block: drop request->hard_* and *nr_sectors
[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) > q->bounce_pfn;
36                         if (high || highprv)
37                                 goto new_segment;
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;
45
46                                 seg_size += bv->bv_len;
47                                 bvprv = bv;
48                                 continue;
49                         }
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;
54
55                         nr_phys_segs++;
56                         bvprv = bv;
57                         seg_size = bv->bv_len;
58                         highprv = high;
59                 }
60                 bbio = bio;
61         }
62
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;
67
68         return nr_phys_segs;
69 }
70
71 void blk_recalc_rq_segments(struct request *rq)
72 {
73         rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio);
74 }
75
76 void blk_recount_segments(struct request_queue *q, struct bio *bio)
77 {
78         struct bio *nxt = bio->bi_next;
79
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);
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 {
90         if (!test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags))
91                 return 0;
92
93         if (bio->bi_seg_back_size + nxt->bi_seg_front_size >
94             q->max_segment_size)
95                 return 0;
96
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
103         /*
104          * bio and nxt are contiguous in memory; check if the queue allows
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
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;
126         cluster = test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
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
171
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;
176
177                 sg->length += pad_len;
178                 rq->extra_len += pad_len;
179         }
180
181         if (q->dma_drain_size && q->dma_drain_needed(rq)) {
182                 if (rq->cmd_flags & REQ_RW)
183                         memset(q->dma_drain_buffer, 0, q->dma_drain_size);
184
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;
193         }
194
195         if (sg)
196                 sg_mark_end(sg);
197
198         return nsegs;
199 }
200 EXPORT_SYMBOL(blk_rq_map_sg);
201
202 static inline int ll_new_hw_segment(struct request_queue *q,
203                                     struct request *req,
204                                     struct bio *bio)
205 {
206         int nr_phys_segs = bio_phys_segments(q, bio);
207
208         if (req->nr_phys_segments + nr_phys_segs > q->max_hw_segments
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          */
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(blk_pc_request(req)))
230                 max_sectors = q->max_hw_sectors;
231         else
232                 max_sectors = q->max_sectors;
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(blk_pc_request(req)))
254                 max_sectors = q->max_hw_sectors;
255         else
256                 max_sectors = q->max_sectors;
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)) > q->max_sectors)
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 > q->max_phys_segments)
303                 return 0;
304
305         if (total_phys_segments > q->max_hw_segments)
306                 return 0;
307
308         /* Merge is OK... */
309         req->nr_phys_segments = total_phys_segments;
310         return 1;
311 }
312
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();
320                 part = disk_map_sector_rcu(req->rq_disk, blk_rq_pos(req));
321
322                 part_round_stats(cpu, part);
323                 part_dec_in_flight(part);
324
325                 part_stat_unlock();
326         }
327 }
328
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          */
341         if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next))
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
349         if (blk_integrity_rq(req) != blk_integrity_rq(next))
350                 return 0;
351
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
373         req->data_len += blk_rq_bytes(next);
374
375         elv_merge_requests(q, req, next);
376
377         /*
378          * 'next' is going away, so update stats accordingly
379          */
380         blk_account_io_merge(next);
381
382         req->ioprio = ioprio_best(req->ioprio, next->ioprio);
383         if (blk_rq_cpu_valid(next))
384                 req->cpu = next->cpu;
385
386         /* owner-ship of bio passed from next to req */
387         next->bio = NULL;
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 }