blob: 651136aae76e45ba821205a830a919a3d6d105c5 [file] [log] [blame]
Jens Axboed6d48192008-01-29 14:04:06 +01001/*
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
12void blk_recalc_rq_sectors(struct request *rq, int nsect)
13{
14 if (blk_fs_request(rq)) {
15 rq->hard_sector += nsect;
16 rq->hard_nr_sectors -= nsect;
17
18 /*
19 * Move the I/O submission pointers ahead if required.
20 */
21 if ((rq->nr_sectors >= rq->hard_nr_sectors) &&
22 (rq->sector <= rq->hard_sector)) {
23 rq->sector = rq->hard_sector;
24 rq->nr_sectors = rq->hard_nr_sectors;
25 rq->hard_cur_sectors = bio_cur_sectors(rq->bio);
26 rq->current_nr_sectors = rq->hard_cur_sectors;
27 rq->buffer = bio_data(rq->bio);
28 }
29
30 /*
31 * if total number of sectors is less than the first segment
32 * size, something has gone terribly wrong
33 */
34 if (rq->nr_sectors < rq->current_nr_sectors) {
Jens Axboe6728cb02008-01-31 13:03:55 +010035 printk(KERN_ERR "blk: request botched\n");
Jens Axboed6d48192008-01-29 14:04:06 +010036 rq->nr_sectors = rq->current_nr_sectors;
37 }
38 }
39}
40
41void blk_recalc_rq_segments(struct request *rq)
42{
43 int nr_phys_segs;
44 int nr_hw_segs;
45 unsigned int phys_size;
46 unsigned int hw_size;
47 struct bio_vec *bv, *bvprv = NULL;
48 int seg_size;
49 int hw_seg_size;
50 int cluster;
51 struct req_iterator iter;
52 int high, highprv = 1;
53 struct request_queue *q = rq->q;
54
55 if (!rq->bio)
56 return;
57
Nick Piggin75ad23b2008-04-29 14:48:33 +020058 cluster = test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
Jens Axboed6d48192008-01-29 14:04:06 +010059 hw_seg_size = seg_size = 0;
60 phys_size = hw_size = nr_phys_segs = nr_hw_segs = 0;
61 rq_for_each_segment(bv, rq, iter) {
62 /*
63 * the trick here is making sure that a high page is never
64 * considered part of another segment, since that might
65 * change with the bounce page.
66 */
67 high = page_to_pfn(bv->bv_page) > q->bounce_pfn;
68 if (high || highprv)
69 goto new_hw_segment;
70 if (cluster) {
71 if (seg_size + bv->bv_len > q->max_segment_size)
72 goto new_segment;
73 if (!BIOVEC_PHYS_MERGEABLE(bvprv, bv))
74 goto new_segment;
75 if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bv))
76 goto new_segment;
77 if (BIOVEC_VIRT_OVERSIZE(hw_seg_size + bv->bv_len))
78 goto new_hw_segment;
79
80 seg_size += bv->bv_len;
81 hw_seg_size += bv->bv_len;
82 bvprv = bv;
83 continue;
84 }
85new_segment:
86 if (BIOVEC_VIRT_MERGEABLE(bvprv, bv) &&
87 !BIOVEC_VIRT_OVERSIZE(hw_seg_size + bv->bv_len))
88 hw_seg_size += bv->bv_len;
89 else {
90new_hw_segment:
91 if (nr_hw_segs == 1 &&
92 hw_seg_size > rq->bio->bi_hw_front_size)
93 rq->bio->bi_hw_front_size = hw_seg_size;
94 hw_seg_size = BIOVEC_VIRT_START_SIZE(bv) + bv->bv_len;
95 nr_hw_segs++;
96 }
97
98 nr_phys_segs++;
99 bvprv = bv;
100 seg_size = bv->bv_len;
101 highprv = high;
102 }
103
104 if (nr_hw_segs == 1 &&
105 hw_seg_size > rq->bio->bi_hw_front_size)
106 rq->bio->bi_hw_front_size = hw_seg_size;
107 if (hw_seg_size > rq->biotail->bi_hw_back_size)
108 rq->biotail->bi_hw_back_size = hw_seg_size;
109 rq->nr_phys_segments = nr_phys_segs;
110 rq->nr_hw_segments = nr_hw_segs;
111}
112
113void blk_recount_segments(struct request_queue *q, struct bio *bio)
114{
115 struct request rq;
116 struct bio *nxt = bio->bi_next;
117 rq.q = q;
118 rq.bio = rq.biotail = bio;
119 bio->bi_next = NULL;
120 blk_recalc_rq_segments(&rq);
121 bio->bi_next = nxt;
122 bio->bi_phys_segments = rq.nr_phys_segments;
123 bio->bi_hw_segments = rq.nr_hw_segments;
124 bio->bi_flags |= (1 << BIO_SEG_VALID);
125}
126EXPORT_SYMBOL(blk_recount_segments);
127
128static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio,
129 struct bio *nxt)
130{
Nick Piggin75ad23b2008-04-29 14:48:33 +0200131 if (!test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags))
Jens Axboed6d48192008-01-29 14:04:06 +0100132 return 0;
133
134 if (!BIOVEC_PHYS_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)))
135 return 0;
136 if (bio->bi_size + nxt->bi_size > q->max_segment_size)
137 return 0;
138
139 /*
140 * bio and nxt are contigous in memory, check if the queue allows
141 * these two to be merged into one
142 */
143 if (BIO_SEG_BOUNDARY(q, bio, nxt))
144 return 1;
145
146 return 0;
147}
148
149static int blk_hw_contig_segment(struct request_queue *q, struct bio *bio,
150 struct bio *nxt)
151{
Jens Axboe2cdf79c2008-05-07 09:33:55 +0200152 if (!bio_flagged(bio, BIO_SEG_VALID))
Jens Axboed6d48192008-01-29 14:04:06 +0100153 blk_recount_segments(q, bio);
Jens Axboe2cdf79c2008-05-07 09:33:55 +0200154 if (!bio_flagged(nxt, BIO_SEG_VALID))
Jens Axboed6d48192008-01-29 14:04:06 +0100155 blk_recount_segments(q, nxt);
156 if (!BIOVEC_VIRT_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)) ||
157 BIOVEC_VIRT_OVERSIZE(bio->bi_hw_back_size + nxt->bi_hw_front_size))
158 return 0;
159 if (bio->bi_hw_back_size + nxt->bi_hw_front_size > q->max_segment_size)
160 return 0;
161
162 return 1;
163}
164
165/*
166 * map a request to scatterlist, return number of sg entries setup. Caller
167 * must make sure sg can hold rq->nr_phys_segments entries
168 */
169int blk_rq_map_sg(struct request_queue *q, struct request *rq,
170 struct scatterlist *sglist)
171{
172 struct bio_vec *bvec, *bvprv;
173 struct req_iterator iter;
174 struct scatterlist *sg;
175 int nsegs, cluster;
176
177 nsegs = 0;
Nick Piggin75ad23b2008-04-29 14:48:33 +0200178 cluster = test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
Jens Axboed6d48192008-01-29 14:04:06 +0100179
180 /*
181 * for each bio in rq
182 */
183 bvprv = NULL;
184 sg = NULL;
185 rq_for_each_segment(bvec, rq, iter) {
186 int nbytes = bvec->bv_len;
187
188 if (bvprv && cluster) {
189 if (sg->length + nbytes > q->max_segment_size)
190 goto new_segment;
191
192 if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec))
193 goto new_segment;
194 if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec))
195 goto new_segment;
196
197 sg->length += nbytes;
198 } else {
199new_segment:
200 if (!sg)
201 sg = sglist;
202 else {
203 /*
204 * If the driver previously mapped a shorter
205 * list, we could see a termination bit
206 * prematurely unless it fully inits the sg
207 * table on each mapping. We KNOW that there
208 * must be more entries here or the driver
209 * would be buggy, so force clear the
210 * termination bit to avoid doing a full
211 * sg_init_table() in drivers for each command.
212 */
213 sg->page_link &= ~0x02;
214 sg = sg_next(sg);
215 }
216
217 sg_set_page(sg, bvec->bv_page, nbytes, bvec->bv_offset);
218 nsegs++;
219 }
220 bvprv = bvec;
221 } /* segments in rq */
222
FUJITA Tomonorif18573a2008-04-11 12:56:52 +0200223
224 if (unlikely(rq->cmd_flags & REQ_COPY_USER) &&
225 (rq->data_len & q->dma_pad_mask)) {
226 unsigned int pad_len = (q->dma_pad_mask & ~rq->data_len) + 1;
227
228 sg->length += pad_len;
229 rq->extra_len += pad_len;
230 }
231
Tejun Heo2fb98e82008-02-19 11:36:53 +0100232 if (q->dma_drain_size && q->dma_drain_needed(rq)) {
Tejun Heodb0a2e02008-02-19 11:36:55 +0100233 if (rq->cmd_flags & REQ_RW)
234 memset(q->dma_drain_buffer, 0, q->dma_drain_size);
235
Jens Axboed6d48192008-01-29 14:04:06 +0100236 sg->page_link &= ~0x02;
237 sg = sg_next(sg);
238 sg_set_page(sg, virt_to_page(q->dma_drain_buffer),
239 q->dma_drain_size,
240 ((unsigned long)q->dma_drain_buffer) &
241 (PAGE_SIZE - 1));
242 nsegs++;
FUJITA Tomonori7a85f882008-03-04 11:17:11 +0100243 rq->extra_len += q->dma_drain_size;
Jens Axboed6d48192008-01-29 14:04:06 +0100244 }
245
246 if (sg)
247 sg_mark_end(sg);
248
249 return nsegs;
250}
Jens Axboed6d48192008-01-29 14:04:06 +0100251EXPORT_SYMBOL(blk_rq_map_sg);
252
253static inline int ll_new_mergeable(struct request_queue *q,
254 struct request *req,
255 struct bio *bio)
256{
257 int nr_phys_segs = bio_phys_segments(q, bio);
258
259 if (req->nr_phys_segments + nr_phys_segs > q->max_phys_segments) {
260 req->cmd_flags |= REQ_NOMERGE;
261 if (req == q->last_merge)
262 q->last_merge = NULL;
263 return 0;
264 }
265
266 /*
267 * A hw segment is just getting larger, bump just the phys
268 * counter.
269 */
270 req->nr_phys_segments += nr_phys_segs;
271 return 1;
272}
273
274static inline int ll_new_hw_segment(struct request_queue *q,
275 struct request *req,
276 struct bio *bio)
277{
278 int nr_hw_segs = bio_hw_segments(q, bio);
279 int nr_phys_segs = bio_phys_segments(q, bio);
280
281 if (req->nr_hw_segments + nr_hw_segs > q->max_hw_segments
282 || req->nr_phys_segments + nr_phys_segs > q->max_phys_segments) {
283 req->cmd_flags |= REQ_NOMERGE;
284 if (req == q->last_merge)
285 q->last_merge = NULL;
286 return 0;
287 }
288
289 /*
290 * This will form the start of a new hw segment. Bump both
291 * counters.
292 */
293 req->nr_hw_segments += nr_hw_segs;
294 req->nr_phys_segments += nr_phys_segs;
295 return 1;
296}
297
298int ll_back_merge_fn(struct request_queue *q, struct request *req,
299 struct bio *bio)
300{
301 unsigned short max_sectors;
302 int len;
303
304 if (unlikely(blk_pc_request(req)))
305 max_sectors = q->max_hw_sectors;
306 else
307 max_sectors = q->max_sectors;
308
309 if (req->nr_sectors + bio_sectors(bio) > max_sectors) {
310 req->cmd_flags |= REQ_NOMERGE;
311 if (req == q->last_merge)
312 q->last_merge = NULL;
313 return 0;
314 }
Jens Axboe2cdf79c2008-05-07 09:33:55 +0200315 if (!bio_flagged(req->biotail, BIO_SEG_VALID))
Jens Axboed6d48192008-01-29 14:04:06 +0100316 blk_recount_segments(q, req->biotail);
Jens Axboe2cdf79c2008-05-07 09:33:55 +0200317 if (!bio_flagged(bio, BIO_SEG_VALID))
Jens Axboed6d48192008-01-29 14:04:06 +0100318 blk_recount_segments(q, bio);
319 len = req->biotail->bi_hw_back_size + bio->bi_hw_front_size;
Jens Axboe6728cb02008-01-31 13:03:55 +0100320 if (BIOVEC_VIRT_MERGEABLE(__BVEC_END(req->biotail), __BVEC_START(bio))
321 && !BIOVEC_VIRT_OVERSIZE(len)) {
Jens Axboed6d48192008-01-29 14:04:06 +0100322 int mergeable = ll_new_mergeable(q, req, bio);
323
324 if (mergeable) {
325 if (req->nr_hw_segments == 1)
326 req->bio->bi_hw_front_size = len;
327 if (bio->bi_hw_segments == 1)
328 bio->bi_hw_back_size = len;
329 }
330 return mergeable;
331 }
332
333 return ll_new_hw_segment(q, req, bio);
334}
335
Jens Axboe6728cb02008-01-31 13:03:55 +0100336int ll_front_merge_fn(struct request_queue *q, struct request *req,
Jens Axboed6d48192008-01-29 14:04:06 +0100337 struct bio *bio)
338{
339 unsigned short max_sectors;
340 int len;
341
342 if (unlikely(blk_pc_request(req)))
343 max_sectors = q->max_hw_sectors;
344 else
345 max_sectors = q->max_sectors;
346
347
348 if (req->nr_sectors + bio_sectors(bio) > max_sectors) {
349 req->cmd_flags |= REQ_NOMERGE;
350 if (req == q->last_merge)
351 q->last_merge = NULL;
352 return 0;
353 }
354 len = bio->bi_hw_back_size + req->bio->bi_hw_front_size;
Jens Axboe2cdf79c2008-05-07 09:33:55 +0200355 if (!bio_flagged(bio, BIO_SEG_VALID))
Jens Axboed6d48192008-01-29 14:04:06 +0100356 blk_recount_segments(q, bio);
Jens Axboe2cdf79c2008-05-07 09:33:55 +0200357 if (!bio_flagged(req->bio, BIO_SEG_VALID))
Jens Axboed6d48192008-01-29 14:04:06 +0100358 blk_recount_segments(q, req->bio);
359 if (BIOVEC_VIRT_MERGEABLE(__BVEC_END(bio), __BVEC_START(req->bio)) &&
360 !BIOVEC_VIRT_OVERSIZE(len)) {
361 int mergeable = ll_new_mergeable(q, req, bio);
362
363 if (mergeable) {
364 if (bio->bi_hw_segments == 1)
365 bio->bi_hw_front_size = len;
366 if (req->nr_hw_segments == 1)
367 req->biotail->bi_hw_back_size = len;
368 }
369 return mergeable;
370 }
371
372 return ll_new_hw_segment(q, req, bio);
373}
374
375static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
376 struct request *next)
377{
378 int total_phys_segments;
379 int total_hw_segments;
380
381 /*
382 * First check if the either of the requests are re-queued
383 * requests. Can't merge them if they are.
384 */
385 if (req->special || next->special)
386 return 0;
387
388 /*
389 * Will it become too large?
390 */
391 if ((req->nr_sectors + next->nr_sectors) > q->max_sectors)
392 return 0;
393
394 total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
395 if (blk_phys_contig_segment(q, req->biotail, next->bio))
396 total_phys_segments--;
397
398 if (total_phys_segments > q->max_phys_segments)
399 return 0;
400
401 total_hw_segments = req->nr_hw_segments + next->nr_hw_segments;
402 if (blk_hw_contig_segment(q, req->biotail, next->bio)) {
Jens Axboe6728cb02008-01-31 13:03:55 +0100403 int len = req->biotail->bi_hw_back_size +
404 next->bio->bi_hw_front_size;
Jens Axboed6d48192008-01-29 14:04:06 +0100405 /*
406 * propagate the combined length to the end of the requests
407 */
408 if (req->nr_hw_segments == 1)
409 req->bio->bi_hw_front_size = len;
410 if (next->nr_hw_segments == 1)
411 next->biotail->bi_hw_back_size = len;
412 total_hw_segments--;
413 }
414
415 if (total_hw_segments > q->max_hw_segments)
416 return 0;
417
418 /* Merge is OK... */
419 req->nr_phys_segments = total_phys_segments;
420 req->nr_hw_segments = total_hw_segments;
421 return 1;
422}
423
424/*
425 * Has to be called with the request spinlock acquired
426 */
427static int attempt_merge(struct request_queue *q, struct request *req,
428 struct request *next)
429{
430 if (!rq_mergeable(req) || !rq_mergeable(next))
431 return 0;
432
433 /*
434 * not contiguous
435 */
436 if (req->sector + req->nr_sectors != next->sector)
437 return 0;
438
439 if (rq_data_dir(req) != rq_data_dir(next)
440 || req->rq_disk != next->rq_disk
441 || next->special)
442 return 0;
443
444 /*
445 * If we are allowed to merge, then append bio list
446 * from next to rq and release next. merge_requests_fn
447 * will have updated segment counts, update sector
448 * counts here.
449 */
450 if (!ll_merge_requests_fn(q, req, next))
451 return 0;
452
453 /*
454 * At this point we have either done a back merge
455 * or front merge. We need the smaller start_time of
456 * the merged requests to be the current request
457 * for accounting purposes.
458 */
459 if (time_after(req->start_time, next->start_time))
460 req->start_time = next->start_time;
461
462 req->biotail->bi_next = next->bio;
463 req->biotail = next->biotail;
464
465 req->nr_sectors = req->hard_nr_sectors += next->hard_nr_sectors;
466
467 elv_merge_requests(q, req, next);
468
469 if (req->rq_disk) {
Jerome Marchand6f2576a2008-02-08 11:04:35 +0100470 struct hd_struct *part
471 = get_part(req->rq_disk, req->sector);
Jens Axboed6d48192008-01-29 14:04:06 +0100472 disk_round_stats(req->rq_disk);
473 req->rq_disk->in_flight--;
Jerome Marchand6f2576a2008-02-08 11:04:35 +0100474 if (part) {
475 part_round_stats(part);
476 part->in_flight--;
477 }
Jens Axboed6d48192008-01-29 14:04:06 +0100478 }
479
480 req->ioprio = ioprio_best(req->ioprio, next->ioprio);
481
482 __blk_put_request(q, next);
483 return 1;
484}
485
486int attempt_back_merge(struct request_queue *q, struct request *rq)
487{
488 struct request *next = elv_latter_request(q, rq);
489
490 if (next)
491 return attempt_merge(q, rq, next);
492
493 return 0;
494}
495
496int attempt_front_merge(struct request_queue *q, struct request *rq)
497{
498 struct request *prev = elv_former_request(q, rq);
499
500 if (prev)
501 return attempt_merge(q, prev, rq);
502
503 return 0;
504}