block: fix missing bio back/front segment size setting in blk_recount_segments()
[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 void blk_recalc_rq_sectors(struct request *rq, int nsect)
13 {
14         if (blk_fs_request(rq) || blk_discard_rq(rq)) {
15                 rq->hard_sector += nsect;
16                 rq->hard_nr_sectors -= nsect;
17
18                 /*
19                  * Move the I/O submission pointers ahead if required.
20                  */
21                 if ((rq->nr_sectors >= rq->hard_nr_sectors) &&
22                     (rq->sector <= rq->hard_sector)) {
23                         rq->sector = rq->hard_sector;
24                         rq->nr_sectors = rq->hard_nr_sectors;
25                         rq->hard_cur_sectors = bio_cur_sectors(rq->bio);
26                         rq->current_nr_sectors = rq->hard_cur_sectors;
27                         rq->buffer = bio_data(rq->bio);
28                 }
29
30                 /*
31                  * if total number of sectors is less than the first segment
32                  * size, something has gone terribly wrong
33                  */
34                 if (rq->nr_sectors < rq->current_nr_sectors) {
35                         printk(KERN_ERR "blk: request botched\n");
36                         rq->nr_sectors = rq->current_nr_sectors;
37                 }
38         }
39 }
40
41 static unsigned int __blk_recalc_rq_segments(struct request_queue *q,
42                                              struct bio *bio)
43 {
44         unsigned int phys_size;
45         struct bio_vec *bv, *bvprv = NULL;
46         int cluster, i, high, highprv = 1;
47         unsigned int seg_size, nr_phys_segs;
48         struct bio *fbio, *bbio;
49
50         if (!bio)
51                 return 0;
52
53         fbio = bio;
54         cluster = test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
55         seg_size = 0;
56         phys_size = nr_phys_segs = 0;
57         for_each_bio(bio) {
58                 bio_for_each_segment(bv, bio, i) {
59                         /*
60                          * the trick here is making sure that a high page is
61                          * never considered part of another segment, since that
62                          * might change with the bounce page.
63                          */
64                         high = page_to_pfn(bv->bv_page) > q->bounce_pfn;
65                         if (high || highprv)
66                                 goto new_segment;
67                         if (cluster) {
68                                 if (seg_size + bv->bv_len > q->max_segment_size)
69                                         goto new_segment;
70                                 if (!BIOVEC_PHYS_MERGEABLE(bvprv, bv))
71                                         goto new_segment;
72                                 if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bv))
73                                         goto new_segment;
74
75                                 seg_size += bv->bv_len;
76                                 bvprv = bv;
77                                 continue;
78                         }
79 new_segment:
80                         if (nr_phys_segs == 1 && seg_size >
81                             fbio->bi_seg_front_size)
82                                 fbio->bi_seg_front_size = seg_size;
83
84                         nr_phys_segs++;
85                         bvprv = bv;
86                         seg_size = bv->bv_len;
87                         highprv = high;
88                 }
89                 bbio = bio;
90         }
91
92         if (nr_phys_segs == 1 && seg_size > fbio->bi_seg_front_size)
93                 fbio->bi_seg_front_size = seg_size;
94         if (seg_size > bbio->bi_seg_back_size)
95                 bbio->bi_seg_back_size = seg_size;
96
97         return nr_phys_segs;
98 }
99
100 void blk_recalc_rq_segments(struct request *rq)
101 {
102         rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio);
103 }
104
105 void blk_recount_segments(struct request_queue *q, struct bio *bio)
106 {
107         struct bio *nxt = bio->bi_next;
108
109         bio->bi_next = NULL;
110         bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio);
111         bio->bi_next = nxt;
112         bio->bi_flags |= (1 << BIO_SEG_VALID);
113 }
114 EXPORT_SYMBOL(blk_recount_segments);
115
116 static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio,
117                                    struct bio *nxt)
118 {
119         if (!test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags))
120                 return 0;
121
122         if (bio->bi_seg_back_size + nxt->bi_seg_front_size >
123             q->max_segment_size)
124                 return 0;
125
126         if (!bio_has_data(bio))
127                 return 1;
128
129         if (!BIOVEC_PHYS_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)))
130                 return 0;
131
132         /*
133          * bio and nxt are contiguous in memory; check if the queue allows
134          * these two to be merged into one
135          */
136         if (BIO_SEG_BOUNDARY(q, bio, nxt))
137                 return 1;
138
139         return 0;
140 }
141
142 /*
143  * map a request to scatterlist, return number of sg entries setup. Caller
144  * must make sure sg can hold rq->nr_phys_segments entries
145  */
146 int blk_rq_map_sg(struct request_queue *q, struct request *rq,
147                   struct scatterlist *sglist)
148 {
149         struct bio_vec *bvec, *bvprv;
150         struct req_iterator iter;
151         struct scatterlist *sg;
152         int nsegs, cluster;
153
154         nsegs = 0;
155         cluster = test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
156
157         /*
158          * for each bio in rq
159          */
160         bvprv = NULL;
161         sg = NULL;
162         rq_for_each_segment(bvec, rq, iter) {
163                 int nbytes = bvec->bv_len;
164
165                 if (bvprv && cluster) {
166                         if (sg->length + nbytes > q->max_segment_size)
167                                 goto new_segment;
168
169                         if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec))
170                                 goto new_segment;
171                         if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec))
172                                 goto new_segment;
173
174                         sg->length += nbytes;
175                 } else {
176 new_segment:
177                         if (!sg)
178                                 sg = sglist;
179                         else {
180                                 /*
181                                  * If the driver previously mapped a shorter
182                                  * list, we could see a termination bit
183                                  * prematurely unless it fully inits the sg
184                                  * table on each mapping. We KNOW that there
185                                  * must be more entries here or the driver
186                                  * would be buggy, so force clear the
187                                  * termination bit to avoid doing a full
188                                  * sg_init_table() in drivers for each command.
189                                  */
190                                 sg->page_link &= ~0x02;
191                                 sg = sg_next(sg);
192                         }
193
194                         sg_set_page(sg, bvec->bv_page, nbytes, bvec->bv_offset);
195                         nsegs++;
196                 }
197                 bvprv = bvec;
198         } /* segments in rq */
199
200
201         if (unlikely(rq->cmd_flags & REQ_COPY_USER) &&
202             (rq->data_len & q->dma_pad_mask)) {
203                 unsigned int pad_len = (q->dma_pad_mask & ~rq->data_len) + 1;
204
205                 sg->length += pad_len;
206                 rq->extra_len += pad_len;
207         }
208
209         if (q->dma_drain_size && q->dma_drain_needed(rq)) {
210                 if (rq->cmd_flags & REQ_RW)
211                         memset(q->dma_drain_buffer, 0, q->dma_drain_size);
212
213                 sg->page_link &= ~0x02;
214                 sg = sg_next(sg);
215                 sg_set_page(sg, virt_to_page(q->dma_drain_buffer),
216                             q->dma_drain_size,
217                             ((unsigned long)q->dma_drain_buffer) &
218                             (PAGE_SIZE - 1));
219                 nsegs++;
220                 rq->extra_len += q->dma_drain_size;
221         }
222
223         if (sg)
224                 sg_mark_end(sg);
225
226         return nsegs;
227 }
228 EXPORT_SYMBOL(blk_rq_map_sg);
229
230 static inline int ll_new_hw_segment(struct request_queue *q,
231                                     struct request *req,
232                                     struct bio *bio)
233 {
234         int nr_phys_segs = bio_phys_segments(q, bio);
235
236         if (req->nr_phys_segments + nr_phys_segs > q->max_hw_segments
237             || req->nr_phys_segments + nr_phys_segs > q->max_phys_segments) {
238                 req->cmd_flags |= REQ_NOMERGE;
239                 if (req == q->last_merge)
240                         q->last_merge = NULL;
241                 return 0;
242         }
243
244         /*
245          * This will form the start of a new hw segment.  Bump both
246          * counters.
247          */
248         req->nr_phys_segments += nr_phys_segs;
249         return 1;
250 }
251
252 int ll_back_merge_fn(struct request_queue *q, struct request *req,
253                      struct bio *bio)
254 {
255         unsigned short max_sectors;
256
257         if (unlikely(blk_pc_request(req)))
258                 max_sectors = q->max_hw_sectors;
259         else
260                 max_sectors = q->max_sectors;
261
262         if (req->nr_sectors + bio_sectors(bio) > max_sectors) {
263                 req->cmd_flags |= REQ_NOMERGE;
264                 if (req == q->last_merge)
265                         q->last_merge = NULL;
266                 return 0;
267         }
268         if (!bio_flagged(req->biotail, BIO_SEG_VALID))
269                 blk_recount_segments(q, req->biotail);
270         if (!bio_flagged(bio, BIO_SEG_VALID))
271                 blk_recount_segments(q, bio);
272
273         return ll_new_hw_segment(q, req, bio);
274 }
275
276 int ll_front_merge_fn(struct request_queue *q, struct request *req,
277                       struct bio *bio)
278 {
279         unsigned short max_sectors;
280
281         if (unlikely(blk_pc_request(req)))
282                 max_sectors = q->max_hw_sectors;
283         else
284                 max_sectors = q->max_sectors;
285
286
287         if (req->nr_sectors + bio_sectors(bio) > max_sectors) {
288                 req->cmd_flags |= REQ_NOMERGE;
289                 if (req == q->last_merge)
290                         q->last_merge = NULL;
291                 return 0;
292         }
293         if (!bio_flagged(bio, BIO_SEG_VALID))
294                 blk_recount_segments(q, bio);
295         if (!bio_flagged(req->bio, BIO_SEG_VALID))
296                 blk_recount_segments(q, req->bio);
297
298         return ll_new_hw_segment(q, req, bio);
299 }
300
301 static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
302                                 struct request *next)
303 {
304         int total_phys_segments;
305         unsigned int seg_size =
306                 req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size;
307
308         /*
309          * First check if the either of the requests are re-queued
310          * requests.  Can't merge them if they are.
311          */
312         if (req->special || next->special)
313                 return 0;
314
315         /*
316          * Will it become too large?
317          */
318         if ((req->nr_sectors + next->nr_sectors) > q->max_sectors)
319                 return 0;
320
321         total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
322         if (blk_phys_contig_segment(q, req->biotail, next->bio)) {
323                 if (req->nr_phys_segments == 1)
324                         req->bio->bi_seg_front_size = seg_size;
325                 if (next->nr_phys_segments == 1)
326                         next->biotail->bi_seg_back_size = seg_size;
327                 total_phys_segments--;
328         }
329
330         if (total_phys_segments > q->max_phys_segments)
331                 return 0;
332
333         if (total_phys_segments > q->max_hw_segments)
334                 return 0;
335
336         /* Merge is OK... */
337         req->nr_phys_segments = total_phys_segments;
338         return 1;
339 }
340
341 /*
342  * Has to be called with the request spinlock acquired
343  */
344 static int attempt_merge(struct request_queue *q, struct request *req,
345                           struct request *next)
346 {
347         if (!rq_mergeable(req) || !rq_mergeable(next))
348                 return 0;
349
350         /*
351          * not contiguous
352          */
353         if (req->sector + req->nr_sectors != next->sector)
354                 return 0;
355
356         if (rq_data_dir(req) != rq_data_dir(next)
357             || req->rq_disk != next->rq_disk
358             || next->special)
359                 return 0;
360
361         if (blk_integrity_rq(req) != blk_integrity_rq(next))
362                 return 0;
363
364         /*
365          * If we are allowed to merge, then append bio list
366          * from next to rq and release next. merge_requests_fn
367          * will have updated segment counts, update sector
368          * counts here.
369          */
370         if (!ll_merge_requests_fn(q, req, next))
371                 return 0;
372
373         /*
374          * At this point we have either done a back merge
375          * or front merge. We need the smaller start_time of
376          * the merged requests to be the current request
377          * for accounting purposes.
378          */
379         if (time_after(req->start_time, next->start_time))
380                 req->start_time = next->start_time;
381
382         req->biotail->bi_next = next->bio;
383         req->biotail = next->biotail;
384
385         req->nr_sectors = req->hard_nr_sectors += next->hard_nr_sectors;
386
387         elv_merge_requests(q, req, next);
388
389         if (req->rq_disk) {
390                 struct hd_struct *part;
391                 int cpu;
392
393                 cpu = part_stat_lock();
394                 part = disk_map_sector_rcu(req->rq_disk, req->sector);
395
396                 part_round_stats(cpu, part);
397                 part_dec_in_flight(part);
398
399                 part_stat_unlock();
400         }
401
402         req->ioprio = ioprio_best(req->ioprio, next->ioprio);
403         if (blk_rq_cpu_valid(next))
404                 req->cpu = next->cpu;
405
406         __blk_put_request(q, next);
407         return 1;
408 }
409
410 int attempt_back_merge(struct request_queue *q, struct request *rq)
411 {
412         struct request *next = elv_latter_request(q, rq);
413
414         if (next)
415                 return attempt_merge(q, rq, next);
416
417         return 0;
418 }
419
420 int attempt_front_merge(struct request_queue *q, struct request *rq)
421 {
422         struct request *prev = elv_former_request(q, rq);
423
424         if (prev)
425                 return attempt_merge(q, prev, rq);
426
427         return 0;
428 }