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/openbmc/linux/drivers/md/bcache/
H A Djournal.cdiff 0f843e65d9eef4936929bb036c5f771fb261eea4 Thu Sep 27 10:41:46 CDT 2018 Guoju Fang <fangguoju@gmail.com> bcache: add separate workqueue for journal_write to avoid deadlock

After write SSD completed, bcache schedules journal_write work to
system_wq, which is a public workqueue in system, without WQ_MEM_RECLAIM
flag. system_wq is also a bound wq, and there may be no idle kworker on
current processor. Creating a new kworker may unfortunately need to
reclaim memory first, by shrinking cache and slab used by vfs, which
depends on bcache device. That's a deadlock.

This patch create a new workqueue for journal_write with WQ_MEM_RECLAIM
flag. It's rescuer thread will work to avoid the deadlock.

Signed-off-by: Guoju Fang <fangguoju@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
H A Dbcache.hdiff 0f843e65d9eef4936929bb036c5f771fb261eea4 Thu Sep 27 10:41:46 CDT 2018 Guoju Fang <fangguoju@gmail.com> bcache: add separate workqueue for journal_write to avoid deadlock

After write SSD completed, bcache schedules journal_write work to
system_wq, which is a public workqueue in system, without WQ_MEM_RECLAIM
flag. system_wq is also a bound wq, and there may be no idle kworker on
current processor. Creating a new kworker may unfortunately need to
reclaim memory first, by shrinking cache and slab used by vfs, which
depends on bcache device. That's a deadlock.

This patch create a new workqueue for journal_write with WQ_MEM_RECLAIM
flag. It's rescuer thread will work to avoid the deadlock.

Signed-off-by: Guoju Fang <fangguoju@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
H A Dsuper.cdiff 0f843e65d9eef4936929bb036c5f771fb261eea4 Thu Sep 27 10:41:46 CDT 2018 Guoju Fang <fangguoju@gmail.com> bcache: add separate workqueue for journal_write to avoid deadlock

After write SSD completed, bcache schedules journal_write work to
system_wq, which is a public workqueue in system, without WQ_MEM_RECLAIM
flag. system_wq is also a bound wq, and there may be no idle kworker on
current processor. Creating a new kworker may unfortunately need to
reclaim memory first, by shrinking cache and slab used by vfs, which
depends on bcache device. That's a deadlock.

This patch create a new workqueue for journal_write with WQ_MEM_RECLAIM
flag. It's rescuer thread will work to avoid the deadlock.

Signed-off-by: Guoju Fang <fangguoju@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>