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author | Mikulas Patocka <mpatocka@redhat.com> | 2020-02-17 07:43:03 -0500 |
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committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-03-11 18:03:08 +0100 |
commit | ec6ddb1aa82fb7fae89ce485ee874eae26de56a8 (patch) | |
tree | 3363272ce0e857a4f048ca991d946175e2c12597 /drivers/usb/host | |
parent | d78934442b62f345338ab4370d3d875ad1891686 (diff) |
dm integrity: fix a deadlock due to offloading to an incorrect workqueue
commit 53770f0ec5fd417429775ba006bc4abe14002335 upstream.
If we need to perform synchronous I/O in dm_integrity_map_continue(),
we must make sure that we are not in the map function - in order to
avoid the deadlock due to bio queuing in generic_make_request. To
avoid the deadlock, we offload the request to metadata_wq.
However, metadata_wq also processes metadata updates for write requests.
If there are too many requests that get offloaded to metadata_wq at the
beginning of dm_integrity_map_continue, the workqueue metadata_wq
becomes clogged and the system is incapable of processing any metadata
updates.
This causes a deadlock because all the requests that need to do metadata
updates wait for metadata_wq to proceed and metadata_wq waits inside
wait_and_add_new_range until some existing request releases its range
lock (which doesn't happen because the range lock is released after
metadata update).
In order to fix the deadlock, we create a new workqueue offload_wq and
offload requests to it - so that processing of offload_wq is independent
from processing of metadata_wq.
Fixes: 7eada909bfd7 ("dm: add integrity target")
Cc: stable@vger.kernel.org # v4.12+
Reported-by: Heinz Mauelshagen <heinzm@redhat.com>
Tested-by: Heinz Mauelshagen <heinzm@redhat.com>
Signed-off-by: Heinz Mauelshagen <heinzm@redhat.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/usb/host')
0 files changed, 0 insertions, 0 deletions