ceph: optimize mds session register

Do memory allocation first, so that avoid unnecessary
initialization of newly allocated session in error case.

Signed-off-by: Chengguang Xu <cgxu519@gmx.com>
Reviewed-by: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index b9cbeeb..a511a77 100644 (file)
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -448,6 +448,25 @@ static struct ceph_mds_session *register_session(struct ceph_mds_client *mdsc,
        s = kzalloc(sizeof(*s), GFP_NOFS);
        if (!s)
                return ERR_PTR(-ENOMEM);
+
+       if (mds >= mdsc->max_sessions) {
+               int newmax = 1 << get_count_order(mds + 1);
+               struct ceph_mds_session **sa;
+
+               dout("%s: realloc to %d\n", __func__, newmax);
+               sa = kcalloc(newmax, sizeof(void *), GFP_NOFS);
+               if (!sa)
+                       goto fail_realloc;
+               if (mdsc->sessions) {
+                       memcpy(sa, mdsc->sessions,
+                              mdsc->max_sessions * sizeof(void *));
+                       kfree(mdsc->sessions);
+               }
+               mdsc->sessions = sa;
+               mdsc->max_sessions = newmax;
+       }
+
+       dout("%s: mds%d\n", __func__, mds);
        s->s_mdsc = mdsc;
        s->s_mds = mds;
        s->s_state = CEPH_MDS_SESSION_NEW;
@@ -476,23 +495,6 @@ static struct ceph_mds_session *register_session(struct ceph_mds_client *mdsc,
        INIT_LIST_HEAD(&s->s_cap_releases);
        INIT_LIST_HEAD(&s->s_cap_flushing);
 
-       dout("register_session mds%d\n", mds);
-       if (mds >= mdsc->max_sessions) {
-               int newmax = 1 << get_count_order(mds+1);
-               struct ceph_mds_session **sa;
-
-               dout("register_session realloc to %d\n", newmax);
-               sa = kcalloc(newmax, sizeof(void *), GFP_NOFS);
-               if (!sa)
-                       goto fail_realloc;
-               if (mdsc->sessions) {
-                       memcpy(sa, mdsc->sessions,
-                              mdsc->max_sessions * sizeof(void *));
-                       kfree(mdsc->sessions);
-               }
-               mdsc->sessions = sa;
-               mdsc->max_sessions = newmax;
-       }
        mdsc->sessions[mds] = s;
        atomic_inc(&mdsc->num_sessions);
        refcount_inc(&s->s_ref);  /* one ref to sessions[], one to caller */