ceph: use ihold when we already have an inode ref

We should use ihold whenever we already have a stable inode ref, even
when we aren't holding i_lock.  This avoids adding new and unnecessary
locking dependencies.

Signed-off-by: Sage Weil <sage@newdream.net>
diff --git a/fs/ceph/file.c b/fs/ceph/file.c
index 203252d..8c5ac4e7 100644
--- a/fs/ceph/file.c
+++ b/fs/ceph/file.c
@@ -191,7 +191,8 @@
 		err = PTR_ERR(req);
 		goto out;
 	}
-	req->r_inode = igrab(inode);
+	req->r_inode = inode;
+	ihold(inode);
 	req->r_num_caps = 1;
 	err = ceph_mdsc_do_request(mdsc, parent_inode, req);
 	if (!err)