linux-kernel - [PATCH 4.9 138/175] gfs2: Dont call dlm after protocol is unmounted

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Message-Id: <20210920163922.587702222@linuxfoundation.org>
Date:   Mon, 20 Sep 2021 18:43:07 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Bob Peterson <rpeterso@...hat.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.9 138/175] gfs2: Dont call dlm after protocol is unmounted

From: Bob Peterson <rpeterso@...hat.com>

[ Upstream commit d1340f80f0b8066321b499a376780da00560e857 ]

In the gfs2 withdraw sequence, the dlm protocol is unmounted with a call
to lm_unmount. After a withdraw, users are allowed to unmount the
withdrawn file system. But at that point we may still have glocks left
over that we need to free via unmount's call to gfs2_gl_hash_clear.
These glocks may have never been completed because of whatever problem
caused the withdraw (IO errors or whatever).

Before this patch, function gdlm_put_lock would still try to call into
dlm to unlock these leftover glocks, which resulted in dlm returning
-EINVAL because the lock space was abandoned. These glocks were never
freed because there was no mechanism after that to free them.

This patch adds a check to gdlm_put_lock to see if the locking protocol
was inactive (DFL_UNMOUNT flag) and if so, free the glock and not
make the invalid call into dlm.

I could have combined this "if" with the one that follows, related to
leftover glock LVBs, but I felt the code was more readable with its own
if clause.

Signed-off-by: Bob Peterson <rpeterso@...hat.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/gfs2/lock_dlm.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/gfs2/lock_dlm.c b/fs/gfs2/lock_dlm.c
index 3cbc9147286d..da9f97911852 100644
--- a/fs/gfs2/lock_dlm.c
+++ b/fs/gfs2/lock_dlm.c
@@ -296,6 +296,11 @@ static void gdlm_put_lock(struct gfs2_glock *gl)
 	gfs2_sbstats_inc(gl, GFS2_LKS_DCOUNT);
 	gfs2_update_request_times(gl);

+	/* don't want to call dlm if we've unmounted the lock protocol */
+	if (test_bit(DFL_UNMOUNT, &ls->ls_recover_flags)) {
+		gfs2_glock_free(gl);
+		return;
+	}
 	/* don't want to skip dlm_unlock writing the lvb when lock has one */

 	if (test_bit(SDF_SKIP_DLM_UNLOCK, &sdp->sd_flags) &&
-- 
2.30.2