Commit 6efddf1e authored Mar 10, 2023 by Yu Kuai Committed by Song Liu Apr 13, 2023

md: fix soft lockup in status_resync



status_resync() will calculate 'curr_resync - recovery_active' to show
user a progress bar like following:

[============>........]  resync = 61.4%

'curr_resync' and 'recovery_active' is updated in md_do_sync(), and
status_resync() can read them concurrently, hence it's possible that
'curr_resync - recovery_active' can overflow to a huge number. In this
case status_resync() will be stuck in the loop to print a large amount
of '=', which will end up soft lockup.

Fix the problem by setting 'resync' to MD_RESYNC_ACTIVE in this case,
this way resync in progress will be reported to user.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20230310073855.1337560-3-yukuai1@huaweicloud.com

parent c31fea2f

drivers/md/md.c

+9 −9

Original line number	Diff line number	Diff line
		@@ -8032,16 +8032,16 @@ static int status_resync(struct seq_file seq, struct mddev mddev)
		} else if (resync > max_sectors) {
		resync = max_sectors;
		} else {
		resync -= atomic_read(&mddev->recovery_active);
		if (resync < MD_RESYNC_ACTIVE) {
		res = atomic_read(&mddev->recovery_active);
		/*
		* Resync has started, but the subtraction has
		* yielded one of the special values. Force it
		* to active to ensure the status reports an
		* active resync.
		* Resync has started, but the subtraction has overflowed or
		* yielded one of the special values. Force it to active to
		* ensure the status reports an active resync.
		*/
		if (resync < res \|\| resync - res < MD_RESYNC_ACTIVE)
		resync = MD_RESYNC_ACTIVE;
		}
		else
		resync -= res;
		}

		if (resync == MD_RESYNC_NONE) {