mtd: sm_ftl: Fix deadlock caused by cancel_work_sync in sm_release

stable inclusion
from stable-v5.10.137
commit b4e150d295ba5234f5e4b3731ddbcb1651b7547f
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I60PLB

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b4e150d295ba5234f5e4b3731ddbcb1651b7547f



--------------------------------

[ Upstream commit a61528d9 ]

There is a deadlock between sm_release and sm_cache_flush_work
which is a work item. The cancel_work_sync in sm_release will
not return until sm_cache_flush_work is finished. If we hold
mutex_lock and use cancel_work_sync to wait the work item to
finish, the work item also requires mutex_lock. As a result,
the sm_release will be blocked forever. The race condition is
shown below:

    (Thread 1)             |   (Thread 2)
sm_release                 |
  mutex_lock(&ftl->mutex)  | sm_cache_flush_work
                           |   mutex_lock(&ftl->mutex)
  cancel_work_sync         |   ...

This patch moves del_timer_sync and cancel_work_sync out of
mutex_lock in order to mitigate deadlock.

Fixes: 7d17c02a ("mtd: Add new SmartMedia/xD FTL")
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20220524044841.10517-1-duoming@zju.edu.cn


Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>
Reviewed-by: Wei Li <liwei391@huawei.com>