123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209210211212213214215216217218219220221222223224225226227228229230231232233234235236237238239240241242243244245246247248249250251252253254255256257258259260261262 |
- /*
- * Functions to sequence FLUSH and FUA writes.
- */
- #include <linux/kernel.h>
- #include <linux/module.h>
- #include <linux/bio.h>
- #include <linux/blkdev.h>
- #include <linux/gfp.h>
- #include "blk.h"
- /* FLUSH/FUA sequences */
- enum {
- QUEUE_FSEQ_STARTED = (1 << 0), /* flushing in progress */
- QUEUE_FSEQ_PREFLUSH = (1 << 1), /* pre-flushing in progress */
- QUEUE_FSEQ_DATA = (1 << 2), /* data write in progress */
- QUEUE_FSEQ_POSTFLUSH = (1 << 3), /* post-flushing in progress */
- QUEUE_FSEQ_DONE = (1 << 4),
- };
- static struct request *queue_next_fseq(struct request_queue *q);
- unsigned blk_flush_cur_seq(struct request_queue *q)
- {
- if (!q->flush_seq)
- return 0;
- return 1 << ffz(q->flush_seq);
- }
- static struct request *blk_flush_complete_seq(struct request_queue *q,
- unsigned seq, int error)
- {
- struct request *next_rq = NULL;
- if (error && !q->flush_err)
- q->flush_err = error;
- BUG_ON(q->flush_seq & seq);
- q->flush_seq |= seq;
- if (blk_flush_cur_seq(q) != QUEUE_FSEQ_DONE) {
- /* not complete yet, queue the next flush sequence */
- next_rq = queue_next_fseq(q);
- } else {
- /* complete this flush request */
- __blk_end_request_all(q->orig_flush_rq, q->flush_err);
- q->orig_flush_rq = NULL;
- q->flush_seq = 0;
- /* dispatch the next flush if there's one */
- if (!list_empty(&q->pending_flushes)) {
- next_rq = list_entry_rq(q->pending_flushes.next);
- list_move(&next_rq->queuelist, &q->queue_head);
- }
- }
- return next_rq;
- }
- static void blk_flush_complete_seq_end_io(struct request_queue *q,
- unsigned seq, int error)
- {
- bool was_empty = elv_queue_empty(q);
- struct request *next_rq;
- next_rq = blk_flush_complete_seq(q, seq, error);
- /*
- * Moving a request silently to empty queue_head may stall the
- * queue. Kick the queue in those cases.
- */
- if (was_empty && next_rq)
- __blk_run_queue(q);
- }
- static void pre_flush_end_io(struct request *rq, int error)
- {
- elv_completed_request(rq->q, rq);
- blk_flush_complete_seq_end_io(rq->q, QUEUE_FSEQ_PREFLUSH, error);
- }
- static void flush_data_end_io(struct request *rq, int error)
- {
- elv_completed_request(rq->q, rq);
- blk_flush_complete_seq_end_io(rq->q, QUEUE_FSEQ_DATA, error);
- }
- static void post_flush_end_io(struct request *rq, int error)
- {
- elv_completed_request(rq->q, rq);
- blk_flush_complete_seq_end_io(rq->q, QUEUE_FSEQ_POSTFLUSH, error);
- }
- static void init_flush_request(struct request *rq, struct gendisk *disk)
- {
- rq->cmd_type = REQ_TYPE_FS;
- rq->cmd_flags = WRITE_FLUSH;
- rq->rq_disk = disk;
- }
- static struct request *queue_next_fseq(struct request_queue *q)
- {
- struct request *orig_rq = q->orig_flush_rq;
- struct request *rq = &q->flush_rq;
- blk_rq_init(q, rq);
- switch (blk_flush_cur_seq(q)) {
- case QUEUE_FSEQ_PREFLUSH:
- init_flush_request(rq, orig_rq->rq_disk);
- rq->end_io = pre_flush_end_io;
- break;
- case QUEUE_FSEQ_DATA:
- init_request_from_bio(rq, orig_rq->bio);
- /*
- * orig_rq->rq_disk may be different from
- * bio->bi_bdev->bd_disk if orig_rq got here through
- * remapping drivers. Make sure rq->rq_disk points
- * to the same one as orig_rq.
- */
- rq->rq_disk = orig_rq->rq_disk;
- rq->cmd_flags &= ~(REQ_FLUSH | REQ_FUA);
- rq->cmd_flags |= orig_rq->cmd_flags & (REQ_FLUSH | REQ_FUA);
- rq->end_io = flush_data_end_io;
- break;
- case QUEUE_FSEQ_POSTFLUSH:
- init_flush_request(rq, orig_rq->rq_disk);
- rq->end_io = post_flush_end_io;
- break;
- default:
- BUG();
- }
- elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
- return rq;
- }
- struct request *blk_do_flush(struct request_queue *q, struct request *rq)
- {
- unsigned int fflags = q->flush_flags; /* may change, cache it */
- bool has_flush = fflags & REQ_FLUSH, has_fua = fflags & REQ_FUA;
- bool do_preflush = has_flush && (rq->cmd_flags & REQ_FLUSH);
- bool do_postflush = has_flush && !has_fua && (rq->cmd_flags & REQ_FUA);
- unsigned skip = 0;
- /*
- * Special case. If there's data but flush is not necessary,
- * the request can be issued directly.
- *
- * Flush w/o data should be able to be issued directly too but
- * currently some drivers assume that rq->bio contains
- * non-zero data if it isn't NULL and empty FLUSH requests
- * getting here usually have bio's without data.
- */
- if (blk_rq_sectors(rq) && !do_preflush && !do_postflush) {
- rq->cmd_flags &= ~REQ_FLUSH;
- if (!has_fua)
- rq->cmd_flags &= ~REQ_FUA;
- return rq;
- }
- /*
- * Sequenced flushes can't be processed in parallel. If
- * another one is already in progress, queue for later
- * processing.
- */
- if (q->flush_seq) {
- list_move_tail(&rq->queuelist, &q->pending_flushes);
- return NULL;
- }
- /*
- * Start a new flush sequence
- */
- q->flush_err = 0;
- q->flush_seq |= QUEUE_FSEQ_STARTED;
- /* adjust FLUSH/FUA of the original request and stash it away */
- rq->cmd_flags &= ~REQ_FLUSH;
- if (!has_fua)
- rq->cmd_flags &= ~REQ_FUA;
- blk_dequeue_request(rq);
- q->orig_flush_rq = rq;
- /* skip unneded sequences and return the first one */
- if (!do_preflush)
- skip |= QUEUE_FSEQ_PREFLUSH;
- if (!blk_rq_sectors(rq))
- skip |= QUEUE_FSEQ_DATA;
- if (!do_postflush)
- skip |= QUEUE_FSEQ_POSTFLUSH;
- return blk_flush_complete_seq(q, skip, 0);
- }
- static void bio_end_flush(struct bio *bio, int err)
- {
- if (err)
- clear_bit(BIO_UPTODATE, &bio->bi_flags);
- if (bio->bi_private)
- complete(bio->bi_private);
- bio_put(bio);
- }
- /**
- * blkdev_issue_flush - queue a flush
- * @bdev: blockdev to issue flush for
- * @gfp_mask: memory allocation flags (for bio_alloc)
- * @error_sector: error sector
- *
- * Description:
- * Issue a flush for the block device in question. Caller can supply
- * room for storing the error offset in case of a flush error, if they
- * wish to. If WAIT flag is not passed then caller may check only what
- * request was pushed in some internal queue for later handling.
- */
- int blkdev_issue_flush(struct block_device *bdev, gfp_t gfp_mask,
- sector_t *error_sector)
- {
- DECLARE_COMPLETION_ONSTACK(wait);
- struct request_queue *q;
- struct bio *bio;
- int ret = 0;
- if (bdev->bd_disk == NULL)
- return -ENXIO;
- q = bdev_get_queue(bdev);
- if (!q)
- return -ENXIO;
- /*
- * some block devices may not have their queue correctly set up here
- * (e.g. loop device without a backing file) and so issuing a flush
- * here will panic. Ensure there is a request function before issuing
- * the flush.
- */
- if (!q->make_request_fn)
- return -ENXIO;
- bio = bio_alloc(gfp_mask, 0);
- bio->bi_end_io = bio_end_flush;
- bio->bi_bdev = bdev;
- bio->bi_private = &wait;
- bio_get(bio);
- submit_bio(WRITE_FLUSH, bio);
- wait_for_completion(&wait);
- /*
- * The driver must store the error location in ->bi_sector, if
- * it supports it. For non-stacked drivers, this should be
- * copied from blk_rq_pos(rq).
- */
- if (error_sector)
- *error_sector = bio->bi_sector;
- if (!bio_flagged(bio, BIO_UPTODATE))
- ret = -EIO;
- bio_put(bio);
- return ret;
- }
- EXPORT_SYMBOL(blkdev_issue_flush);
|