Add missing blk_trace_remove_sysfs to be in pair with blk_trace_init_sysfs
[linux-2.6.git] / block / blk-barrier.c
1 /*
2  * Functions related to barrier IO handling
3  */
4 #include <linux/kernel.h>
5 #include <linux/module.h>
6 #include <linux/bio.h>
7 #include <linux/blkdev.h>
8
9 #include "blk.h"
10
11 /**
12  * blk_queue_ordered - does this queue support ordered writes
13  * @q:        the request queue
14  * @ordered:  one of QUEUE_ORDERED_*
15  * @prepare_flush_fn: rq setup helper for cache flush ordered writes
16  *
17  * Description:
18  *   For journalled file systems, doing ordered writes on a commit
19  *   block instead of explicitly doing wait_on_buffer (which is bad
20  *   for performance) can be a big win. Block drivers supporting this
21  *   feature should call this function and indicate so.
22  *
23  **/
24 int blk_queue_ordered(struct request_queue *q, unsigned ordered,
25                       prepare_flush_fn *prepare_flush_fn)
26 {
27         if (!prepare_flush_fn && (ordered & (QUEUE_ORDERED_DO_PREFLUSH |
28                                              QUEUE_ORDERED_DO_POSTFLUSH))) {
29                 printk(KERN_ERR "%s: prepare_flush_fn required\n", __func__);
30                 return -EINVAL;
31         }
32
33         if (ordered != QUEUE_ORDERED_NONE &&
34             ordered != QUEUE_ORDERED_DRAIN &&
35             ordered != QUEUE_ORDERED_DRAIN_FLUSH &&
36             ordered != QUEUE_ORDERED_DRAIN_FUA &&
37             ordered != QUEUE_ORDERED_TAG &&
38             ordered != QUEUE_ORDERED_TAG_FLUSH &&
39             ordered != QUEUE_ORDERED_TAG_FUA) {
40                 printk(KERN_ERR "blk_queue_ordered: bad value %d\n", ordered);
41                 return -EINVAL;
42         }
43
44         q->ordered = ordered;
45         q->next_ordered = ordered;
46         q->prepare_flush_fn = prepare_flush_fn;
47
48         return 0;
49 }
50 EXPORT_SYMBOL(blk_queue_ordered);
51
52 /*
53  * Cache flushing for ordered writes handling
54  */
55 unsigned blk_ordered_cur_seq(struct request_queue *q)
56 {
57         if (!q->ordseq)
58                 return 0;
59         return 1 << ffz(q->ordseq);
60 }
61
62 unsigned blk_ordered_req_seq(struct request *rq)
63 {
64         struct request_queue *q = rq->q;
65
66         BUG_ON(q->ordseq == 0);
67
68         if (rq == &q->pre_flush_rq)
69                 return QUEUE_ORDSEQ_PREFLUSH;
70         if (rq == &q->bar_rq)
71                 return QUEUE_ORDSEQ_BAR;
72         if (rq == &q->post_flush_rq)
73                 return QUEUE_ORDSEQ_POSTFLUSH;
74
75         /*
76          * !fs requests don't need to follow barrier ordering.  Always
77          * put them at the front.  This fixes the following deadlock.
78          *
79          * http://thread.gmane.org/gmane.linux.kernel/537473
80          */
81         if (!blk_fs_request(rq))
82                 return QUEUE_ORDSEQ_DRAIN;
83
84         if ((rq->cmd_flags & REQ_ORDERED_COLOR) ==
85             (q->orig_bar_rq->cmd_flags & REQ_ORDERED_COLOR))
86                 return QUEUE_ORDSEQ_DRAIN;
87         else
88                 return QUEUE_ORDSEQ_DONE;
89 }
90
91 bool blk_ordered_complete_seq(struct request_queue *q, unsigned seq, int error)
92 {
93         struct request *rq;
94
95         if (error && !q->orderr)
96                 q->orderr = error;
97
98         BUG_ON(q->ordseq & seq);
99         q->ordseq |= seq;
100
101         if (blk_ordered_cur_seq(q) != QUEUE_ORDSEQ_DONE)
102                 return false;
103
104         /*
105          * Okay, sequence complete.
106          */
107         q->ordseq = 0;
108         rq = q->orig_bar_rq;
109         __blk_end_request_all(rq, q->orderr);
110         return true;
111 }
112
113 static void pre_flush_end_io(struct request *rq, int error)
114 {
115         elv_completed_request(rq->q, rq);
116         blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_PREFLUSH, error);
117 }
118
119 static void bar_end_io(struct request *rq, int error)
120 {
121         elv_completed_request(rq->q, rq);
122         blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_BAR, error);
123 }
124
125 static void post_flush_end_io(struct request *rq, int error)
126 {
127         elv_completed_request(rq->q, rq);
128         blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_POSTFLUSH, error);
129 }
130
131 static void queue_flush(struct request_queue *q, unsigned which)
132 {
133         struct request *rq;
134         rq_end_io_fn *end_io;
135
136         if (which == QUEUE_ORDERED_DO_PREFLUSH) {
137                 rq = &q->pre_flush_rq;
138                 end_io = pre_flush_end_io;
139         } else {
140                 rq = &q->post_flush_rq;
141                 end_io = post_flush_end_io;
142         }
143
144         blk_rq_init(q, rq);
145         rq->cmd_flags = REQ_HARDBARRIER;
146         rq->rq_disk = q->bar_rq.rq_disk;
147         rq->end_io = end_io;
148         q->prepare_flush_fn(q, rq);
149
150         elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
151 }
152
153 static inline bool start_ordered(struct request_queue *q, struct request **rqp)
154 {
155         struct request *rq = *rqp;
156         unsigned skip = 0;
157
158         q->orderr = 0;
159         q->ordered = q->next_ordered;
160         q->ordseq |= QUEUE_ORDSEQ_STARTED;
161
162         /*
163          * For an empty barrier, there's no actual BAR request, which
164          * in turn makes POSTFLUSH unnecessary.  Mask them off.
165          */
166         if (!blk_rq_sectors(rq)) {
167                 q->ordered &= ~(QUEUE_ORDERED_DO_BAR |
168                                 QUEUE_ORDERED_DO_POSTFLUSH);
169                 /*
170                  * Empty barrier on a write-through device w/ ordered
171                  * tag has no command to issue and without any command
172                  * to issue, ordering by tag can't be used.  Drain
173                  * instead.
174                  */
175                 if ((q->ordered & QUEUE_ORDERED_BY_TAG) &&
176                     !(q->ordered & QUEUE_ORDERED_DO_PREFLUSH)) {
177                         q->ordered &= ~QUEUE_ORDERED_BY_TAG;
178                         q->ordered |= QUEUE_ORDERED_BY_DRAIN;
179                 }
180         }
181
182         /* stash away the original request */
183         blk_dequeue_request(rq);
184         q->orig_bar_rq = rq;
185         rq = NULL;
186
187         /*
188          * Queue ordered sequence.  As we stack them at the head, we
189          * need to queue in reverse order.  Note that we rely on that
190          * no fs request uses ELEVATOR_INSERT_FRONT and thus no fs
191          * request gets inbetween ordered sequence.
192          */
193         if (q->ordered & QUEUE_ORDERED_DO_POSTFLUSH) {
194                 queue_flush(q, QUEUE_ORDERED_DO_POSTFLUSH);
195                 rq = &q->post_flush_rq;
196         } else
197                 skip |= QUEUE_ORDSEQ_POSTFLUSH;
198
199         if (q->ordered & QUEUE_ORDERED_DO_BAR) {
200                 rq = &q->bar_rq;
201
202                 /* initialize proxy request and queue it */
203                 blk_rq_init(q, rq);
204                 if (bio_data_dir(q->orig_bar_rq->bio) == WRITE)
205                         rq->cmd_flags |= REQ_RW;
206                 if (q->ordered & QUEUE_ORDERED_DO_FUA)
207                         rq->cmd_flags |= REQ_FUA;
208                 init_request_from_bio(rq, q->orig_bar_rq->bio);
209                 rq->end_io = bar_end_io;
210
211                 elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
212         } else
213                 skip |= QUEUE_ORDSEQ_BAR;
214
215         if (q->ordered & QUEUE_ORDERED_DO_PREFLUSH) {
216                 queue_flush(q, QUEUE_ORDERED_DO_PREFLUSH);
217                 rq = &q->pre_flush_rq;
218         } else
219                 skip |= QUEUE_ORDSEQ_PREFLUSH;
220
221         if ((q->ordered & QUEUE_ORDERED_BY_DRAIN) && queue_in_flight(q))
222                 rq = NULL;
223         else
224                 skip |= QUEUE_ORDSEQ_DRAIN;
225
226         *rqp = rq;
227
228         /*
229          * Complete skipped sequences.  If whole sequence is complete,
230          * return false to tell elevator that this request is gone.
231          */
232         return !blk_ordered_complete_seq(q, skip, 0);
233 }
234
235 bool blk_do_ordered(struct request_queue *q, struct request **rqp)
236 {
237         struct request *rq = *rqp;
238         const int is_barrier = blk_fs_request(rq) && blk_barrier_rq(rq);
239
240         if (!q->ordseq) {
241                 if (!is_barrier)
242                         return true;
243
244                 if (q->next_ordered != QUEUE_ORDERED_NONE)
245                         return start_ordered(q, rqp);
246                 else {
247                         /*
248                          * Queue ordering not supported.  Terminate
249                          * with prejudice.
250                          */
251                         blk_dequeue_request(rq);
252                         __blk_end_request_all(rq, -EOPNOTSUPP);
253                         *rqp = NULL;
254                         return false;
255                 }
256         }
257
258         /*
259          * Ordered sequence in progress
260          */
261
262         /* Special requests are not subject to ordering rules. */
263         if (!blk_fs_request(rq) &&
264             rq != &q->pre_flush_rq && rq != &q->post_flush_rq)
265                 return true;
266
267         if (q->ordered & QUEUE_ORDERED_BY_TAG) {
268                 /* Ordered by tag.  Blocking the next barrier is enough. */
269                 if (is_barrier && rq != &q->bar_rq)
270                         *rqp = NULL;
271         } else {
272                 /* Ordered by draining.  Wait for turn. */
273                 WARN_ON(blk_ordered_req_seq(rq) < blk_ordered_cur_seq(q));
274                 if (blk_ordered_req_seq(rq) > blk_ordered_cur_seq(q))
275                         *rqp = NULL;
276         }
277
278         return true;
279 }
280
281 static void bio_end_empty_barrier(struct bio *bio, int err)
282 {
283         if (err) {
284                 if (err == -EOPNOTSUPP)
285                         set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
286                 clear_bit(BIO_UPTODATE, &bio->bi_flags);
287         }
288
289         complete(bio->bi_private);
290 }
291
292 /**
293  * blkdev_issue_flush - queue a flush
294  * @bdev:       blockdev to issue flush for
295  * @error_sector:       error sector
296  *
297  * Description:
298  *    Issue a flush for the block device in question. Caller can supply
299  *    room for storing the error offset in case of a flush error, if they
300  *    wish to.
301  */
302 int blkdev_issue_flush(struct block_device *bdev, sector_t *error_sector)
303 {
304         DECLARE_COMPLETION_ONSTACK(wait);
305         struct request_queue *q;
306         struct bio *bio;
307         int ret;
308
309         if (bdev->bd_disk == NULL)
310                 return -ENXIO;
311
312         q = bdev_get_queue(bdev);
313         if (!q)
314                 return -ENXIO;
315
316         bio = bio_alloc(GFP_KERNEL, 0);
317         bio->bi_end_io = bio_end_empty_barrier;
318         bio->bi_private = &wait;
319         bio->bi_bdev = bdev;
320         submit_bio(WRITE_BARRIER, bio);
321
322         wait_for_completion(&wait);
323
324         /*
325          * The driver must store the error location in ->bi_sector, if
326          * it supports it. For non-stacked drivers, this should be copied
327          * from blk_rq_pos(rq).
328          */
329         if (error_sector)
330                 *error_sector = bio->bi_sector;
331
332         ret = 0;
333         if (bio_flagged(bio, BIO_EOPNOTSUPP))
334                 ret = -EOPNOTSUPP;
335         else if (!bio_flagged(bio, BIO_UPTODATE))
336                 ret = -EIO;
337
338         bio_put(bio);
339         return ret;
340 }
341 EXPORT_SYMBOL(blkdev_issue_flush);
342
343 static void blkdev_discard_end_io(struct bio *bio, int err)
344 {
345         if (err) {
346                 if (err == -EOPNOTSUPP)
347                         set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
348                 clear_bit(BIO_UPTODATE, &bio->bi_flags);
349         }
350
351         if (bio->bi_private)
352                 complete(bio->bi_private);
353
354         bio_put(bio);
355 }
356
357 /**
358  * blkdev_issue_discard - queue a discard
359  * @bdev:       blockdev to issue discard for
360  * @sector:     start sector
361  * @nr_sects:   number of sectors to discard
362  * @gfp_mask:   memory allocation flags (for bio_alloc)
363  * @flags:      DISCARD_FL_* flags to control behaviour
364  *
365  * Description:
366  *    Issue a discard request for the sectors in question.
367  */
368 int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
369                 sector_t nr_sects, gfp_t gfp_mask, int flags)
370 {
371         DECLARE_COMPLETION_ONSTACK(wait);
372         struct request_queue *q = bdev_get_queue(bdev);
373         int type = flags & DISCARD_FL_BARRIER ?
374                 DISCARD_BARRIER : DISCARD_NOBARRIER;
375         int ret = 0;
376
377         if (!q)
378                 return -ENXIO;
379
380         if (!q->prepare_discard_fn)
381                 return -EOPNOTSUPP;
382
383         while (nr_sects && !ret) {
384                 struct bio *bio = bio_alloc(gfp_mask, 0);
385                 if (!bio)
386                         return -ENOMEM;
387
388                 bio->bi_end_io = blkdev_discard_end_io;
389                 bio->bi_bdev = bdev;
390                 if (flags & DISCARD_FL_WAIT)
391                         bio->bi_private = &wait;
392
393                 bio->bi_sector = sector;
394
395                 if (nr_sects > queue_max_hw_sectors(q)) {
396                         bio->bi_size = queue_max_hw_sectors(q) << 9;
397                         nr_sects -= queue_max_hw_sectors(q);
398                         sector += queue_max_hw_sectors(q);
399                 } else {
400                         bio->bi_size = nr_sects << 9;
401                         nr_sects = 0;
402                 }
403
404                 bio_get(bio);
405                 submit_bio(type, bio);
406
407                 if (flags & DISCARD_FL_WAIT)
408                         wait_for_completion(&wait);
409
410                 if (bio_flagged(bio, BIO_EOPNOTSUPP))
411                         ret = -EOPNOTSUPP;
412                 else if (!bio_flagged(bio, BIO_UPTODATE))
413                         ret = -EIO;
414                 bio_put(bio);
415         }
416         return ret;
417 }
418 EXPORT_SYMBOL(blkdev_issue_discard);