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 pre_flush_end_io(struct request *rq, int error)
61 elv_completed_request(rq->q, rq);
62 blk_flush_complete_seq(rq->q, QUEUE_FSEQ_PREFLUSH, error);
65 static void flush_data_end_io(struct request *rq, int error)
67 elv_completed_request(rq->q, rq);
68 blk_flush_complete_seq(rq->q, QUEUE_FSEQ_DATA, error);
71 static void post_flush_end_io(struct request *rq, int error)
73 elv_completed_request(rq->q, rq);
74 blk_flush_complete_seq(rq->q, QUEUE_FSEQ_POSTFLUSH, error);
77 static void queue_flush(struct request_queue *q, struct request *rq,
81 rq->cmd_type = REQ_TYPE_FS;
82 rq->cmd_flags = REQ_FLUSH;
83 rq->rq_disk = q->orig_flush_rq->rq_disk;
86 elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
89 static struct request *queue_next_fseq(struct request_queue *q)
91 struct request *orig_rq = q->orig_flush_rq;
92 struct request *rq = &q->flush_rq;
94 switch (blk_flush_cur_seq(q)) {
95 case QUEUE_FSEQ_PREFLUSH:
96 queue_flush(q, rq, pre_flush_end_io);
100 /* initialize proxy request, inherit FLUSH/FUA and queue it */
102 init_request_from_bio(rq, orig_rq->bio);
103 rq->cmd_flags &= ~(REQ_FLUSH | REQ_FUA);
104 rq->cmd_flags |= orig_rq->cmd_flags & (REQ_FLUSH | REQ_FUA);
105 rq->end_io = flush_data_end_io;
107 elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
110 case QUEUE_FSEQ_POSTFLUSH:
111 queue_flush(q, rq, post_flush_end_io);
120 struct request *blk_do_flush(struct request_queue *q, struct request *rq)
122 unsigned int fflags = q->flush_flags; /* may change, cache it */
123 bool has_flush = fflags & REQ_FLUSH, has_fua = fflags & REQ_FUA;
124 bool do_preflush = has_flush && (rq->cmd_flags & REQ_FLUSH);
125 bool do_postflush = has_flush && !has_fua && (rq->cmd_flags & REQ_FUA);
129 * Special case. If there's data but flush is not necessary,
130 * the request can be issued directly.
132 * Flush w/o data should be able to be issued directly too but
133 * currently some drivers assume that rq->bio contains
134 * non-zero data if it isn't NULL and empty FLUSH requests
135 * getting here usually have bio's without data.
137 if (blk_rq_sectors(rq) && !do_preflush && !do_postflush) {
138 rq->cmd_flags &= ~REQ_FLUSH;
140 rq->cmd_flags &= ~REQ_FUA;
145 * Sequenced flushes can't be processed in parallel. If
146 * another one is already in progress, queue for later
150 list_move_tail(&rq->queuelist, &q->pending_flushes);
155 * Start a new flush sequence
158 q->flush_seq |= QUEUE_FSEQ_STARTED;
160 /* adjust FLUSH/FUA of the original request and stash it away */
161 rq->cmd_flags &= ~REQ_FLUSH;
163 rq->cmd_flags &= ~REQ_FUA;
164 blk_dequeue_request(rq);
165 q->orig_flush_rq = rq;
167 /* skip unneded sequences and return the first one */
169 skip |= QUEUE_FSEQ_PREFLUSH;
170 if (!blk_rq_sectors(rq))
171 skip |= QUEUE_FSEQ_DATA;
173 skip |= QUEUE_FSEQ_POSTFLUSH;
174 return blk_flush_complete_seq(q, skip, 0);
177 static void bio_end_empty_barrier(struct bio *bio, int err)
180 if (err == -EOPNOTSUPP)
181 set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
182 clear_bit(BIO_UPTODATE, &bio->bi_flags);
185 complete(bio->bi_private);
190 * blkdev_issue_flush - queue a flush
191 * @bdev: blockdev to issue flush for
192 * @gfp_mask: memory allocation flags (for bio_alloc)
193 * @error_sector: error sector
194 * @flags: BLKDEV_IFL_* flags to control behaviour
197 * Issue a flush for the block device in question. Caller can supply
198 * room for storing the error offset in case of a flush error, if they
199 * wish to. If WAIT flag is not passed then caller may check only what
200 * request was pushed in some internal queue for later handling.
202 int blkdev_issue_flush(struct block_device *bdev, gfp_t gfp_mask,
203 sector_t *error_sector, unsigned long flags)
205 DECLARE_COMPLETION_ONSTACK(wait);
206 struct request_queue *q;
210 if (bdev->bd_disk == NULL)
213 q = bdev_get_queue(bdev);
218 * some block devices may not have their queue correctly set up here
219 * (e.g. loop device without a backing file) and so issuing a flush
220 * here will panic. Ensure there is a request function before issuing
223 if (!q->make_request_fn)
226 bio = bio_alloc(gfp_mask, 0);
227 bio->bi_end_io = bio_end_empty_barrier;
229 if (test_bit(BLKDEV_WAIT, &flags))
230 bio->bi_private = &wait;
233 submit_bio(WRITE_BARRIER, bio);
234 if (test_bit(BLKDEV_WAIT, &flags)) {
235 wait_for_completion(&wait);
237 * The driver must store the error location in ->bi_sector, if
238 * it supports it. For non-stacked drivers, this should be
239 * copied from blk_rq_pos(rq).
242 *error_sector = bio->bi_sector;
245 if (bio_flagged(bio, BIO_EOPNOTSUPP))
247 else if (!bio_flagged(bio, BIO_UPTODATE))
253 EXPORT_SYMBOL(blkdev_issue_flush);