diff options
Diffstat (limited to 'block/blk-flush.c')
-rw-r--r-- | block/blk-flush.c | 262 |
1 files changed, 262 insertions, 0 deletions
diff --git a/block/blk-flush.c b/block/blk-flush.c new file mode 100644 index 0000000..54b123d --- /dev/null +++ b/block/blk-flush.c @@ -0,0 +1,262 @@ +/* + * 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); |