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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 | unsigned int phys_size; | |
16 | struct bio_vec *bv, *bvprv = NULL; | |
17 | int cluster, i, high, highprv = 1; | |
18 | unsigned int seg_size, nr_phys_segs; | |
19 | struct bio *fbio, *bbio; | |
20 | ||
21 | if (!bio) | |
22 | return 0; | |
23 | ||
24 | fbio = bio; | |
25 | cluster = test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags); | |
26 | seg_size = 0; | |
27 | phys_size = nr_phys_segs = 0; | |
28 | for_each_bio(bio) { | |
29 | bio_for_each_segment(bv, bio, i) { | |
30 | /* | |
31 | * the trick here is making sure that a high page is | |
32 | * never considered part of another segment, since that | |
33 | * might change with the bounce page. | |
34 | */ | |
35 | high = page_to_pfn(bv->bv_page) > queue_bounce_pfn(q); | |
36 | if (high || highprv) | |
37 | goto new_segment; | |
38 | if (cluster) { | |
39 | if (seg_size + bv->bv_len | |
40 | > queue_max_segment_size(q)) | |
41 | goto new_segment; | |
42 | if (!BIOVEC_PHYS_MERGEABLE(bvprv, bv)) | |
43 | goto new_segment; | |
44 | if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bv)) | |
45 | goto new_segment; | |
46 | ||
47 | seg_size += bv->bv_len; | |
48 | bvprv = bv; | |
49 | continue; | |
50 | } | |
51 | new_segment: | |
52 | if (nr_phys_segs == 1 && seg_size > | |
53 | fbio->bi_seg_front_size) | |
54 | fbio->bi_seg_front_size = seg_size; | |
55 | ||
56 | nr_phys_segs++; | |
57 | bvprv = bv; | |
58 | seg_size = bv->bv_len; | |
59 | highprv = high; | |
60 | } | |
61 | bbio = bio; | |
62 | } | |
63 | ||
64 | if (nr_phys_segs == 1 && seg_size > fbio->bi_seg_front_size) | |
65 | fbio->bi_seg_front_size = seg_size; | |
66 | if (seg_size > bbio->bi_seg_back_size) | |
67 | bbio->bi_seg_back_size = seg_size; | |
68 | ||
69 | return nr_phys_segs; | |
70 | } | |
71 | ||
72 | void blk_recalc_rq_segments(struct request *rq) | |
73 | { | |
74 | rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio); | |
75 | } | |
76 | ||
77 | void blk_recount_segments(struct request_queue *q, struct bio *bio) | |
78 | { | |
79 | struct bio *nxt = bio->bi_next; | |
80 | ||
81 | bio->bi_next = NULL; | |
82 | bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio); | |
83 | bio->bi_next = nxt; | |
84 | bio->bi_flags |= (1 << BIO_SEG_VALID); | |
85 | } | |
86 | EXPORT_SYMBOL(blk_recount_segments); | |
87 | ||
88 | static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio, | |
89 | struct bio *nxt) | |
90 | { | |
91 | if (!test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags)) | |
92 | return 0; | |
93 | ||
94 | if (bio->bi_seg_back_size + nxt->bi_seg_front_size > | |
95 | queue_max_segment_size(q)) | |
96 | return 0; | |
97 | ||
98 | if (!bio_has_data(bio)) | |
99 | return 1; | |
100 | ||
101 | if (!BIOVEC_PHYS_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt))) | |
102 | return 0; | |
103 | ||
104 | /* | |
105 | * bio and nxt are contiguous in memory; check if the queue allows | |
106 | * these two to be merged into one | |
107 | */ | |
108 | if (BIO_SEG_BOUNDARY(q, bio, nxt)) | |
109 | return 1; | |
110 | ||
111 | return 0; | |
112 | } | |
113 | ||
114 | /* | |
115 | * map a request to scatterlist, return number of sg entries setup. Caller | |
116 | * must make sure sg can hold rq->nr_phys_segments entries | |
117 | */ | |
118 | int blk_rq_map_sg(struct request_queue *q, struct request *rq, | |
119 | struct scatterlist *sglist) | |
120 | { | |
121 | struct bio_vec *bvec, *bvprv; | |
122 | struct req_iterator iter; | |
123 | struct scatterlist *sg; | |
124 | int nsegs, cluster; | |
125 | ||
126 | nsegs = 0; | |
127 | cluster = test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags); | |
128 | ||
129 | /* | |
130 | * for each bio in rq | |
131 | */ | |
132 | bvprv = NULL; | |
133 | sg = NULL; | |
134 | rq_for_each_segment(bvec, rq, iter) { | |
135 | int nbytes = bvec->bv_len; | |
136 | ||
137 | if (bvprv && cluster) { | |
138 | if (sg->length + nbytes > queue_max_segment_size(q)) | |
139 | goto new_segment; | |
140 | ||
141 | if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec)) | |
142 | goto new_segment; | |
143 | if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec)) | |
144 | goto new_segment; | |
145 | ||
146 | sg->length += nbytes; | |
147 | } else { | |
148 | new_segment: | |
149 | if (!sg) | |
150 | sg = sglist; | |
151 | else { | |
152 | /* | |
153 | * If the driver previously mapped a shorter | |
154 | * list, we could see a termination bit | |
155 | * prematurely unless it fully inits the sg | |
156 | * table on each mapping. We KNOW that there | |
157 | * must be more entries here or the driver | |
158 | * would be buggy, so force clear the | |
159 | * termination bit to avoid doing a full | |
160 | * sg_init_table() in drivers for each command. | |
161 | */ | |
162 | sg->page_link &= ~0x02; | |
163 | sg = sg_next(sg); | |
164 | } | |
165 | ||
166 | sg_set_page(sg, bvec->bv_page, nbytes, bvec->bv_offset); | |
167 | nsegs++; | |
168 | } | |
169 | bvprv = bvec; | |
170 | } /* segments in rq */ | |
171 | ||
172 | ||
173 | if (unlikely(rq->cmd_flags & REQ_COPY_USER) && | |
174 | (blk_rq_bytes(rq) & q->dma_pad_mask)) { | |
175 | unsigned int pad_len = | |
176 | (q->dma_pad_mask & ~blk_rq_bytes(rq)) + 1; | |
177 | ||
178 | sg->length += pad_len; | |
179 | rq->extra_len += pad_len; | |
180 | } | |
181 | ||
182 | if (q->dma_drain_size && q->dma_drain_needed(rq)) { | |
183 | if (rq->cmd_flags & REQ_RW) | |
184 | memset(q->dma_drain_buffer, 0, q->dma_drain_size); | |
185 | ||
186 | sg->page_link &= ~0x02; | |
187 | sg = sg_next(sg); | |
188 | sg_set_page(sg, virt_to_page(q->dma_drain_buffer), | |
189 | q->dma_drain_size, | |
190 | ((unsigned long)q->dma_drain_buffer) & | |
191 | (PAGE_SIZE - 1)); | |
192 | nsegs++; | |
193 | rq->extra_len += q->dma_drain_size; | |
194 | } | |
195 | ||
196 | if (sg) | |
197 | sg_mark_end(sg); | |
198 | ||
199 | return nsegs; | |
200 | } | |
201 | EXPORT_SYMBOL(blk_rq_map_sg); | |
202 | ||
203 | static inline int ll_new_hw_segment(struct request_queue *q, | |
204 | struct request *req, | |
205 | struct bio *bio) | |
206 | { | |
207 | int nr_phys_segs = bio_phys_segments(q, bio); | |
208 | ||
209 | if (req->nr_phys_segments + nr_phys_segs > queue_max_hw_segments(q) || | |
210 | req->nr_phys_segments + nr_phys_segs > queue_max_phys_segments(q)) { | |
211 | req->cmd_flags |= REQ_NOMERGE; | |
212 | if (req == q->last_merge) | |
213 | q->last_merge = NULL; | |
214 | return 0; | |
215 | } | |
216 | ||
217 | /* | |
218 | * This will form the start of a new hw segment. Bump both | |
219 | * counters. | |
220 | */ | |
221 | req->nr_phys_segments += nr_phys_segs; | |
222 | return 1; | |
223 | } | |
224 | ||
225 | int ll_back_merge_fn(struct request_queue *q, struct request *req, | |
226 | struct bio *bio) | |
227 | { | |
228 | unsigned short max_sectors; | |
229 | ||
230 | if (unlikely(blk_pc_request(req))) | |
231 | max_sectors = queue_max_hw_sectors(q); | |
232 | else | |
233 | max_sectors = queue_max_sectors(q); | |
234 | ||
235 | if (blk_rq_sectors(req) + bio_sectors(bio) > max_sectors) { | |
236 | req->cmd_flags |= REQ_NOMERGE; | |
237 | if (req == q->last_merge) | |
238 | q->last_merge = NULL; | |
239 | return 0; | |
240 | } | |
241 | if (!bio_flagged(req->biotail, BIO_SEG_VALID)) | |
242 | blk_recount_segments(q, req->biotail); | |
243 | if (!bio_flagged(bio, BIO_SEG_VALID)) | |
244 | blk_recount_segments(q, bio); | |
245 | ||
246 | return ll_new_hw_segment(q, req, bio); | |
247 | } | |
248 | ||
249 | int ll_front_merge_fn(struct request_queue *q, struct request *req, | |
250 | struct bio *bio) | |
251 | { | |
252 | unsigned short max_sectors; | |
253 | ||
254 | if (unlikely(blk_pc_request(req))) | |
255 | max_sectors = queue_max_hw_sectors(q); | |
256 | else | |
257 | max_sectors = queue_max_sectors(q); | |
258 | ||
259 | ||
260 | if (blk_rq_sectors(req) + bio_sectors(bio) > max_sectors) { | |
261 | req->cmd_flags |= REQ_NOMERGE; | |
262 | if (req == q->last_merge) | |
263 | q->last_merge = NULL; | |
264 | return 0; | |
265 | } | |
266 | if (!bio_flagged(bio, BIO_SEG_VALID)) | |
267 | blk_recount_segments(q, bio); | |
268 | if (!bio_flagged(req->bio, BIO_SEG_VALID)) | |
269 | blk_recount_segments(q, req->bio); | |
270 | ||
271 | return ll_new_hw_segment(q, req, bio); | |
272 | } | |
273 | ||
274 | static int ll_merge_requests_fn(struct request_queue *q, struct request *req, | |
275 | struct request *next) | |
276 | { | |
277 | int total_phys_segments; | |
278 | unsigned int seg_size = | |
279 | req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size; | |
280 | ||
281 | /* | |
282 | * First check if the either of the requests are re-queued | |
283 | * requests. Can't merge them if they are. | |
284 | */ | |
285 | if (req->special || next->special) | |
286 | return 0; | |
287 | ||
288 | /* | |
289 | * Will it become too large? | |
290 | */ | |
291 | if ((blk_rq_sectors(req) + blk_rq_sectors(next)) > queue_max_sectors(q)) | |
292 | return 0; | |
293 | ||
294 | total_phys_segments = req->nr_phys_segments + next->nr_phys_segments; | |
295 | if (blk_phys_contig_segment(q, req->biotail, next->bio)) { | |
296 | if (req->nr_phys_segments == 1) | |
297 | req->bio->bi_seg_front_size = seg_size; | |
298 | if (next->nr_phys_segments == 1) | |
299 | next->biotail->bi_seg_back_size = seg_size; | |
300 | total_phys_segments--; | |
301 | } | |
302 | ||
303 | if (total_phys_segments > queue_max_phys_segments(q)) | |
304 | return 0; | |
305 | ||
306 | if (total_phys_segments > queue_max_hw_segments(q)) | |
307 | return 0; | |
308 | ||
309 | /* Merge is OK... */ | |
310 | req->nr_phys_segments = total_phys_segments; | |
311 | return 1; | |
312 | } | |
313 | ||
314 | /** | |
315 | * blk_rq_set_mixed_merge - mark a request as mixed merge | |
316 | * @rq: request to mark as mixed merge | |
317 | * | |
318 | * Description: | |
319 | * @rq is about to be mixed merged. Make sure the attributes | |
320 | * which can be mixed are set in each bio and mark @rq as mixed | |
321 | * merged. | |
322 | */ | |
323 | void blk_rq_set_mixed_merge(struct request *rq) | |
324 | { | |
325 | unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK; | |
326 | struct bio *bio; | |
327 | ||
328 | if (rq->cmd_flags & REQ_MIXED_MERGE) | |
329 | return; | |
330 | ||
331 | /* | |
332 | * @rq will no longer represent mixable attributes for all the | |
333 | * contained bios. It will just track those of the first one. | |
334 | * Distributes the attributs to each bio. | |
335 | */ | |
336 | for (bio = rq->bio; bio; bio = bio->bi_next) { | |
337 | WARN_ON_ONCE((bio->bi_rw & REQ_FAILFAST_MASK) && | |
338 | (bio->bi_rw & REQ_FAILFAST_MASK) != ff); | |
339 | bio->bi_rw |= ff; | |
340 | } | |
341 | rq->cmd_flags |= REQ_MIXED_MERGE; | |
342 | } | |
343 | ||
344 | static void blk_account_io_merge(struct request *req) | |
345 | { | |
346 | if (blk_do_io_stat(req)) { | |
347 | struct hd_struct *part; | |
348 | int cpu; | |
349 | ||
350 | cpu = part_stat_lock(); | |
351 | part = disk_map_sector_rcu(req->rq_disk, blk_rq_pos(req)); | |
352 | ||
353 | part_round_stats(cpu, part); | |
354 | part_dec_in_flight(part, rq_data_dir(req)); | |
355 | ||
356 | part_stat_unlock(); | |
357 | } | |
358 | } | |
359 | ||
360 | /* | |
361 | * Has to be called with the request spinlock acquired | |
362 | */ | |
363 | static int attempt_merge(struct request_queue *q, struct request *req, | |
364 | struct request *next) | |
365 | { | |
366 | if (!rq_mergeable(req) || !rq_mergeable(next)) | |
367 | return 0; | |
368 | ||
369 | /* | |
370 | * not contiguous | |
371 | */ | |
372 | if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next)) | |
373 | return 0; | |
374 | ||
375 | if (rq_data_dir(req) != rq_data_dir(next) | |
376 | || req->rq_disk != next->rq_disk | |
377 | || next->special) | |
378 | return 0; | |
379 | ||
380 | if (blk_integrity_rq(req) != blk_integrity_rq(next)) | |
381 | return 0; | |
382 | ||
383 | /* | |
384 | * If we are allowed to merge, then append bio list | |
385 | * from next to rq and release next. merge_requests_fn | |
386 | * will have updated segment counts, update sector | |
387 | * counts here. | |
388 | */ | |
389 | if (!ll_merge_requests_fn(q, req, next)) | |
390 | return 0; | |
391 | ||
392 | /* | |
393 | * If failfast settings disagree or any of the two is already | |
394 | * a mixed merge, mark both as mixed before proceeding. This | |
395 | * makes sure that all involved bios have mixable attributes | |
396 | * set properly. | |
397 | */ | |
398 | if ((req->cmd_flags | next->cmd_flags) & REQ_MIXED_MERGE || | |
399 | (req->cmd_flags & REQ_FAILFAST_MASK) != | |
400 | (next->cmd_flags & REQ_FAILFAST_MASK)) { | |
401 | blk_rq_set_mixed_merge(req); | |
402 | blk_rq_set_mixed_merge(next); | |
403 | } | |
404 | ||
405 | /* | |
406 | * At this point we have either done a back merge | |
407 | * or front merge. We need the smaller start_time of | |
408 | * the merged requests to be the current request | |
409 | * for accounting purposes. | |
410 | */ | |
411 | if (time_after(req->start_time, next->start_time)) | |
412 | req->start_time = next->start_time; | |
413 | ||
414 | req->biotail->bi_next = next->bio; | |
415 | req->biotail = next->biotail; | |
416 | ||
417 | req->__data_len += blk_rq_bytes(next); | |
418 | ||
419 | elv_merge_requests(q, req, next); | |
420 | ||
421 | /* | |
422 | * 'next' is going away, so update stats accordingly | |
423 | */ | |
424 | blk_account_io_merge(next); | |
425 | ||
426 | req->ioprio = ioprio_best(req->ioprio, next->ioprio); | |
427 | if (blk_rq_cpu_valid(next)) | |
428 | req->cpu = next->cpu; | |
429 | ||
430 | /* owner-ship of bio passed from next to req */ | |
431 | next->bio = NULL; | |
432 | __blk_put_request(q, next); | |
433 | return 1; | |
434 | } | |
435 | ||
436 | int attempt_back_merge(struct request_queue *q, struct request *rq) | |
437 | { | |
438 | struct request *next = elv_latter_request(q, rq); | |
439 | ||
440 | if (next) | |
441 | return attempt_merge(q, rq, next); | |
442 | ||
443 | return 0; | |
444 | } | |
445 | ||
446 | int attempt_front_merge(struct request_queue *q, struct request *rq) | |
447 | { | |
448 | struct request *prev = elv_former_request(q, rq); | |
449 | ||
450 | if (prev) | |
451 | return attempt_merge(q, prev, rq); | |
452 | ||
453 | return 0; | |
454 | } |