
2328         __elv_add_request(q, req, ELEVATOR_INSERT_SORT, 0);
2329 }
2330  
2331 /*
2332  * disk_round_stats()   - Round off the performance stats on a struct
2333  * disk_stats.
2334  *
2335  * The average IO queue length and utilisation statistics are maintained
2336  * by observing the current state of the queue length and the amount of
2337  * time it has been in this state for.
2338  *
2339  * Normally, that accounting is done on IO completion, but that can result
2340  * in more than a second's worth of IO being accounted for within any one
2341  * second, leading to >100% utilisation.  To deal with that, we call this
2342  * function to do a round-off before returning the results when reading
2343  * /proc/diskstats.  This accounts immediately for all queue usage up to
2344  * the current jiffies and restarts the counters again.
2345  */
2346 void disk_round_stats(struct gendisk *disk)
2347 {
2348         unsigned long now = jiffies;
2349
2350         __disk_stat_add(disk, time_in_queue,
2351                         disk->in_flight * (now - disk->stamp));
2352         disk->stamp = now;
2353
2354         if (disk->in_flight)
2355                 __disk_stat_add(disk, io_ticks, (now - disk->stamp_idle));
2356         disk->stamp_idle = now;
2357 }
2358
2359 /*
2360  * queue lock must be held
2361  */
2362 static void __blk_put_request(request_queue_t *q, struct request *req)
2363 {
2364         struct request_list *rl = req->rl;
2365
2366         if (unlikely(!q))
2367                 return;
2368         if (unlikely(--req->ref_count))
2369                 return;
2370
2371         req->rq_status = RQ_INACTIVE;
2372         req->q = NULL;
2373         req->rl = NULL;
2374
2375         /*
2376          * Request may not have originated from ll_rw_blk. if not,
2377          * it didn't come out of our reserved rq pools
2378          */
2379         if (rl) {
2380                 int rw = rq_data_dir(req);
2381
2382                 elv_completed_request(q, req);
2383
2384                 BUG_ON(!list_empty(&req->queuelist));
2385
2386                 blk_free_request(q, req);
2387                 freed_request(q, rw);
2388         }
2389 }
2390
2391 void blk_put_request(struct request *req)
2392 {
2393         /*
2394          * if req->rl isn't set, this request didnt originate from the
2395          * block layer, so it's safe to just disregard it
2396          */
2397         if (req->rl) {
2398                 unsigned long flags;
2399                 request_queue_t *q = req->q;
2400
2401                 spin_lock_irqsave(q->queue_lock, flags);
2402                 __blk_put_request(q, req);
2403                 spin_unlock_irqrestore(q->queue_lock, flags);
2404         }
2405 }
2406
2407 EXPORT_SYMBOL(blk_put_request);
2408
2409 /**
2410  * blk_end_sync_rq - executes a completion event on a request
2411  * @rq: request to complete
2412  */
2413 void blk_end_sync_rq(struct request *rq)
2414 {
2415         struct completion *waiting = rq->waiting;
2416
2417         rq->waiting = NULL;
2418         __blk_put_request(rq->q, rq);
2419
2420         /*
2421          * complete last, if this is a stack request the process (and thus
2422          * the rq pointer) could be invalid right after this complete()
2423          */
2424         complete(waiting);
2425 }
2426 EXPORT_SYMBOL(blk_end_sync_rq);
2427
2428 /**
2429  * blk_congestion_wait - wait for a queue to become uncongested
2430  * @rw: READ or WRITE
2431  * @timeout: timeout in jiffies
2432  *
2433  * Waits for up to @timeout jiffies for a queue (any queue) to exit congestion.
2434  * If no queues are congested then just wait for the next request to be
2435  * returned.
2436  */
2437 long blk_congestion_wait(int rw, long timeout)
2438 {
2439         long ret;
2440         DEFINE_WAIT(wait);
2441         wait_queue_head_t *wqh = &congestion_wqh[rw];
2442
2443         prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
2444         ret = io_schedule_timeout(timeout);
2445         finish_wait(wqh, &wait);
2446         return ret;
2447 }
2448
2449 EXPORT_SYMBOL(blk_congestion_wait);
2450
2451 /*
2452  * Has to be called with the request spinlock acquired
2453  */
2454 static int attempt_merge(request_queue_t *q, struct request *req,
2455                           struct request *next)
2456 {
2457         if (!rq_mergeable(req) || !rq_mergeable(next))
2458                 return 0;
2459
2460         /*
2461          * not contigious
2462          */
2463         if (req->sector + req->nr_sectors != next->sector)
2464                 return 0;
2465
2466         if (rq_data_dir(req) != rq_data_dir(next)
2467             || req->rq_disk != next->rq_disk
2468             || next->waiting || next->special)
2469                 return 0;
2470
2471         /*
2472          * If we are allowed to merge, then append bio list
2473          * from next to rq and release next. merge_requests_fn
2474          * will have updated segment counts, update sector
2475          * counts here.
2476          */
2477         if (!q->merge_requests_fn(q, req, next))
2478                 return 0;
2479
2480         /*
2481          * At this point we have either done a back merge
2482          * or front merge. We need the smaller start_time of
2483          * the merged requests to be the current request
2484          * for accounting purposes.
2485          */
2486         if (time_after(req->start_time, next->start_time))
2487                 req->start_time = next->start_time;
2488
2489         req->biotail->bi_next = next->bio;
2490         req->biotail = next->biotail;
2491
2492         req->nr_sectors = req->hard_nr_sectors += next->hard_nr_sectors;
2493
2494         elv_merge_requests(q, req, next);
2495
2496         if (req->rq_disk) {
2497                 disk_round_stats(req->rq_disk);
2498                 req->rq_disk->in_flight--;
2499         }
2500
2501         __blk_put_request(q, next);
2502         return 1;
2503 }
2504
2505 static inline int attempt_back_merge(request_queue_t *q, struct request *rq)
2506 {
2507         struct request *next = elv_latter_request(q, rq);
2508
2509         if (next)
2510                 return attempt_merge(q, rq, next);
2511
2512         return 0;
2513 }
2514
2515 static inline int attempt_front_merge(request_queue_t *q, struct request *rq)
2516 {
2517         struct request *prev = elv_former_request(q, rq);
2518
2519         if (prev)
2520                 return attempt_merge(q, prev, rq);
2521
2522         return 0;
2523 }
2524
2525 /**
2526  * blk_attempt_remerge  - attempt to remerge active head with next request
2527  * @q:    The &request_queue_t belonging to the device
2528  * @rq:   The head request (usually)
2529  *
2530  * Description:
2531  *    For head-active devices, the queue can easily be unplugged so quickly
2532  *    that proper merging is not done on the front request. This may hurt
2533  *    performance greatly for some devices. The block layer cannot safely
2534  *    do merging on that first request for these queues, but the driver can
2535  *    call this function and make it happen any way. Only the driver knows
2536  *    when it is safe to do so.
2537  **/
2538 void blk_attempt_remerge(request_queue_t *q, struct request *rq)
2539 {
2540         unsigned long flags;
2541
2542         spin_lock_irqsave(q->queue_lock, flags);
2543         attempt_back_merge(q, rq);
2544         spin_unlock_irqrestore(q->queue_lock, flags);
2545 }
2546
2547 EXPORT_SYMBOL(blk_attempt_remerge);
2548
2549 /*
2550  * Non-locking blk_attempt_remerge variant.
2551  */
2552 void __blk_attempt_remerge(request_queue_t *q, struct request *rq)
2553 {
2554         attempt_back_merge(q, rq);
2555 }
2556
2557 EXPORT_SYMBOL(__blk_attempt_remerge);
2558
2559 static int __make_request(request_queue_t *q, struct bio *bio)
2560 {
2561         struct request *req, *freereq = NULL;
2562         int el_ret, rw, nr_sectors, cur_nr_sectors, barrier, err;
2563         sector_t sector;
2564
2565         sector = bio->bi_sector;
2566         nr_sectors = bio_sectors(bio);
2567         cur_nr_sectors = bio_cur_sectors(bio);
2568
2569         rw = bio_data_dir(bio);
2570
2571         /*
2572          * low level driver can indicate that it wants pages above a
2573          * certain limit bounced to low memory (ie for highmem, or even
2574          * ISA dma in theory)
2575          */
2576         blk_queue_bounce(q, &bio);
2577
2578         spin_lock_prefetch(q->queue_lock);
2579
2580         barrier = bio_barrier(bio);
2581         if (barrier && (q->ordered == QUEUE_ORDERED_NONE)) {
2582                 err = -EOPNOTSUPP;
2583                 goto end_io;
2584         }
2585
2586 again:
2587         spin_lock_irq(q->queue_lock);
2588
2589         if (elv_queue_empty(q)) {
2590                 blk_plug_device(q);
2591                 goto get_rq;
2592         }
2593         if (barrier)
2594                 goto get_rq;
2595
2596         el_ret = elv_merge(q, &req, bio);
2597         switch (el_ret) {
2598                 case ELEVATOR_BACK_MERGE:
2599                         BUG_ON(!rq_mergeable(req));
2600
2601                         if (!q->back_merge_fn(q, req, bio))
2602                                 break;
2603
2604                         req->biotail->bi_next = bio;
2605                         req->biotail = bio;
2606                         req->nr_sectors = req->hard_nr_sectors += nr_sectors;
2607                         drive_stat_acct(req, nr_sectors, 0);
2608                         if (!attempt_back_merge(q, req))
2609                                 elv_merged_request(q, req);
2610                         goto out;
2611
2612                 case ELEVATOR_FRONT_MERGE:
2613                         BUG_ON(!rq_mergeable(req));
2614
2615                         if (!q->front_merge_fn(q, req, bio))
2616                                 break;
2617
2618                         bio->bi_next = req->bio;
2619                         req->bio = bio;
2620
2621                         /*
2622                          * may not be valid. if the low level driver said
2623                          * it didn't need a bounce buffer then it better
2624                          * not touch req->buffer either...
2625                          */
2626                         req->buffer = bio_data(bio);
2627                         req->current_nr_sectors = cur_nr_sectors;
2628                         req->hard_cur_sectors = cur_nr_sectors;
2629                         req->sector = req->hard_sector = sector;
2630                         req->nr_sectors = req->hard_nr_sectors += nr_sectors;
2631                         drive_stat_acct(req, nr_sectors, 0);
2632                         if (!attempt_front_merge(q, req))
2633                                 elv_merged_request(q, req);
2634                         goto out;
2635
2636                 /*
2637                  * elevator says don't/can't merge. get new request
2638                  */
2639                 case ELEVATOR_NO_MERGE:
2640                         break;
2641
2642                 default:
2643                         printk("elevator returned crap (%d)\n", el_ret);
2644                         BUG();
2645         }
2646
2647         /*
2648          * Grab a free request from the freelist - if that is empty, check
2649          * if we are doing read ahead and abort instead of blocking for
2650          * a free slot.
2651          */
2652 get_rq:
2653         if (freereq) {
2654                 req = freereq;
2655                 freereq = NULL;
2656         } else {
2657                 spin_unlock_irq(q->queue_lock);
2658                 if ((freereq = get_request(q, rw, GFP_ATOMIC)) == NULL) {
2659                         /*
2660                          * READA bit set
2661                          */
2662                         err = -EWOULDBLOCK;
2663                         if (bio_rw_ahead(bio))
2664                                 goto end_io;
2665         
2666                         freereq = get_request_wait(q, rw);
2667                 }
2668                 goto again;
2669         }
2670
2671         req->flags |= REQ_CMD;
2672
2673         /*
2674          * inherit FAILFAST from bio (for read-ahead, and explicit FAILFAST)
2675          */
2676         if (bio_rw_ahead(bio) || bio_failfast(bio))
2677                 req->flags |= REQ_FAILFAST;
2678
2679         /*
2680          * REQ_BARRIER implies no merging, but lets make it explicit
2681          */
2682         if (barrier)
2683                 req->flags |= (REQ_HARDBARRIER | REQ_NOMERGE);
2684
2685         req->errors = 0;
2686         req->hard_sector = req->sector = sector;
2687         req->hard_nr_sectors = req->nr_sectors = nr_sectors;
2688         req->current_nr_sectors = req->hard_cur_sectors = cur_nr_sectors;
2689         req->nr_phys_segments = bio_phys_segments(q, bio);
2690         req->nr_hw_segments = bio_hw_segments(q, bio);
2691         req->buffer = bio_data(bio);    /* see ->buffer comment above */
2692         req->waiting = NULL;
2693         req->bio = req->biotail = bio;
2694         req->rq_disk = bio->bi_bdev->bd_disk;
2695         req->start_time = jiffies;
2696
2697         add_request(q, req);
2698 out:
2699         if (freereq)
2700                 __blk_put_request(q, freereq);
2701         if (bio_sync(bio))
2702                 __generic_unplug_device(q);
2703
2704         spin_unlock_irq(q->queue_lock);
2705         return 0;
2706
2707 end_io:
2708         bio_endio(bio, nr_sectors << 9, err);
2709         return 0;
2710 }
2711
2712 /*
2713  * If bio->bi_dev is a partition, remap the location
2714  */
2715 static inline void blk_partition_remap(struct bio *bio)
2716 {
2717         struct block_device *bdev = bio->bi_bdev;
2718
2719         if (bdev != bdev->bd_contains) {
2720                 struct hd_struct *p = bdev->bd_part;
2721
2722                 switch (bio->bi_rw) {
2723                 case READ:
2724                         p->read_sectors += bio_sectors(bio);
2725                         p->reads++;
2726                         break;
2727                 case WRITE:
2728                         p->write_sectors += bio_sectors(bio);
2729                         p->writes++;
2730                         break;
2731                 }
2732                 bio->bi_sector += p->start_sect;
2733                 bio->bi_bdev = bdev->bd_contains;
2734         }
2735 }
2736
2737 void blk_finish_queue_drain(request_queue_t *q)
2738 {
2739         struct request_list *rl = &q->rq;
2740         struct request *rq;
2741
2742         spin_lock_irq(q->queue_lock);
2743         clear_bit(QUEUE_FLAG_DRAIN, &q->queue_flags);
2744
2745         while (!list_empty(&q->drain_list)) {
2746                 rq = list_entry_rq(q->drain_list.next);
2747
2748                 list_del_init(&rq->queuelist);
2749                 __elv_add_request(q, rq, ELEVATOR_INSERT_BACK, 1);
2750         }
2751
2752         spin_unlock_irq(q->queue_lock);
2753
2754         wake_up(&rl->wait[0]);
2755         wake_up(&rl->wait[1]);
2756         wake_up(&rl->drain);
2757 }
2758
2759 static int wait_drain(request_queue_t *q, struct request_list *rl, int dispatch)
2760 {
2761         int wait = rl->count[READ] + rl->count[WRITE];
2762
2763         if (dispatch)
2764                 wait += !list_empty(&q->queue_head);
2765
2766         return wait;
2767 }
2768
2769 /*
2770  * We rely on the fact that only requests allocated through blk_alloc_request()
2771  * have io scheduler private data structures associated with them. Any other
2772  * type of request (allocated on stack or through kmalloc()) should not go
2773  * to the io scheduler core, but be attached to the queue head instead.
2774  */
2775 void blk_wait_queue_drained(request_queue_t *q, int wait_dispatch)
2776 {
2777         struct request_list *rl = &q->rq;
2778         DEFINE_WAIT(wait);
2779
2780         spin_lock_irq(q->queue_lock);
2781         set_bit(QUEUE_FLAG_DRAIN, &q->queue_flags);
2782
2783         while (wait_drain(q, rl, wait_dispatch)) {
2784                 prepare_to_wait(&rl->drain, &wait, TASK_UNINTERRUPTIBLE);
2785
2786                 if (wait_drain(q, rl, wait_dispatch)) {
2787                         __generic_unplug_device(q);
2788                         spin_unlock_irq(q->queue_lock);
2789                         io_schedule();
2790                         spin_lock_irq(q->queue_lock);
2791                 }
2792
2793                 finish_wait(&rl->drain, &wait);
2794         }
2795
2796         spin_unlock_irq(q->queue_lock);
2797 }
2798
2799 /*
2800  * block waiting for the io scheduler being started again.
2801  */
2802 static inline void block_wait_queue_running(request_queue_t *q)
2803 {
2804         DEFINE_WAIT(wait);
2805
2806         while (test_bit(QUEUE_FLAG_DRAIN, &q->queue_flags)) {
2807                 struct request_list *rl = &q->rq;
2808
2809                 prepare_to_wait_exclusive(&rl->drain, &wait,
2810                                 TASK_UNINTERRUPTIBLE);
2811
2812                 /*
2813                  * re-check the condition. avoids using prepare_to_wait()
2814                  * in the fast path (queue is running)
2815                  */
2816                 if (test_bit(QUEUE_FLAG_DRAIN, &q->queue_flags))
2817                         io_schedule();
2818
2819                 finish_wait(&rl->drain, &wait);
2820         }
2821 }
2822
2823 static void handle_bad_sector(struct bio *bio)
2824 {
2825         char b[BDEVNAME_SIZE];
2826
2827         printk(KERN_INFO "attempt to access beyond end of device\n");
2828         printk(KERN_INFO "%s: rw=%ld, want=%Lu, limit=%Lu\n",
2829                         bdevname(bio->bi_bdev, b),
2830                         bio->bi_rw,
2831                         (unsigned long long)bio->bi_sector + bio_sectors(bio),
2832                         (long long)(bio->bi_bdev->bd_inode->i_size >> 9));
2833
2834         set_bit(BIO_EOF, &bio->bi_flags);
2835 }
2836
2837 /**
2838  * generic_make_request: hand a buffer to its device driver for I/O
2839  * @bio:  The bio describing the location in memory and on the device.
2840  *
2841  * generic_make_request() is used to make I/O requests of block
2842  * devices. It is passed a &struct bio, which describes the I/O that needs
2843  * to be done.
2844  *
2845  * generic_make_request() does not return any status.  The
2846  * success/failure status of the request, along with notification of
2847  * completion, is delivered asynchronously through the bio->bi_end_io
2848  * function described (one day) else where.
2849  *
2850  * The caller of generic_make_request must make sure that bi_io_vec
2851  * are set to describe the memory buffer, and that bi_dev and bi_sector are
2852  * set to describe the device address, and the
2853  * bi_end_io and optionally bi_private are set to describe how
2854  * completion notification should be signaled.
2855  *
2856  * generic_make_request and the drivers it calls may use bi_next if this
2857  * bio happens to be merged with someone else, and may change bi_dev and
2858  * bi_sector for remaps as it sees fit.  So the values of these fields
2859  * should NOT be depended on after the call to generic_make_request.
2860  */
2861 void generic_make_request(struct bio *bio)
2862 {
2863         request_queue_t *q;
2864         sector_t maxsector;
2865         int ret, nr_sectors = bio_sectors(bio);
2866
2867         might_sleep();
2868         /* Test device or partition size, when known. */
2869         maxsector = bio->bi_bdev->bd_inode->i_size >> 9;
2870         if (maxsector) {
2871                 sector_t sector = bio->bi_sector;
2872
2873                 if (maxsector < nr_sectors || maxsector - nr_sectors < sector) {
2874                         /*
2875                          * This may well happen - the kernel calls bread()
2876                          * without checking the size of the device, e.g., when
2877                          * mounting a device.
2878                          */
2879                         handle_bad_sector(bio);
2880                         goto end_io;
2881                 }
2882         }
2883
2884         /*
2885          * Resolve the mapping until finished. (drivers are
2886          * still free to implement/resolve their own stacking
2887          * by explicitly returning 0)
2888          *
2889          * NOTE: we don't repeat the blk_size check for each new device.
2890          * Stacking drivers are expected to know what they are doing.
2891          */
2892         do {
2893                 char b[BDEVNAME_SIZE];
2894
2895                 q = bdev_get_queue(bio->bi_bdev);
2896                 if (!q) {
2897                         printk(KERN_ERR
2898                                "generic_make_request: Trying to access "
2899                                 "nonexistent block-device %s (%Lu)\n",
2900                                 bdevname(bio->bi_bdev, b),
2901                                 (long long) bio->bi_sector);
2902 end_io:
2903                         bio_endio(bio, bio->bi_size, -EIO);
2904                         break;
2905                 }
2906
2907                 if (unlikely(bio_sectors(bio) > q->max_hw_sectors)) {
2908                         printk("bio too big device %s (%u > %u)\n", 
2909                                 bdevname(bio->bi_bdev, b),
2910                                 bio_sectors(bio),
2911                                 q->max_hw_sectors);
2912                         goto end_io;
2913                 }
2914
2915                 if (test_bit(QUEUE_FLAG_DEAD, &q->queue_flags))
2916                         goto end_io;
2917
2918                 block_wait_queue_running(q);
2919
2920                 /*
2921                  * If this device has partitions, remap block n
2922                  * of partition p to block n+start(p) of the disk.
2923                  */
2924                 blk_partition_remap(bio);
2925
2926                 ret = q->make_request_fn(q, bio);
2927         } while (ret);
2928 }
2929
2930 EXPORT_SYMBOL(generic_make_request);
2931
2932 /**
2933  * submit_bio: submit a bio to the block device layer for I/O
2934  * @rw: whether to %READ or %WRITE, or maybe to %READA (read ahead)
2935  * @bio: The &struct bio which describes the I/O
2936  *
2937  * submit_bio() is very similar in purpose to generic_make_request(), and
2938  * uses that function to do most of the work. Both are fairly rough
2939  * interfaces, @bio must be presetup and ready for I/O.
2940  *
2941  */
2942 void submit_bio(int rw, struct bio *bio)
2943 {
2944         int count = bio_sectors(bio);
2945
2946         BIO_BUG_ON(!bio->bi_size);
2947         BIO_BUG_ON(!bio->bi_io_vec);
2948         bio->bi_rw = rw;
2949         if (rw & WRITE)
2950                 mod_page_state(pgpgout, count);
2951         else
2952                 mod_page_state(pgpgin, count);
2953
2954         if (unlikely(block_dump)) {
2955                 char b[BDEVNAME_SIZE];
2956                 printk(KERN_DEBUG "%s(%d): %s block %Lu on %s\n",
2957                         current->comm, current->pid,
2958                         (rw & WRITE) ? "WRITE" : "READ",
2959                         (unsigned long long)bio->bi_sector,
2960                         bdevname(bio->bi_bdev,b));
2961         }
2962
2963         generic_make_request(bio);
2964 }
2965
2966 EXPORT_SYMBOL(submit_bio);
2967
2968 void blk_recalc_rq_segments(struct request *rq)
2969 {
2970         struct bio *bio, *prevbio = NULL;
2971         int nr_phys_segs, nr_hw_segs;
2972         unsigned int phys_size, hw_size;
2973         request_queue_t *q = rq->q;
2974
2975         if (!rq->bio)
2976                 return;
2977
2978         phys_size = hw_size = nr_phys_segs = nr_hw_segs = 0;
2979         rq_for_each_bio(bio, rq) {
2980                 /* Force bio hw/phys segs to be recalculated. */
2981                 bio->bi_flags &= ~(1 << BIO_SEG_VALID);
2982
2983                 nr_phys_segs += bio_phys_segments(q, bio);
2984                 nr_hw_segs += bio_hw_segments(q, bio);
2985                 if (prevbio) {
2986                         int pseg = phys_size + prevbio->bi_size + bio->bi_size;
2987                         int hseg = hw_size + prevbio->bi_size + bio->bi_size;
2988
2989                         if (blk_phys_contig_segment(q, prevbio, bio) &&
2990                             pseg <= q->max_segment_size) {
2991                                 nr_phys_segs--;
2992                                 phys_size += prevbio->bi_size + bio->bi_size;
2993                         } else
2994                                 phys_size = 0;
2995
2996                         if (blk_hw_contig_segment(q, prevbio, bio) &&
2997                             hseg <= q->max_segment_size) {
2998                                 nr_hw_segs--;
2999                                 hw_size += prevbio->bi_size + bio->bi_size;
3000                         } else
3001                                 hw_size = 0;
3002                 }
3003                 prevbio = bio;
3004         }
3005
3006         rq->nr_phys_segments = nr_phys_segs;
3007         rq->nr_hw_segments = nr_hw_segs;
3008 }
3009
3010 void blk_recalc_rq_sectors(struct request *rq, int nsect)
3011 {
3012         if (blk_fs_request(rq)) {
3013                 rq->hard_sector += nsect;
3014                 rq->hard_nr_sectors -= nsect;
3015
3016                 /*
3017                  * Move the I/O submission pointers ahead if required.
3018                  */
3019                 if ((rq->nr_sectors >= rq->hard_nr_sectors) &&
3020                     (rq->sector <= rq->hard_sector)) {
3021                         rq->sector = rq->hard_sector;
3022                         rq->nr_sectors = rq->hard_nr_sectors;
3023                         rq->hard_cur_sectors = bio_cur_sectors(rq->bio);
3024                         rq->current_nr_sectors = rq->hard_cur_sectors;
3025                         rq->buffer = bio_data(rq->bio);
3026                 }
3027
3028                 /*
3029                  * if total number of sectors is less than the first segment
3030                  * size, something has gone terribly wrong
3031                  */
3032                 if (rq->nr_sectors < rq->current_nr_sectors) {
3033                         printk("blk: request botched\n");
3034                         rq->nr_sectors = rq->current_nr_sectors;
3035                 }
3036         }
3037 }
3038
3039 static int __end_that_request_first(struct request *req, int uptodate,
3040                                     int nr_bytes)
3041 {
3042         int total_bytes, bio_nbytes, error, next_idx = 0;
3043         struct bio *bio;
3044
3045         /*
3046          * extend uptodate bool to allow < 0 value to be direct io error
3047          */
3048         error = 0;
3049         if (end_io_error(uptodate))
3050                 error = !uptodate ? -EIO : uptodate;
3051
3052         /*
3053          * for a REQ_BLOCK_PC request, we want to carry any eventual
3054          * sense key with us all the way through
3055          */
3056         if (!blk_pc_request(req))
3057                 req->errors = 0;
3058
3059         if (!uptodate) {
3060                 if (blk_fs_request(req) && !(req->flags & REQ_QUIET))
3061                         printk("end_request: I/O error, dev %s, sector %llu\n",
3062                                 req->rq_disk ? req->rq_disk->disk_name : "?",
3063                                 (unsigned long long)req->sector);
3064         }
3065
3066         total_bytes = bio_nbytes = 0;
3067         while ((bio = req->bio) != NULL) {
3068                 int nbytes;
3069
3070                 if (nr_bytes >= bio->bi_size) {
3071                         req->bio = bio->bi_next;
3072                         nbytes = bio->bi_size;
3073                         bio_endio(bio, nbytes, error);
3074                         next_idx = 0;
3075                         bio_nbytes = 0;
3076                 } else {
3077                         int idx = bio->bi_idx + next_idx;
3078
3079                         if (unlikely(bio->bi_idx >= bio->bi_vcnt)) {
3080                                 blk_dump_rq_flags(req, "__end_that");
3081                                 printk("%s: bio idx %d >= vcnt %d\n",
3082                                                 __FUNCTION__,
3083                                                 bio->bi_idx, bio->bi_vcnt);
3084                                 break;
3085                         }
3086
3087                         nbytes = bio_iovec_idx(bio, idx)->bv_len;
3088                         BIO_BUG_ON(nbytes > bio->bi_size);
3089
3090                         /*
3091                          * not a complete bvec done
3092                          */
3093                         if (unlikely(nbytes > nr_bytes)) {
3094                                 bio_nbytes += nr_bytes;
3095                                 total_bytes += nr_bytes;
3096                                 break;
3097                         }
3098
3099                         /*
3100                          * advance to the next vector
3101                          */
3102                         next_idx++;
3103                         bio_nbytes += nbytes;
3104                 }
3105
3106                 total_bytes += nbytes;
3107                 nr_bytes -= nbytes;
3108
3109                 if ((bio = req->bio)) {
3110                         /*
3111                          * end more in this run, or just return 'not-done'
3112                          */
3113                         if (unlikely(nr_bytes <= 0))
3114                                 break;
3115                 }
3116         }
3117
3118         /*
3119          * completely done
3120          */
3121         if (!req->bio)
3122                 return 0;
3123
3124         /*
3125          * if the request wasn't completed, update state
3126          */
3127         if (bio_nbytes) {
3128                 bio_endio(bio, bio_nbytes, error);
3129                 bio->bi_idx += next_idx;
3130                 bio_iovec(bio)->bv_offset += nr_bytes;
3131                 bio_iovec(bio)->bv_len -= nr_bytes;
3132         }
3133
3134         blk_recalc_rq_sectors(req, total_bytes >> 9);
3135         blk_recalc_rq_segments(req);
3136         return 1;
3137 }
3138
3139 /**
3140  * end_that_request_first - end I/O on a request
3141  * @req:      the request being processed
3142  * @uptodate: 1 for success, 0 for I/O error, < 0 for specific error
3143  * @nr_sectors: number of sectors to end I/O on
3144  *
3145  * Description:
3146  *     Ends I/O on a number of sectors attached to @req, and sets it up
3147  *     for the next range of segments (if any) in the cluster.
3148  *
3149  * Return:
3150  *     0 - we are done with this request, call end_that_request_last()
3151  *     1 - still buffers pending for this request
3152  **/
3153 int end_that_request_first(struct request *req, int uptodate, int nr_sectors)
3154 {
3155         return __end_that_request_first(req, uptodate, nr_sectors << 9);
3156 }
3157
3158 EXPORT_SYMBOL(end_that_request_first);
3159
3160 /**
3161  * end_that_request_chunk - end I/O on a request
3162  * @req:      the request being processed
3163  * @uptodate: 1 for success, 0 for I/O error, < 0 for specific error
3164  * @nr_bytes: number of bytes to complete
3165  *
3166  * Description:
3167  *     Ends I/O on a number of bytes attached to @req, and sets it up
3168  *     for the next range of segments (if any). Like end_that_request_first(),
3169  *     but deals with bytes instead of sectors.
3170  *
3171  * Return:
3172  *     0 - we are done with this request, call end_that_request_last()
3173  *     1 - still buffers pending for this request
3174  **/
3175 int end_that_request_chunk(struct request *req, int uptodate, int nr_bytes)
3176 {
3177         return __end_that_request_first(req, uptodate, nr_bytes);
3178 }
3179
3180 EXPORT_SYMBOL(end_that_request_chunk);
3181
3182 /*
3183  * queue lock must be held
3184  */
3185 void end_that_request_last(struct request *req)
3186 {
3187         struct gendisk *disk = req->rq_disk;
3188
3189         if (unlikely(laptop_mode) && blk_fs_request(req))
3190                 laptop_io_completion();
3191
3192         if (disk && blk_fs_request(req)) {
3193                 unsigned long duration = jiffies - req->start_time;
3194                 switch (rq_data_dir(req)) {
3195                     case WRITE:
3196                         __disk_stat_inc(disk, writes);
3197                         __disk_stat_add(disk, write_ticks, duration);
3198                         break;
3199                     case READ:
3200                         __disk_stat_inc(disk, reads);
3201                         __disk_stat_add(disk, read_ticks, duration);
3202                         break;
3203                 }
3204                 disk_round_stats(disk);
3205                 disk->in_flight--;
3206         }
3207         if (req->end_io)
3208                 req->end_io(req);
3209         else
3210                 __blk_put_request(req->q, req);
3211 }
3212
3213 EXPORT_SYMBOL(end_that_request_last);
3214
3215 void end_request(struct request *req, int uptodate)
3216 {
3217         if (!end_that_request_first(req, uptodate, req->hard_cur_sectors)) {
3218                 add_disk_randomness(req->rq_disk);
3219                 blkdev_dequeue_request(req);
3220                 end_that_request_last(req);
3221         }
3222 }
3223
3224 EXPORT_SYMBOL(end_request);
3225
3226 void blk_rq_bio_prep(request_queue_t *q, struct request *rq, struct bio *bio)
3227 {
3228         /* first three bits are identical in rq->flags and bio->bi_rw */
3229         rq->flags |= (bio->bi_rw & 7);
3230
3231         rq->nr_phys_segments = bio_phys_segments(q, bio);
3232         rq->nr_hw_segments = bio_hw_segments(q, bio);
3233         rq->current_nr_sectors = bio_cur_sectors(bio);
3234         rq->hard_cur_sectors = rq->current_nr_sectors;
3235         rq->hard_nr_sectors = rq->nr_sectors = bio_sectors(bio);
3236         rq->buffer = bio_data(bio);
3237
3238         rq->bio = rq->biotail = bio;
3239 }
3240
3241 EXPORT_SYMBOL(blk_rq_bio_prep);
3242
3243 int kblockd_schedule_work(struct work_struct *work)
3244 {
3245         return queue_work(kblockd_workqueue, work);
3246 }
3247
3248 EXPORT_SYMBOL(kblockd_schedule_work);
3249
3250 void kblockd_flush(void)
3251 {
3252         flush_workqueue(kblockd_workqueue);
3253 }
3254 EXPORT_SYMBOL(kblockd_flush);
3255
3256 int __init blk_dev_init(void)
3257 {
3258         kblockd_workqueue = create_workqueue("kblockd");
3259         if (!kblockd_workqueue)
3260                 panic("Failed to create kblockd\n");
3261
3262         request_cachep = kmem_cache_create("blkdev_requests",
3263                         sizeof(struct request), 0, SLAB_PANIC, NULL, NULL);
3264
3265         requestq_cachep = kmem_cache_create("blkdev_queue",
3266                         sizeof(request_queue_t), 0, SLAB_PANIC, NULL, NULL);
3267
3268         iocontext_cachep = kmem_cache_create("blkdev_ioc",
3269                         sizeof(struct io_context), 0, SLAB_PANIC, NULL, NULL);
3270
3271         blk_max_low_pfn = max_low_pfn;
3272         blk_max_pfn = max_pfn;
3273
3274         return 0;
3275 }
3276
3277 /*
3278  * IO Context helper functions
3279  */
3280 void put_io_context(struct io_context *ioc)
3281 {
3282         if (ioc == NULL)
3283                 return;
3284
3285         BUG_ON(atomic_read(&ioc->refcount) == 0);
3286
3287         if (atomic_dec_and_test(&ioc->refcount)) {
3288                 if (ioc->aic && ioc->aic->dtor)
3289                         ioc->aic->dtor(ioc->aic);
3290                 if (ioc->cic && ioc->cic->dtor)
3291                         ioc->cic->dtor(ioc->cic);
3292
3293                 kmem_cache_free(iocontext_cachep, ioc);
3294         }
3295 }
3296 EXPORT_SYMBOL(put_io_context);
3297
3298 /* Called by the exitting task */
3299 void exit_io_context(void)
3300 {
3301         unsigned long flags;
3302         struct io_context *ioc;
3303
3304         local_irq_save(flags);
3305         ioc = current->io_context;
3306         current->io_context = NULL;
3307         local_irq_restore(flags);
3308
3309         if (ioc->aic && ioc->aic->exit)
3310                 ioc->aic->exit(ioc->aic);
3311         if (ioc->cic && ioc->cic->exit)
3312                 ioc->cic->exit(ioc->cic);
3313
3314         put_io_context(ioc);
3315 }
3316
3317 /*
3318  * If the current task has no IO context then create one and initialise it.
3319  * If it does have a context, take a ref on it.
3320  *
3321  * This is always called in the context of the task which submitted the I/O.
3322  * But weird things happen, so we disable local interrupts to ensure exclusive
3323  * access to *current.
3324  */
3325 struct io_context *get_io_context(int gfp_flags)
3326 {
3327         struct task_struct *tsk = current;
3328         unsigned long flags;
3329         struct io_context *ret;
3330
3331         local_irq_save(flags);
3332         ret = tsk->io_context;
3333         if (ret)
3334                 goto out;
3335
3336         local_irq_restore(flags);
3337
3338         ret = kmem_cache_alloc(iocontext_cachep, gfp_flags);
3339         if (ret) {
3340                 atomic_set(&ret->refcount, 1);
3341                 ret->pid = tsk->pid;
3342                 ret->last_waited = jiffies; /* doesn't matter... */
3343                 ret->nr_batch_requests = 0; /* because this is 0 */
3344                 ret->aic = NULL;
3345                 ret->cic = NULL;
3346                 spin_lock_init(&ret->lock);
3347
3348                 local_irq_save(flags);
3349
3350                 /*
3351                  * very unlikely, someone raced with us in setting up the task
3352                  * io context. free new context and just grab a reference.
3353                  */
3354                 if (!tsk->io_context)
3355                         tsk->io_context = ret;
3356                 else {
3357                         kmem_cache_free(iocontext_cachep, ret);
3358                         ret = tsk->io_context;
3359                 }
3360
3361 out:
3362                 atomic_inc(&ret->refcount);
3363                 local_irq_restore(flags);
3364         }
3365
3366         return ret;
3367 }
3368 EXPORT_SYMBOL(get_io_context);
3369
3370 void copy_io_context(struct io_context **pdst, struct io_context **psrc)
3371 {
3372         struct io_context *src = *psrc;
3373         struct io_context *dst = *pdst;
3374
3375         if (src) {
3376                 BUG_ON(atomic_read(&src->refcount) == 0);
3377                 atomic_inc(&src->refcount);
3378                 put_io_context(dst);
3379                 *pdst = src;
3380         }
3381 }
3382 EXPORT_SYMBOL(copy_io_context);
3383
3384 void swap_io_context(struct io_context **ioc1, struct io_context **ioc2)
3385 {
3386         struct io_context *temp;
3387         temp = *ioc1;
3388         *ioc1 = *ioc2;
3389         *ioc2 = temp;
3390 }
3391 EXPORT_SYMBOL(swap_io_context);
3392
3393 /*
3394  * sysfs parts below
3395  */
3396 struct queue_sysfs_entry {
3397         struct attribute attr;
3398         ssize_t (*show)(struct request_queue *, char *);
3399         ssize_t (*store)(struct request_queue *, const char *, size_t);
3400 };
3401
3402 static ssize_t
3403 queue_var_show(unsigned int var, char *page)
3404 {
3405         return sprintf(page, "%d\n", var);
3406 }
3407
3408 static ssize_t
3409 queue_var_store(unsigned long *var, const char *page, size_t count)
3410 {
3411         char *p = (char *) page;
3412
3413         *var = simple_strtoul(p, &p, 10);
3414         return count;
3415 }
3416
3417 static ssize_t queue_requests_show(struct request_queue *q, char *page)
3418 {
3419         return queue_var_show(q->nr_requests, (page));
3420 }
3421
3422 static ssize_t
3423 queue_requests_store(struct request_queue *q, const char *page, size_t count)
3424 {
3425         struct request_list *rl = &q->rq;
3426
3427         int ret = queue_var_store(&q->nr_requests, page, count);
3428         if (q->nr_requests < BLKDEV_MIN_RQ)
3429                 q->nr_requests = BLKDEV_MIN_RQ;
3430         blk_queue_congestion_threshold(q);
3431
3432         if (rl->count[READ] >= queue_congestion_on_threshold(q))
3433                 set_queue_congested(q, READ);
3434         else if (rl->count[READ] < queue_congestion_off_threshold(q))
3435                 clear_queue_congested(q, READ);
3436
3437         if (rl->count[WRITE] >= queue_congestion_on_threshold(q))
3438                 set_queue_congested(q, WRITE);
3439         else if (rl->count[WRITE] < queue_congestion_off_threshold(q))
3440                 clear_queue_congested(q, WRITE);
3441
3442         if (rl->count[READ] >= q->nr_requests) {
3443                 blk_set_queue_full(q, READ);
3444         } else if (rl->count[READ]+1 <= q->nr_requests) {
3445                 blk_clear_queue_full(q, READ);
3446                 wake_up(&rl->wait[READ]);
3447         }
3448
3449         if (rl->count[WRITE] >= q->nr_requests) {
3450                 blk_set_queue_full(q, WRITE);
3451         } else if (rl->count[WRITE]+1 <= q->nr_requests) {
3452                 blk_clear_queue_full(q, WRITE);
3453                 wake_up(&rl->wait[WRITE]);
3454         }
3455         return ret;
3456 }
3457
3458 static ssize_t queue_ra_show(struct request_queue *q, char *page)
3459 {
3460         int ra_kb = q->backing_dev_info.ra_pages << (PAGE_CACHE_SHIFT - 10);
3461
3462         return queue_var_show(ra_kb, (page));
3463 }
3464
3465 static ssize_t
3466 queue_ra_store(struct request_queue *q, const char *page, size_t count)
3467 {
3468         unsigned long ra_kb;
3469         ssize_t ret = queue_var_store(&ra_kb, page, count);
3470
3471         spin_lock_irq(q->queue_lock);
3472         if (ra_kb > (q->max_sectors >> 1))
3473                 ra_kb = (q->max_sectors >> 1);
3474
3475         q->backing_dev_info.ra_pages = ra_kb >> (PAGE_CACHE_SHIFT - 10);
3476         spin_unlock_irq(q->queue_lock);
3477
3478         return ret;
3479 }
3480
3481 static ssize_t queue_max_sectors_show(struct request_queue *q, char *page)
3482 {
3483         int max_sectors_kb = q->max_sectors >> 1;
3484
3485         return queue_var_show(max_sectors_kb, (page));
3486 }
3487
3488 static ssize_t
3489 queue_max_sectors_store(struct request_queue *q, const char *page, size_t count)
3490 {
3491         unsigned long max_sectors_kb,
3492                         max_hw_sectors_kb = q->max_hw_sectors >> 1,
3493                         page_kb = 1 << (PAGE_CACHE_SHIFT - 10);
3494         ssize_t ret = queue_var_store(&max_sectors_kb, page, count);
3495         int ra_kb;
3496
3497         if (max_sectors_kb > max_hw_sectors_kb || max_sectors_kb < page_kb)
3498                 return -EINVAL;
3499         /*
3500          * Take the queue lock to update the readahead and max_sectors
3501          * values synchronously:
3502          */
3503         spin_lock_irq(q->queue_lock);
3504         /*
3505          * Trim readahead window as well, if necessary:
3506          */
3507         ra_kb = q->backing_dev_info.ra_pages << (PAGE_CACHE_SHIFT - 10);
3508         if (ra_kb > max_sectors_kb)
3509                 q->backing_dev_info.ra_pages =
3510                                 max_sectors_kb >> (PAGE_CACHE_SHIFT - 10);
3511
3512         q->max_sectors = max_sectors_kb << 1;
3513         spin_unlock_irq(q->queue_lock);
3514
3515         return ret;
3516 }
3517
3518 static ssize_t queue_max_hw_sectors_show(struct request_queue *q, char *page)
3519 {
3520         int max_hw_sectors_kb = q->max_hw_sectors >> 1;
3521
3522         return queue_var_show(max_hw_sectors_kb, (page));
3523 }
3524
3525
3526 static struct queue_sysfs_entry queue_requests_entry = {
3527         .attr = {.name = "nr_requests", .mode = S_IRUGO | S_IWUSR },
3528         .show = queue_requests_show,
3529         .store = queue_requests_store,
3530 };
3531
3532 static struct queue_sysfs_entry queue_ra_entry = {
3533         .attr = {.name = "read_ahead_kb", .mode = S_IRUGO | S_IWUSR },
3534         .show = queue_ra_show,
3535         .store = queue_ra_store,
3536 };
3537
3538 static struct queue_sysfs_entry queue_max_sectors_entry = {
3539         .attr = {.name = "max_sectors_kb", .mode = S_IRUGO | S_IWUSR },
3540         .show = queue_max_sectors_show,
3541         .store = queue_max_sectors_store,
3542 };
3543
3544 static struct queue_sysfs_entry queue_max_hw_sectors_entry = {
3545         .attr = {.name = "max_hw_sectors_kb", .mode = S_IRUGO },
3546         .show = queue_max_hw_sectors_show,
3547 };
3548
3549 static struct queue_sysfs_entry queue_iosched_entry = {
3550         .attr = {.name = "scheduler", .mode = S_IRUGO | S_IWUSR },
3551         .show = elv_iosched_show,
3552         .store = elv_iosched_store,
3553 };
3554
3555 static struct attribute *default_attrs[] = {
3556         &queue_requests_entry.attr,
3557         &queue_ra_entry.attr,
3558         &queue_max_hw_sectors_entry.attr,
3559         &queue_max_sectors_entry.attr,
3560         &queue_iosched_entry.attr,
3561         NULL,
3562 };
3563
3564 #define to_queue(atr) container_of((atr), struct queue_sysfs_entry, attr)
3565
3566 static ssize_t
3567 queue_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
3568 {
3569         struct queue_sysfs_entry *entry = to_queue(attr);
3570         struct request_queue *q;
3571
3572         q = container_of(kobj, struct request_queue, kobj);
3573         if (!entry->show)
3574                 return 0;
3575
3576         return entry->show(q, page);
3577 }
3578
3579 static ssize_t
3580 queue_attr_store(struct kobject *kobj, struct attribute *attr,
3581                     const char *page, size_t length)
3582 {
3583         struct queue_sysfs_entry *entry = to_queue(attr);
3584         struct request_queue *q;
3585
3586         q = container_of(kobj, struct request_queue, kobj);
3587         if (!entry->store)
3588                 return -EINVAL;
3589
3590         return entry->store(q, page, length);
3591 }
3592
3593 static struct sysfs_ops queue_sysfs_ops = {
3594         .show   = queue_attr_show,
3595         .store  = queue_attr_store,
3596 };
3597
3598 struct kobj_type queue_ktype = {
3599         .sysfs_ops      = &queue_sysfs_ops,
3600         .default_attrs  = default_attrs,
3601 };
3602
3603 int blk_register_queue(struct gendisk *disk)
3604 {
3605         int ret;
3606
3607         request_queue_t *q = disk->queue;
3608
3609         if (!q || !q->request_fn)
3610                 return -ENXIO;
3611
3612         q->kobj.parent = kobject_get(&disk->kobj);
3613         if (!q->kobj.parent)
3614                 return -EBUSY;
3615
3616         snprintf(q->kobj.name, KOBJ_NAME_LEN, "%s", "queue");
3617         q->kobj.ktype = &queue_ktype;
3618
3619         ret = kobject_register(&q->kobj);
3620         if (ret < 0)
3621                 return ret;
3622
3623         ret = elv_register_queue(q);
3624         if (ret) {
3625                 kobject_unregister(&q->kobj);
3626                 return ret;
3627         }
3628
3629         return 0;
3630 }
3631
3632 void blk_unregister_queue(struct gendisk *disk)
3633 {
3634         request_queue_t *q = disk->queue;
3635
3636         if (q && q->request_fn) {
3637                 elv_unregister_queue(q);
3638
3639                 kobject_unregister(&q->kobj);
3640                 kobject_put(&disk->kobj);
3641         }
3642 }