ceph: avoid block operation when !TASK_RUNNING (ceph_mdsc_close_sessions)

use an atomic variable to track number of sessions, this can avoid block
operation inside wait loops.

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

2 files changed, 5 insertions, 9 deletions

diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index fdf5cc8737ee..c90ca99331be 100644
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -480,6 +480,7 @@ static struct ceph_mds_session *register_session(struct ceph_mds_client *mdsc,
                 mdsc->max_sessions = newmax;
         }
         mdsc->sessions[mds] = s;
+        atomic_inc(&mdsc->num_sessions);
         atomic_inc(&s->s_ref);  /* one ref to sessions[], one to caller */
 
         ceph_con_open(&s->s_con, CEPH_ENTITY_TYPE_MDS, mds,
@@ -503,6 +504,7 @@ static void __unregister_session(struct ceph_mds_client *mdsc,
         mdsc->sessions[s->s_mds] = NULL;
         ceph_con_close(&s->s_con);
         ceph_put_mds_session(s);
+        atomic_dec(&mdsc->num_sessions);
 }
 
 /*
@@ -3328,6 +3330,7 @@ int ceph_mdsc_init(struct ceph_fs_client *fsc)
         init_waitqueue_head(&mdsc->session_close_wq);
         INIT_LIST_HEAD(&mdsc->waiting_for_map);
         mdsc->sessions = NULL;
+        atomic_set(&mdsc->num_sessions, 0);
         mdsc->max_sessions = 0;
         mdsc->stopping = 0;
         init_rwsem(&mdsc->snap_rwsem);
@@ -3479,17 +3482,9 @@ void ceph_mdsc_sync(struct ceph_mds_client *mdsc)
  */
 static bool done_closing_sessions(struct ceph_mds_client *mdsc)
 {
-        int i, n = 0;
-
         if (mdsc->fsc->mount_state == CEPH_MOUNT_SHUTDOWN)
                 return true;
-
-        mutex_lock(&mdsc->mutex);
-        for (i = 0; i < mdsc->max_sessions; i++)
-                if (mdsc->sessions[i])
-                        n++;
-        mutex_unlock(&mdsc->mutex);
-        return n == 0;
+        return atomic_read(&mdsc->num_sessions) == 0;
 }
 
 /*
diff --git a/fs/ceph/mds_client.h b/fs/ceph/mds_client.h
index a87b92f500bb..1875b5d985c6 100644
--- a/fs/ceph/mds_client.h
+++ b/fs/ceph/mds_client.h
@@ -273,6 +273,7 @@ struct ceph_mds_client {
         struct list_head        waiting_for_map;
 
         struct ceph_mds_session **sessions;    /* NULL for mds if no session */
+        atomic_t                num_sessions;
         int                     max_sessions;  /* len of s_mds_sessions */
         int                     stopping;      /* true if shutting down */