On 12/9/21 8:57 PM, Donald Buczek wrote:
[Update Guoqing’s email address]
On 15.02.21 12:07, Paul Menzel wrote:
[+cc Donald]
Am 13.02.21 um 01:49 schrieb Guoqing Jiang:
Unregister sync_thread doesn't need to hold reconfig_mutex since it
doesn't reconfigure array.
And it could cause deadlock problem for raid5 as follows:
1. process A tried to reap sync thread with reconfig_mutex held
after echo
idle to sync_action.
2. raid5 sync thread was blocked if there were too many active stripes.
3. SB_CHANGE_PENDING was set (because of write IO comes from upper
layer)
which causes the number of active stripes can't be decreased.
4. SB_CHANGE_PENDING can't be cleared since md_check_recovery was
not able
to hold reconfig_mutex.
More details in the link:
https://lore.kernel.org/linux-raid/5ed54ffc-ce82-bf66-4eff-390cb23bc1ac@xxxxxxxxxxxxx/T/#t
And add one parameter to md_reap_sync_thread since it could be
called by
dm-raid which doesn't hold reconfig_mutex.
Reported-and-tested-by: Donald Buczek <buczek@xxxxxxxxxxxxx>
Thanks, Paul, for putting me into the cc.
Guoqing, I don't think, I've tested this patch. Please remove the
tested-by.
This version is basically the similar as the change in the thread.
https://lore.kernel.org/linux-raid/5ed54ffc-ce82-bf66-4eff-390cb23bc1ac@xxxxxxxxxxxxx/T/#m546d8c55a42f308985b9d31d4be85832edcd15ab
Anyway, I will remove your tested-by per the request if I will update
the patch.
Thanks,
Guoqing
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