Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 4.12 10/41] md: always clear ->safemode when md_check_recovery gets the mddev lock. | Date | Tue, 22 Aug 2017 12:13:38 -0700 |
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4.12-stable review patch. If anyone has any objections, please let me know.
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From: NeilBrown <neilb@suse.com>
commit 33182d15c6bf182f7ae32a66ea4a547d979cd6d7 upstream.
If ->safemode == 1, md_check_recovery() will try to get the mddev lock and perform various other checks. If mddev->in_sync is zero, it will call set_in_sync, and clear ->safemode. However if mddev->in_sync is not zero, ->safemode will not be cleared.
When md_check_recovery() drops the mddev lock, the thread is woken up again. Normally it would just check if there was anything else to do, find nothing, and go to sleep. However as ->safemode was not cleared, it will take the mddev lock again, then wake itself up when unlocking.
This results in an infinite loop, repeatedly calling md_check_recovery(), which RCU or the soft-lockup detector will eventually complain about.
Prior to commit 4ad23a976413 ("MD: use per-cpu counter for writes_pending"), safemode would only be set to one when the writes_pending counter reached zero, and would be cleared again when writes_pending is incremented. Since that patch, safemode is set more freely, but is not reliably cleared.
So in md_check_recovery() clear ->safemode before checking ->in_sync.
Fixes: 4ad23a976413 ("MD: use per-cpu counter for writes_pending") Reported-by: Dominik Brodowski <linux@dominikbrodowski.net> Reported-by: David R <david@unsolicited.net> Signed-off-by: NeilBrown <neilb@suse.com> Signed-off-by: Shaohua Li <shli@fb.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- drivers/md/md.c | 3 +++ 1 file changed, 3 insertions(+)
--- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -8639,6 +8639,9 @@ void md_check_recovery(struct mddev *mdd if (mddev_trylock(mddev)) { int spares = 0; + if (mddev->safemode == 1) + mddev->safemode = 0; + if (mddev->ro) { struct md_rdev *rdev; if (!mddev->external && mddev->in_sync)
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