BKL: Remove BKL from fat
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / block / blk-merge.c
blobeafc94f68d79f2ceb1c0a89fce8e449c3a5ff3f6
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>
10 #include "blk.h"
12 static unsigned int __blk_recalc_rq_segments(struct request_queue *q,
13 struct bio *bio)
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;
20 if (!bio)
21 return 0;
23 fbio = bio;
24 cluster = test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
25 seg_size = 0;
26 nr_phys_segs = 0;
27 for_each_bio(bio) {
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);
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;
46 seg_size += bv->bv_len;
47 bvprv = bv;
48 continue;
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;
55 nr_phys_segs++;
56 bvprv = bv;
57 seg_size = bv->bv_len;
58 highprv = high;
60 bbio = bio;
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;
68 return nr_phys_segs;
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;
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);
85 EXPORT_SYMBOL(blk_recount_segments);
87 static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio,
88 struct bio *nxt)
90 if (!test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags))
91 return 0;
93 if (bio->bi_seg_back_size + nxt->bi_seg_front_size >
94 queue_max_segment_size(q))
95 return 0;
97 if (!bio_has_data(bio))
98 return 1;
100 if (!BIOVEC_PHYS_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)))
101 return 0;
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))
108 return 1;
110 return 0;
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;
123 int nsegs, cluster;
125 nsegs = 0;
126 cluster = test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
129 * for each bio in rq
131 bvprv = NULL;
132 sg = NULL;
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))
138 goto new_segment;
140 if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec))
141 goto new_segment;
142 if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec))
143 goto new_segment;
145 sg->length += nbytes;
146 } else {
147 new_segment:
148 if (!sg)
149 sg = sglist;
150 else {
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;
162 sg = sg_next(sg);
165 sg_set_page(sg, bvec->bv_page, nbytes, bvec->bv_offset);
166 nsegs++;
168 bvprv = bvec;
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;
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;
195 if (sg)
196 sg_mark_end(sg);
198 return nsegs;
200 EXPORT_SYMBOL(blk_rq_map_sg);
202 static inline int ll_new_hw_segment(struct request_queue *q,
203 struct request *req,
204 struct bio *bio)
206 int nr_phys_segs = bio_phys_segments(q, bio);
208 if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q)) {
209 req->cmd_flags |= REQ_NOMERGE;
210 if (req == q->last_merge)
211 q->last_merge = NULL;
212 return 0;
216 * This will form the start of a new hw segment. Bump both
217 * counters.
219 req->nr_phys_segments += nr_phys_segs;
220 return 1;
223 int ll_back_merge_fn(struct request_queue *q, struct request *req,
224 struct bio *bio)
226 unsigned short max_sectors;
228 if (unlikely(req->cmd_type == REQ_TYPE_BLOCK_PC))
229 max_sectors = queue_max_hw_sectors(q);
230 else
231 max_sectors = queue_max_sectors(q);
233 if (blk_rq_sectors(req) + bio_sectors(bio) > max_sectors) {
234 req->cmd_flags |= REQ_NOMERGE;
235 if (req == q->last_merge)
236 q->last_merge = NULL;
237 return 0;
239 if (!bio_flagged(req->biotail, BIO_SEG_VALID))
240 blk_recount_segments(q, req->biotail);
241 if (!bio_flagged(bio, BIO_SEG_VALID))
242 blk_recount_segments(q, bio);
244 return ll_new_hw_segment(q, req, bio);
247 int ll_front_merge_fn(struct request_queue *q, struct request *req,
248 struct bio *bio)
250 unsigned short max_sectors;
252 if (unlikely(req->cmd_type == REQ_TYPE_BLOCK_PC))
253 max_sectors = queue_max_hw_sectors(q);
254 else
255 max_sectors = queue_max_sectors(q);
258 if (blk_rq_sectors(req) + bio_sectors(bio) > max_sectors) {
259 req->cmd_flags |= REQ_NOMERGE;
260 if (req == q->last_merge)
261 q->last_merge = NULL;
262 return 0;
264 if (!bio_flagged(bio, BIO_SEG_VALID))
265 blk_recount_segments(q, bio);
266 if (!bio_flagged(req->bio, BIO_SEG_VALID))
267 blk_recount_segments(q, req->bio);
269 return ll_new_hw_segment(q, req, bio);
272 static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
273 struct request *next)
275 int total_phys_segments;
276 unsigned int seg_size =
277 req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size;
280 * First check if the either of the requests are re-queued
281 * requests. Can't merge them if they are.
283 if (req->special || next->special)
284 return 0;
287 * Will it become too large?
289 if ((blk_rq_sectors(req) + blk_rq_sectors(next)) > queue_max_sectors(q))
290 return 0;
292 total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
293 if (blk_phys_contig_segment(q, req->biotail, next->bio)) {
294 if (req->nr_phys_segments == 1)
295 req->bio->bi_seg_front_size = seg_size;
296 if (next->nr_phys_segments == 1)
297 next->biotail->bi_seg_back_size = seg_size;
298 total_phys_segments--;
301 if (total_phys_segments > queue_max_segments(q))
302 return 0;
304 /* Merge is OK... */
305 req->nr_phys_segments = total_phys_segments;
306 return 1;
310 * blk_rq_set_mixed_merge - mark a request as mixed merge
311 * @rq: request to mark as mixed merge
313 * Description:
314 * @rq is about to be mixed merged. Make sure the attributes
315 * which can be mixed are set in each bio and mark @rq as mixed
316 * merged.
318 void blk_rq_set_mixed_merge(struct request *rq)
320 unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK;
321 struct bio *bio;
323 if (rq->cmd_flags & REQ_MIXED_MERGE)
324 return;
327 * @rq will no longer represent mixable attributes for all the
328 * contained bios. It will just track those of the first one.
329 * Distributes the attributs to each bio.
331 for (bio = rq->bio; bio; bio = bio->bi_next) {
332 WARN_ON_ONCE((bio->bi_rw & REQ_FAILFAST_MASK) &&
333 (bio->bi_rw & REQ_FAILFAST_MASK) != ff);
334 bio->bi_rw |= ff;
336 rq->cmd_flags |= REQ_MIXED_MERGE;
339 static void blk_account_io_merge(struct request *req)
341 if (blk_do_io_stat(req)) {
342 struct hd_struct *part;
343 int cpu;
345 cpu = part_stat_lock();
346 part = disk_map_sector_rcu(req->rq_disk, blk_rq_pos(req));
348 part_round_stats(cpu, part);
349 part_dec_in_flight(part, rq_data_dir(req));
351 part_stat_unlock();
356 * Has to be called with the request spinlock acquired
358 static int attempt_merge(struct request_queue *q, struct request *req,
359 struct request *next)
361 if (!rq_mergeable(req) || !rq_mergeable(next))
362 return 0;
365 * Don't merge file system requests and discard requests
367 if ((req->cmd_flags & REQ_DISCARD) != (next->cmd_flags & REQ_DISCARD))
368 return 0;
371 * Don't merge discard requests and secure discard requests
373 if ((req->cmd_flags & REQ_SECURE) != (next->cmd_flags & REQ_SECURE))
374 return 0;
377 * not contiguous
379 if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next))
380 return 0;
382 if (rq_data_dir(req) != rq_data_dir(next)
383 || req->rq_disk != next->rq_disk
384 || next->special)
385 return 0;
387 if (blk_integrity_rq(req) != blk_integrity_rq(next))
388 return 0;
391 * If we are allowed to merge, then append bio list
392 * from next to rq and release next. merge_requests_fn
393 * will have updated segment counts, update sector
394 * counts here.
396 if (!ll_merge_requests_fn(q, req, next))
397 return 0;
400 * If failfast settings disagree or any of the two is already
401 * a mixed merge, mark both as mixed before proceeding. This
402 * makes sure that all involved bios have mixable attributes
403 * set properly.
405 if ((req->cmd_flags | next->cmd_flags) & REQ_MIXED_MERGE ||
406 (req->cmd_flags & REQ_FAILFAST_MASK) !=
407 (next->cmd_flags & REQ_FAILFAST_MASK)) {
408 blk_rq_set_mixed_merge(req);
409 blk_rq_set_mixed_merge(next);
413 * At this point we have either done a back merge
414 * or front merge. We need the smaller start_time of
415 * the merged requests to be the current request
416 * for accounting purposes.
418 if (time_after(req->start_time, next->start_time))
419 req->start_time = next->start_time;
421 req->biotail->bi_next = next->bio;
422 req->biotail = next->biotail;
424 req->__data_len += blk_rq_bytes(next);
426 elv_merge_requests(q, req, next);
429 * 'next' is going away, so update stats accordingly
431 blk_account_io_merge(next);
433 req->ioprio = ioprio_best(req->ioprio, next->ioprio);
434 if (blk_rq_cpu_valid(next))
435 req->cpu = next->cpu;
437 /* owner-ship of bio passed from next to req */
438 next->bio = NULL;
439 __blk_put_request(q, next);
440 return 1;
443 int attempt_back_merge(struct request_queue *q, struct request *rq)
445 struct request *next = elv_latter_request(q, rq);
447 if (next)
448 return attempt_merge(q, rq, next);
450 return 0;
453 int attempt_front_merge(struct request_queue *q, struct request *rq)
455 struct request *prev = elv_former_request(q, rq);
457 if (prev)
458 return attempt_merge(q, prev, rq);
460 return 0;