From fb2dce862d9f9a68e6b9374579056ec9eca02a63 Mon Sep 17 00:00:00 2001 From: David Woodhouse Date: Tue, 5 Aug 2008 18:01:53 +0100 Subject: Add 'discard' request handling Some block devices benefit from a hint that they can forget the contents of certain sectors. Add basic support for this to the block core, along with a 'blkdev_issue_discard()' helper function which issues such requests. The caller doesn't get to provide an end_io functio, since blkdev_issue_discard() will automatically split the request up into multiple bios if appropriate. Neither does the function wait for completion -- it's expected that callers won't care about when, or even _if_, the request completes. It's only a hint to the device anyway. By definition, the file system doesn't _care_ about these sectors any more. [With feedback from OGAWA Hirofumi and Jens Axboe Signed-off-by: Jens Axboe --- block/blk-barrier.c | 69 ++++++++++++++++++++++++++++++++++++++++++++++++++++ block/blk-core.c | 28 +++++++++++++++------ block/blk-settings.c | 17 +++++++++++++ 3 files changed, 106 insertions(+), 8 deletions(-) (limited to 'block') diff --git a/block/blk-barrier.c b/block/blk-barrier.c index a09ead19f9c5..273121c0eb80 100644 --- a/block/blk-barrier.c +++ b/block/blk-barrier.c @@ -315,3 +315,72 @@ int blkdev_issue_flush(struct block_device *bdev, sector_t *error_sector) return ret; } EXPORT_SYMBOL(blkdev_issue_flush); + +static void blkdev_discard_end_io(struct bio *bio, int err) +{ + if (err) { + if (err == -EOPNOTSUPP) + set_bit(BIO_EOPNOTSUPP, &bio->bi_flags); + clear_bit(BIO_UPTODATE, &bio->bi_flags); + } + + bio_put(bio); +} + +/** + * blkdev_issue_discard - queue a discard + * @bdev: blockdev to issue discard for + * @sector: start sector + * @nr_sects: number of sectors to discard + * + * Description: + * Issue a discard request for the sectors in question. Does not wait. + */ +int blkdev_issue_discard(struct block_device *bdev, sector_t sector, + unsigned nr_sects) +{ + 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; + + if (!q->prepare_discard_fn) + return -EOPNOTSUPP; + + while (nr_sects && !ret) { + bio = bio_alloc(GFP_KERNEL, 0); + if (!bio) + return -ENOMEM; + + bio->bi_end_io = blkdev_discard_end_io; + bio->bi_bdev = bdev; + + bio->bi_sector = sector; + + if (nr_sects > q->max_hw_sectors) { + bio->bi_size = q->max_hw_sectors << 9; + nr_sects -= q->max_hw_sectors; + sector += q->max_hw_sectors; + } else { + bio->bi_size = nr_sects << 9; + nr_sects = 0; + } + bio_get(bio); + submit_bio(WRITE_DISCARD, bio); + + /* Check if it failed immediately */ + if (bio_flagged(bio, BIO_EOPNOTSUPP)) + ret = -EOPNOTSUPP; + else if (!bio_flagged(bio, BIO_UPTODATE)) + ret = -EIO; + bio_put(bio); + } + return ret; +} +EXPORT_SYMBOL(blkdev_issue_discard); diff --git a/block/blk-core.c b/block/blk-core.c index a496727df7ef..1e143c4f9d34 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -1079,6 +1079,10 @@ void init_request_from_bio(struct request *req, struct bio *bio) */ if (unlikely(bio_barrier(bio))) req->cmd_flags |= (REQ_HARDBARRIER | REQ_NOMERGE); + if (unlikely(bio_discard(bio))) { + req->cmd_flags |= (REQ_SOFTBARRIER | REQ_DISCARD); + req->q->prepare_discard_fn(req->q, req); + } if (bio_sync(bio)) req->cmd_flags |= REQ_RW_SYNC; @@ -1095,7 +1099,7 @@ void init_request_from_bio(struct request *req, struct bio *bio) static int __make_request(struct request_queue *q, struct bio *bio) { struct request *req; - int el_ret, nr_sectors, barrier, err; + int el_ret, nr_sectors, barrier, discard, err; const unsigned short prio = bio_prio(bio); const int sync = bio_sync(bio); int rw_flags; @@ -1115,6 +1119,12 @@ static int __make_request(struct request_queue *q, struct bio *bio) goto end_io; } + discard = bio_discard(bio); + if (unlikely(discard) && !q->prepare_discard_fn) { + err = -EOPNOTSUPP; + goto end_io; + } + spin_lock_irq(q->queue_lock); if (unlikely(barrier) || elv_queue_empty(q)) @@ -1405,7 +1415,8 @@ end_io: if (bio_check_eod(bio, nr_sectors)) goto end_io; - if (bio_empty_barrier(bio) && !q->prepare_flush_fn) { + if ((bio_empty_barrier(bio) && !q->prepare_flush_fn) || + (bio_discard(bio) && !q->prepare_discard_fn)) { err = -EOPNOTSUPP; goto end_io; } @@ -1487,7 +1498,6 @@ void submit_bio(int rw, struct bio *bio) * go through the normal accounting stuff before submission. */ if (bio_has_data(bio)) { - if (rw & WRITE) { count_vm_events(PGPGOUT, count); } else { @@ -1881,7 +1891,7 @@ static int blk_end_io(struct request *rq, int error, unsigned int nr_bytes, struct request_queue *q = rq->q; unsigned long flags = 0UL; - if (bio_has_data(rq->bio)) { + if (bio_has_data(rq->bio) || blk_discard_rq(rq)) { if (__end_that_request_first(rq, error, nr_bytes)) return 1; @@ -1939,7 +1949,7 @@ EXPORT_SYMBOL_GPL(blk_end_request); **/ int __blk_end_request(struct request *rq, int error, unsigned int nr_bytes) { - if (bio_has_data(rq->bio) && + if ((bio_has_data(rq->bio) || blk_discard_rq(rq)) && __end_that_request_first(rq, error, nr_bytes)) return 1; @@ -2012,12 +2022,14 @@ void blk_rq_bio_prep(struct request_queue *q, struct request *rq, we want BIO_RW_AHEAD (bit 1) to imply REQ_FAILFAST (bit 1). */ rq->cmd_flags |= (bio->bi_rw & 3); - rq->nr_phys_segments = bio_phys_segments(q, bio); - rq->nr_hw_segments = bio_hw_segments(q, bio); + if (bio_has_data(bio)) { + rq->nr_phys_segments = bio_phys_segments(q, bio); + rq->nr_hw_segments = bio_hw_segments(q, bio); + rq->buffer = bio_data(bio); + } rq->current_nr_sectors = bio_cur_sectors(bio); rq->hard_cur_sectors = rq->current_nr_sectors; rq->hard_nr_sectors = rq->nr_sectors = bio_sectors(bio); - rq->buffer = bio_data(bio); rq->data_len = bio->bi_size; rq->bio = rq->biotail = bio; diff --git a/block/blk-settings.c b/block/blk-settings.c index dfc77012843f..539d873c820d 100644 --- a/block/blk-settings.c +++ b/block/blk-settings.c @@ -32,6 +32,23 @@ void blk_queue_prep_rq(struct request_queue *q, prep_rq_fn *pfn) } EXPORT_SYMBOL(blk_queue_prep_rq); +/** + * blk_queue_set_discard - set a discard_sectors function for queue + * @q: queue + * @dfn: prepare_discard function + * + * It's possible for a queue to register a discard callback which is used + * to transform a discard request into the appropriate type for the + * hardware. If none is registered, then discard requests are failed + * with %EOPNOTSUPP. + * + */ +void blk_queue_set_discard(struct request_queue *q, prepare_discard_fn *dfn) +{ + q->prepare_discard_fn = dfn; +} +EXPORT_SYMBOL(blk_queue_set_discard); + /** * blk_queue_merge_bvec - set a merge_bvec function for queue * @q: queue -- cgit v1.2.2