linux-kernel - FAILED: Patch "dm snapshot: fix lockup in dm_exception_table_exit" failed to apply to 4.19-stable tree

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Date: Wed, 27 Mar 2024 08:28:27 -0400
From: Sasha Levin <sashal@...nel.org>
To: stable@...r.kernel.org,
	mpatocka@...hat.com
Cc: John Pittman <jpittman@...hat.com>,
	Mike Snitzer <snitzer@...nel.org>,
	dm-devel@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: FAILED: Patch "dm snapshot: fix lockup in dm_exception_table_exit" failed to apply to 4.19-stable tree

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@...r.kernel.org>.

Thanks,
Sasha

------------------ original commit in Linus's tree ------------------

>From 6e7132ed3c07bd8a6ce3db4bb307ef2852b322dc Mon Sep 17 00:00:00 2001
From: Mikulas Patocka <mpatocka@...hat.com>
Date: Wed, 20 Mar 2024 18:43:11 +0100
Subject: [PATCH] dm snapshot: fix lockup in dm_exception_table_exit

There was reported lockup when we exit a snapshot with many exceptions.
Fix this by adding "cond_resched" to the loop that frees the exceptions.

Reported-by: John Pittman <jpittman@...hat.com>
Cc: stable@...r.kernel.org
Signed-off-by: Mikulas Patocka <mpatocka@...hat.com>
Signed-off-by: Mike Snitzer <snitzer@...nel.org>
---
 drivers/md/dm-snap.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index bf7a574499a34..0ace06d1bee38 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -684,8 +684,10 @@ static void dm_exception_table_exit(struct dm_exception_table *et,
 	for (i = 0; i < size; i++) {
 		slot = et->table + i;
 
-		hlist_bl_for_each_entry_safe(ex, pos, n, slot, hash_list)
+		hlist_bl_for_each_entry_safe(ex, pos, n, slot, hash_list) {
 			kmem_cache_free(mem, ex);
+			cond_resched();
+		}
 	}
 
 	kvfree(et->table);
-- 
2.43.0