ceph: do not touch_caps while iterating over caps list

Avoid confusing iterate_session_caps(), flag the session while we are
iterating so that __touch_cap does not rearrange items on the list.

All other modifiers of session->s_caps do so under the protection of
s_mutex.

Signed-off-by: Sage Weil <sage@newdream.net>

1 files changed, 8 insertions, 3 deletions

diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
index dfb509f53542..93c1afe3f0b3 100644
--- a/fs/ceph/caps.c
+++ b/fs/ceph/caps.c
@@ -697,10 +697,15 @@ static void __touch_cap(struct ceph_cap *cap)
 {
         struct ceph_mds_session *s = cap->session;
 
-        dout("__touch_cap %p cap %p mds%d\n", &cap->ci->vfs_inode, cap,
-             s->s_mds);
         spin_lock(&s->s_cap_lock);
-        list_move_tail(&cap->session_caps, &s->s_caps);
+        if (!s->s_iterating_caps) {
+                dout("__touch_cap %p cap %p mds%d\n", &cap->ci->vfs_inode, cap,
+                     s->s_mds);
+                list_move_tail(&cap->session_caps, &s->s_caps);
+        } else {
+                dout("__touch_cap %p cap %p mds%d NOP, iterating over caps\n",
+                     &cap->ci->vfs_inode, cap, s->s_mds);
+        }
         spin_unlock(&s->s_cap_lock);
 }