GFS2: Fix potential race in glock code
We need to be careful of the ordering between clearing the
GLF_LOCK bit and scheduling the workqueue.
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index 8b674b1..a3f90ad 100644
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -672,12 +672,17 @@
return;
out_sched:
+ clear_bit(GLF_LOCK, &gl->gl_flags);
+ smp_mb__after_clear_bit();
gfs2_glock_hold(gl);
if (queue_delayed_work(glock_workqueue, &gl->gl_work, 0) == 0)
gfs2_glock_put_nolock(gl);
+ return;
+
out_unlock:
clear_bit(GLF_LOCK, &gl->gl_flags);
- goto out;
+ smp_mb__after_clear_bit();
+ return;
}
static void delete_work_func(struct work_struct *work)
@@ -1375,10 +1380,11 @@
handle_callback(gl, LM_ST_UNLOCKED, 0);
nr--;
}
+ clear_bit(GLF_LOCK, &gl->gl_flags);
+ smp_mb__after_clear_bit();
if (queue_delayed_work(glock_workqueue, &gl->gl_work, 0) == 0)
gfs2_glock_put_nolock(gl);
spin_unlock(&gl->gl_spin);
- clear_bit(GLF_LOCK, &gl->gl_flags);
spin_lock(&lru_lock);
continue;
}