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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 | ||
1e428079 | 12 | static unsigned int __blk_recalc_rq_segments(struct request_queue *q, |
59247eae | 13 | struct bio *bio) |
d6d48196 | 14 | { |
d6d48196 | 15 | unsigned int phys_size; |
d6d48196 | 16 | struct bio_vec *bv, *bvprv = NULL; |
1e428079 JA |
17 | int cluster, i, high, highprv = 1; |
18 | unsigned int seg_size, nr_phys_segs; | |
59247eae | 19 | struct bio *fbio, *bbio; |
d6d48196 | 20 | |
1e428079 JA |
21 | if (!bio) |
22 | return 0; | |
d6d48196 | 23 | |
1e428079 | 24 | fbio = bio; |
75ad23bc | 25 | cluster = test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags); |
5df97b91 MP |
26 | seg_size = 0; |
27 | phys_size = nr_phys_segs = 0; | |
1e428079 JA |
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) > q->bounce_pfn; | |
36 | if (high || highprv) | |
d6d48196 | 37 | goto new_segment; |
1e428079 JA |
38 | if (cluster) { |
39 | if (seg_size + bv->bv_len > q->max_segment_size) | |
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; | |
d6d48196 | 45 | |
1e428079 JA |
46 | seg_size += bv->bv_len; |
47 | bvprv = bv; | |
48 | continue; | |
49 | } | |
d6d48196 | 50 | new_segment: |
1e428079 JA |
51 | if (nr_phys_segs == 1 && seg_size > |
52 | fbio->bi_seg_front_size) | |
53 | fbio->bi_seg_front_size = seg_size; | |
86771427 | 54 | |
1e428079 JA |
55 | nr_phys_segs++; |
56 | bvprv = bv; | |
57 | seg_size = bv->bv_len; | |
58 | highprv = high; | |
59 | } | |
59247eae | 60 | bbio = bio; |
d6d48196 JA |
61 | } |
62 | ||
59247eae JA |
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; | |
1e428079 JA |
67 | |
68 | return nr_phys_segs; | |
69 | } | |
70 | ||
71 | void blk_recalc_rq_segments(struct request *rq) | |
72 | { | |
59247eae | 73 | rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio); |
d6d48196 JA |
74 | } |
75 | ||
76 | void blk_recount_segments(struct request_queue *q, struct bio *bio) | |
77 | { | |
d6d48196 | 78 | struct bio *nxt = bio->bi_next; |
1e428079 | 79 | |
d6d48196 | 80 | bio->bi_next = NULL; |
59247eae | 81 | bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio); |
d6d48196 | 82 | bio->bi_next = nxt; |
d6d48196 JA |
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 | { | |
75ad23bc | 90 | if (!test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags)) |
d6d48196 JA |
91 | return 0; |
92 | ||
86771427 FT |
93 | if (bio->bi_seg_back_size + nxt->bi_seg_front_size > |
94 | q->max_segment_size) | |
d6d48196 JA |
95 | return 0; |
96 | ||
e17fc0a1 DW |
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 | ||
d6d48196 | 103 | /* |
e17fc0a1 | 104 | * bio and nxt are contiguous in memory; check if the queue allows |
d6d48196 JA |
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 | ||
d6d48196 JA |
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; | |
75ad23bc | 126 | cluster = test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags); |
d6d48196 JA |
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 > q->max_segment_size) | |
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 | ||
f18573ab FT |
171 | |
172 | if (unlikely(rq->cmd_flags & REQ_COPY_USER) && | |
2e46e8b2 TH |
173 | (blk_rq_bytes(rq) & q->dma_pad_mask)) { |
174 | unsigned int pad_len = | |
175 | (q->dma_pad_mask & ~blk_rq_bytes(rq)) + 1; | |
f18573ab FT |
176 | |
177 | sg->length += pad_len; | |
178 | rq->extra_len += pad_len; | |
179 | } | |
180 | ||
2fb98e84 | 181 | if (q->dma_drain_size && q->dma_drain_needed(rq)) { |
db0a2e00 TH |
182 | if (rq->cmd_flags & REQ_RW) |
183 | memset(q->dma_drain_buffer, 0, q->dma_drain_size); | |
184 | ||
d6d48196 JA |
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++; | |
7a85f889 | 192 | rq->extra_len += q->dma_drain_size; |
d6d48196 JA |
193 | } |
194 | ||
195 | if (sg) | |
196 | sg_mark_end(sg); | |
197 | ||
198 | return nsegs; | |
199 | } | |
d6d48196 JA |
200 | EXPORT_SYMBOL(blk_rq_map_sg); |
201 | ||
d6d48196 JA |
202 | static inline int ll_new_hw_segment(struct request_queue *q, |
203 | struct request *req, | |
204 | struct bio *bio) | |
205 | { | |
d6d48196 JA |
206 | int nr_phys_segs = bio_phys_segments(q, bio); |
207 | ||
5df97b91 | 208 | if (req->nr_phys_segments + nr_phys_segs > q->max_hw_segments |
d6d48196 JA |
209 | || req->nr_phys_segments + nr_phys_segs > q->max_phys_segments) { |
210 | req->cmd_flags |= REQ_NOMERGE; | |
211 | if (req == q->last_merge) | |
212 | q->last_merge = NULL; | |
213 | return 0; | |
214 | } | |
215 | ||
216 | /* | |
217 | * This will form the start of a new hw segment. Bump both | |
218 | * counters. | |
219 | */ | |
d6d48196 JA |
220 | req->nr_phys_segments += nr_phys_segs; |
221 | return 1; | |
222 | } | |
223 | ||
224 | int ll_back_merge_fn(struct request_queue *q, struct request *req, | |
225 | struct bio *bio) | |
226 | { | |
227 | unsigned short max_sectors; | |
d6d48196 JA |
228 | |
229 | if (unlikely(blk_pc_request(req))) | |
230 | max_sectors = q->max_hw_sectors; | |
231 | else | |
232 | max_sectors = q->max_sectors; | |
233 | ||
83096ebf | 234 | if (blk_rq_sectors(req) + bio_sectors(bio) > max_sectors) { |
d6d48196 JA |
235 | req->cmd_flags |= REQ_NOMERGE; |
236 | if (req == q->last_merge) | |
237 | q->last_merge = NULL; | |
238 | return 0; | |
239 | } | |
2cdf79ca | 240 | if (!bio_flagged(req->biotail, BIO_SEG_VALID)) |
d6d48196 | 241 | blk_recount_segments(q, req->biotail); |
2cdf79ca | 242 | if (!bio_flagged(bio, BIO_SEG_VALID)) |
d6d48196 | 243 | blk_recount_segments(q, bio); |
d6d48196 JA |
244 | |
245 | return ll_new_hw_segment(q, req, bio); | |
246 | } | |
247 | ||
6728cb0e | 248 | int ll_front_merge_fn(struct request_queue *q, struct request *req, |
d6d48196 JA |
249 | struct bio *bio) |
250 | { | |
251 | unsigned short max_sectors; | |
d6d48196 JA |
252 | |
253 | if (unlikely(blk_pc_request(req))) | |
254 | max_sectors = q->max_hw_sectors; | |
255 | else | |
256 | max_sectors = q->max_sectors; | |
257 | ||
258 | ||
83096ebf | 259 | if (blk_rq_sectors(req) + bio_sectors(bio) > max_sectors) { |
d6d48196 JA |
260 | req->cmd_flags |= REQ_NOMERGE; |
261 | if (req == q->last_merge) | |
262 | q->last_merge = NULL; | |
263 | return 0; | |
264 | } | |
2cdf79ca | 265 | if (!bio_flagged(bio, BIO_SEG_VALID)) |
d6d48196 | 266 | blk_recount_segments(q, bio); |
2cdf79ca | 267 | if (!bio_flagged(req->bio, BIO_SEG_VALID)) |
d6d48196 | 268 | blk_recount_segments(q, req->bio); |
d6d48196 JA |
269 | |
270 | return ll_new_hw_segment(q, req, bio); | |
271 | } | |
272 | ||
273 | static int ll_merge_requests_fn(struct request_queue *q, struct request *req, | |
274 | struct request *next) | |
275 | { | |
276 | int total_phys_segments; | |
86771427 FT |
277 | unsigned int seg_size = |
278 | req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size; | |
d6d48196 JA |
279 | |
280 | /* | |
281 | * First check if the either of the requests are re-queued | |
282 | * requests. Can't merge them if they are. | |
283 | */ | |
284 | if (req->special || next->special) | |
285 | return 0; | |
286 | ||
287 | /* | |
288 | * Will it become too large? | |
289 | */ | |
83096ebf | 290 | if ((blk_rq_sectors(req) + blk_rq_sectors(next)) > q->max_sectors) |
d6d48196 JA |
291 | return 0; |
292 | ||
293 | total_phys_segments = req->nr_phys_segments + next->nr_phys_segments; | |
86771427 FT |
294 | if (blk_phys_contig_segment(q, req->biotail, next->bio)) { |
295 | if (req->nr_phys_segments == 1) | |
296 | req->bio->bi_seg_front_size = seg_size; | |
297 | if (next->nr_phys_segments == 1) | |
298 | next->biotail->bi_seg_back_size = seg_size; | |
d6d48196 | 299 | total_phys_segments--; |
86771427 | 300 | } |
d6d48196 JA |
301 | |
302 | if (total_phys_segments > q->max_phys_segments) | |
303 | return 0; | |
304 | ||
5df97b91 | 305 | if (total_phys_segments > q->max_hw_segments) |
d6d48196 JA |
306 | return 0; |
307 | ||
308 | /* Merge is OK... */ | |
309 | req->nr_phys_segments = total_phys_segments; | |
d6d48196 JA |
310 | return 1; |
311 | } | |
312 | ||
26308eab JM |
313 | static void blk_account_io_merge(struct request *req) |
314 | { | |
315 | if (blk_do_io_stat(req)) { | |
316 | struct hd_struct *part; | |
317 | int cpu; | |
318 | ||
319 | cpu = part_stat_lock(); | |
83096ebf | 320 | part = disk_map_sector_rcu(req->rq_disk, blk_rq_pos(req)); |
26308eab JM |
321 | |
322 | part_round_stats(cpu, part); | |
323 | part_dec_in_flight(part); | |
324 | ||
325 | part_stat_unlock(); | |
326 | } | |
327 | } | |
328 | ||
d6d48196 JA |
329 | /* |
330 | * Has to be called with the request spinlock acquired | |
331 | */ | |
332 | static int attempt_merge(struct request_queue *q, struct request *req, | |
333 | struct request *next) | |
334 | { | |
335 | if (!rq_mergeable(req) || !rq_mergeable(next)) | |
336 | return 0; | |
337 | ||
338 | /* | |
339 | * not contiguous | |
340 | */ | |
83096ebf | 341 | if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next)) |
d6d48196 JA |
342 | return 0; |
343 | ||
344 | if (rq_data_dir(req) != rq_data_dir(next) | |
345 | || req->rq_disk != next->rq_disk | |
346 | || next->special) | |
347 | return 0; | |
348 | ||
7ba1ba12 MP |
349 | if (blk_integrity_rq(req) != blk_integrity_rq(next)) |
350 | return 0; | |
351 | ||
d6d48196 JA |
352 | /* |
353 | * If we are allowed to merge, then append bio list | |
354 | * from next to rq and release next. merge_requests_fn | |
355 | * will have updated segment counts, update sector | |
356 | * counts here. | |
357 | */ | |
358 | if (!ll_merge_requests_fn(q, req, next)) | |
359 | return 0; | |
360 | ||
361 | /* | |
362 | * At this point we have either done a back merge | |
363 | * or front merge. We need the smaller start_time of | |
364 | * the merged requests to be the current request | |
365 | * for accounting purposes. | |
366 | */ | |
367 | if (time_after(req->start_time, next->start_time)) | |
368 | req->start_time = next->start_time; | |
369 | ||
370 | req->biotail->bi_next = next->bio; | |
371 | req->biotail = next->biotail; | |
372 | ||
a2dec7b3 | 373 | req->__data_len += blk_rq_bytes(next); |
d6d48196 JA |
374 | |
375 | elv_merge_requests(q, req, next); | |
376 | ||
42dad764 JM |
377 | /* |
378 | * 'next' is going away, so update stats accordingly | |
379 | */ | |
380 | blk_account_io_merge(next); | |
d6d48196 JA |
381 | |
382 | req->ioprio = ioprio_best(req->ioprio, next->ioprio); | |
ab780f1e JA |
383 | if (blk_rq_cpu_valid(next)) |
384 | req->cpu = next->cpu; | |
d6d48196 | 385 | |
1cd96c24 BH |
386 | /* owner-ship of bio passed from next to req */ |
387 | next->bio = NULL; | |
d6d48196 JA |
388 | __blk_put_request(q, next); |
389 | return 1; | |
390 | } | |
391 | ||
392 | int attempt_back_merge(struct request_queue *q, struct request *rq) | |
393 | { | |
394 | struct request *next = elv_latter_request(q, rq); | |
395 | ||
396 | if (next) | |
397 | return attempt_merge(q, rq, next); | |
398 | ||
399 | return 0; | |
400 | } | |
401 | ||
402 | int attempt_front_merge(struct request_queue *q, struct request *rq) | |
403 | { | |
404 | struct request *prev = elv_former_request(q, rq); | |
405 | ||
406 | if (prev) | |
407 | return attempt_merge(q, prev, rq); | |
408 | ||
409 | return 0; | |
410 | } |