From: Ming Lei ming.lei@redhat.com
commit 866663b7b52d2da267b28e12eed89ee781b8fed1 upstream.
When merging one bio to request, if they are discard IO and the queue supports multi-range discard, we need to return ELEVATOR_DISCARD_MERGE because both block core and related drivers(nvme, virtio-blk) doesn't handle mixed discard io merge(traditional IO merge together with discard merge) well.
Fix the issue by returning ELEVATOR_DISCARD_MERGE in this situation, so both blk-mq and drivers just need to handle multi-range discard.
Reported-by: Oleksandr Natalenko oleksandr@natalenko.name Signed-off-by: Ming Lei ming.lei@redhat.com Tested-by: Oleksandr Natalenko oleksandr@natalenko.name Fixes: 2705dfb20947 ("block: fix discard request merge") Link: https://lore.kernel.org/r/20210729034226.1591070-1-ming.lei@redhat.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Gwendal Grignou gwendal@chromium.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- block/bfq-iosched.c | 3 +++ block/blk-merge.c | 15 --------------- block/elevator.c | 3 +++ block/mq-deadline.c | 2 ++ include/linux/blkdev.h | 16 ++++++++++++++++ 5 files changed, 24 insertions(+), 15 deletions(-)
--- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -2251,6 +2251,9 @@ static int bfq_request_merge(struct requ __rq = bfq_find_rq_fmerge(bfqd, bio, q); if (__rq && elv_bio_merge_ok(__rq, bio)) { *req = __rq; + + if (blk_discard_mergable(__rq)) + return ELEVATOR_DISCARD_MERGE; return ELEVATOR_FRONT_MERGE; }
--- a/block/blk-merge.c +++ b/block/blk-merge.c @@ -721,21 +721,6 @@ static void blk_account_io_merge(struct part_stat_unlock(); } } -/* - * Two cases of handling DISCARD merge: - * If max_discard_segments > 1, the driver takes every bio - * as a range and send them to controller together. The ranges - * needn't to be contiguous. - * Otherwise, the bios/requests will be handled as same as - * others which should be contiguous. - */ -static inline bool blk_discard_mergable(struct request *req) -{ - if (req_op(req) == REQ_OP_DISCARD && - queue_max_discard_segments(req->q) > 1) - return true; - return false; -}
static enum elv_merge blk_try_req_merge(struct request *req, struct request *next) --- a/block/elevator.c +++ b/block/elevator.c @@ -337,6 +337,9 @@ enum elv_merge elv_merge(struct request_ __rq = elv_rqhash_find(q, bio->bi_iter.bi_sector); if (__rq && elv_bio_merge_ok(__rq, bio)) { *req = __rq; + + if (blk_discard_mergable(__rq)) + return ELEVATOR_DISCARD_MERGE; return ELEVATOR_BACK_MERGE; }
--- a/block/mq-deadline.c +++ b/block/mq-deadline.c @@ -452,6 +452,8 @@ static int dd_request_merge(struct reque
if (elv_bio_merge_ok(__rq, bio)) { *rq = __rq; + if (blk_discard_mergable(__rq)) + return ELEVATOR_DISCARD_MERGE; return ELEVATOR_FRONT_MERGE; } } --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -1409,6 +1409,22 @@ static inline int queue_limit_discard_al return offset << SECTOR_SHIFT; }
+/* + * Two cases of handling DISCARD merge: + * If max_discard_segments > 1, the driver takes every bio + * as a range and send them to controller together. The ranges + * needn't to be contiguous. + * Otherwise, the bios/requests will be handled as same as + * others which should be contiguous. + */ +static inline bool blk_discard_mergable(struct request *req) +{ + if (req_op(req) == REQ_OP_DISCARD && + queue_max_discard_segments(req->q) > 1) + return true; + return false; +} + static inline int bdev_discard_alignment(struct block_device *bdev) { struct request_queue *q = bdev_get_queue(bdev);