2 * Functions to sequence FLUSH and FUA writes.
4 #include <linux/kernel.h>
5 #include <linux/module.h>
7 #include <linux/blkdev.h>
12 /* FLUSH/FUA sequences */
14 QUEUE_FSEQ_STARTED = (1 << 0), /* flushing in progress */
15 QUEUE_FSEQ_PREFLUSH = (1 << 1), /* pre-flushing in progress */
16 QUEUE_FSEQ_DATA = (1 << 2), /* data write in progress */
17 QUEUE_FSEQ_POSTFLUSH = (1 << 3), /* post-flushing in progress */
18 QUEUE_FSEQ_DONE = (1 << 4),
21 static struct request *queue_next_fseq(struct request_queue *q);
23 unsigned blk_flush_cur_seq(struct request_queue *q)
27 return 1 << ffz(q->flush_seq);
30 static struct request *blk_flush_complete_seq(struct request_queue *q,
31 unsigned seq, int error)
33 struct request *next_rq = NULL;
35 if (error && !q->flush_err)
38 BUG_ON(q->flush_seq & seq);
41 if (blk_flush_cur_seq(q) != QUEUE_FSEQ_DONE) {
42 /* not complete yet, queue the next flush sequence */
43 next_rq = queue_next_fseq(q);
45 /* complete this flush request */
46 __blk_end_request_all(q->orig_flush_rq, q->flush_err);
47 q->orig_flush_rq = NULL;
50 /* dispatch the next flush if there's one */
51 if (!list_empty(&q->pending_flushes)) {
52 next_rq = list_entry_rq(q->pending_flushes.next);
53 list_move(&next_rq->queuelist, &q->queue_head);
59 static void blk_flush_complete_seq_end_io(struct request_queue *q,
60 unsigned seq, int error)
62 bool was_empty = elv_queue_empty(q);
63 struct request *next_rq;
65 next_rq = blk_flush_complete_seq(q, seq, error);
68 * Moving a request silently to empty queue_head may stall the
69 * queue. Kick the queue in those cases.
71 if (was_empty && next_rq)
75 static void pre_flush_end_io(struct request *rq, int error)
77 elv_completed_request(rq->q, rq);
78 blk_flush_complete_seq_end_io(rq->q, QUEUE_FSEQ_PREFLUSH, error);
81 static void flush_data_end_io(struct request *rq, int error)
83 elv_completed_request(rq->q, rq);
84 blk_flush_complete_seq_end_io(rq->q, QUEUE_FSEQ_DATA, error);
87 static void post_flush_end_io(struct request *rq, int error)
89 elv_completed_request(rq->q, rq);
90 blk_flush_complete_seq_end_io(rq->q, QUEUE_FSEQ_POSTFLUSH, error);
93 static void init_flush_request(struct request *rq, struct gendisk *disk)
95 rq->cmd_type = REQ_TYPE_FS;
96 rq->cmd_flags = WRITE_FLUSH;
100 static struct request *queue_next_fseq(struct request_queue *q)
102 struct request *orig_rq = q->orig_flush_rq;
103 struct request *rq = &q->flush_rq;
107 switch (blk_flush_cur_seq(q)) {
108 case QUEUE_FSEQ_PREFLUSH:
109 init_flush_request(rq, orig_rq->rq_disk);
110 rq->end_io = pre_flush_end_io;
112 case QUEUE_FSEQ_DATA:
113 init_request_from_bio(rq, orig_rq->bio);
114 rq->cmd_flags &= ~(REQ_FLUSH | REQ_FUA);
115 rq->cmd_flags |= orig_rq->cmd_flags & (REQ_FLUSH | REQ_FUA);
116 rq->end_io = flush_data_end_io;
118 case QUEUE_FSEQ_POSTFLUSH:
119 init_flush_request(rq, orig_rq->rq_disk);
120 rq->end_io = post_flush_end_io;
126 elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
130 struct request *blk_do_flush(struct request_queue *q, struct request *rq)
132 unsigned int fflags = q->flush_flags; /* may change, cache it */
133 bool has_flush = fflags & REQ_FLUSH, has_fua = fflags & REQ_FUA;
134 bool do_preflush = has_flush && (rq->cmd_flags & REQ_FLUSH);
135 bool do_postflush = has_flush && !has_fua && (rq->cmd_flags & REQ_FUA);
139 * Special case. If there's data but flush is not necessary,
140 * the request can be issued directly.
142 * Flush w/o data should be able to be issued directly too but
143 * currently some drivers assume that rq->bio contains
144 * non-zero data if it isn't NULL and empty FLUSH requests
145 * getting here usually have bio's without data.
147 if (blk_rq_sectors(rq) && !do_preflush && !do_postflush) {
148 rq->cmd_flags &= ~REQ_FLUSH;
150 rq->cmd_flags &= ~REQ_FUA;
155 * Sequenced flushes can't be processed in parallel. If
156 * another one is already in progress, queue for later
160 list_move_tail(&rq->queuelist, &q->pending_flushes);
165 * Start a new flush sequence
168 q->flush_seq |= QUEUE_FSEQ_STARTED;
170 /* adjust FLUSH/FUA of the original request and stash it away */
171 rq->cmd_flags &= ~REQ_FLUSH;
173 rq->cmd_flags &= ~REQ_FUA;
174 blk_dequeue_request(rq);
175 q->orig_flush_rq = rq;
177 /* skip unneded sequences and return the first one */
179 skip |= QUEUE_FSEQ_PREFLUSH;
180 if (!blk_rq_sectors(rq))
181 skip |= QUEUE_FSEQ_DATA;
183 skip |= QUEUE_FSEQ_POSTFLUSH;
184 return blk_flush_complete_seq(q, skip, 0);
187 static void bio_end_empty_barrier(struct bio *bio, int err)
190 if (err == -EOPNOTSUPP)
191 set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
192 clear_bit(BIO_UPTODATE, &bio->bi_flags);
195 complete(bio->bi_private);
200 * blkdev_issue_flush - queue a flush
201 * @bdev: blockdev to issue flush for
202 * @gfp_mask: memory allocation flags (for bio_alloc)
203 * @error_sector: error sector
204 * @flags: BLKDEV_IFL_* flags to control behaviour
207 * Issue a flush for the block device in question. Caller can supply
208 * room for storing the error offset in case of a flush error, if they
209 * wish to. If WAIT flag is not passed then caller may check only what
210 * request was pushed in some internal queue for later handling.
212 int blkdev_issue_flush(struct block_device *bdev, gfp_t gfp_mask,
213 sector_t *error_sector, unsigned long flags)
215 DECLARE_COMPLETION_ONSTACK(wait);
216 struct request_queue *q;
220 if (bdev->bd_disk == NULL)
223 q = bdev_get_queue(bdev);
228 * some block devices may not have their queue correctly set up here
229 * (e.g. loop device without a backing file) and so issuing a flush
230 * here will panic. Ensure there is a request function before issuing
233 if (!q->make_request_fn)
236 bio = bio_alloc(gfp_mask, 0);
237 bio->bi_end_io = bio_end_empty_barrier;
239 if (test_bit(BLKDEV_WAIT, &flags))
240 bio->bi_private = &wait;
243 submit_bio(WRITE_BARRIER, bio);
244 if (test_bit(BLKDEV_WAIT, &flags)) {
245 wait_for_completion(&wait);
247 * The driver must store the error location in ->bi_sector, if
248 * it supports it. For non-stacked drivers, this should be
249 * copied from blk_rq_pos(rq).
252 *error_sector = bio->bi_sector;
255 if (bio_flagged(bio, BIO_EOPNOTSUPP))
257 else if (!bio_flagged(bio, BIO_UPTODATE))
263 EXPORT_SYMBOL(blkdev_issue_flush);