block: unify flags for struct bio and struct request
[linux-2.6.git] / block / blk-merge.c
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_WRITE)
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_segments(q)) {
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          */
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;
228
229         if (unlikely(req->cmd_type == REQ_TYPE_BLOCK_PC))
230                 max_sectors = queue_max_hw_sectors(q);
231         else
232                 max_sectors = queue_max_sectors(q);
233
234         if (blk_rq_sectors(req) + bio_sectors(bio) > max_sectors) {
235                 req->cmd_flags |= REQ_NOMERGE;
236                 if (req == q->last_merge)
237                         q->last_merge = NULL;
238                 return 0;
239         }
240         if (!bio_flagged(req->biotail, BIO_SEG_VALID))
241                 blk_recount_segments(q, req->biotail);
242         if (!bio_flagged(bio, BIO_SEG_VALID))
243                 blk_recount_segments(q, bio);
244
245         return ll_new_hw_segment(q, req, bio);
246 }
247
248 int ll_front_merge_fn(struct request_queue *q, struct request *req,
249                       struct bio *bio)
250 {
251         unsigned short max_sectors;
252
253         if (unlikely(req->cmd_type == REQ_TYPE_BLOCK_PC))
254                 max_sectors = queue_max_hw_sectors(q);
255         else
256                 max_sectors = queue_max_sectors(q);
257
258
259         if (blk_rq_sectors(req) + bio_sectors(bio) > max_sectors) {
260                 req->cmd_flags |= REQ_NOMERGE;
261                 if (req == q->last_merge)
262                         q->last_merge = NULL;
263                 return 0;
264         }
265         if (!bio_flagged(bio, BIO_SEG_VALID))
266                 blk_recount_segments(q, bio);
267         if (!bio_flagged(req->bio, BIO_SEG_VALID))
268                 blk_recount_segments(q, req->bio);
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;
277         unsigned int seg_size =
278                 req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size;
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          */
290         if ((blk_rq_sectors(req) + blk_rq_sectors(next)) > queue_max_sectors(q))
291                 return 0;
292
293         total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
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;
299                 total_phys_segments--;
300         }
301
302         if (total_phys_segments > queue_max_segments(q))
303                 return 0;
304
305         /* Merge is OK... */
306         req->nr_phys_segments = total_phys_segments;
307         return 1;
308 }
309
310 /**
311  * blk_rq_set_mixed_merge - mark a request as mixed merge
312  * @rq: request to mark as mixed merge
313  *
314  * Description:
315  *     @rq is about to be mixed merged.  Make sure the attributes
316  *     which can be mixed are set in each bio and mark @rq as mixed
317  *     merged.
318  */
319 void blk_rq_set_mixed_merge(struct request *rq)
320 {
321         unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK;
322         struct bio *bio;
323
324         if (rq->cmd_flags & REQ_MIXED_MERGE)
325                 return;
326
327         /*
328          * @rq will no longer represent mixable attributes for all the
329          * contained bios.  It will just track those of the first one.
330          * Distributes the attributs to each bio.
331          */
332         for (bio = rq->bio; bio; bio = bio->bi_next) {
333                 WARN_ON_ONCE((bio->bi_rw & REQ_FAILFAST_MASK) &&
334                              (bio->bi_rw & REQ_FAILFAST_MASK) != ff);
335                 bio->bi_rw |= ff;
336         }
337         rq->cmd_flags |= REQ_MIXED_MERGE;
338 }
339
340 static void blk_account_io_merge(struct request *req)
341 {
342         if (blk_do_io_stat(req)) {
343                 struct hd_struct *part;
344                 int cpu;
345
346                 cpu = part_stat_lock();
347                 part = disk_map_sector_rcu(req->rq_disk, blk_rq_pos(req));
348
349                 part_round_stats(cpu, part);
350                 part_dec_in_flight(part, rq_data_dir(req));
351
352                 part_stat_unlock();
353         }
354 }
355
356 /*
357  * Has to be called with the request spinlock acquired
358  */
359 static int attempt_merge(struct request_queue *q, struct request *req,
360                           struct request *next)
361 {
362         if (!rq_mergeable(req) || !rq_mergeable(next))
363                 return 0;
364
365         /*
366          * not contiguous
367          */
368         if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next))
369                 return 0;
370
371         if (rq_data_dir(req) != rq_data_dir(next)
372             || req->rq_disk != next->rq_disk
373             || next->special)
374                 return 0;
375
376         if (blk_integrity_rq(req) != blk_integrity_rq(next))
377                 return 0;
378
379         /*
380          * If we are allowed to merge, then append bio list
381          * from next to rq and release next. merge_requests_fn
382          * will have updated segment counts, update sector
383          * counts here.
384          */
385         if (!ll_merge_requests_fn(q, req, next))
386                 return 0;
387
388         /*
389          * If failfast settings disagree or any of the two is already
390          * a mixed merge, mark both as mixed before proceeding.  This
391          * makes sure that all involved bios have mixable attributes
392          * set properly.
393          */
394         if ((req->cmd_flags | next->cmd_flags) & REQ_MIXED_MERGE ||
395             (req->cmd_flags & REQ_FAILFAST_MASK) !=
396             (next->cmd_flags & REQ_FAILFAST_MASK)) {
397                 blk_rq_set_mixed_merge(req);
398                 blk_rq_set_mixed_merge(next);
399         }
400
401         /*
402          * At this point we have either done a back merge
403          * or front merge. We need the smaller start_time of
404          * the merged requests to be the current request
405          * for accounting purposes.
406          */
407         if (time_after(req->start_time, next->start_time))
408                 req->start_time = next->start_time;
409
410         req->biotail->bi_next = next->bio;
411         req->biotail = next->biotail;
412
413         req->__data_len += blk_rq_bytes(next);
414
415         elv_merge_requests(q, req, next);
416
417         /*
418          * 'next' is going away, so update stats accordingly
419          */
420         blk_account_io_merge(next);
421
422         req->ioprio = ioprio_best(req->ioprio, next->ioprio);
423         if (blk_rq_cpu_valid(next))
424                 req->cpu = next->cpu;
425
426         /* owner-ship of bio passed from next to req */
427         next->bio = NULL;
428         __blk_put_request(q, next);
429         return 1;
430 }
431
432 int attempt_back_merge(struct request_queue *q, struct request *rq)
433 {
434         struct request *next = elv_latter_request(q, rq);
435
436         if (next)
437                 return attempt_merge(q, rq, next);
438
439         return 0;
440 }
441
442 int attempt_front_merge(struct request_queue *q, struct request *rq)
443 {
444         struct request *prev = elv_former_request(q, rq);
445
446         if (prev)
447                 return attempt_merge(q, prev, rq);
448
449         return 0;
450 }