ceph: handle cap export race in try_flush_caps()

auth cap may change after releasing the i_ceph_lock

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>

diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
index 80dad0d..1012099 100644 (file)
--- a/fs/ceph/caps.c
+++ b/fs/ceph/caps.c
@@ -1735,13 +1735,12 @@ ack:
 /*
  * Try to flush dirty caps back to the auth mds.
  */
-static int try_flush_caps(struct inode *inode, struct ceph_mds_session *session,
-                         unsigned *flush_tid)
+static int try_flush_caps(struct inode *inode, unsigned *flush_tid)
 {
        struct ceph_mds_client *mdsc = ceph_sb_to_client(inode->i_sb)->mdsc;
        struct ceph_inode_info *ci = ceph_inode(inode);
-       int unlock_session = session ? 0 : 1;
        int flushing = 0;
+       struct ceph_mds_session *session = NULL;
 
 retry:
        spin_lock(&ci->i_ceph_lock);
@@ -1755,13 +1754,14 @@ retry:
                int want = __ceph_caps_wanted(ci);
                int delayed;
 
-               if (!session) {
+               if (!session || session != cap->session) {
                        spin_unlock(&ci->i_ceph_lock);
+                       if (session)
+                               mutex_unlock(&session->s_mutex);
                        session = cap->session;
                        mutex_lock(&session->s_mutex);
                        goto retry;
                }
-               BUG_ON(session != cap->session);
                if (cap->session->s_state < CEPH_MDS_SESSION_OPEN)
                        goto out;
 
@@ -1780,7 +1780,7 @@ retry:
 out:
        spin_unlock(&ci->i_ceph_lock);
 out_unlocked:
-       if (session && unlock_session)
+       if (session)
                mutex_unlock(&session->s_mutex);
        return flushing;
 }
@@ -1865,7 +1865,7 @@ int ceph_fsync(struct file *file, loff_t start, loff_t end, int datasync)
                return ret;
        mutex_lock(&inode->i_mutex);
 
-       dirty = try_flush_caps(inode, NULL, &flush_tid);
+       dirty = try_flush_caps(inode, &flush_tid);
        dout("fsync dirty caps are %s\n", ceph_cap_string(dirty));
 
        /*
@@ -1900,7 +1900,7 @@ int ceph_write_inode(struct inode *inode, struct writeback_control *wbc)
 
        dout("write_inode %p wait=%d\n", inode, wait);
        if (wait) {
-               dirty = try_flush_caps(inode, NULL, &flush_tid);
+               dirty = try_flush_caps(inode, &flush_tid);
                if (dirty)
                        err = wait_event_interruptible(ci->i_cap_wq,
                                       caps_are_flushed(inode, flush_tid));