ceph: clean up spinlocking and list handling around cleanup_cap_releases()

Functions that release a lock taken in a parent frame are notoriously
hard to follow. Split cleanup_cap_releases into two functions, one to
detach the cap releases from the session (which should be called with
the spinlock held), and another to dispose of those caps.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Reviewed-by: "Yan, Zheng" <zyan@redhat.com>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

1 files changed, 21 insertions, 13 deletions

diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index b76506be4228..53cde84e698a 100644
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -1039,22 +1039,23 @@ void ceph_mdsc_open_export_target_sessions(struct ceph_mds_client *mdsc,
  * session caps
  */
 
-/* caller holds s_cap_lock, we drop it */
-static void cleanup_cap_releases(struct ceph_mds_client *mdsc,
-                                 struct ceph_mds_session *session)
-        __releases(session->s_cap_lock)
+static void detach_cap_releases(struct ceph_mds_session *session,
+                                struct list_head *target)
 {
-        LIST_HEAD(tmp_list);
-        list_splice_init(&session->s_cap_releases, &tmp_list);
+        lockdep_assert_held(&session->s_cap_lock);
+
+        list_splice_init(&session->s_cap_releases, target);
         session->s_num_cap_releases = 0;
-        spin_unlock(&session->s_cap_lock);
+        dout("dispose_cap_releases mds%d\n", session->s_mds);
+}
 
-        dout("cleanup_cap_releases mds%d\n", session->s_mds);
-        while (!list_empty(&tmp_list)) {
+static void dispose_cap_releases(struct ceph_mds_client *mdsc,
+                                 struct list_head *dispose)
+{
+        while (!list_empty(dispose)) {
                 struct ceph_cap *cap;
                 /* zero out the in-progress message */
-                cap = list_first_entry(&tmp_list,
-                                        struct ceph_cap, session_caps);
+                cap = list_first_entry(dispose, struct ceph_cap, session_caps);
                 list_del(&cap->session_caps);
                 ceph_put_cap(mdsc, cap);
         }
@@ -1251,6 +1252,8 @@ static void remove_session_caps(struct ceph_mds_session *session)
 {
         struct ceph_fs_client *fsc = session->s_mdsc->fsc;
         struct super_block *sb = fsc->sb;
+        LIST_HEAD(dispose);
+
         dout("remove_session_caps on %p\n", session);
         iterate_session_caps(session, remove_session_caps_cb, fsc);
 
@@ -1285,10 +1288,12 @@ static void remove_session_caps(struct ceph_mds_session *session)
         }
 
         // drop cap expires and unlock s_cap_lock
-        cleanup_cap_releases(session->s_mdsc, session);
+        detach_cap_releases(session, &dispose);
 
         BUG_ON(session->s_nr_caps > 0);
         BUG_ON(!list_empty(&session->s_cap_flushing));
+        spin_unlock(&session->s_cap_lock);
+        dispose_cap_releases(session->s_mdsc, &dispose);
 }
 
 /*
@@ -3015,6 +3020,7 @@ static void send_mds_reconnect(struct ceph_mds_client *mdsc,
         int s_nr_caps;
         struct ceph_pagelist *pagelist;
         struct ceph_reconnect_state recon_state;
+        LIST_HEAD(dispose);
 
         pr_info("mds%d reconnect start\n", mds);
 
@@ -3048,7 +3054,9 @@ static void send_mds_reconnect(struct ceph_mds_client *mdsc,
          */
         session->s_cap_reconnect = 1;
         /* drop old cap expires; we're about to reestablish that state */
-        cleanup_cap_releases(mdsc, session);
+        detach_cap_releases(session, &dispose);
+        spin_unlock(&session->s_cap_lock);
+        dispose_cap_releases(mdsc, &dispose);
 
         /* trim unused caps to reduce MDS's cache rejoin time */
         if (mdsc->fsc->sb->s_root)