On Mon, 9 Mar 2020, gregkh@xxxxxxxxxxxxxxxxxxx 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@xxxxxxxxxxxxxxx>.
>
> 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@xxxxxxxxxx>
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@xxxxxxxxxxxxxxx # v4.12+
Reported-by: Heinz Mauelshagen <heinzm@xxxxxxxxxx>
Tested-by: Heinz Mauelshagen <heinzm@xxxxxxxxxx>
Signed-off-by: Heinz Mauelshagen <heinzm@xxxxxxxxxx>
Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
---
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)
