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Date:   Thu, 23 Nov 2017 13:08:28 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     "Darrick J. Wong" <darrick.wong@...cle.com>
Cc:     Dave Chinner <david@...morbit.com>,
        Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        linux-xfs@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        Michal Hocko <mhocko@...e.com>
Subject: [PATCH] xfs: handle register_shrinker error

From: Michal Hocko <mhocko@...e.com>

xfs_alloc_buftarg doesn't handle register_shrinker error path. While it
is unlikely to trigger it is not impossible especially with large NUMAs.
Let's handle the failure to make the code more robust.

Signed-off-by: Michal Hocko <mhocko@...e.com>
---

Hi,
this is not tested but it looks quite straightforward. There is one more
unchecked register_shrinker in xfs_qm_init_quotainfo but my absolute
lack of familiarity with the code didn't allow me to come up with a
mechanical fix like this one.

 fs/xfs/xfs_buf.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index 4db6e8d780f6..dd0e18af990c 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -1827,7 +1827,10 @@ xfs_alloc_buftarg(
 	btp->bt_shrinker.scan_objects = xfs_buftarg_shrink_scan;
 	btp->bt_shrinker.seeks = DEFAULT_SEEKS;
 	btp->bt_shrinker.flags = SHRINKER_NUMA_AWARE;
-	register_shrinker(&btp->bt_shrinker);
+	if (register_shrinker(&btp->bt_shrinker)) {
+		percpu_counter_destroy(&btp->bt_io_count);
+		goto error;
+	}
 	return btp;
 
 error:
-- 
2.15.0

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