Commit 4043b886 authored by Steven Whitehouse's avatar Steven Whitehouse
Browse files

GFS2: Fix race between lru_list and glock ref count 



This patch fixes a narrow race window between the glock ref count
hitting zero and glocks being removed from the lru_list.

Signed-off-by: default avatarSteven Whitehouse <swhiteho@redhat.com>
parent 586c6e70

fs/gfs2/glock.c

+10 −4
Original line number Diff line number Diff line
@@ -167,14 +167,19 @@ void gfs2_glock_add_to_lru(struct gfs2_glock *gl) 
	spin_unlock(&lru_lock);

}



static void gfs2_glock_remove_from_lru(struct gfs2_glock *gl)

static void __gfs2_glock_remove_from_lru(struct gfs2_glock *gl)

{

	spin_lock(&lru_lock);

	if (!list_empty(&gl->gl_lru)) {

		list_del_init(&gl->gl_lru);

		atomic_dec(&lru_count);

		clear_bit(GLF_LRU, &gl->gl_flags);

	}

}



static void gfs2_glock_remove_from_lru(struct gfs2_glock *gl)

{

	spin_lock(&lru_lock);

	__gfs2_glock_remove_from_lru(gl);

	spin_unlock(&lru_lock);

}
@@ -217,11 +222,12 @@ void gfs2_glock_put(struct gfs2_glock *gl) 
	struct gfs2_sbd *sdp = gl->gl_sbd;

	struct address_space *mapping = gfs2_glock2aspace(gl);



	if (atomic_dec_and_test(&gl->gl_ref)) {

	if (atomic_dec_and_lock(&gl->gl_ref, &lru_lock)) {

		__gfs2_glock_remove_from_lru(gl);

		spin_unlock(&lru_lock);

		spin_lock_bucket(gl->gl_hash);

		hlist_bl_del_rcu(&gl->gl_list);

		spin_unlock_bucket(gl->gl_hash);

		gfs2_glock_remove_from_lru(gl);

		GLOCK_BUG_ON(gl, !list_empty(&gl->gl_holders));

		GLOCK_BUG_ON(gl, mapping && mapping->nrpages);

		trace_gfs2_glock_put(gl);