On Mon, 9 Mar 2020, gregkh@linuxfoundation.org wrote:
The patch below does not apply to the 4.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
Hi
Here I'm sending the patch for the stable branches 4.14 and 4.19.
Mikulas
------------------ original commit in Linus's tree ------------------
From 53770f0ec5fd417429775ba006bc4abe14002335 Mon Sep 17 00:00:00 2001
From: Mikulas Patocka mpatocka@redhat.com Date: Mon, 17 Feb 2020 07:43:03 -0500 Subject: [PATCH] dm integrity: fix a deadlock due to offloading to an incorrect workqueue
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
--- drivers/md/dm-integrity.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-)
Index: linux-stable/drivers/md/dm-integrity.c =================================================================== --- linux-stable.orig/drivers/md/dm-integrity.c 2020-03-10 09:53:57.000000000 +0100 +++ linux-stable/drivers/md/dm-integrity.c 2020-03-10 09:53:57.000000000 +0100 @@ -197,6 +197,7 @@ 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]; @@ -1236,7 +1237,7 @@ static void dec_in_flight(struct dm_inte 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); @@ -1656,7 +1657,7 @@ static void dm_integrity_map_continue(st
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; }
@@ -3310,6 +3311,14 @@ static int dm_integrity_ctr(struct dm_ta 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"; @@ -3546,6 +3555,8 @@ static void dm_integrity_dtr(struct dm_t 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)