ceph: avoid repeatedly adding inode to mdsc->snap_flush_list

BugLink: https://bugs.launchpad.net/bugs/1837813
commit 04242ff3ac0abbaa4362f97781dac268e6c3541a upstream.

Otherwise, mdsc->snap_flush_list may get corrupted.

Cc: stable@vger.kernel.org
Signed-off-by: "Yan, Zheng" <zyan@redhat.com>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/fs/ceph/snap.c b/fs/ceph/snap.c
index c304ca4139231e771f5541eb3f8515b73b37b3a0..0f3e21b1dd1dce6c8afb6e425710d99f6770a850 100644 (file)
--- a/fs/ceph/snap.c
+++ b/fs/ceph/snap.c
@@ -616,7 +616,8 @@ int __ceph_finish_cap_snap(struct ceph_inode_info *ci,
             capsnap->size);
 
        spin_lock(&mdsc->snap_flush_lock);
-       list_add_tail(&ci->i_snap_flush_item, &mdsc->snap_flush_list);
+       if (list_empty(&ci->i_snap_flush_item))
+               list_add_tail(&ci->i_snap_flush_item, &mdsc->snap_flush_list);
        spin_unlock(&mdsc->snap_flush_lock);
        return 1;  /* caller may want to ceph_flush_snaps */
 }