FAILED: patch "[PATCH] gfs2: Wake up when sd_glock_disposal becomes zero" failed to apply to 4.9-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 4.9-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From da7d554f7c62d0c17c1ac3cc2586473c2d99f0bd Mon Sep 17 00:00:00 2001
From: Alexander Aring <aahringo@redhat.com>
Date: Mon, 26 Oct 2020 10:52:29 -0400
Subject: [PATCH] gfs2: Wake up when sd_glock_disposal becomes zero

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@vger.kernel.org # v2.6.39+
Signed-off-by: Alexander Aring <aahringo@redhat.com>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index 5441c17562c5..d98a2e5dab9f 100644
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -1078,7 +1078,8 @@ int gfs2_glock_get(struct gfs2_sbd *sdp, u64 number,
 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;