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>

diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index 60a9a4ae47bef2af2190e3bf92114c692d648664..eccc0ecad1a26b7a15371e5d1b6c7a897c6060b8 100644 (file)
--- 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;
 }