linux-kernel - [PATCH 4.19 40/71] gfs2: Wake up when sd_glock

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Date:   Mon,  9 Nov 2020 13:55:34 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Alexander Aring <aahringo@...hat.com>,
        Andreas Gruenbacher <agruenba@...hat.com>
Subject: [PATCH 4.19 40/71] gfs2: Wake up when sd_glock_disposal becomes zero

From: Alexander Aring <aahringo@...hat.com>

commit da7d554f7c62d0c17c1ac3cc2586473c2d99f0bd upstream.

Commit fc0e38dae645 ("GFS2: Fix glock deallocation race") fixed a
sd_glock_disposal accounting bug by adding a missing atomic_dec
statement, but it failed to wake up sd_glock_wait when that decrement
causes sd_glock_disposal to reach zero.  As a consequence,
gfs2_gl_hash_clear can now run into a 10-minute timeout instead of
being woken up.  Add the missing wakeup.

Fixes: fc0e38dae645 ("GFS2: Fix glock deallocation race")
Cc: stable@...r.kernel.org # v2.6.39+
Signed-off-by: Alexander Aring <aahringo@...hat.com>
Signed-off-by: Andreas Gruenbacher <agruenba@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/gfs2/glock.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -870,7 +870,8 @@ int gfs2_glock_get(struct gfs2_sbd *sdp,
 out_free:
 	kfree(gl->gl_lksb.sb_lvbptr);
 	kmem_cache_free(cachep, gl);
-	atomic_dec(&sdp->sd_glock_disposal);
+	if (atomic_dec_and_test(&sdp->sd_glock_disposal))
+		wake_up(&sdp->sd_glock_wait);
 
 out:
 	return ret;