2 * Functions related to segment and merge handling
4 #include <linux/kernel.h>
5 #include <linux/module.h>
7 #include <linux/blkdev.h>
8 #include <linux/scatterlist.h>
12 static unsigned int __blk_recalc_rq_segments(struct request_queue
*q
,
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
;
24 cluster
= test_bit(QUEUE_FLAG_CLUSTER
, &q
->queue_flags
);
28 bio_for_each_segment(bv
, bio
, i
) {
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.
34 high
= page_to_pfn(bv
->bv_page
) > queue_bounce_pfn(q
);
38 if (seg_size
+ bv
->bv_len
39 > queue_max_segment_size(q
))
41 if (!BIOVEC_PHYS_MERGEABLE(bvprv
, bv
))
43 if (!BIOVEC_SEG_BOUNDARY(q
, bvprv
, bv
))
46 seg_size
+= bv
->bv_len
;
51 if (nr_phys_segs
== 1 && seg_size
>
52 fbio
->bi_seg_front_size
)
53 fbio
->bi_seg_front_size
= seg_size
;
57 seg_size
= bv
->bv_len
;
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
;
71 void blk_recalc_rq_segments(struct request
*rq
)
73 rq
->nr_phys_segments
= __blk_recalc_rq_segments(rq
->q
, rq
->bio
);
76 void blk_recount_segments(struct request_queue
*q
, struct bio
*bio
)
78 struct bio
*nxt
= bio
->bi_next
;
81 bio
->bi_phys_segments
= __blk_recalc_rq_segments(q
, bio
);
83 bio
->bi_flags
|= (1 << BIO_SEG_VALID
);
85 EXPORT_SYMBOL(blk_recount_segments
);
87 static int blk_phys_contig_segment(struct request_queue
*q
, struct bio
*bio
,
90 if (!test_bit(QUEUE_FLAG_CLUSTER
, &q
->queue_flags
))
93 if (bio
->bi_seg_back_size
+ nxt
->bi_seg_front_size
>
94 queue_max_segment_size(q
))
97 if (!bio_has_data(bio
))
100 if (!BIOVEC_PHYS_MERGEABLE(__BVEC_END(bio
), __BVEC_START(nxt
)))
104 * bio and nxt are contiguous in memory; check if the queue allows
105 * these two to be merged into one
107 if (BIO_SEG_BOUNDARY(q
, bio
, nxt
))
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
117 int blk_rq_map_sg(struct request_queue
*q
, struct request
*rq
,
118 struct scatterlist
*sglist
)
120 struct bio_vec
*bvec
, *bvprv
;
121 struct req_iterator iter
;
122 struct scatterlist
*sg
;
126 cluster
= test_bit(QUEUE_FLAG_CLUSTER
, &q
->queue_flags
);
133 rq_for_each_segment(bvec
, rq
, iter
) {
134 int nbytes
= bvec
->bv_len
;
136 if (bvprv
&& cluster
) {
137 if (sg
->length
+ nbytes
> queue_max_segment_size(q
))
140 if (!BIOVEC_PHYS_MERGEABLE(bvprv
, bvec
))
142 if (!BIOVEC_SEG_BOUNDARY(q
, bvprv
, bvec
))
145 sg
->length
+= nbytes
;
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.
161 sg
->page_link
&= ~0x02;
165 sg_set_page(sg
, bvec
->bv_page
, nbytes
, bvec
->bv_offset
);
169 } /* segments in rq */
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;
177 sg
->length
+= pad_len
;
178 rq
->extra_len
+= pad_len
;
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
);
185 sg
->page_link
&= ~0x02;
187 sg_set_page(sg
, virt_to_page(q
->dma_drain_buffer
),
189 ((unsigned long)q
->dma_drain_buffer
) &
192 rq
->extra_len
+= q
->dma_drain_size
;
200 EXPORT_SYMBOL(blk_rq_map_sg
);
202 static inline int ll_new_hw_segment(struct request_queue
*q
,
206 int nr_phys_segs
= bio_phys_segments(q
, bio
);
208 if (req
->nr_phys_segments
+ nr_phys_segs
> queue_max_segments(q
))
211 if (bio_integrity(bio
) && blk_integrity_merge_bio(q
, req
, bio
))
215 * This will form the start of a new hw segment. Bump both
218 req
->nr_phys_segments
+= nr_phys_segs
;
222 req
->cmd_flags
|= REQ_NOMERGE
;
223 if (req
== q
->last_merge
)
224 q
->last_merge
= NULL
;
228 int ll_back_merge_fn(struct request_queue
*q
, struct request
*req
,
231 unsigned short max_sectors
;
233 if (unlikely(req
->cmd_type
== REQ_TYPE_BLOCK_PC
))
234 max_sectors
= queue_max_hw_sectors(q
);
236 max_sectors
= queue_max_sectors(q
);
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
;
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
);
249 return ll_new_hw_segment(q
, req
, bio
);
252 int ll_front_merge_fn(struct request_queue
*q
, struct request
*req
,
255 unsigned short max_sectors
;
257 if (unlikely(req
->cmd_type
== REQ_TYPE_BLOCK_PC
))
258 max_sectors
= queue_max_hw_sectors(q
);
260 max_sectors
= queue_max_sectors(q
);
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
;
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
);
274 return ll_new_hw_segment(q
, req
, bio
);
277 static int ll_merge_requests_fn(struct request_queue
*q
, struct request
*req
,
278 struct request
*next
)
280 int total_phys_segments
;
281 unsigned int seg_size
=
282 req
->biotail
->bi_seg_back_size
+ next
->bio
->bi_seg_front_size
;
285 * First check if the either of the requests are re-queued
286 * requests. Can't merge them if they are.
288 if (req
->special
|| next
->special
)
292 * Will it become too large?
294 if ((blk_rq_sectors(req
) + blk_rq_sectors(next
)) > queue_max_sectors(q
))
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
--;
306 if (total_phys_segments
> queue_max_segments(q
))
309 if (blk_integrity_rq(req
) && blk_integrity_merge_rq(q
, req
, next
))
313 req
->nr_phys_segments
= total_phys_segments
;
318 * blk_rq_set_mixed_merge - mark a request as mixed merge
319 * @rq: request to mark as mixed merge
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
326 void blk_rq_set_mixed_merge(struct request
*rq
)
328 unsigned int ff
= rq
->cmd_flags
& REQ_FAILFAST_MASK
;
331 if (rq
->cmd_flags
& REQ_MIXED_MERGE
)
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.
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
);
344 rq
->cmd_flags
|= REQ_MIXED_MERGE
;
347 static void blk_account_io_merge(struct request
*req
)
349 if (blk_do_io_stat(req
)) {
350 struct hd_struct
*part
;
353 cpu
= part_stat_lock();
354 part
= disk_map_sector_rcu(req
->rq_disk
, blk_rq_pos(req
));
356 part_round_stats(cpu
, part
);
357 part_dec_in_flight(part
, rq_data_dir(req
));
364 * Has to be called with the request spinlock acquired
366 static int attempt_merge(struct request_queue
*q
, struct request
*req
,
367 struct request
*next
)
369 if (!rq_mergeable(req
) || !rq_mergeable(next
))
373 * Don't merge file system requests and discard requests
375 if ((req
->cmd_flags
& REQ_DISCARD
) != (next
->cmd_flags
& REQ_DISCARD
))
379 * Don't merge discard requests and secure discard requests
381 if ((req
->cmd_flags
& REQ_SECURE
) != (next
->cmd_flags
& REQ_SECURE
))
387 if (blk_rq_pos(req
) + blk_rq_sectors(req
) != blk_rq_pos(next
))
390 if (rq_data_dir(req
) != rq_data_dir(next
)
391 || req
->rq_disk
!= next
->rq_disk
396 * If we are allowed to merge, then append bio list
397 * from next to rq and release next. merge_requests_fn
398 * will have updated segment counts, update sector
401 if (!ll_merge_requests_fn(q
, req
, next
))
405 * If failfast settings disagree or any of the two is already
406 * a mixed merge, mark both as mixed before proceeding. This
407 * makes sure that all involved bios have mixable attributes
410 if ((req
->cmd_flags
| next
->cmd_flags
) & REQ_MIXED_MERGE
||
411 (req
->cmd_flags
& REQ_FAILFAST_MASK
) !=
412 (next
->cmd_flags
& REQ_FAILFAST_MASK
)) {
413 blk_rq_set_mixed_merge(req
);
414 blk_rq_set_mixed_merge(next
);
418 * At this point we have either done a back merge
419 * or front merge. We need the smaller start_time of
420 * the merged requests to be the current request
421 * for accounting purposes.
423 if (time_after(req
->start_time
, next
->start_time
))
424 req
->start_time
= next
->start_time
;
426 req
->biotail
->bi_next
= next
->bio
;
427 req
->biotail
= next
->biotail
;
429 req
->__data_len
+= blk_rq_bytes(next
);
431 elv_merge_requests(q
, req
, next
);
434 * 'next' is going away, so update stats accordingly
436 blk_account_io_merge(next
);
438 req
->ioprio
= ioprio_best(req
->ioprio
, next
->ioprio
);
439 if (blk_rq_cpu_valid(next
))
440 req
->cpu
= next
->cpu
;
442 /* owner-ship of bio passed from next to req */
444 __blk_put_request(q
, next
);
448 int attempt_back_merge(struct request_queue
*q
, struct request
*rq
)
450 struct request
*next
= elv_latter_request(q
, rq
);
453 return attempt_merge(q
, rq
, next
);
458 int attempt_front_merge(struct request_queue
*q
, struct request
*rq
)
460 struct request
*prev
= elv_former_request(q
, rq
);
463 return attempt_merge(q
, prev
, rq
);
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