Re: [PATCH] fs/ceph:fix double unlock in handle_cap_export()

[Wu Bo]

On 2020/4/28 21:41, Yan, Zheng wrote:

On Tue, Apr 28, 2020 at 8:50 PM Wu Bo <wub...@huawei.com> wrote:

If the ceph_mdsc_open_export_target_session() return fails,
should add a lock to avoid twice unlocking.
Because the lock will be released at the retry or out_unlock tag.

at retry label, i_ceph_lock get locked. I don't see how i_ceph_lock
can get double unlock

sorry, maybe I didn't describe it clearly enough, not i_ceph_lock, but

session->s_mutex.

Thanks.

Wu Bo

Signed-off-by: Wu Bo <wub...@huawei.com>
---
  fs/ceph/caps.c | 26 ++++++++++++++------------
  1 file changed, 14 insertions(+), 12 deletions(-)

diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
index 185db76..b5a62a8 100644
--- a/fs/ceph/caps.c
+++ b/fs/ceph/caps.c
@@ -3731,22 +3731,24 @@ static void handle_cap_export(struct inode *inode, 
struct ceph_mds_caps *ex,

         /* open target session */
         tsession = ceph_mdsc_open_export_target_session(mdsc, target);
-       if (!IS_ERR(tsession)) {
-               if (mds > target) {
-                       mutex_lock(&session->s_mutex);
-                       mutex_lock_nested(&tsession->s_mutex,
-                                         SINGLE_DEPTH_NESTING);
-               } else {
-                       mutex_lock(&tsession->s_mutex);
-                       mutex_lock_nested(&session->s_mutex,
-                                         SINGLE_DEPTH_NESTING);
-               }
-               new_cap = ceph_get_cap(mdsc, NULL);
-       } else {
+       if (IS_ERR(tsession)) {
                 WARN_ON(1);
                 tsession = NULL;
                 target = -1;
+               mutex_lock(&session->s_mutex);
+               goto out_unlock;
+       }
+
+       if (mds > target) {
+               mutex_lock(&session->s_mutex);
+               mutex_lock_nested(&tsession->s_mutex,
+                                       SINGLE_DEPTH_NESTING);
+       } else {
+               mutex_lock(&tsession->s_mutex);
+               mutex_lock_nested(&session->s_mutex,
+                                       SINGLE_DEPTH_NESTING);
         }
+       new_cap = ceph_get_cap(mdsc, NULL);
         goto retry;

  out_unlock:
--
1.8.3.1

.