ceph: do not touch_caps while iterating over caps list
Sage Weil [Tue, 22 Dec 2009 04:40:34 +0000 (20:40 -0800)]
Avoid confusing iterate_session_caps(), flag the session while we are
iterating so that __touch_cap does not rearrange items on the list.

All other modifiers of session->s_caps do so under the protection of
s_mutex.

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

fs/ceph/caps.c
fs/ceph/mds_client.c
fs/ceph/mds_client.h

index dfb509f..93c1afe 100644 (file)
@@ -697,10 +697,15 @@ static void __touch_cap(struct ceph_cap *cap)
 {
        struct ceph_mds_session *s = cap->session;
 
-       dout("__touch_cap %p cap %p mds%d\n", &cap->ci->vfs_inode, cap,
-            s->s_mds);
        spin_lock(&s->s_cap_lock);
-       list_move_tail(&cap->session_caps, &s->s_caps);
+       if (!s->s_iterating_caps) {
+               dout("__touch_cap %p cap %p mds%d\n", &cap->ci->vfs_inode, cap,
+                    s->s_mds);
+               list_move_tail(&cap->session_caps, &s->s_caps);
+       } else {
+               dout("__touch_cap %p cap %p mds%d NOP, iterating over caps\n",
+                    &cap->ci->vfs_inode, cap, s->s_mds);
+       }
        spin_unlock(&s->s_cap_lock);
 }
 
index d7cecc3..63ca3b1 100644 (file)
@@ -337,10 +337,12 @@ static struct ceph_mds_session *register_session(struct ceph_mds_client *mdsc,
        s->s_renew_seq = 0;
        INIT_LIST_HEAD(&s->s_caps);
        s->s_nr_caps = 0;
+       s->s_trim_caps = 0;
        atomic_set(&s->s_ref, 1);
        INIT_LIST_HEAD(&s->s_waiting);
        INIT_LIST_HEAD(&s->s_unsafe);
        s->s_num_cap_releases = 0;
+       s->s_iterating_caps = false;
        INIT_LIST_HEAD(&s->s_cap_releases);
        INIT_LIST_HEAD(&s->s_cap_releases_done);
        INIT_LIST_HEAD(&s->s_cap_flushing);
@@ -699,6 +701,7 @@ static int iterate_session_caps(struct ceph_mds_session *session,
 
        dout("iterate_session_caps %p mds%d\n", session, session->s_mds);
        spin_lock(&session->s_cap_lock);
+       session->s_iterating_caps = true;
        list_for_each_entry_safe(cap, ncap, &session->s_caps, session_caps) {
                inode = igrab(&cap->ci->vfs_inode);
                if (!inode)
@@ -706,13 +709,15 @@ static int iterate_session_caps(struct ceph_mds_session *session,
                spin_unlock(&session->s_cap_lock);
                ret = cb(inode, cap, arg);
                iput(inode);
-               if (ret < 0)
-                       return ret;
                spin_lock(&session->s_cap_lock);
+               if (ret < 0)
+                       goto out;
        }
+       ret = 0;
+out:
+       session->s_iterating_caps = false;
        spin_unlock(&session->s_cap_lock);
-
-       return 0;
+       return ret;
 }
 
 static int remove_session_caps_cb(struct inode *inode, struct ceph_cap *cap,
@@ -935,6 +940,7 @@ static int trim_caps(struct ceph_mds_client *mdsc,
                dout("trim_caps mds%d done: %d / %d, trimmed %d\n",
                     session->s_mds, session->s_nr_caps, max_caps,
                        trim_caps - session->s_trim_caps);
+               session->s_trim_caps = 0;
        }
        return 0;
 }
index 41af5ca..b1c2025 100644 (file)
@@ -114,6 +114,7 @@ struct ceph_mds_session {
        int               s_num_cap_releases;
        struct list_head  s_cap_releases; /* waiting cap_release messages */
        struct list_head  s_cap_releases_done; /* ready to send */
+       bool              s_iterating_caps;
 
        /* protected by mutex */
        struct list_head  s_cap_flushing;     /* inodes w/ flushing caps */