ceph: keep i_snap_realm while there are writers

when reconnecting to MDS is denied, we remove session caps
forcibly. But it's possible there are ongoing write, the
write code needs to reference i_snap_realm. So if there are
ongoing write, we keep i_snap_realm.

Signed-off-by: Yan, Zheng <zyan@redhat.com>

diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
index 8172775..4ddadc1 100644 (file)
--- a/fs/ceph/caps.c
+++ b/fs/ceph/caps.c
@@ -896,6 +896,18 @@ int ceph_is_any_caps(struct inode *inode)
        return ret;
 }
 
+static void drop_inode_snap_realm(struct ceph_inode_info *ci)
+{
+       struct ceph_snap_realm *realm = ci->i_snap_realm;
+       spin_lock(&realm->inodes_with_caps_lock);
+       list_del_init(&ci->i_snap_realm_item);
+       ci->i_snap_realm_counter++;
+       ci->i_snap_realm = NULL;
+       spin_unlock(&realm->inodes_with_caps_lock);
+       ceph_put_snap_realm(ceph_sb_to_client(ci->vfs_inode.i_sb)->mdsc,
+                           realm);
+}
+
 /*
  * Remove a cap.  Take steps to deal with a racing iterate_session_caps.
  *
@@ -946,15 +958,13 @@ void __ceph_remove_cap(struct ceph_cap *cap, bool queue_release)
        if (removed)
                ceph_put_cap(mdsc, cap);
 
-       if (!__ceph_is_any_caps(ci) && ci->i_snap_realm) {
-               struct ceph_snap_realm *realm = ci->i_snap_realm;
-               spin_lock(&realm->inodes_with_caps_lock);
-               list_del_init(&ci->i_snap_realm_item);
-               ci->i_snap_realm_counter++;
-               ci->i_snap_realm = NULL;
-               spin_unlock(&realm->inodes_with_caps_lock);
-               ceph_put_snap_realm(mdsc, realm);
-       }
+       /* when reconnect denied, we remove session caps forcibly,
+        * i_wr_ref can be non-zero. If there are ongoing write,
+        * keep i_snap_realm.
+        */
+       if (!__ceph_is_any_caps(ci) && ci->i_wr_ref == 0 && ci->i_snap_realm)
+               drop_inode_snap_realm(ci);
+
        if (!__ceph_is_any_real_caps(ci))
                __cap_delay_cancel(mdsc, ci);
 }
@@ -2309,6 +2319,9 @@ void ceph_put_cap_refs(struct ceph_inode_info *ci, int had)
                                        wake = 1;
                                }
                        }
+                       /* see comment in __ceph_remove_cap() */
+                       if (!__ceph_is_any_caps(ci) && ci->i_snap_realm)
+                               drop_inode_snap_realm(ci);
                }
        spin_unlock(&ci->i_ceph_lock);