ceph: fix readdir vs fragmentation race

following sequence of events tigger the race

- client readdir frag 0* -> got item 'A'
- MDS merges frag 0* and frag 1*
- client send readdir request (frag 1*, offset 2, readdir_start 'A')
- MDS reply items (that are after item 'A') in frag *

Link: http://tracker.ceph.com/issues/17286
Signed-off-by: Yan, Zheng <zyan@redhat.com>

diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
index bca1b49c1c4b1bc8d2f83e4389a48c1f107de661..ef4d046473256009843b6b4c82e1b5b1e451b02d 100644 (file)
--- a/fs/ceph/inode.c
+++ b/fs/ceph/inode.c
@@ -1511,7 +1511,8 @@ int ceph_readdir_prepopulate(struct ceph_mds_request *req,
                        ceph_fill_dirfrag(d_inode(parent), rinfo->dir_dir);
        }
 
-       if (ceph_frag_is_leftmost(frag) && req->r_readdir_offset == 2) {
+       if (ceph_frag_is_leftmost(frag) && req->r_readdir_offset == 2 &&
+           !(rinfo->hash_order && req->r_path2)) {
                /* note dir version at start of readdir so we can tell
                 * if any dentries get dropped */
                req->r_dir_release_cnt = atomic64_read(&ci->i_release_count);