[Cluster-devel] GFS2: Fix panic in glock memory shrinker
Bob Peterson
rpeterso at redhat.com
Tue Jun 30 19:02:32 UTC 2009
----- "Benjamin Marzinski" <bmarzins at redhat.com> wrote:
| To: cluster-devel at redhat.com
| Subject: 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 at redhat.com>
| ---
| fs/gfs2/glock.c | 4 ++++
| 1 file changed, 4 insertions(+)
|
| Index: kernel-upstream/fs/gfs2/glock.c
| ===================================================================
| --- kernel-upstream.orig/fs/gfs2/glock.c
| +++ kernel-upstream/fs/gfs2/glock.c
| @@ -1314,6 +1314,10 @@ static int gfs2_shrink_glock_memory(int
| 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);
Hi,
ACKed by Bob Peterson <rpeterso at redhat.com>
Regards,
Bob Peterson
Red Hat File Systems
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