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dm integrity: fix a deadlock due to offloading to an incorrect workqueue

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commit 53770f0ec5 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: 7eada909bf ("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>
This commit is contained in:
Mikulas Patocka
2020-03-11 18:03:08 +01:00
committed by Greg Kroah-Hartman
parent d78934442b
commit ec6ddb1aa8
1 changed files with 13 additions and 2 deletions
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drivers/md/dm-integrity.c
+13 -2
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@@ -187,6 +187,7 @@ struct dm_integrity_c {
struct rb_root in_progress;
wait_queue_head_t endio_wait;
struct workqueue_struct *wait_wq;
struct workqueue_struct *offload_wq;
unsigned char commit_seq;
commit_id_t commit_ids[N_COMMIT_IDS];
@@ -1157,7 +1158,7 @@ static void dec_in_flight(struct dm_integrity_io *dio)
dio->range.logical_sector += dio->range.n_sectors;
bio_advance(bio, dio->range.n_sectors << SECTOR_SHIFT);
INIT_WORK(&dio->work, integrity_bio_wait);
queue_work(ic->wait_wq, &dio->work);
queue_work(ic->offload_wq, &dio->work);
return;
}
do_endio_flush(ic, dio);
@@ -1577,7 +1578,7 @@ static void dm_integrity_map_continue(struct dm_integrity_io *dio, bool from_map
if (need_sync_io && from_map) {
INIT_WORK(&dio->work, integrity_bio_wait);
queue_work(ic->metadata_wq, &dio->work);
queue_work(ic->offload_wq, &dio->work);
return;
}
@@ -3005,6 +3006,14 @@ static int dm_integrity_ctr(struct dm_target *ti, unsigned argc, char **argv)
goto bad;
}
ic->offload_wq = alloc_workqueue("dm-integrity-offload", WQ_MEM_RECLAIM,
METADATA_WORKQUEUE_MAX_ACTIVE);
if (!ic->offload_wq) {
ti->error = "Cannot allocate workqueue";
r = -ENOMEM;
goto bad;
}
ic->commit_wq = alloc_workqueue("dm-integrity-commit", WQ_MEM_RECLAIM, 1);
if (!ic->commit_wq) {
ti->error = "Cannot allocate workqueue";
@@ -3189,6 +3198,8 @@ static void dm_integrity_dtr(struct dm_target *ti)
destroy_workqueue(ic->metadata_wq);
if (ic->wait_wq)
destroy_workqueue(ic->wait_wq);
if (ic->offload_wq)
destroy_workqueue(ic->offload_wq);
if (ic->commit_wq)
destroy_workqueue(ic->commit_wq);
if (ic->writer_wq)