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Commit 9ea8e6a8 authored by Ming Lei's avatar Ming Lei Committed by Greg Kroah-Hartman
Browse files

block: return ELEVATOR_DISCARD_MERGE if possible 



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: default avatarOleksandr Natalenko <oleksandr@natalenko.name>
Signed-off-by: default avatarMing Lei <ming.lei@redhat.com>
Tested-by: default avatarOleksandr 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: default avatarJens Axboe <axboe@kernel.dk>
Signed-off-by: default avatarGwendal Grignou <gwendal@chromium.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 36ac6caf

block/bfq-iosched.c

+3 −0
Original line number Diff line number Diff line
@@ -2251,6 +2251,9 @@ static int bfq_request_merge(struct request_queue *q, struct request **req, 
	__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;

	}

block/blk-merge.c

+0 −15
Original line number Diff line number Diff line
@@ -721,21 +721,6 @@ static void blk_account_io_merge(struct request *req) 
		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)

block/elevator.c

+3 −0
Original line number Diff line number Diff line
@@ -337,6 +337,9 @@ enum elv_merge elv_merge(struct request_queue *q, struct request **req, 
	__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;

	}

block/mq-deadline.c

+2 −0
Original line number Diff line number Diff line
@@ -452,6 +452,8 @@ static int dd_request_merge(struct request_queue *q, struct request **rq, 


		if (elv_bio_merge_ok(__rq, bio)) {

			*rq = __rq;

			if (blk_discard_mergable(__rq))

				return ELEVATOR_DISCARD_MERGE;

			return ELEVATOR_FRONT_MERGE;

		}

	}

include/linux/blkdev.h

+16 −0
Original line number Diff line number Diff line
@@ -1409,6 +1409,22 @@ static inline int queue_limit_discard_alignment(struct queue_limits *lim, sector 
	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);