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authorJunxiao Bi <junxiao.bi@oracle.com>2015-05-05 16:24:02 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2015-05-05 17:10:11 -0700
commitb1432a2a35565f538586774a03bf277c27fc267d (patch)
treefb75af1bd5c0e4c91b7bb114ca31880ecfbfc0d6 /fs/ocfs2/dlm/dlmmaster.c
parentd8fd150fe3935e1692bf57c66691e17409ebb9c1 (diff)
ocfs2: dlm: fix race between purge and get lock resource
There is a race window in dlm_get_lock_resource(), which may return a lock resource which has been purged. This will cause the process to hang forever in dlmlock() as the ast msg can't be handled due to its lock resource not existing. dlm_get_lock_resource { ... spin_lock(&dlm->spinlock); tmpres = __dlm_lookup_lockres_full(dlm, lockid, namelen, hash); if (tmpres) { spin_unlock(&dlm->spinlock); >>>>>>>> race window, dlm_run_purge_list() may run and purge the lock resource spin_lock(&tmpres->spinlock); ... spin_unlock(&tmpres->spinlock); } } Signed-off-by: Junxiao Bi <junxiao.bi@oracle.com> Cc: Joseph Qi <joseph.qi@huawei.com> Cc: Mark Fasheh <mfasheh@suse.com> Cc: Joel Becker <jlbec@evilplan.org> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/ocfs2/dlm/dlmmaster.c')
-rw-r--r--fs/ocfs2/dlm/dlmmaster.c13
1 files changed, 13 insertions, 0 deletions
diff --git a/fs/ocfs2/dlm/dlmmaster.c b/fs/ocfs2/dlm/dlmmaster.c
index a6944b25fd5b..fdf4b41d0609 100644
--- a/fs/ocfs2/dlm/dlmmaster.c
+++ b/fs/ocfs2/dlm/dlmmaster.c
@@ -757,6 +757,19 @@ lookup:
if (tmpres) {
spin_unlock(&dlm->spinlock);
spin_lock(&tmpres->spinlock);
+
+ /*
+ * Right after dlm spinlock was released, dlm_thread could have
+ * purged the lockres. Check if lockres got unhashed. If so
+ * start over.
+ */
+ if (hlist_unhashed(&tmpres->hash_node)) {
+ spin_unlock(&tmpres->spinlock);
+ dlm_lockres_put(tmpres);
+ tmpres = NULL;
+ goto lookup;
+ }
+
/* Wait on the thread that is mastering the resource */
if (tmpres->owner == DLM_LOCK_RES_OWNER_UNKNOWN) {
__dlm_wait_on_lockres(tmpres);