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md: Don't ignore read-only array in md_check_recovery()

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Usually if the array is not read-write, md_check_recovery() won't
register new sync_thread in the first place. And if the array is
read-write and sync_thread is registered, md_set_readonly() will
unregister sync_thread before setting the array read-only. md/raid
follow this behavior hence there is no problem.

After commit f52f5c71f3d4 ("md: fix stopping sync thread"), following
hang can be triggered by test shell/integrity-caching.sh:

1) array is read-only. dm-raid update super block:
rs_update_sbs
 ro = mddev->ro
 mddev->ro = 0
  -> set array read-write
 md_update_sb

2) register new sync thread concurrently.

3) dm-raid set array back to read-only:
rs_update_sbs
 mddev->ro = ro

4) stop the array:
raid_dtr
 md_stop
  stop_sync_thread
    set_bit(MD_RECOVERY_INTR, &mddev->recovery);
    md_wakeup_thread_directly(mddev->sync_thread);
    wait_event(..., !test_bit(MD_RECOVERY_RUNNING, &mddev->recovery))

5) sync thread done:
 md_do_sync
 set_bit(MD_RECOVERY_DONE, &mddev->recovery);
 md_wakeup_thread(mddev->thread);

6) daemon thread can't unregister sync thread:
 md_check_recovery
  if (!md_is_rdwr(mddev) &&
      !test_bit(MD_RECOVERY_NEEDED, &mddev->recovery))
   return;
  -> -> MD_RECOVERY_RUNNING can't be cleared, hence step 4 hang;

The root cause is that dm-raid manipulate 'mddev->ro' by itself,
however, dm-raid really should stop sync thread before setting the
array read-only. Unfortunately, I need to read more code before I
can refacter the handler of 'mddev->ro' in dm-raid, hence let's fix
the problem the easy way for now to prevent dm-raid regression.

Reported-by: Mikulas Patocka <mpatocka@redhat.com>
Closes: https://lore.kernel.org/all/9801e40-8ac7-e225-6a71-309dcf9dc9aa@redhat.com/
Fixes: ecbfb9f118bc ("dm raid: add raid level takeover support")
Fixes: f52f5c71f3d4 ("md: fix stopping sync thread")
Cc: stable@vger.kernel.org # v6.7+
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20240201092559.910982-3-yukuai1@huaweicloud.com
This commit is contained in:
Yu Kuai 2024-02-01 17:25:47 +08:00 committed by Song Liu
parent 1baae052cc
commit 55a48ad2db
1 changed files with 18 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

31
drivers/md/md.c
View File

@ -9449,6 +9449,20 @@ not_running:
sysfs_notify_dirent_safe(mddev->sysfs_action);
}
static void unregister_sync_thread(struct mddev *mddev)
{
if (!test_bit(MD_RECOVERY_DONE, &mddev->recovery)) {
/* resync/recovery still happening */
clear_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
return;
}
if (WARN_ON_ONCE(!mddev->sync_thread))
return;
md_reap_sync_thread(mddev);
}
/*
* This routine is regularly called by all per-raid-array threads to
* deal with generic issues like resync and super-block update.
@ -9486,7 +9500,8 @@ void md_check_recovery(struct mddev *mddev)
}
if (!md_is_rdwr(mddev) &&
!test_bit(MD_RECOVERY_NEEDED, &mddev->recovery))
!test_bit(MD_RECOVERY_NEEDED, &mddev->recovery) &&
!test_bit(MD_RECOVERY_DONE, &mddev->recovery))
return;
if ( ! (
(mddev->sb_flags & ~ (1<<MD_SB_CHANGE_PENDING)) ||
@ -9508,8 +9523,7 @@ void md_check_recovery(struct mddev *mddev)
struct md_rdev *rdev;
if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery)) {
/* sync_work already queued. */
clear_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
unregister_sync_thread(mddev);
goto unlock;
}
@ -9572,16 +9586,7 @@ void md_check_recovery(struct mddev *mddev)
* still set.
*/
if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery)) {
if (!test_bit(MD_RECOVERY_DONE, &mddev->recovery)) {
/* resync/recovery still happening */
clear_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
goto unlock;
}
if (WARN_ON_ONCE(!mddev->sync_thread))
goto unlock;
md_reap_sync_thread(mddev);
unregister_sync_thread(mddev);
goto unlock;
}