ceph: fix locking for waking session requests after reconnect

The session->s_waiting list is protected by mdsc->mutex, not s_mutex.  This
was causing (rare) s_waiting list corruption.

Fix errors paths too, while we're here.  A more thorough cleanup of this
function is coming soon.

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

1 files changed, 16 insertions, 13 deletions

diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index 60a9a4ae47be..eccc0ecad1a2 100644
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -2136,7 +2136,7 @@ static void send_mds_reconnect(struct ceph_mds_client *mdsc, int mds)
         struct ceph_mds_session *session = NULL;
         struct ceph_msg *reply;
         struct rb_node *p;
-        int err;
+        int err = -ENOMEM;
         struct ceph_pagelist *pagelist;
 
         pr_info("reconnect to recovering mds%d\n", mds);
@@ -2185,7 +2185,7 @@ static void send_mds_reconnect(struct ceph_mds_client *mdsc, int mds)
                 goto fail;
         err = iterate_session_caps(session, encode_caps_cb, pagelist);
         if (err < 0)
-                goto out;
+                goto fail;
 
         /*
          * snaprealms.  we provide mds with the ino, seq (version), and
@@ -2213,28 +2213,31 @@ send:
         reply->nr_pages = calc_pages_for(0, pagelist->length);
         ceph_con_send(&session->s_con, reply);
 
-        if (session) {
-                session->s_state = CEPH_MDS_SESSION_OPEN;
-                __wake_requests(mdsc, &session->s_waiting);
-        }
+        session->s_state = CEPH_MDS_SESSION_OPEN;
+        mutex_unlock(&session->s_mutex);
+
+        mutex_lock(&mdsc->mutex);
+        __wake_requests(mdsc, &session->s_waiting);
+        mutex_unlock(&mdsc->mutex);
+
+        ceph_put_mds_session(session);
 
-out:
         up_read(&mdsc->snap_rwsem);
-        if (session) {
-                mutex_unlock(&session->s_mutex);
-                ceph_put_mds_session(session);
-        }
         mutex_lock(&mdsc->mutex);
         return;
 
 fail:
         ceph_msg_put(reply);
+        up_read(&mdsc->snap_rwsem);
+        mutex_unlock(&session->s_mutex);
+        ceph_put_mds_session(session);
 fail_nomsg:
         ceph_pagelist_release(pagelist);
         kfree(pagelist);
 fail_nopagelist:
-        pr_err("ENOMEM preparing reconnect for mds%d\n", mds);
-        goto out;
+        pr_err("error %d preparing reconnect for mds%d\n", err, mds);
+        mutex_lock(&mdsc->mutex);
+        return;
 }