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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 | static unsigned int __blk_recalc_rq_segments(struct request_queue *q, |
13 | struct bio *bio) |
14 | { |
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; |
19 | |
20 | if (!bio) |
21 | return 0; |
22 | |
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) { |
29 | /* |
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. |
33 | */ |
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; |
45 | |
46 | seg_size += bv->bv_len; |
47 | bvprv = bv; |
48 | continue; |
49 | } |
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; |
54 | |
55 | nr_phys_segs++; |
56 | bvprv = bv; |
57 | seg_size = bv->bv_len; |
58 | highprv = high; |
59 | } |
60 | bbio = bio; |
61 | } |
62 | |
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; |
67 | |
68 | return nr_phys_segs; |
69 | } |
70 | |
71 | void blk_recalc_rq_segments(struct request *rq) |
72 | { |
73 | rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio); |
74 | } |
75 | |
76 | void blk_recount_segments(struct request_queue *q, struct bio *bio) |
77 | { |
78 | struct bio *nxt = bio->bi_next; |
79 | |
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); |
84 | } |
85 | EXPORT_SYMBOL(blk_recount_segments); |
86 | |
87 | static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio, |
88 | struct bio *nxt) |
89 | { |
90 | if (!blk_queue_cluster(q)) |
91 | return 0; |
92 | |
93 | if (bio->bi_seg_back_size + nxt->bi_seg_front_size > |
94 | queue_max_segment_size(q)) |
95 | return 0; |
96 | |
97 | if (!bio_has_data(bio)) |
98 | return 1; |
99 | |
100 | if (!BIOVEC_PHYS_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt))) |
101 | return 0; |
102 | |
103 | /* |
104 | * bio and nxt are contiguous in memory; check if the queue allows |
105 | * these two to be merged into one |
106 | */ |
107 | if (BIO_SEG_BOUNDARY(q, bio, nxt)) |
108 | return 1; |
109 | |
110 | return 0; |
111 | } |
112 | |
113 | /* |
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 |
116 | */ |
117 | int blk_rq_map_sg(struct request_queue *q, struct request *rq, |
118 | struct scatterlist *sglist) |
119 | { |
120 | struct bio_vec *bvec, *bvprv; |
121 | struct req_iterator iter; |
122 | struct scatterlist *sg; |
123 | int nsegs, cluster; |
124 | |
125 | nsegs = 0; |
126 | cluster = blk_queue_cluster(q); |
127 | |
128 | /* |
129 | * for each bio in rq |
130 | */ |
131 | bvprv = NULL; |
132 | sg = NULL; |
133 | rq_for_each_segment(bvec, rq, iter) { |
134 | int nbytes = bvec->bv_len; |
135 | |
136 | if (bvprv && cluster) { |
137 | if (sg->length + nbytes > queue_max_segment_size(q)) |
138 | goto new_segment; |
139 | |
140 | if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec)) |
141 | goto new_segment; |
142 | if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec)) |
143 | goto new_segment; |
144 | |
145 | sg->length += nbytes; |
146 | } else { |
147 | new_segment: |
148 | if (!sg) |
149 | sg = sglist; |
150 | else { |
151 | /* |
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. |
160 | */ |
161 | sg->page_link &= ~0x02; |
162 | sg = sg_next(sg); |
163 | } |
164 | |
165 | sg_set_page(sg, bvec->bv_page, nbytes, bvec->bv_offset); |
166 | nsegs++; |
167 | } |
168 | bvprv = bvec; |
169 | } /* segments in rq */ |
170 | |
171 | |
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; |
176 | |
177 | sg->length += pad_len; |
178 | rq->extra_len += pad_len; |
179 | } |
180 | |
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); |
184 | |
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; |
193 | } |
194 | |
195 | if (sg) |
196 | sg_mark_end(sg); |
197 | |
198 | return nsegs; |
199 | } |
200 | EXPORT_SYMBOL(blk_rq_map_sg); |
201 | |
202 | static inline int ll_new_hw_segment(struct request_queue *q, |
203 | struct request *req, |
204 | struct bio *bio) |
205 | { |
206 | int nr_phys_segs = bio_phys_segments(q, bio); |
207 | |
208 | if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q)) |
209 | goto no_merge; |
210 | |
211 | if (bio_integrity(bio) && blk_integrity_merge_bio(q, req, bio)) |
212 | goto no_merge; |
213 | |
214 | /* |
215 | * This will form the start of a new hw segment. Bump both |
216 | * counters. |
217 | */ |
218 | req->nr_phys_segments += nr_phys_segs; |
219 | return 1; |
220 | |
221 | no_merge: |
222 | req->cmd_flags |= REQ_NOMERGE; |
223 | if (req == q->last_merge) |
224 | q->last_merge = NULL; |
225 | return 0; |
226 | } |
227 | |
228 | int ll_back_merge_fn(struct request_queue *q, struct request *req, |
229 | struct bio *bio) |
230 | { |
231 | unsigned short max_sectors; |
232 | |
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); |
237 | |
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; |
243 | } |
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); |
248 | |
249 | return ll_new_hw_segment(q, req, bio); |
250 | } |
251 | |
252 | int ll_front_merge_fn(struct request_queue *q, struct request *req, |
253 | struct bio *bio) |
254 | { |
255 | unsigned short max_sectors; |
256 | |
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); |
261 | |
262 | |
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; |
268 | } |
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); |
273 | |
274 | return ll_new_hw_segment(q, req, bio); |
275 | } |
276 | |
277 | static int ll_merge_requests_fn(struct request_queue *q, struct request *req, |
278 | struct request *next) |
279 | { |
280 | int total_phys_segments; |
281 | unsigned int seg_size = |
282 | req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size; |
283 | |
284 | /* |
285 | * First check if the either of the requests are re-queued |
286 | * requests. Can't merge them if they are. |
287 | */ |
288 | if (req->special || next->special) |
289 | return 0; |
290 | |
291 | /* |
292 | * Will it become too large? |
293 | */ |
294 | if ((blk_rq_sectors(req) + blk_rq_sectors(next)) > queue_max_sectors(q)) |
295 | return 0; |
296 | |
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--; |
304 | } |
305 | |
306 | if (total_phys_segments > queue_max_segments(q)) |
307 | return 0; |
308 | |
309 | if (blk_integrity_rq(req) && blk_integrity_merge_rq(q, req, next)) |
310 | return 0; |
311 | |
312 | /* Merge is OK... */ |
313 | req->nr_phys_segments = total_phys_segments; |
314 | return 1; |
315 | } |
316 | |
317 | /** |
318 | * blk_rq_set_mixed_merge - mark a request as mixed merge |
319 | * @rq: request to mark as mixed merge |
320 | * |
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. |
325 | */ |
326 | void blk_rq_set_mixed_merge(struct request *rq) |
327 | { |
328 | unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK; |
329 | struct bio *bio; |
330 | |
331 | if (rq->cmd_flags & REQ_MIXED_MERGE) |
332 | return; |
333 | |
334 | /* |
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. |
338 | */ |
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; |
343 | } |
344 | rq->cmd_flags |= REQ_MIXED_MERGE; |
345 | } |
346 | |
347 | static void blk_account_io_merge(struct request *req) |
348 | { |
349 | if (blk_do_io_stat(req)) { |
350 | struct hd_struct *part; |
351 | int cpu; |
352 | |
353 | cpu = part_stat_lock(); |
354 | part = req->part; |
355 | |
356 | part_round_stats(cpu, part); |
357 | part_dec_in_flight(part, rq_data_dir(req)); |
358 | |
359 | hd_struct_put(part); |
360 | part_stat_unlock(); |
361 | } |
362 | } |
363 | |
364 | /* |
365 | * Has to be called with the request spinlock acquired |
366 | */ |
367 | static int attempt_merge(struct request_queue *q, struct request *req, |
368 | struct request *next) |
369 | { |
370 | if (!rq_mergeable(req) || !rq_mergeable(next)) |
371 | return 0; |
372 | |
373 | /* |
374 | * Don't merge file system requests and discard requests |
375 | */ |
376 | if ((req->cmd_flags & REQ_DISCARD) != (next->cmd_flags & REQ_DISCARD)) |
377 | return 0; |
378 | |
379 | /* |
380 | * Don't merge discard requests and secure discard requests |
381 | */ |
382 | if ((req->cmd_flags & REQ_SECURE) != (next->cmd_flags & REQ_SECURE)) |
383 | return 0; |
384 | |
385 | /* |
386 | * not contiguous |
387 | */ |
388 | if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next)) |
389 | return 0; |
390 | |
391 | if (rq_data_dir(req) != rq_data_dir(next) |
392 | || req->rq_disk != next->rq_disk |
393 | || next->special) |
394 | return 0; |
395 | |
396 | /* |
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. |
401 | */ |
402 | if (!ll_merge_requests_fn(q, req, next)) |
403 | return 0; |
404 | |
405 | /* |
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. |
410 | */ |
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); |
416 | } |
417 | |
418 | /* |
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. |
423 | */ |
424 | if (time_after(req->start_time, next->start_time)) |
425 | req->start_time = next->start_time; |
426 | |
427 | req->biotail->bi_next = next->bio; |
428 | req->biotail = next->biotail; |
429 | |
430 | req->__data_len += blk_rq_bytes(next); |
431 | |
432 | elv_merge_requests(q, req, next); |
433 | |
434 | /* |
435 | * 'next' is going away, so update stats accordingly |
436 | */ |
437 | blk_account_io_merge(next); |
438 | |
439 | req->ioprio = ioprio_best(req->ioprio, next->ioprio); |
440 | if (blk_rq_cpu_valid(next)) |
441 | req->cpu = next->cpu; |
442 | |
443 | /* owner-ship of bio passed from next to req */ |
444 | next->bio = NULL; |
445 | __blk_put_request(q, next); |
446 | return 1; |
447 | } |
448 | |
449 | int attempt_back_merge(struct request_queue *q, struct request *rq) |
450 | { |
451 | struct request *next = elv_latter_request(q, rq); |
452 | |
453 | if (next) |
454 | return attempt_merge(q, rq, next); |
455 | |
456 | return 0; |
457 | } |
458 | |
459 | int attempt_front_merge(struct request_queue *q, struct request *rq) |
460 | { |
461 | struct request *prev = elv_former_request(q, rq); |
462 | |
463 | if (prev) |
464 | return attempt_merge(q, prev, rq); |
465 | |
466 | return 0; |
467 | } |
468 | |
469 | int blk_attempt_req_merge(struct request_queue *q, struct request *rq, |
470 | struct request *next) |
471 | { |
472 | return attempt_merge(q, rq, next); |
473 | } |
474 |
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