dm mpath: check if scsi_dh module already loaded before trying to load
[zen-stable.git] / block / blk-merge.c
blob160035f548823482968bcd58298fcf9c309e7d62
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>
10 #include "blk.h"
12 static unsigned int __blk_recalc_rq_segments(struct request_queue *q,
13 struct bio *bio)
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;
20 if (!bio)
21 return 0;
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) {
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.
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;
46 seg_size += bv->bv_len;
47 bvprv = bv;
48 continue;
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;
55 nr_phys_segs++;
56 bvprv = bv;
57 seg_size = bv->bv_len;
58 highprv = high;
60 bbio = bio;
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;
68 return nr_phys_segs;
71 void blk_recalc_rq_segments(struct request *rq)
73 rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio);
76 void blk_recount_segments(struct request_queue *q, struct bio *bio)
78 struct bio *nxt = bio->bi_next;
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);
85 EXPORT_SYMBOL(blk_recount_segments);
87 static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio,
88 struct bio *nxt)
90 if (!blk_queue_cluster(q))
91 return 0;
93 if (bio->bi_seg_back_size + nxt->bi_seg_front_size >
94 queue_max_segment_size(q))
95 return 0;
97 if (!bio_has_data(bio))
98 return 1;
100 if (!BIOVEC_PHYS_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)))
101 return 0;
104 * bio and nxt are contiguous in memory; check if the queue allows
105 * these two to be merged into one
107 if (BIO_SEG_BOUNDARY(q, bio, nxt))
108 return 1;
110 return 0;
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
117 int blk_rq_map_sg(struct request_queue *q, struct request *rq,
118 struct scatterlist *sglist)
120 struct bio_vec *bvec, *bvprv;
121 struct req_iterator iter;
122 struct scatterlist *sg;
123 int nsegs, cluster;
125 nsegs = 0;
126 cluster = blk_queue_cluster(q);
129 * for each bio in rq
131 bvprv = NULL;
132 sg = NULL;
133 rq_for_each_segment(bvec, rq, iter) {
134 int nbytes = bvec->bv_len;
136 if (bvprv && cluster) {
137 if (sg->length + nbytes > queue_max_segment_size(q))
138 goto new_segment;
140 if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec))
141 goto new_segment;
142 if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec))
143 goto new_segment;
145 sg->length += nbytes;
146 } else {
147 new_segment:
148 if (!sg)
149 sg = sglist;
150 else {
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.
161 sg->page_link &= ~0x02;
162 sg = sg_next(sg);
165 sg_set_page(sg, bvec->bv_page, nbytes, bvec->bv_offset);
166 nsegs++;
168 bvprv = bvec;
169 } /* segments in rq */
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;
177 sg->length += pad_len;
178 rq->extra_len += pad_len;
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);
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;
195 if (sg)
196 sg_mark_end(sg);
198 return nsegs;
200 EXPORT_SYMBOL(blk_rq_map_sg);
202 static inline int ll_new_hw_segment(struct request_queue *q,
203 struct request *req,
204 struct bio *bio)
206 int nr_phys_segs = bio_phys_segments(q, bio);
208 if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q))
209 goto no_merge;
211 if (bio_integrity(bio) && blk_integrity_merge_bio(q, req, bio))
212 goto no_merge;
215 * This will form the start of a new hw segment. Bump both
216 * counters.
218 req->nr_phys_segments += nr_phys_segs;
219 return 1;
221 no_merge:
222 req->cmd_flags |= REQ_NOMERGE;
223 if (req == q->last_merge)
224 q->last_merge = NULL;
225 return 0;
228 int ll_back_merge_fn(struct request_queue *q, struct request *req,
229 struct bio *bio)
231 unsigned short max_sectors;
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);
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;
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);
249 return ll_new_hw_segment(q, req, bio);
252 int ll_front_merge_fn(struct request_queue *q, struct request *req,
253 struct bio *bio)
255 unsigned short max_sectors;
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);
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;
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);
274 return ll_new_hw_segment(q, req, bio);
277 static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
278 struct request *next)
280 int total_phys_segments;
281 unsigned int seg_size =
282 req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size;
285 * First check if the either of the requests are re-queued
286 * requests. Can't merge them if they are.
288 if (req->special || next->special)
289 return 0;
292 * Will it become too large?
294 if ((blk_rq_sectors(req) + blk_rq_sectors(next)) > queue_max_sectors(q))
295 return 0;
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--;
306 if (total_phys_segments > queue_max_segments(q))
307 return 0;
309 if (blk_integrity_rq(req) && blk_integrity_merge_rq(q, req, next))
310 return 0;
312 /* Merge is OK... */
313 req->nr_phys_segments = total_phys_segments;
314 return 1;
318 * blk_rq_set_mixed_merge - mark a request as mixed merge
319 * @rq: request to mark as mixed merge
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.
326 void blk_rq_set_mixed_merge(struct request *rq)
328 unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK;
329 struct bio *bio;
331 if (rq->cmd_flags & REQ_MIXED_MERGE)
332 return;
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.
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;
344 rq->cmd_flags |= REQ_MIXED_MERGE;
347 static void blk_account_io_merge(struct request *req)
349 if (blk_do_io_stat(req)) {
350 struct hd_struct *part;
351 int cpu;
353 cpu = part_stat_lock();
354 part = req->part;
356 part_round_stats(cpu, part);
357 part_dec_in_flight(part, rq_data_dir(req));
359 hd_struct_put(part);
360 part_stat_unlock();
365 * Has to be called with the request spinlock acquired
367 static int attempt_merge(struct request_queue *q, struct request *req,
368 struct request *next)
370 if (!rq_mergeable(req) || !rq_mergeable(next))
371 return 0;
374 * Don't merge file system requests and discard requests
376 if ((req->cmd_flags & REQ_DISCARD) != (next->cmd_flags & REQ_DISCARD))
377 return 0;
380 * Don't merge discard requests and secure discard requests
382 if ((req->cmd_flags & REQ_SECURE) != (next->cmd_flags & REQ_SECURE))
383 return 0;
386 * not contiguous
388 if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next))
389 return 0;
391 if (rq_data_dir(req) != rq_data_dir(next)
392 || req->rq_disk != next->rq_disk
393 || next->special)
394 return 0;
397 * If we are allowed to merge, then append bio list
398 * from next to rq and release next. merge_requests_fn
399 * will have updated segment counts, update sector
400 * counts here.
402 if (!ll_merge_requests_fn(q, req, next))
403 return 0;
406 * If failfast settings disagree or any of the two is already
407 * a mixed merge, mark both as mixed before proceeding. This
408 * makes sure that all involved bios have mixable attributes
409 * set properly.
411 if ((req->cmd_flags | next->cmd_flags) & REQ_MIXED_MERGE ||
412 (req->cmd_flags & REQ_FAILFAST_MASK) !=
413 (next->cmd_flags & REQ_FAILFAST_MASK)) {
414 blk_rq_set_mixed_merge(req);
415 blk_rq_set_mixed_merge(next);
419 * At this point we have either done a back merge
420 * or front merge. We need the smaller start_time of
421 * the merged requests to be the current request
422 * for accounting purposes.
424 if (time_after(req->start_time, next->start_time))
425 req->start_time = next->start_time;
427 req->biotail->bi_next = next->bio;
428 req->biotail = next->biotail;
430 req->__data_len += blk_rq_bytes(next);
432 elv_merge_requests(q, req, next);
435 * 'next' is going away, so update stats accordingly
437 blk_account_io_merge(next);
439 req->ioprio = ioprio_best(req->ioprio, next->ioprio);
440 if (blk_rq_cpu_valid(next))
441 req->cpu = next->cpu;
443 /* owner-ship of bio passed from next to req */
444 next->bio = NULL;
445 __blk_put_request(q, next);
446 return 1;
449 int attempt_back_merge(struct request_queue *q, struct request *rq)
451 struct request *next = elv_latter_request(q, rq);
453 if (next)
454 return attempt_merge(q, rq, next);
456 return 0;
459 int attempt_front_merge(struct request_queue *q, struct request *rq)
461 struct request *prev = elv_former_request(q, rq);
463 if (prev)
464 return attempt_merge(q, prev, rq);
466 return 0;
469 int blk_attempt_req_merge(struct request_queue *q, struct request *rq,
470 struct request *next)
472 return attempt_merge(q, rq, next);
475 bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
477 if (!rq_mergeable(rq))
478 return false;
480 /* don't merge file system requests and discard requests */
481 if ((bio->bi_rw & REQ_DISCARD) != (rq->bio->bi_rw & REQ_DISCARD))
482 return false;
484 /* don't merge discard requests and secure discard requests */
485 if ((bio->bi_rw & REQ_SECURE) != (rq->bio->bi_rw & REQ_SECURE))
486 return false;
488 /* different data direction or already started, don't merge */
489 if (bio_data_dir(bio) != rq_data_dir(rq))
490 return false;
492 /* must be same device and not a special request */
493 if (rq->rq_disk != bio->bi_bdev->bd_disk || rq->special)
494 return false;
496 /* only merge integrity protected bio into ditto rq */
497 if (bio_integrity(bio) != blk_integrity_rq(rq))
498 return false;
500 return true;
503 int blk_try_merge(struct request *rq, struct bio *bio)
505 if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_sector)
506 return ELEVATOR_BACK_MERGE;
507 else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_sector)
508 return ELEVATOR_FRONT_MERGE;
509 return ELEVATOR_NO_MERGE;