Commit a51b56ff authored Jun 30, 2009 by Benjamin Marzinski Committed by Steven Whitehouse Jul 30, 2009

GFS2: Fix panic in glock memory shrinker



It is possible for gfs2_shrink_glock_memory() to check a glock for
demotion
that's in the process of being freed by gfs2_glock_put().  In this case,
gfs2_shrink_glock_memory() will acquire a new reference to this glock,
and
then try to free the glock itself when it drops the refernce.  To solve
this, gfs2_shrink_glock_memory() just needs to check if the glock is in
the process of being freed, and if so skip it without ever unlocking the
lru_lock.

Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
Acked-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

parent 1946f70a

fs/gfs2/glock.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -1314,6 +1314,10 @@ static int gfs2_shrink_glock_memory(int nr, gfp_t gfp_mask)
		list_del_init(&gl->gl_lru);
		atomic_dec(&lru_count);

		/* Check if glock is about to be freed */
		if (atomic_read(&gl->gl_ref) == 0)
		continue;

		/* Test for being demotable */
		if (!test_and_set_bit(GLF_LOCK, &gl->gl_flags)) {
		gfs2_glock_hold(gl);