2 * Functions related to barrier IO handling
4 #include <linux/kernel.h>
5 #include <linux/module.h>
7 #include <linux/blkdev.h>
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
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.
24 int blk_queue_ordered(struct request_queue *q, unsigned ordered,
25 prepare_flush_fn *prepare_flush_fn)
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__);
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);
45 q->next_ordered = ordered;
46 q->prepare_flush_fn = prepare_flush_fn;
50 EXPORT_SYMBOL(blk_queue_ordered);
53 * Cache flushing for ordered writes handling
55 unsigned blk_ordered_cur_seq(struct request_queue *q)
59 return 1 << ffz(q->ordseq);
62 unsigned blk_ordered_req_seq(struct request *rq)
64 struct request_queue *q = rq->q;
66 BUG_ON(q->ordseq == 0);
68 if (rq == &q->pre_flush_rq)
69 return QUEUE_ORDSEQ_PREFLUSH;
71 return QUEUE_ORDSEQ_BAR;
72 if (rq == &q->post_flush_rq)
73 return QUEUE_ORDSEQ_POSTFLUSH;
76 * !fs requests don't need to follow barrier ordering. Always
77 * put them at the front. This fixes the following deadlock.
79 * http://thread.gmane.org/gmane.linux.kernel/537473
81 if (!blk_fs_request(rq))
82 return QUEUE_ORDSEQ_DRAIN;
84 if ((rq->cmd_flags & REQ_ORDERED_COLOR) ==
85 (q->orig_bar_rq->cmd_flags & REQ_ORDERED_COLOR))
86 return QUEUE_ORDSEQ_DRAIN;
88 return QUEUE_ORDSEQ_DONE;
91 bool blk_ordered_complete_seq(struct request_queue *q, unsigned seq, int error)
95 if (error && !q->orderr)
98 BUG_ON(q->ordseq & seq);
101 if (blk_ordered_cur_seq(q) != QUEUE_ORDSEQ_DONE)
105 * Okay, sequence complete.
110 if (__blk_end_request(rq, q->orderr, blk_rq_bytes(rq)))
116 static void pre_flush_end_io(struct request *rq, int error)
118 elv_completed_request(rq->q, rq);
119 blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_PREFLUSH, error);
122 static void bar_end_io(struct request *rq, int error)
124 elv_completed_request(rq->q, rq);
125 blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_BAR, error);
128 static void post_flush_end_io(struct request *rq, int error)
130 elv_completed_request(rq->q, rq);
131 blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_POSTFLUSH, error);
134 static void queue_flush(struct request_queue *q, unsigned which)
137 rq_end_io_fn *end_io;
139 if (which == QUEUE_ORDERED_DO_PREFLUSH) {
140 rq = &q->pre_flush_rq;
141 end_io = pre_flush_end_io;
143 rq = &q->post_flush_rq;
144 end_io = post_flush_end_io;
148 rq->cmd_flags = REQ_HARDBARRIER;
149 rq->rq_disk = q->bar_rq.rq_disk;
151 q->prepare_flush_fn(q, rq);
153 elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
156 static inline bool start_ordered(struct request_queue *q, struct request **rqp)
158 struct request *rq = *rqp;
162 q->ordered = q->next_ordered;
163 q->ordseq |= QUEUE_ORDSEQ_STARTED;
165 /* stash away the original request */
166 elv_dequeue_request(q, rq);
171 * Queue ordered sequence. As we stack them at the head, we
172 * need to queue in reverse order. Note that we rely on that
173 * no fs request uses ELEVATOR_INSERT_FRONT and thus no fs
174 * request gets inbetween ordered sequence. If this request is
175 * an empty barrier, we don't need to do a postflush ever since
176 * there will be no data written between the pre and post flush.
177 * Hence a single flush will suffice.
179 if ((q->ordered & QUEUE_ORDERED_DO_POSTFLUSH) &&
180 !blk_empty_barrier(q->orig_bar_rq)) {
181 queue_flush(q, QUEUE_ORDERED_DO_POSTFLUSH);
182 rq = &q->post_flush_rq;
184 skip |= QUEUE_ORDSEQ_POSTFLUSH;
186 if (q->ordered & QUEUE_ORDERED_DO_BAR) {
189 /* initialize proxy request and queue it */
191 if (bio_data_dir(q->orig_bar_rq->bio) == WRITE)
192 rq->cmd_flags |= REQ_RW;
193 if (q->ordered & QUEUE_ORDERED_DO_FUA)
194 rq->cmd_flags |= REQ_FUA;
195 init_request_from_bio(rq, q->orig_bar_rq->bio);
196 rq->end_io = bar_end_io;
198 elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
200 skip |= QUEUE_ORDSEQ_BAR;
202 if (q->ordered & QUEUE_ORDERED_DO_PREFLUSH) {
203 queue_flush(q, QUEUE_ORDERED_DO_PREFLUSH);
204 rq = &q->pre_flush_rq;
206 skip |= QUEUE_ORDSEQ_PREFLUSH;
208 if ((q->ordered & QUEUE_ORDERED_BY_DRAIN) && q->in_flight)
211 skip |= QUEUE_ORDSEQ_DRAIN;
216 * Complete skipped sequences. If whole sequence is complete,
217 * return false to tell elevator that this request is gone.
219 return !blk_ordered_complete_seq(q, skip, 0);
222 bool blk_do_ordered(struct request_queue *q, struct request **rqp)
224 struct request *rq = *rqp;
225 const int is_barrier = blk_fs_request(rq) && blk_barrier_rq(rq);
231 if (q->next_ordered != QUEUE_ORDERED_NONE)
232 return start_ordered(q, rqp);
235 * Queue ordering not supported. Terminate
238 elv_dequeue_request(q, rq);
239 if (__blk_end_request(rq, -EOPNOTSUPP,
248 * Ordered sequence in progress
251 /* Special requests are not subject to ordering rules. */
252 if (!blk_fs_request(rq) &&
253 rq != &q->pre_flush_rq && rq != &q->post_flush_rq)
256 if (q->ordered & QUEUE_ORDERED_BY_TAG) {
257 /* Ordered by tag. Blocking the next barrier is enough. */
258 if (is_barrier && rq != &q->bar_rq)
261 /* Ordered by draining. Wait for turn. */
262 WARN_ON(blk_ordered_req_seq(rq) < blk_ordered_cur_seq(q));
263 if (blk_ordered_req_seq(rq) > blk_ordered_cur_seq(q))
270 static void bio_end_empty_barrier(struct bio *bio, int err)
273 if (err == -EOPNOTSUPP)
274 set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
275 clear_bit(BIO_UPTODATE, &bio->bi_flags);
278 complete(bio->bi_private);
282 * blkdev_issue_flush - queue a flush
283 * @bdev: blockdev to issue flush for
284 * @error_sector: error sector
287 * Issue a flush for the block device in question. Caller can supply
288 * room for storing the error offset in case of a flush error, if they
289 * wish to. Caller must run wait_for_completion() on its own.
291 int blkdev_issue_flush(struct block_device *bdev, sector_t *error_sector)
293 DECLARE_COMPLETION_ONSTACK(wait);
294 struct request_queue *q;
298 if (bdev->bd_disk == NULL)
301 q = bdev_get_queue(bdev);
305 bio = bio_alloc(GFP_KERNEL, 0);
309 bio->bi_end_io = bio_end_empty_barrier;
310 bio->bi_private = &wait;
312 submit_bio(WRITE_BARRIER, bio);
314 wait_for_completion(&wait);
317 * The driver must store the error location in ->bi_sector, if
318 * it supports it. For non-stacked drivers, this should be copied
322 *error_sector = bio->bi_sector;
325 if (bio_flagged(bio, BIO_EOPNOTSUPP))
327 else if (!bio_flagged(bio, BIO_UPTODATE))
333 EXPORT_SYMBOL(blkdev_issue_flush);
335 static void blkdev_discard_end_io(struct bio *bio, int err)
338 if (err == -EOPNOTSUPP)
339 set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
340 clear_bit(BIO_UPTODATE, &bio->bi_flags);
347 * blkdev_issue_discard - queue a discard
348 * @bdev: blockdev to issue discard for
349 * @sector: start sector
350 * @nr_sects: number of sectors to discard
351 * @gfp_mask: memory allocation flags (for bio_alloc)
354 * Issue a discard request for the sectors in question. Does not wait.
356 int blkdev_issue_discard(struct block_device *bdev,
357 sector_t sector, sector_t nr_sects, gfp_t gfp_mask)
359 struct request_queue *q;
363 if (bdev->bd_disk == NULL)
366 q = bdev_get_queue(bdev);
370 if (!q->prepare_discard_fn)
373 while (nr_sects && !ret) {
374 bio = bio_alloc(gfp_mask, 0);
378 bio->bi_end_io = blkdev_discard_end_io;
381 bio->bi_sector = sector;
383 if (nr_sects > q->max_hw_sectors) {
384 bio->bi_size = q->max_hw_sectors << 9;
385 nr_sects -= q->max_hw_sectors;
386 sector += q->max_hw_sectors;
388 bio->bi_size = nr_sects << 9;
392 submit_bio(DISCARD_BARRIER, bio);
394 /* Check if it failed immediately */
395 if (bio_flagged(bio, BIO_EOPNOTSUPP))
397 else if (!bio_flagged(bio, BIO_UPTODATE))
403 EXPORT_SYMBOL(blkdev_issue_discard);