Commit 9e55a22f authored by Yu Kuai's avatar Yu Kuai Committed by Song Liu
Browse files

md/raid1: don't split discard io for write behind 



Currently, discad io is treated the same as normal write io, and for
write behind case, io size is limited to:

BIO_MAX_VECS * (PAGE_SIZE >> 9)

For 0.5KB sector size and 4KB PAGE_SIZE, this is just 1MB. For
consequence, if 'WriteMostly' is set to one of the underlying disks,
then diskcard io will be splited into 1MB and it will take a long time
for the diskcard to finish.

Fix this problem by disable write behind for discard io.

Reported-by: default avatarRoman Mamedov <rm@romanrm.net>
Closes: https://lore.kernel.org/all/6a1165f7-c792-c054-b8f0-1ad4f7b8ae01@ultracoder.org/


Reported-and-tested-by: default avatarKirill Kirilenko <kirill@ultracoder.org>
Signed-off-by: default avatarYu Kuai <yukuai3@huawei.com>
Signed-off-by: default avatarSong Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20231007112105.407449-1-yukuai1@huaweicloud.com
parent 09f894af

drivers/md/raid1.c

+2 −1
Original line number Diff line number Diff line
@@ -1345,6 +1345,7 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio, 
	int first_clone;

	int max_sectors;

	bool write_behind = false;

	bool is_discard = (bio_op(bio) == REQ_OP_DISCARD);



	if (mddev_is_clustered(mddev) &&

	     md_cluster_ops->area_resyncing(mddev, WRITE,
@@ -1405,7 +1406,7 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio, 
		 * write-mostly, which means we could allocate write behind

		 * bio later.

		 */

		if (rdev && test_bit(WriteMostly, &rdev->flags))

		if (!is_discard && rdev && test_bit(WriteMostly, &rdev->flags))

			write_behind = true;



		if (rdev && unlikely(test_bit(Blocked, &rdev->flags))) {