Commit | Line | Data |
---|---|---|
d6d48196 JA |
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 | void blk_recalc_rq_sectors(struct request *rq, int nsect) | |
13 | { | |
e17fc0a1 | 14 | if (blk_fs_request(rq) || blk_discard_rq(rq)) { |
d6d48196 JA |
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) { | |
6728cb0e | 35 | printk(KERN_ERR "blk: request botched\n"); |
d6d48196 JA |
36 | rq->nr_sectors = rq->current_nr_sectors; |
37 | } | |
38 | } | |
39 | } | |
40 | ||
41 | void blk_recalc_rq_segments(struct request *rq) | |
42 | { | |
43 | int nr_phys_segs; | |
d6d48196 | 44 | unsigned int phys_size; |
d6d48196 JA |
45 | struct bio_vec *bv, *bvprv = NULL; |
46 | int seg_size; | |
d6d48196 JA |
47 | int cluster; |
48 | struct req_iterator iter; | |
49 | int high, highprv = 1; | |
50 | struct request_queue *q = rq->q; | |
51 | ||
52 | if (!rq->bio) | |
53 | return; | |
54 | ||
75ad23bc | 55 | cluster = test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags); |
5df97b91 MP |
56 | seg_size = 0; |
57 | phys_size = nr_phys_segs = 0; | |
d6d48196 JA |
58 | rq_for_each_segment(bv, rq, iter) { |
59 | /* | |
60 | * the trick here is making sure that a high page is never | |
61 | * considered part of another segment, since that might | |
62 | * change with the bounce page. | |
63 | */ | |
64 | high = page_to_pfn(bv->bv_page) > q->bounce_pfn; | |
65 | if (high || highprv) | |
b8b3e16c | 66 | goto new_segment; |
d6d48196 JA |
67 | if (cluster) { |
68 | if (seg_size + bv->bv_len > q->max_segment_size) | |
69 | goto new_segment; | |
70 | if (!BIOVEC_PHYS_MERGEABLE(bvprv, bv)) | |
71 | goto new_segment; | |
72 | if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bv)) | |
73 | goto new_segment; | |
d6d48196 JA |
74 | |
75 | seg_size += bv->bv_len; | |
d6d48196 JA |
76 | bvprv = bv; |
77 | continue; | |
78 | } | |
79 | new_segment: | |
86771427 FT |
80 | if (nr_phys_segs == 1 && seg_size > rq->bio->bi_seg_front_size) |
81 | rq->bio->bi_seg_front_size = seg_size; | |
82 | ||
d6d48196 JA |
83 | nr_phys_segs++; |
84 | bvprv = bv; | |
85 | seg_size = bv->bv_len; | |
86 | highprv = high; | |
87 | } | |
88 | ||
86771427 FT |
89 | if (nr_phys_segs == 1 && seg_size > rq->bio->bi_seg_front_size) |
90 | rq->bio->bi_seg_front_size = seg_size; | |
91 | if (seg_size > rq->biotail->bi_seg_back_size) | |
92 | rq->biotail->bi_seg_back_size = seg_size; | |
93 | ||
d6d48196 | 94 | rq->nr_phys_segments = nr_phys_segs; |
d6d48196 JA |
95 | } |
96 | ||
97 | void blk_recount_segments(struct request_queue *q, struct bio *bio) | |
98 | { | |
99 | struct request rq; | |
100 | struct bio *nxt = bio->bi_next; | |
101 | rq.q = q; | |
102 | rq.bio = rq.biotail = bio; | |
103 | bio->bi_next = NULL; | |
104 | blk_recalc_rq_segments(&rq); | |
105 | bio->bi_next = nxt; | |
106 | bio->bi_phys_segments = rq.nr_phys_segments; | |
d6d48196 JA |
107 | bio->bi_flags |= (1 << BIO_SEG_VALID); |
108 | } | |
109 | EXPORT_SYMBOL(blk_recount_segments); | |
110 | ||
111 | static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio, | |
112 | struct bio *nxt) | |
113 | { | |
75ad23bc | 114 | if (!test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags)) |
d6d48196 JA |
115 | return 0; |
116 | ||
86771427 FT |
117 | if (bio->bi_seg_back_size + nxt->bi_seg_front_size > |
118 | q->max_segment_size) | |
d6d48196 JA |
119 | return 0; |
120 | ||
e17fc0a1 DW |
121 | if (!bio_has_data(bio)) |
122 | return 1; | |
123 | ||
124 | if (!BIOVEC_PHYS_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt))) | |
125 | return 0; | |
126 | ||
d6d48196 | 127 | /* |
e17fc0a1 | 128 | * bio and nxt are contiguous in memory; check if the queue allows |
d6d48196 JA |
129 | * these two to be merged into one |
130 | */ | |
131 | if (BIO_SEG_BOUNDARY(q, bio, nxt)) | |
132 | return 1; | |
133 | ||
134 | return 0; | |
135 | } | |
136 | ||
d6d48196 JA |
137 | /* |
138 | * map a request to scatterlist, return number of sg entries setup. Caller | |
139 | * must make sure sg can hold rq->nr_phys_segments entries | |
140 | */ | |
141 | int blk_rq_map_sg(struct request_queue *q, struct request *rq, | |
142 | struct scatterlist *sglist) | |
143 | { | |
144 | struct bio_vec *bvec, *bvprv; | |
145 | struct req_iterator iter; | |
146 | struct scatterlist *sg; | |
147 | int nsegs, cluster; | |
148 | ||
149 | nsegs = 0; | |
75ad23bc | 150 | cluster = test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags); |
d6d48196 JA |
151 | |
152 | /* | |
153 | * for each bio in rq | |
154 | */ | |
155 | bvprv = NULL; | |
156 | sg = NULL; | |
157 | rq_for_each_segment(bvec, rq, iter) { | |
158 | int nbytes = bvec->bv_len; | |
159 | ||
160 | if (bvprv && cluster) { | |
161 | if (sg->length + nbytes > q->max_segment_size) | |
162 | goto new_segment; | |
163 | ||
164 | if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec)) | |
165 | goto new_segment; | |
166 | if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec)) | |
167 | goto new_segment; | |
168 | ||
169 | sg->length += nbytes; | |
170 | } else { | |
171 | new_segment: | |
172 | if (!sg) | |
173 | sg = sglist; | |
174 | else { | |
175 | /* | |
176 | * If the driver previously mapped a shorter | |
177 | * list, we could see a termination bit | |
178 | * prematurely unless it fully inits the sg | |
179 | * table on each mapping. We KNOW that there | |
180 | * must be more entries here or the driver | |
181 | * would be buggy, so force clear the | |
182 | * termination bit to avoid doing a full | |
183 | * sg_init_table() in drivers for each command. | |
184 | */ | |
185 | sg->page_link &= ~0x02; | |
186 | sg = sg_next(sg); | |
187 | } | |
188 | ||
189 | sg_set_page(sg, bvec->bv_page, nbytes, bvec->bv_offset); | |
190 | nsegs++; | |
191 | } | |
192 | bvprv = bvec; | |
193 | } /* segments in rq */ | |
194 | ||
f18573ab FT |
195 | |
196 | if (unlikely(rq->cmd_flags & REQ_COPY_USER) && | |
197 | (rq->data_len & q->dma_pad_mask)) { | |
198 | unsigned int pad_len = (q->dma_pad_mask & ~rq->data_len) + 1; | |
199 | ||
200 | sg->length += pad_len; | |
201 | rq->extra_len += pad_len; | |
202 | } | |
203 | ||
2fb98e84 | 204 | if (q->dma_drain_size && q->dma_drain_needed(rq)) { |
db0a2e00 TH |
205 | if (rq->cmd_flags & REQ_RW) |
206 | memset(q->dma_drain_buffer, 0, q->dma_drain_size); | |
207 | ||
d6d48196 JA |
208 | sg->page_link &= ~0x02; |
209 | sg = sg_next(sg); | |
210 | sg_set_page(sg, virt_to_page(q->dma_drain_buffer), | |
211 | q->dma_drain_size, | |
212 | ((unsigned long)q->dma_drain_buffer) & | |
213 | (PAGE_SIZE - 1)); | |
214 | nsegs++; | |
7a85f889 | 215 | rq->extra_len += q->dma_drain_size; |
d6d48196 JA |
216 | } |
217 | ||
218 | if (sg) | |
219 | sg_mark_end(sg); | |
220 | ||
221 | return nsegs; | |
222 | } | |
d6d48196 JA |
223 | EXPORT_SYMBOL(blk_rq_map_sg); |
224 | ||
d6d48196 JA |
225 | static inline int ll_new_hw_segment(struct request_queue *q, |
226 | struct request *req, | |
227 | struct bio *bio) | |
228 | { | |
d6d48196 JA |
229 | int nr_phys_segs = bio_phys_segments(q, bio); |
230 | ||
5df97b91 | 231 | if (req->nr_phys_segments + nr_phys_segs > q->max_hw_segments |
d6d48196 JA |
232 | || req->nr_phys_segments + nr_phys_segs > q->max_phys_segments) { |
233 | req->cmd_flags |= REQ_NOMERGE; | |
234 | if (req == q->last_merge) | |
235 | q->last_merge = NULL; | |
236 | return 0; | |
237 | } | |
238 | ||
239 | /* | |
240 | * This will form the start of a new hw segment. Bump both | |
241 | * counters. | |
242 | */ | |
d6d48196 JA |
243 | req->nr_phys_segments += nr_phys_segs; |
244 | return 1; | |
245 | } | |
246 | ||
247 | int ll_back_merge_fn(struct request_queue *q, struct request *req, | |
248 | struct bio *bio) | |
249 | { | |
250 | unsigned short max_sectors; | |
d6d48196 JA |
251 | |
252 | if (unlikely(blk_pc_request(req))) | |
253 | max_sectors = q->max_hw_sectors; | |
254 | else | |
255 | max_sectors = q->max_sectors; | |
256 | ||
257 | if (req->nr_sectors + bio_sectors(bio) > max_sectors) { | |
258 | req->cmd_flags |= REQ_NOMERGE; | |
259 | if (req == q->last_merge) | |
260 | q->last_merge = NULL; | |
261 | return 0; | |
262 | } | |
2cdf79ca | 263 | if (!bio_flagged(req->biotail, BIO_SEG_VALID)) |
d6d48196 | 264 | blk_recount_segments(q, req->biotail); |
2cdf79ca | 265 | if (!bio_flagged(bio, BIO_SEG_VALID)) |
d6d48196 | 266 | blk_recount_segments(q, bio); |
d6d48196 JA |
267 | |
268 | return ll_new_hw_segment(q, req, bio); | |
269 | } | |
270 | ||
6728cb0e | 271 | int ll_front_merge_fn(struct request_queue *q, struct request *req, |
d6d48196 JA |
272 | struct bio *bio) |
273 | { | |
274 | unsigned short max_sectors; | |
d6d48196 JA |
275 | |
276 | if (unlikely(blk_pc_request(req))) | |
277 | max_sectors = q->max_hw_sectors; | |
278 | else | |
279 | max_sectors = q->max_sectors; | |
280 | ||
281 | ||
282 | if (req->nr_sectors + bio_sectors(bio) > max_sectors) { | |
283 | req->cmd_flags |= REQ_NOMERGE; | |
284 | if (req == q->last_merge) | |
285 | q->last_merge = NULL; | |
286 | return 0; | |
287 | } | |
2cdf79ca | 288 | if (!bio_flagged(bio, BIO_SEG_VALID)) |
d6d48196 | 289 | blk_recount_segments(q, bio); |
2cdf79ca | 290 | if (!bio_flagged(req->bio, BIO_SEG_VALID)) |
d6d48196 | 291 | blk_recount_segments(q, req->bio); |
d6d48196 JA |
292 | |
293 | return ll_new_hw_segment(q, req, bio); | |
294 | } | |
295 | ||
296 | static int ll_merge_requests_fn(struct request_queue *q, struct request *req, | |
297 | struct request *next) | |
298 | { | |
299 | int total_phys_segments; | |
86771427 FT |
300 | unsigned int seg_size = |
301 | req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size; | |
d6d48196 JA |
302 | |
303 | /* | |
304 | * First check if the either of the requests are re-queued | |
305 | * requests. Can't merge them if they are. | |
306 | */ | |
307 | if (req->special || next->special) | |
308 | return 0; | |
309 | ||
310 | /* | |
311 | * Will it become too large? | |
312 | */ | |
313 | if ((req->nr_sectors + next->nr_sectors) > q->max_sectors) | |
314 | return 0; | |
315 | ||
316 | total_phys_segments = req->nr_phys_segments + next->nr_phys_segments; | |
86771427 FT |
317 | if (blk_phys_contig_segment(q, req->biotail, next->bio)) { |
318 | if (req->nr_phys_segments == 1) | |
319 | req->bio->bi_seg_front_size = seg_size; | |
320 | if (next->nr_phys_segments == 1) | |
321 | next->biotail->bi_seg_back_size = seg_size; | |
d6d48196 | 322 | total_phys_segments--; |
86771427 | 323 | } |
d6d48196 JA |
324 | |
325 | if (total_phys_segments > q->max_phys_segments) | |
326 | return 0; | |
327 | ||
5df97b91 | 328 | if (total_phys_segments > q->max_hw_segments) |
d6d48196 JA |
329 | return 0; |
330 | ||
331 | /* Merge is OK... */ | |
332 | req->nr_phys_segments = total_phys_segments; | |
d6d48196 JA |
333 | return 1; |
334 | } | |
335 | ||
336 | /* | |
337 | * Has to be called with the request spinlock acquired | |
338 | */ | |
339 | static int attempt_merge(struct request_queue *q, struct request *req, | |
340 | struct request *next) | |
341 | { | |
342 | if (!rq_mergeable(req) || !rq_mergeable(next)) | |
343 | return 0; | |
344 | ||
345 | /* | |
346 | * not contiguous | |
347 | */ | |
348 | if (req->sector + req->nr_sectors != next->sector) | |
349 | return 0; | |
350 | ||
351 | if (rq_data_dir(req) != rq_data_dir(next) | |
352 | || req->rq_disk != next->rq_disk | |
353 | || next->special) | |
354 | return 0; | |
355 | ||
7ba1ba12 MP |
356 | if (blk_integrity_rq(req) != blk_integrity_rq(next)) |
357 | return 0; | |
358 | ||
d6d48196 JA |
359 | /* |
360 | * If we are allowed to merge, then append bio list | |
361 | * from next to rq and release next. merge_requests_fn | |
362 | * will have updated segment counts, update sector | |
363 | * counts here. | |
364 | */ | |
365 | if (!ll_merge_requests_fn(q, req, next)) | |
366 | return 0; | |
367 | ||
368 | /* | |
369 | * At this point we have either done a back merge | |
370 | * or front merge. We need the smaller start_time of | |
371 | * the merged requests to be the current request | |
372 | * for accounting purposes. | |
373 | */ | |
374 | if (time_after(req->start_time, next->start_time)) | |
375 | req->start_time = next->start_time; | |
376 | ||
377 | req->biotail->bi_next = next->bio; | |
378 | req->biotail = next->biotail; | |
379 | ||
380 | req->nr_sectors = req->hard_nr_sectors += next->hard_nr_sectors; | |
381 | ||
382 | elv_merge_requests(q, req, next); | |
383 | ||
384 | if (req->rq_disk) { | |
e71bf0d0 | 385 | struct hd_struct *part; |
c9959059 | 386 | int cpu; |
e71bf0d0 | 387 | |
074a7aca | 388 | cpu = part_stat_lock(); |
e71bf0d0 | 389 | part = disk_map_sector_rcu(req->rq_disk, req->sector); |
c9959059 | 390 | |
074a7aca TH |
391 | part_round_stats(cpu, part); |
392 | part_dec_in_flight(part); | |
e71bf0d0 | 393 | |
074a7aca | 394 | part_stat_unlock(); |
d6d48196 JA |
395 | } |
396 | ||
397 | req->ioprio = ioprio_best(req->ioprio, next->ioprio); | |
ab780f1e JA |
398 | if (blk_rq_cpu_valid(next)) |
399 | req->cpu = next->cpu; | |
d6d48196 JA |
400 | |
401 | __blk_put_request(q, next); | |
402 | return 1; | |
403 | } | |
404 | ||
405 | int attempt_back_merge(struct request_queue *q, struct request *rq) | |
406 | { | |
407 | struct request *next = elv_latter_request(q, rq); | |
408 | ||
409 | if (next) | |
410 | return attempt_merge(q, rq, next); | |
411 | ||
412 | return 0; | |
413 | } | |
414 | ||
415 | int attempt_front_merge(struct request_queue *q, struct request *rq) | |
416 | { | |
417 | struct request *prev = elv_former_request(q, rq); | |
418 | ||
419 | if (prev) | |
420 | return attempt_merge(q, prev, rq); | |
421 | ||
422 | return 0; | |
423 | } |