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md: fix soft lockup in status_resync

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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
This commit is contained in:
Yu Kuai 2023-03-10 15:38:51 +08:00 committed by Song Liu
parent c31fea2f8e
commit 6efddf1e32
1 changed files with 9 additions and 9 deletions
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14
drivers/md/md.c
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@ -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) {