block: Deprecate QUEUE_FLAG_CLUSTER and use queue_limits instead
[linux-2.6.git] / block / blk-merge.c
1 /*
2  * Functions related to segment and merge handling
3  */
4 #include <linux/kernel.h>
5 #include <linux/module.h>
6 #include <linux/bio.h>
7 #include <linux/blkdev.h>
8 #include <linux/scatterlist.h>
9
10 #include "blk.h"
11
12 static unsigned int __blk_recalc_rq_segments(struct request_queue *q,
13                                              struct bio *bio)
14 {
15         struct bio_vec *bv, *bvprv = NULL;
16         int cluster, i, high, highprv = 1;
17         unsigned int seg_size, nr_phys_segs;
18         struct bio *fbio, *bbio;
19
20         if (!bio)
21                 return 0;
22
23         fbio = bio;
24         cluster = blk_queue_cluster(q);
25         seg_size = 0;
26         nr_phys_segs = 0;
27         for_each_bio(bio) {
28                 bio_for_each_segment(bv, bio, i) {
29                         /*
30                          * the trick here is making sure that a high page is
31                          * never considered part of another segment, since that
32                          * might change with the bounce page.
33                          */
34                         high = page_to_pfn(bv->bv_page) > queue_bounce_pfn(q);
35                         if (high || highprv)
36                                 goto new_segment;
37                         if (cluster) {
38                                 if (seg_size + bv->bv_len
39                                     > queue_max_segment_size(q))
40                                         goto new_segment;
41                                 if (!BIOVEC_PHYS_MERGEABLE(bvprv, bv))
42                                         goto new_segment;
43                                 if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bv))
44                                         goto new_segment;
45
46                                 seg_size += bv->bv_len;
47                                 bvprv = bv;
48                                 continue;
49                         }
50 new_segment:
51                         if (nr_phys_segs == 1 && seg_size >
52                             fbio->bi_seg_front_size)
53                                 fbio->bi_seg_front_size = seg_size;
54
55                         nr_phys_segs++;
56                         bvprv = bv;
57                         seg_size = bv->bv_len;
58                         highprv = high;
59                 }
60                 bbio = bio;
61         }
62
63         if (nr_phys_segs == 1 && seg_size > fbio->bi_seg_front_size)
64                 fbio->bi_seg_front_size = seg_size;
65         if (seg_size > bbio->bi_seg_back_size)
66                 bbio->bi_seg_back_size = seg_size;
67
68         return nr_phys_segs;
69 }
70
71 void blk_recalc_rq_segments(struct request *rq)
72 {
73         rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio);
74 }
75
76 void blk_recount_segments(struct request_queue *q, struct bio *bio)
77 {
78         struct bio *nxt = bio->bi_next;
79
80         bio->bi_next = NULL;
81         bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio);
82         bio->bi_next = nxt;
83         bio->bi_flags |= (1 << BIO_SEG_VALID);
84 }
85 EXPORT_SYMBOL(blk_recount_segments);
86
87 static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio,
88                                    struct bio *nxt)
89 {
90         if (!blk_queue_cluster(q))
91                 return 0;
92
93         if (bio->bi_seg_back_size + nxt->bi_seg_front_size >
94             queue_max_segment_size(q))
95                 return 0;
96
97         if (!bio_has_data(bio))
98                 return 1;
99
100         if (!BIOVEC_PHYS_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)))
101                 return 0;
102
103         /*
104          * bio and nxt are contiguous in memory; check if the queue allows
105          * these two to be merged into one
106          */
107         if (BIO_SEG_BOUNDARY(q, bio, nxt))
108                 return 1;
109
110         return 0;
111 }
112
113 /*
114  * map a request to scatterlist, return number of sg entries setup. Caller
115  * must make sure sg can hold rq->nr_phys_segments entries
116  */
117 int blk_rq_map_sg(struct request_queue *q, struct request *rq,
118                   struct scatterlist *sglist)
119 {
120         struct bio_vec *bvec, *bvprv;
121         struct req_iterator iter;
122         struct scatterlist *sg;
123         int nsegs, cluster;
124
125         nsegs = 0;
126         cluster = blk_queue_cluster(q);
127
128         /*
129          * for each bio in rq
130          */
131         bvprv = NULL;
132         sg = NULL;
133         rq_for_each_segment(bvec, rq, iter) {
134                 int nbytes = bvec->bv_len;
135
136                 if (bvprv && cluster) {
137                         if (sg->length + nbytes > queue_max_segment_size(q))
138                                 goto new_segment;
139
140                         if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec))
141                                 goto new_segment;
142                         if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec))
143                                 goto new_segment;
144
145                         sg->length += nbytes;
146                 } else {
147 new_segment:
148                         if (!sg)
149                                 sg = sglist;
150                         else {
151                                 /*
152                                  * If the driver previously mapped a shorter
153                                  * list, we could see a termination bit
154                                  * prematurely unless it fully inits the sg
155                                  * table on each mapping. We KNOW that there
156                                  * must be more entries here or the driver
157                                  * would be buggy, so force clear the
158                                  * termination bit to avoid doing a full
159                                  * sg_init_table() in drivers for each command.
160                                  */
161                                 sg->page_link &= ~0x02;
162                                 sg = sg_next(sg);
163                         }
164
165                         sg_set_page(sg, bvec->bv_page, nbytes, bvec->bv_offset);
166                         nsegs++;
167                 }
168                 bvprv = bvec;
169         } /* segments in rq */
170
171
172         if (unlikely(rq->cmd_flags & REQ_COPY_USER) &&
173             (blk_rq_bytes(rq) & q->dma_pad_mask)) {
174                 unsigned int pad_len =
175                         (q->dma_pad_mask & ~blk_rq_bytes(rq)) + 1;
176
177                 sg->length += pad_len;
178                 rq->extra_len += pad_len;
179         }
180
181         if (q->dma_drain_size && q->dma_drain_needed(rq)) {
182                 if (rq->cmd_flags & REQ_WRITE)
183                         memset(q->dma_drain_buffer, 0, q->dma_drain_size);
184
185                 sg->page_link &= ~0x02;
186                 sg = sg_next(sg);
187                 sg_set_page(sg, virt_to_page(q->dma_drain_buffer),
188                             q->dma_drain_size,
189                             ((unsigned long)q->dma_drain_buffer) &
190                             (PAGE_SIZE - 1));
191                 nsegs++;
192                 rq->extra_len += q->dma_drain_size;
193         }
194
195         if (sg)
196                 sg_mark_end(sg);
197
198         return nsegs;
199 }
200 EXPORT_SYMBOL(blk_rq_map_sg);
201
202 static inline int ll_new_hw_segment(struct request_queue *q,
203                                     struct request *req,
204                                     struct bio *bio)
205 {
206         int nr_phys_segs = bio_phys_segments(q, bio);
207
208         if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q))
209                 goto no_merge;
210
211         if (bio_integrity(bio) && blk_integrity_merge_bio(q, req, bio))
212                 goto no_merge;
213
214         /*
215          * This will form the start of a new hw segment.  Bump both
216          * counters.
217          */
218         req->nr_phys_segments += nr_phys_segs;
219         return 1;
220
221 no_merge:
222         req->cmd_flags |= REQ_NOMERGE;
223         if (req == q->last_merge)
224                 q->last_merge = NULL;
225         return 0;
226 }
227
228 int ll_back_merge_fn(struct request_queue *q, struct request *req,
229                      struct bio *bio)
230 {
231         unsigned short max_sectors;
232
233         if (unlikely(req->cmd_type == REQ_TYPE_BLOCK_PC))
234                 max_sectors = queue_max_hw_sectors(q);
235         else
236                 max_sectors = queue_max_sectors(q);
237
238         if (blk_rq_sectors(req) + bio_sectors(bio) > max_sectors) {
239                 req->cmd_flags |= REQ_NOMERGE;
240                 if (req == q->last_merge)
241                         q->last_merge = NULL;
242                 return 0;
243         }
244         if (!bio_flagged(req->biotail, BIO_SEG_VALID))
245                 blk_recount_segments(q, req->biotail);
246         if (!bio_flagged(bio, BIO_SEG_VALID))
247                 blk_recount_segments(q, bio);
248
249         return ll_new_hw_segment(q, req, bio);
250 }
251
252 int ll_front_merge_fn(struct request_queue *q, struct request *req,
253                       struct bio *bio)
254 {
255         unsigned short max_sectors;
256
257         if (unlikely(req->cmd_type == REQ_TYPE_BLOCK_PC))
258                 max_sectors = queue_max_hw_sectors(q);
259         else
260                 max_sectors = queue_max_sectors(q);
261
262
263         if (blk_rq_sectors(req) + bio_sectors(bio) > max_sectors) {
264                 req->cmd_flags |= REQ_NOMERGE;
265                 if (req == q->last_merge)
266                         q->last_merge = NULL;
267                 return 0;
268         }
269         if (!bio_flagged(bio, BIO_SEG_VALID))
270                 blk_recount_segments(q, bio);
271         if (!bio_flagged(req->bio, BIO_SEG_VALID))
272                 blk_recount_segments(q, req->bio);
273
274         return ll_new_hw_segment(q, req, bio);
275 }
276
277 static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
278                                 struct request *next)
279 {
280         int total_phys_segments;
281         unsigned int seg_size =
282                 req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size;
283
284         /*
285          * First check if the either of the requests are re-queued
286          * requests.  Can't merge them if they are.
287          */
288         if (req->special || next->special)
289                 return 0;
290
291         /*
292          * Will it become too large?
293          */
294         if ((blk_rq_sectors(req) + blk_rq_sectors(next)) > queue_max_sectors(q))
295                 return 0;
296
297         total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
298         if (blk_phys_contig_segment(q, req->biotail, next->bio)) {
299                 if (req->nr_phys_segments == 1)
300                         req->bio->bi_seg_front_size = seg_size;
301                 if (next->nr_phys_segments == 1)
302                         next->biotail->bi_seg_back_size = seg_size;
303                 total_phys_segments--;
304         }
305
306         if (total_phys_segments > queue_max_segments(q))
307                 return 0;
308
309         if (blk_integrity_rq(req) && blk_integrity_merge_rq(q, req, next))
310                 return 0;
311
312         /* Merge is OK... */
313         req->nr_phys_segments = total_phys_segments;
314         return 1;
315 }
316
317 /**
318  * blk_rq_set_mixed_merge - mark a request as mixed merge
319  * @rq: request to mark as mixed merge
320  *
321  * Description:
322  *     @rq is about to be mixed merged.  Make sure the attributes
323  *     which can be mixed are set in each bio and mark @rq as mixed
324  *     merged.
325  */
326 void blk_rq_set_mixed_merge(struct request *rq)
327 {
328         unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK;
329         struct bio *bio;
330
331         if (rq->cmd_flags & REQ_MIXED_MERGE)
332                 return;
333
334         /*
335          * @rq will no longer represent mixable attributes for all the
336          * contained bios.  It will just track those of the first one.
337          * Distributes the attributs to each bio.
338          */
339         for (bio = rq->bio; bio; bio = bio->bi_next) {
340                 WARN_ON_ONCE((bio->bi_rw & REQ_FAILFAST_MASK) &&
341                              (bio->bi_rw & REQ_FAILFAST_MASK) != ff);
342                 bio->bi_rw |= ff;
343         }
344         rq->cmd_flags |= REQ_MIXED_MERGE;
345 }
346
347 static void blk_account_io_merge(struct request *req)
348 {
349         if (blk_do_io_stat(req)) {
350                 struct hd_struct *part;
351                 int cpu;
352
353                 cpu = part_stat_lock();
354                 part = disk_map_sector_rcu(req->rq_disk, blk_rq_pos(req));
355
356                 part_round_stats(cpu, part);
357                 part_dec_in_flight(part, rq_data_dir(req));
358
359                 part_stat_unlock();
360         }
361 }
362
363 /*
364  * Has to be called with the request spinlock acquired
365  */
366 static int attempt_merge(struct request_queue *q, struct request *req,
367                           struct request *next)
368 {
369         if (!rq_mergeable(req) || !rq_mergeable(next))
370                 return 0;
371
372         /*
373          * Don't merge file system requests and discard requests
374          */
375         if ((req->cmd_flags & REQ_DISCARD) != (next->cmd_flags & REQ_DISCARD))
376                 return 0;
377
378         /*
379          * Don't merge discard requests and secure discard requests
380          */
381         if ((req->cmd_flags & REQ_SECURE) != (next->cmd_flags & REQ_SECURE))
382                 return 0;
383
384         /*
385          * not contiguous
386          */
387         if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next))
388                 return 0;
389
390         if (rq_data_dir(req) != rq_data_dir(next)
391             || req->rq_disk != next->rq_disk
392             || next->special)
393                 return 0;
394
395         /*
396          * If we are allowed to merge, then append bio list
397          * from next to rq and release next. merge_requests_fn
398          * will have updated segment counts, update sector
399          * counts here.
400          */
401         if (!ll_merge_requests_fn(q, req, next))
402                 return 0;
403
404         /*
405          * If failfast settings disagree or any of the two is already
406          * a mixed merge, mark both as mixed before proceeding.  This
407          * makes sure that all involved bios have mixable attributes
408          * set properly.
409          */
410         if ((req->cmd_flags | next->cmd_flags) & REQ_MIXED_MERGE ||
411             (req->cmd_flags & REQ_FAILFAST_MASK) !=
412             (next->cmd_flags & REQ_FAILFAST_MASK)) {
413                 blk_rq_set_mixed_merge(req);
414                 blk_rq_set_mixed_merge(next);
415         }
416
417         /*
418          * At this point we have either done a back merge
419          * or front merge. We need the smaller start_time of
420          * the merged requests to be the current request
421          * for accounting purposes.
422          */
423         if (time_after(req->start_time, next->start_time))
424                 req->start_time = next->start_time;
425
426         req->biotail->bi_next = next->bio;
427         req->biotail = next->biotail;
428
429         req->__data_len += blk_rq_bytes(next);
430
431         elv_merge_requests(q, req, next);
432
433         /*
434          * 'next' is going away, so update stats accordingly
435          */
436         blk_account_io_merge(next);
437
438         req->ioprio = ioprio_best(req->ioprio, next->ioprio);
439         if (blk_rq_cpu_valid(next))
440                 req->cpu = next->cpu;
441
442         /* owner-ship of bio passed from next to req */
443         next->bio = NULL;
444         __blk_put_request(q, next);
445         return 1;
446 }
447
448 int attempt_back_merge(struct request_queue *q, struct request *rq)
449 {
450         struct request *next = elv_latter_request(q, rq);
451
452         if (next)
453                 return attempt_merge(q, rq, next);
454
455         return 0;
456 }
457
458 int attempt_front_merge(struct request_queue *q, struct request *rq)
459 {
460         struct request *prev = elv_former_request(q, rq);
461
462         if (prev)
463                 return attempt_merge(q, prev, rq);
464
465         return 0;
466 }