Patch "dm snapshot: fix lockup in dm_exception_table_exit" has been added to the 5.4-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    dm snapshot: fix lockup in dm_exception_table_exit

to the 5.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     dm-snapshot-fix-lockup-in-dm_exception_table_exit.patch
and it can be found in the queue-5.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 101f87a83c2afb4bffda0905079ba6250f134db7
Author: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Date:   Wed Mar 20 18:43:11 2024 +0100

    dm snapshot: fix lockup in dm_exception_table_exit
    
    [ Upstream commit 6e7132ed3c07bd8a6ce3db4bb307ef2852b322dc ]
    
    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@xxxxxxxxxx>
    Cc: stable@xxxxxxxxxxxxxxx
    Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
    Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index e902aae685af9..d8902d2b6aa66 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -685,8 +685,10 @@ 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();
+		}
 	}
 
 	vfree(et->table);