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Commit | Line | Data |
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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 | ||
1e428079 JA |
41 | static unsigned int __blk_recalc_rq_segments(struct request_queue *q, |
42 | struct bio *bio, | |
43 | unsigned int *seg_size_ptr) | |
d6d48196 | 44 | { |
d6d48196 | 45 | unsigned int phys_size; |
d6d48196 | 46 | struct bio_vec *bv, *bvprv = NULL; |
1e428079 JA |
47 | int cluster, i, high, highprv = 1; |
48 | unsigned int seg_size, nr_phys_segs; | |
49 | struct bio *fbio; | |
d6d48196 | 50 | |
1e428079 JA |
51 | if (!bio) |
52 | return 0; | |
d6d48196 | 53 | |
1e428079 | 54 | fbio = bio; |
75ad23bc | 55 | cluster = test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags); |
5df97b91 MP |
56 | seg_size = 0; |
57 | phys_size = nr_phys_segs = 0; | |
1e428079 JA |
58 | for_each_bio(bio) { |
59 | bio_for_each_segment(bv, bio, i) { | |
60 | /* | |
61 | * the trick here is making sure that a high page is | |
62 | * never considered part of another segment, since that | |
63 | * might change with the bounce page. | |
64 | */ | |
65 | high = page_to_pfn(bv->bv_page) > q->bounce_pfn; | |
66 | if (high || highprv) | |
d6d48196 | 67 | goto new_segment; |
1e428079 JA |
68 | if (cluster) { |
69 | if (seg_size + bv->bv_len > q->max_segment_size) | |
70 | goto new_segment; | |
71 | if (!BIOVEC_PHYS_MERGEABLE(bvprv, bv)) | |
72 | goto new_segment; | |
73 | if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bv)) | |
74 | goto new_segment; | |
d6d48196 | 75 | |
1e428079 JA |
76 | seg_size += bv->bv_len; |
77 | bvprv = bv; | |
78 | continue; | |
79 | } | |
d6d48196 | 80 | new_segment: |
1e428079 JA |
81 | if (nr_phys_segs == 1 && seg_size > |
82 | fbio->bi_seg_front_size) | |
83 | fbio->bi_seg_front_size = seg_size; | |
86771427 | 84 | |
1e428079 JA |
85 | nr_phys_segs++; |
86 | bvprv = bv; | |
87 | seg_size = bv->bv_len; | |
88 | highprv = high; | |
89 | } | |
d6d48196 JA |
90 | } |
91 | ||
1e428079 JA |
92 | if (seg_size_ptr) |
93 | *seg_size_ptr = seg_size; | |
94 | ||
95 | return nr_phys_segs; | |
96 | } | |
97 | ||
98 | void blk_recalc_rq_segments(struct request *rq) | |
99 | { | |
100 | unsigned int seg_size = 0, phys_segs; | |
101 | ||
102 | phys_segs = __blk_recalc_rq_segments(rq->q, rq->bio, &seg_size); | |
103 | ||
104 | if (phys_segs == 1 && seg_size > rq->bio->bi_seg_front_size) | |
86771427 FT |
105 | rq->bio->bi_seg_front_size = seg_size; |
106 | if (seg_size > rq->biotail->bi_seg_back_size) | |
107 | rq->biotail->bi_seg_back_size = seg_size; | |
108 | ||
1e428079 | 109 | rq->nr_phys_segments = phys_segs; |
d6d48196 JA |
110 | } |
111 | ||
112 | void blk_recount_segments(struct request_queue *q, struct bio *bio) | |
113 | { | |
d6d48196 | 114 | struct bio *nxt = bio->bi_next; |
1e428079 | 115 | |
d6d48196 | 116 | bio->bi_next = NULL; |
1e428079 | 117 | bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio, NULL); |
d6d48196 | 118 | bio->bi_next = nxt; |
d6d48196 JA |
119 | bio->bi_flags |= (1 << BIO_SEG_VALID); |
120 | } | |
121 | EXPORT_SYMBOL(blk_recount_segments); | |
122 | ||
123 | static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio, | |
124 | struct bio *nxt) | |
125 | { | |
75ad23bc | 126 | if (!test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags)) |
d6d48196 JA |
127 | return 0; |
128 | ||
86771427 FT |
129 | if (bio->bi_seg_back_size + nxt->bi_seg_front_size > |
130 | q->max_segment_size) | |
d6d48196 JA |
131 | return 0; |
132 | ||
e17fc0a1 DW |
133 | if (!bio_has_data(bio)) |
134 | return 1; | |
135 | ||
136 | if (!BIOVEC_PHYS_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt))) | |
137 | return 0; | |
138 | ||
d6d48196 | 139 | /* |
e17fc0a1 | 140 | * bio and nxt are contiguous in memory; check if the queue allows |
d6d48196 JA |
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 | ||
d6d48196 JA |
149 | /* |
150 | * map a request to scatterlist, return number of sg entries setup. Caller | |
151 | * must make sure sg can hold rq->nr_phys_segments entries | |
152 | */ | |
153 | int blk_rq_map_sg(struct request_queue *q, struct request *rq, | |
154 | struct scatterlist *sglist) | |
155 | { | |
156 | struct bio_vec *bvec, *bvprv; | |
157 | struct req_iterator iter; | |
158 | struct scatterlist *sg; | |
159 | int nsegs, cluster; | |
160 | ||
161 | nsegs = 0; | |
75ad23bc | 162 | cluster = test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags); |
d6d48196 JA |
163 | |
164 | /* | |
165 | * for each bio in rq | |
166 | */ | |
167 | bvprv = NULL; | |
168 | sg = NULL; | |
169 | rq_for_each_segment(bvec, rq, iter) { | |
170 | int nbytes = bvec->bv_len; | |
171 | ||
172 | if (bvprv && cluster) { | |
173 | if (sg->length + nbytes > q->max_segment_size) | |
174 | goto new_segment; | |
175 | ||
176 | if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec)) | |
177 | goto new_segment; | |
178 | if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec)) | |
179 | goto new_segment; | |
180 | ||
181 | sg->length += nbytes; | |
182 | } else { | |
183 | new_segment: | |
184 | if (!sg) | |
185 | sg = sglist; | |
186 | else { | |
187 | /* | |
188 | * If the driver previously mapped a shorter | |
189 | * list, we could see a termination bit | |
190 | * prematurely unless it fully inits the sg | |
191 | * table on each mapping. We KNOW that there | |
192 | * must be more entries here or the driver | |
193 | * would be buggy, so force clear the | |
194 | * termination bit to avoid doing a full | |
195 | * sg_init_table() in drivers for each command. | |
196 | */ | |
197 | sg->page_link &= ~0x02; | |
198 | sg = sg_next(sg); | |
199 | } | |
200 | ||
201 | sg_set_page(sg, bvec->bv_page, nbytes, bvec->bv_offset); | |
202 | nsegs++; | |
203 | } | |
204 | bvprv = bvec; | |
205 | } /* segments in rq */ | |
206 | ||
f18573ab FT |
207 | |
208 | if (unlikely(rq->cmd_flags & REQ_COPY_USER) && | |
209 | (rq->data_len & q->dma_pad_mask)) { | |
210 | unsigned int pad_len = (q->dma_pad_mask & ~rq->data_len) + 1; | |
211 | ||
212 | sg->length += pad_len; | |
213 | rq->extra_len += pad_len; | |
214 | } | |
215 | ||
2fb98e84 | 216 | if (q->dma_drain_size && q->dma_drain_needed(rq)) { |
db0a2e00 TH |
217 | if (rq->cmd_flags & REQ_RW) |
218 | memset(q->dma_drain_buffer, 0, q->dma_drain_size); | |
219 | ||
d6d48196 JA |
220 | sg->page_link &= ~0x02; |
221 | sg = sg_next(sg); | |
222 | sg_set_page(sg, virt_to_page(q->dma_drain_buffer), | |
223 | q->dma_drain_size, | |
224 | ((unsigned long)q->dma_drain_buffer) & | |
225 | (PAGE_SIZE - 1)); | |
226 | nsegs++; | |
7a85f889 | 227 | rq->extra_len += q->dma_drain_size; |
d6d48196 JA |
228 | } |
229 | ||
230 | if (sg) | |
231 | sg_mark_end(sg); | |
232 | ||
233 | return nsegs; | |
234 | } | |
d6d48196 JA |
235 | EXPORT_SYMBOL(blk_rq_map_sg); |
236 | ||
d6d48196 JA |
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; | |
86771427 FT |
312 | unsigned int seg_size = |
313 | req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size; | |
d6d48196 JA |
314 | |
315 | /* | |
316 | * First check if the either of the requests are re-queued | |
317 | * requests. Can't merge them if they are. | |
318 | */ | |
319 | if (req->special || next->special) | |
320 | return 0; | |
321 | ||
322 | /* | |
323 | * Will it become too large? | |
324 | */ | |
325 | if ((req->nr_sectors + next->nr_sectors) > q->max_sectors) | |
326 | return 0; | |
327 | ||
328 | total_phys_segments = req->nr_phys_segments + next->nr_phys_segments; | |
86771427 FT |
329 | if (blk_phys_contig_segment(q, req->biotail, next->bio)) { |
330 | if (req->nr_phys_segments == 1) | |
331 | req->bio->bi_seg_front_size = seg_size; | |
332 | if (next->nr_phys_segments == 1) | |
333 | next->biotail->bi_seg_back_size = seg_size; | |
d6d48196 | 334 | total_phys_segments--; |
86771427 | 335 | } |
d6d48196 JA |
336 | |
337 | if (total_phys_segments > q->max_phys_segments) | |
338 | return 0; | |
339 | ||
5df97b91 | 340 | if (total_phys_segments > q->max_hw_segments) |
d6d48196 JA |
341 | return 0; |
342 | ||
343 | /* Merge is OK... */ | |
344 | req->nr_phys_segments = total_phys_segments; | |
d6d48196 JA |
345 | return 1; |
346 | } | |
347 | ||
348 | /* | |
349 | * Has to be called with the request spinlock acquired | |
350 | */ | |
351 | static int attempt_merge(struct request_queue *q, struct request *req, | |
352 | struct request *next) | |
353 | { | |
354 | if (!rq_mergeable(req) || !rq_mergeable(next)) | |
355 | return 0; | |
356 | ||
357 | /* | |
358 | * not contiguous | |
359 | */ | |
360 | if (req->sector + req->nr_sectors != next->sector) | |
361 | return 0; | |
362 | ||
363 | if (rq_data_dir(req) != rq_data_dir(next) | |
364 | || req->rq_disk != next->rq_disk | |
365 | || next->special) | |
366 | return 0; | |
367 | ||
7ba1ba12 MP |
368 | if (blk_integrity_rq(req) != blk_integrity_rq(next)) |
369 | return 0; | |
370 | ||
d6d48196 JA |
371 | /* |
372 | * If we are allowed to merge, then append bio list | |
373 | * from next to rq and release next. merge_requests_fn | |
374 | * will have updated segment counts, update sector | |
375 | * counts here. | |
376 | */ | |
377 | if (!ll_merge_requests_fn(q, req, next)) | |
378 | return 0; | |
379 | ||
380 | /* | |
381 | * At this point we have either done a back merge | |
382 | * or front merge. We need the smaller start_time of | |
383 | * the merged requests to be the current request | |
384 | * for accounting purposes. | |
385 | */ | |
386 | if (time_after(req->start_time, next->start_time)) | |
387 | req->start_time = next->start_time; | |
388 | ||
389 | req->biotail->bi_next = next->bio; | |
390 | req->biotail = next->biotail; | |
391 | ||
392 | req->nr_sectors = req->hard_nr_sectors += next->hard_nr_sectors; | |
393 | ||
394 | elv_merge_requests(q, req, next); | |
395 | ||
396 | if (req->rq_disk) { | |
e71bf0d0 | 397 | struct hd_struct *part; |
c9959059 | 398 | int cpu; |
e71bf0d0 | 399 | |
074a7aca | 400 | cpu = part_stat_lock(); |
e71bf0d0 | 401 | part = disk_map_sector_rcu(req->rq_disk, req->sector); |
c9959059 | 402 | |
074a7aca TH |
403 | part_round_stats(cpu, part); |
404 | part_dec_in_flight(part); | |
e71bf0d0 | 405 | |
074a7aca | 406 | part_stat_unlock(); |
d6d48196 JA |
407 | } |
408 | ||
409 | req->ioprio = ioprio_best(req->ioprio, next->ioprio); | |
ab780f1e JA |
410 | if (blk_rq_cpu_valid(next)) |
411 | req->cpu = next->cpu; | |
d6d48196 JA |
412 | |
413 | __blk_put_request(q, next); | |
414 | return 1; | |
415 | } | |
416 | ||
417 | int attempt_back_merge(struct request_queue *q, struct request *rq) | |
418 | { | |
419 | struct request *next = elv_latter_request(q, rq); | |
420 | ||
421 | if (next) | |
422 | return attempt_merge(q, rq, next); | |
423 | ||
424 | return 0; | |
425 | } | |
426 | ||
427 | int attempt_front_merge(struct request_queue *q, struct request *rq) | |
428 | { | |
429 | struct request *prev = elv_former_request(q, rq); | |
430 | ||
431 | if (prev) | |
432 | return attempt_merge(q, prev, rq); | |
433 | ||
434 | return 0; | |
435 | } |