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

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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>
This commit is contained in:
Mikulas Patocka 2020-02-17 07:43:03 -05:00 committed by Mike Snitzer
parent d5bdf66108
commit 53770f0ec5
1 changed files with 15 additions and 4 deletions
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19
drivers/md/dm-integrity.c
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@ -212,6 +212,7 @@ struct dm_integrity_c {
struct list_head wait_list;
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];
@ -1439,7 +1440,7 @@ 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);
@ -1865,7 +1866,7 @@ 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;
}
@ -2501,7 +2502,7 @@ static void bitmap_block_work(struct work_struct *w)
dio->range.n_sectors, BITMAP_OP_TEST_ALL_SET)) {
remove_range(ic, &dio->range);
INIT_WORK(&dio->work, integrity_bio_wait);
queue_work(ic->wait_wq, &dio->work);
queue_work(ic->offload_wq, &dio->work);
} else {
block_bitmap_op(ic, ic->journal, dio->range.logical_sector,
dio->range.n_sectors, BITMAP_OP_SET);
@ -2524,7 +2525,7 @@ static void bitmap_block_work(struct work_struct *w)
remove_range(ic, &dio->range);
INIT_WORK(&dio->work, integrity_bio_wait);
queue_work(ic->wait_wq, &dio->work);
queue_work(ic->offload_wq, &dio->work);
}
queue_delayed_work(ic->commit_wq, &ic->bitmap_flush_work, ic->bitmap_flush_interval);
@ -3843,6 +3844,14 @@ 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";
@ -4147,6 +4156,8 @@ 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)