Commit a1c6ae3d authored Jul 31, 2020 by ChangSyun Peng Committed by Song Liu Aug 02, 2020

md/raid5: Fix Force reconstruct-write io stuck in degraded raid5



In degraded raid5, we need to read parity to do reconstruct-write when
data disks fail. However, we can not read parity from
handle_stripe_dirtying() in force reconstruct-write mode.

Reproducible Steps:

1. Create degraded raid5
mdadm -C /dev/md2 --assume-clean -l5 -n3 /dev/sda2 /dev/sdb2 missing
2. Set rmw_level to 0
echo 0 > /sys/block/md2/md/rmw_level
3. IO to raid5

Now some io may be stuck in raid5. We can use handle_stripe_fill() to read
the parity in this situation.

Cc: <stable@vger.kernel.org> # v4.4+
Reviewed-by: Alex Wu <alexwu@synology.com>
Reviewed-by: BingJing Chang <bingjingc@synology.com>
Reviewed-by: Danny Shih <dannyshih@synology.com>
Signed-off-by: ChangSyun Peng <allenpeng@synology.com>
Signed-off-by: Song Liu <songliubraving@fb.com>

parent 3a31cf3d

drivers/md/raid5.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -3626,6 +3626,7 @@ static int need_this_block(struct stripe_head sh, struct stripe_head_state s,
		* is missing/faulty, then we need to read everything we can.
		*/
		if (sh->raid_conf->level != 6 &&
		sh->raid_conf->rmw_level != PARITY_DISABLE_RMW &&
		sh->sector < sh->raid_conf->mddev->recovery_cp)
		/* reconstruct-write isn't being forced */
		return 0;
		@@ -4862,7 +4863,7 @@ static void handle_stripe(struct stripe_head *sh)
		* or to load a block that is being partially written.
		*/
		if (s.to_read \|\| s.non_overwrite
		\|\| (conf->level == 6 && s.to_write && s.failed)
		\|\| (s.to_write && s.failed)
		\|\| (s.syncing && (s.uptodate + s.compute < disks))
		\|\| s.replacing
		\|\| s.expanding)

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