[PATCH 4.19 135/361] md: fix memleak for mempool

[Greg Kroah-Hartman]

4.19-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jack Wang <jinpu.wang@xxxxxxxxxxxxxxxx>

[ Upstream commit 6aaa58c994277647f8b05ffef3b9b225a2d08f36 ]

I noticed kmemleak report memory leak when run create/stop
md in a loop, backtrace:
[<000000001ca975e7>] mempool_create_node+0x86/0xd0
[<0000000095576bcd>] md_run+0x1057/0x1410 [md_mod]
[<000000007b45c5fc>] do_md_run+0x15/0x130 [md_mod]
[<000000001ede9ec0>] md_ioctl+0x1f49/0x25d0 [md_mod]
[<000000004142cacf>] blkdev_ioctl+0x680/0xd00

The root cause is we alloc mddev->flush_pool and
mddev->flush_bio_pool in md_run, but from do_md_stop
will not call into md_stop but __md_stop, move the
mempool_destroy to __md_stop fixes the problem for me.

The bug was introduced in 5a409b4f56d5, the fixes should go to
4.18+

Fixes: 5a409b4f56d5 ("MD: fix lock contention for flush bios")
Signed-off-by: Jack Wang <jinpu.wang@xxxxxxxxxxxxxxxx>
Reviewed-by: Xiao Ni <xni@xxxxxxxxxx>
Signed-off-by: Shaohua Li <shli@xxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/md/md.c |   16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -5906,14 +5906,6 @@ static void __md_stop(struct mddev *mdde
 		mddev->to_remove = &md_redundancy_group;
 	module_put(pers->owner);
 	clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
-}
-
-void md_stop(struct mddev *mddev)
-{
-	/* stop the array and free an attached data structures.
-	 * This is called from dm-raid
-	 */
-	__md_stop(mddev);
 	if (mddev->flush_bio_pool) {
 		mempool_destroy(mddev->flush_bio_pool);
 		mddev->flush_bio_pool = NULL;
@@ -5922,6 +5914,14 @@ void md_stop(struct mddev *mddev)
 		mempool_destroy(mddev->flush_pool);
 		mddev->flush_pool = NULL;
 	}
+}
+
+void md_stop(struct mddev *mddev)
+{
+	/* stop the array and free an attached data structures.
+	 * This is called from dm-raid
+	 */
+	__md_stop(mddev);
 	bioset_exit(&mddev->bio_set);
 	bioset_exit(&mddev->sync_set);
 }