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: | |
d6d48196 JA |
80 | nr_phys_segs++; |
81 | bvprv = bv; | |
82 | seg_size = bv->bv_len; | |
83 | highprv = high; | |
84 | } | |
85 | ||
d6d48196 | 86 | rq->nr_phys_segments = nr_phys_segs; |
d6d48196 JA |
87 | } |
88 | ||
89 | void blk_recount_segments(struct request_queue *q, struct bio *bio) | |
90 | { | |
91 | struct request rq; | |
92 | struct bio *nxt = bio->bi_next; | |
93 | rq.q = q; | |
94 | rq.bio = rq.biotail = bio; | |
95 | bio->bi_next = NULL; | |
96 | blk_recalc_rq_segments(&rq); | |
97 | bio->bi_next = nxt; | |
98 | bio->bi_phys_segments = rq.nr_phys_segments; | |
d6d48196 JA |
99 | bio->bi_flags |= (1 << BIO_SEG_VALID); |
100 | } | |
101 | EXPORT_SYMBOL(blk_recount_segments); | |
102 | ||
103 | static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio, | |
104 | struct bio *nxt) | |
105 | { | |
75ad23bc | 106 | if (!test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags)) |
d6d48196 JA |
107 | return 0; |
108 | ||
d6d48196 JA |
109 | if (bio->bi_size + nxt->bi_size > q->max_segment_size) |
110 | return 0; | |
111 | ||
e17fc0a1 DW |
112 | if (!bio_has_data(bio)) |
113 | return 1; | |
114 | ||
115 | if (!BIOVEC_PHYS_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt))) | |
116 | return 0; | |
117 | ||
d6d48196 | 118 | /* |
e17fc0a1 | 119 | * bio and nxt are contiguous in memory; check if the queue allows |
d6d48196 JA |
120 | * these two to be merged into one |
121 | */ | |
122 | if (BIO_SEG_BOUNDARY(q, bio, nxt)) | |
123 | return 1; | |
124 | ||
125 | return 0; | |
126 | } | |
127 | ||
d6d48196 JA |
128 | /* |
129 | * map a request to scatterlist, return number of sg entries setup. Caller | |
130 | * must make sure sg can hold rq->nr_phys_segments entries | |
131 | */ | |
132 | int blk_rq_map_sg(struct request_queue *q, struct request *rq, | |
133 | struct scatterlist *sglist) | |
134 | { | |
135 | struct bio_vec *bvec, *bvprv; | |
136 | struct req_iterator iter; | |
137 | struct scatterlist *sg; | |
138 | int nsegs, cluster; | |
139 | ||
140 | nsegs = 0; | |
75ad23bc | 141 | cluster = test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags); |
d6d48196 JA |
142 | |
143 | /* | |
144 | * for each bio in rq | |
145 | */ | |
146 | bvprv = NULL; | |
147 | sg = NULL; | |
148 | rq_for_each_segment(bvec, rq, iter) { | |
149 | int nbytes = bvec->bv_len; | |
150 | ||
151 | if (bvprv && cluster) { | |
152 | if (sg->length + nbytes > q->max_segment_size) | |
153 | goto new_segment; | |
154 | ||
155 | if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec)) | |
156 | goto new_segment; | |
157 | if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec)) | |
158 | goto new_segment; | |
159 | ||
160 | sg->length += nbytes; | |
161 | } else { | |
162 | new_segment: | |
163 | if (!sg) | |
164 | sg = sglist; | |
165 | else { | |
166 | /* | |
167 | * If the driver previously mapped a shorter | |
168 | * list, we could see a termination bit | |
169 | * prematurely unless it fully inits the sg | |
170 | * table on each mapping. We KNOW that there | |
171 | * must be more entries here or the driver | |
172 | * would be buggy, so force clear the | |
173 | * termination bit to avoid doing a full | |
174 | * sg_init_table() in drivers for each command. | |
175 | */ | |
176 | sg->page_link &= ~0x02; | |
177 | sg = sg_next(sg); | |
178 | } | |
179 | ||
180 | sg_set_page(sg, bvec->bv_page, nbytes, bvec->bv_offset); | |
181 | nsegs++; | |
182 | } | |
183 | bvprv = bvec; | |
184 | } /* segments in rq */ | |
185 | ||
f18573ab FT |
186 | |
187 | if (unlikely(rq->cmd_flags & REQ_COPY_USER) && | |
188 | (rq->data_len & q->dma_pad_mask)) { | |
189 | unsigned int pad_len = (q->dma_pad_mask & ~rq->data_len) + 1; | |
190 | ||
191 | sg->length += pad_len; | |
192 | rq->extra_len += pad_len; | |
193 | } | |
194 | ||
2fb98e84 | 195 | if (q->dma_drain_size && q->dma_drain_needed(rq)) { |
db0a2e00 TH |
196 | if (rq->cmd_flags & REQ_RW) |
197 | memset(q->dma_drain_buffer, 0, q->dma_drain_size); | |
198 | ||
d6d48196 JA |
199 | sg->page_link &= ~0x02; |
200 | sg = sg_next(sg); | |
201 | sg_set_page(sg, virt_to_page(q->dma_drain_buffer), | |
202 | q->dma_drain_size, | |
203 | ((unsigned long)q->dma_drain_buffer) & | |
204 | (PAGE_SIZE - 1)); | |
205 | nsegs++; | |
7a85f889 | 206 | rq->extra_len += q->dma_drain_size; |
d6d48196 JA |
207 | } |
208 | ||
209 | if (sg) | |
210 | sg_mark_end(sg); | |
211 | ||
212 | return nsegs; | |
213 | } | |
d6d48196 JA |
214 | EXPORT_SYMBOL(blk_rq_map_sg); |
215 | ||
216 | static inline int ll_new_mergeable(struct request_queue *q, | |
217 | struct request *req, | |
218 | struct bio *bio) | |
219 | { | |
220 | int nr_phys_segs = bio_phys_segments(q, bio); | |
221 | ||
222 | if (req->nr_phys_segments + nr_phys_segs > q->max_phys_segments) { | |
223 | req->cmd_flags |= REQ_NOMERGE; | |
224 | if (req == q->last_merge) | |
225 | q->last_merge = NULL; | |
226 | return 0; | |
227 | } | |
228 | ||
229 | /* | |
230 | * A hw segment is just getting larger, bump just the phys | |
231 | * counter. | |
232 | */ | |
233 | req->nr_phys_segments += nr_phys_segs; | |
234 | return 1; | |
235 | } | |
236 | ||
237 | static inline int ll_new_hw_segment(struct request_queue *q, | |
238 | struct request *req, | |
239 | struct bio *bio) | |
240 | { | |
d6d48196 JA |
241 | int nr_phys_segs = bio_phys_segments(q, bio); |
242 | ||
5df97b91 | 243 | if (req->nr_phys_segments + nr_phys_segs > q->max_hw_segments |
d6d48196 JA |
244 | || req->nr_phys_segments + nr_phys_segs > q->max_phys_segments) { |
245 | req->cmd_flags |= REQ_NOMERGE; | |
246 | if (req == q->last_merge) | |
247 | q->last_merge = NULL; | |
248 | return 0; | |
249 | } | |
250 | ||
251 | /* | |
252 | * This will form the start of a new hw segment. Bump both | |
253 | * counters. | |
254 | */ | |
d6d48196 JA |
255 | req->nr_phys_segments += nr_phys_segs; |
256 | return 1; | |
257 | } | |
258 | ||
259 | int ll_back_merge_fn(struct request_queue *q, struct request *req, | |
260 | struct bio *bio) | |
261 | { | |
262 | unsigned short max_sectors; | |
d6d48196 JA |
263 | |
264 | if (unlikely(blk_pc_request(req))) | |
265 | max_sectors = q->max_hw_sectors; | |
266 | else | |
267 | max_sectors = q->max_sectors; | |
268 | ||
269 | if (req->nr_sectors + bio_sectors(bio) > max_sectors) { | |
270 | req->cmd_flags |= REQ_NOMERGE; | |
271 | if (req == q->last_merge) | |
272 | q->last_merge = NULL; | |
273 | return 0; | |
274 | } | |
2cdf79ca | 275 | if (!bio_flagged(req->biotail, BIO_SEG_VALID)) |
d6d48196 | 276 | blk_recount_segments(q, req->biotail); |
2cdf79ca | 277 | if (!bio_flagged(bio, BIO_SEG_VALID)) |
d6d48196 | 278 | blk_recount_segments(q, bio); |
d6d48196 JA |
279 | |
280 | return ll_new_hw_segment(q, req, bio); | |
281 | } | |
282 | ||
6728cb0e | 283 | int ll_front_merge_fn(struct request_queue *q, struct request *req, |
d6d48196 JA |
284 | struct bio *bio) |
285 | { | |
286 | unsigned short max_sectors; | |
d6d48196 JA |
287 | |
288 | if (unlikely(blk_pc_request(req))) | |
289 | max_sectors = q->max_hw_sectors; | |
290 | else | |
291 | max_sectors = q->max_sectors; | |
292 | ||
293 | ||
294 | if (req->nr_sectors + bio_sectors(bio) > max_sectors) { | |
295 | req->cmd_flags |= REQ_NOMERGE; | |
296 | if (req == q->last_merge) | |
297 | q->last_merge = NULL; | |
298 | return 0; | |
299 | } | |
2cdf79ca | 300 | if (!bio_flagged(bio, BIO_SEG_VALID)) |
d6d48196 | 301 | blk_recount_segments(q, bio); |
2cdf79ca | 302 | if (!bio_flagged(req->bio, BIO_SEG_VALID)) |
d6d48196 | 303 | blk_recount_segments(q, req->bio); |
d6d48196 JA |
304 | |
305 | return ll_new_hw_segment(q, req, bio); | |
306 | } | |
307 | ||
308 | static int ll_merge_requests_fn(struct request_queue *q, struct request *req, | |
309 | struct request *next) | |
310 | { | |
311 | int total_phys_segments; | |
d6d48196 JA |
312 | |
313 | /* | |
314 | * First check if the either of the requests are re-queued | |
315 | * requests. Can't merge them if they are. | |
316 | */ | |
317 | if (req->special || next->special) | |
318 | return 0; | |
319 | ||
320 | /* | |
321 | * Will it become too large? | |
322 | */ | |
323 | if ((req->nr_sectors + next->nr_sectors) > q->max_sectors) | |
324 | return 0; | |
325 | ||
326 | total_phys_segments = req->nr_phys_segments + next->nr_phys_segments; | |
327 | if (blk_phys_contig_segment(q, req->biotail, next->bio)) | |
328 | total_phys_segments--; | |
329 | ||
330 | if (total_phys_segments > q->max_phys_segments) | |
331 | return 0; | |
332 | ||
5df97b91 | 333 | if (total_phys_segments > q->max_hw_segments) |
d6d48196 JA |
334 | return 0; |
335 | ||
336 | /* Merge is OK... */ | |
337 | req->nr_phys_segments = total_phys_segments; | |
d6d48196 JA |
338 | return 1; |
339 | } | |
340 | ||
341 | /* | |
342 | * Has to be called with the request spinlock acquired | |
343 | */ | |
344 | static int attempt_merge(struct request_queue *q, struct request *req, | |
345 | struct request *next) | |
346 | { | |
347 | if (!rq_mergeable(req) || !rq_mergeable(next)) | |
348 | return 0; | |
349 | ||
350 | /* | |
351 | * not contiguous | |
352 | */ | |
353 | if (req->sector + req->nr_sectors != next->sector) | |
354 | return 0; | |
355 | ||
356 | if (rq_data_dir(req) != rq_data_dir(next) | |
357 | || req->rq_disk != next->rq_disk | |
358 | || next->special) | |
359 | return 0; | |
360 | ||
7ba1ba12 MP |
361 | if (blk_integrity_rq(req) != blk_integrity_rq(next)) |
362 | return 0; | |
363 | ||
d6d48196 JA |
364 | /* |
365 | * If we are allowed to merge, then append bio list | |
366 | * from next to rq and release next. merge_requests_fn | |
367 | * will have updated segment counts, update sector | |
368 | * counts here. | |
369 | */ | |
370 | if (!ll_merge_requests_fn(q, req, next)) | |
371 | return 0; | |
372 | ||
373 | /* | |
374 | * At this point we have either done a back merge | |
375 | * or front merge. We need the smaller start_time of | |
376 | * the merged requests to be the current request | |
377 | * for accounting purposes. | |
378 | */ | |
379 | if (time_after(req->start_time, next->start_time)) | |
380 | req->start_time = next->start_time; | |
381 | ||
382 | req->biotail->bi_next = next->bio; | |
383 | req->biotail = next->biotail; | |
384 | ||
385 | req->nr_sectors = req->hard_nr_sectors += next->hard_nr_sectors; | |
386 | ||
387 | elv_merge_requests(q, req, next); | |
388 | ||
389 | if (req->rq_disk) { | |
e71bf0d0 | 390 | struct hd_struct *part; |
c9959059 | 391 | int cpu; |
e71bf0d0 | 392 | |
074a7aca | 393 | cpu = part_stat_lock(); |
e71bf0d0 | 394 | part = disk_map_sector_rcu(req->rq_disk, req->sector); |
c9959059 | 395 | |
074a7aca TH |
396 | part_round_stats(cpu, part); |
397 | part_dec_in_flight(part); | |
e71bf0d0 | 398 | |
074a7aca | 399 | part_stat_unlock(); |
d6d48196 JA |
400 | } |
401 | ||
402 | req->ioprio = ioprio_best(req->ioprio, next->ioprio); | |
ab780f1e JA |
403 | if (blk_rq_cpu_valid(next)) |
404 | req->cpu = next->cpu; | |
d6d48196 JA |
405 | |
406 | __blk_put_request(q, next); | |
407 | return 1; | |
408 | } | |
409 | ||
410 | int attempt_back_merge(struct request_queue *q, struct request *rq) | |
411 | { | |
412 | struct request *next = elv_latter_request(q, rq); | |
413 | ||
414 | if (next) | |
415 | return attempt_merge(q, rq, next); | |
416 | ||
417 | return 0; | |
418 | } | |
419 | ||
420 | int attempt_front_merge(struct request_queue *q, struct request *rq) | |
421 | { | |
422 | struct request *prev = elv_former_request(q, rq); | |
423 | ||
424 | if (prev) | |
425 | return attempt_merge(q, prev, rq); | |
426 | ||
427 | return 0; | |
428 | } |