From: Andreas Gruenbacher <agruenba@redhat.com>
Date: Thu, 6 Feb 2025 13:58:39 +0000 (+0100)
Subject: gfs2: Check for empty queue in run_queue
X-Git-Tag: v6.15-rc1~154^2~16
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d838605fea6eabae3746a276fd448f6719eb3926;p=thirdparty%2Fkernel%2Flinux.git

gfs2: Check for empty queue in run_queue

In run_queue(), check if the queue of pending requests is empty instead
of blindly assuming that it won't be.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
---

diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index dd82bc27c27a0..5d4d7b7f3af3d 100644
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -845,12 +845,13 @@ static void run_queue(struct gfs2_glock *gl, const int nonblock)
 __releases(&gl->gl_lockref.lock)
 __acquires(&gl->gl_lockref.lock)
 {
-	struct gfs2_holder *gh = NULL;
+	struct gfs2_holder *gh;
 
 	if (test_bit(GLF_LOCK, &gl->gl_flags))
 		return;
 	set_bit(GLF_LOCK, &gl->gl_flags);
 
+	/* While a demote is in progress, the GLF_LOCK flag must be set. */
 	GLOCK_BUG_ON(gl, test_bit(GLF_DEMOTE_IN_PROGRESS, &gl->gl_flags));
 
 	if (test_bit(GLF_DEMOTE, &gl->gl_flags) &&
@@ -862,18 +863,22 @@ __acquires(&gl->gl_lockref.lock)
 		set_bit(GLF_DEMOTE_IN_PROGRESS, &gl->gl_flags);
 		GLOCK_BUG_ON(gl, gl->gl_demote_state == LM_ST_EXCLUSIVE);
 		gl->gl_target = gl->gl_demote_state;
+		do_xmote(gl, NULL, gl->gl_target);
+		return;
 	} else {
 		if (test_bit(GLF_DEMOTE, &gl->gl_flags))
 			gfs2_demote_wake(gl);
 		if (do_promote(gl))
 			goto out_unlock;
 		gh = find_first_waiter(gl);
+		if (!gh)
+			goto out_unlock;
 		gl->gl_target = gh->gh_state;
 		if (!(gh->gh_flags & (LM_FLAG_TRY | LM_FLAG_TRY_1CB)))
 			do_error(gl, 0); /* Fail queued try locks */
+		do_xmote(gl, gh, gl->gl_target);
+		return;
 	}
-	do_xmote(gl, gh, gl->gl_target);
-	return;
 
 out_sched:
 	clear_bit(GLF_LOCK, &gl->gl_flags);