scsi: block: pm: Always set request queue runtime active in blk_post_runtime_resume()
authorAlan Stern <stern@rowland.harvard.edu>
Mon, 20 Dec 2021 11:21:26 +0000 (19:21 +0800)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Thu, 27 Jan 2022 10:04:15 +0000 (11:04 +0100)
commitaf8cab36bfb8b6836daf1b9a94a8bc211fe6f207
tree12b14e88ceeca8999bb05d2d8e34a7eb3d030120
parente421973fbe6e9490e3cf3ee2ab38a739928243d0
scsi: block: pm: Always set request queue runtime active in blk_post_runtime_resume()

[ Upstream commit 6e1fcab00a23f7fe9f4fe9704905a790efa1eeab ]

John Garry reported a deadlock that occurs when trying to access a
runtime-suspended SATA device.  For obscure reasons, the rescan procedure
causes the link to be hard-reset, which disconnects the device.

The rescan tries to carry out a runtime resume when accessing the device.
scsi_rescan_device() holds the SCSI device lock and won't release it until
it can put commands onto the device's block queue.  This can't happen until
the queue is successfully runtime-resumed or the device is unregistered.
But the runtime resume fails because the device is disconnected, and
__scsi_remove_device() can't do the unregistration because it can't get the
device lock.

The best way to resolve this deadlock appears to be to allow the block
queue to start running again even after an unsuccessful runtime resume.
The idea is that the driver or the SCSI error handler will need to be able
to use the queue to resolve the runtime resume failure.

This patch removes the err argument to blk_post_runtime_resume() and makes
the routine act as though the resume was successful always.  This fixes the
deadlock.

Link: https://lore.kernel.org/r/1639999298-244569-4-git-send-email-chenxiang66@hisilicon.com
Fixes: e27829dc92e5 ("scsi: serialize ->rescan against ->remove")
Reported-and-tested-by: John Garry <john.garry@huawei.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Xiang Chen <chenxiang66@hisilicon.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
block/blk-pm.c
drivers/scsi/scsi_pm.c
include/linux/blk-pm.h