ceph: handle frag mismatch between readdir request and reply

If client has outdated directory fragments information, it may request
readdir an non-existent directory fragment. In this case, the MDS finds
an approximate directory fragment and sends its contents back to the
client. When receiving a reply with fragment that is different than the
requested one, the client need to reset the 'readdir offset'.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Reviewed-by: Sage Weil <sage@inktank.com>

3 files changed, 25 insertions, 5 deletions

diff --git a/fs/ceph/dir.c b/fs/ceph/dir.c
index 868b61d56cac..2a0bcaeb189a 100644
--- a/fs/ceph/dir.c
+++ b/fs/ceph/dir.c
@@ -352,8 +352,18 @@ more:
                 }
 
                 /* note next offset and last dentry name */
+                rinfo = &req->r_reply_info;
+                if (le32_to_cpu(rinfo->dir_dir->frag) != frag) {
+                        frag = le32_to_cpu(rinfo->dir_dir->frag);
+                        if (ceph_frag_is_leftmost(frag))
+                                fi->next_offset = 2;
+                        else
+                                fi->next_offset = 0;
+                        off = fi->next_offset;
+                }
                 fi->offset = fi->next_offset;
                 fi->last_readdir = req;
+                fi->frag = frag;
 
                 if (req->r_reply_info.dir_end) {
                         kfree(fi->last_name);
@@ -363,7 +373,6 @@ more:
                         else
                                 fi->next_offset = 0;
                 } else {
-                        rinfo = &req->r_reply_info;
                         err = note_last_dentry(fi,
                                        rinfo->dir_dname[rinfo->dir_nr-1],
                                        rinfo->dir_dname_len[rinfo->dir_nr-1]);
diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
index 1c9fea0c9834..9a8e396aed89 100644
--- a/fs/ceph/inode.c
+++ b/fs/ceph/inode.c
@@ -1275,8 +1275,20 @@ int ceph_readdir_prepopulate(struct ceph_mds_request *req,
         int err = 0, i;
         struct inode *snapdir = NULL;
         struct ceph_mds_request_head *rhead = req->r_request->front.iov_base;
-        u64 frag = le32_to_cpu(rhead->args.readdir.frag);
         struct ceph_dentry_info *di;
+        u64 r_readdir_offset = req->r_readdir_offset;
+        u32 frag = le32_to_cpu(rhead->args.readdir.frag);
+
+        if (rinfo->dir_dir &&
+            le32_to_cpu(rinfo->dir_dir->frag) != frag) {
+                dout("readdir_prepopulate got new frag %x -> %x\n",
+                     frag, le32_to_cpu(rinfo->dir_dir->frag));
+                frag = le32_to_cpu(rinfo->dir_dir->frag);
+                if (ceph_frag_is_leftmost(frag))
+                        r_readdir_offset = 2;
+                else
+                        r_readdir_offset = 0;
+        }
 
         if (req->r_aborted)
                 return readdir_prepopulate_inodes_only(req, session);
@@ -1340,7 +1352,7 @@ retry_lookup:
                 }
 
                 di = dn->d_fsdata;
-                di->offset = ceph_make_fpos(frag, i + req->r_readdir_offset);
+                di->offset = ceph_make_fpos(frag, i + r_readdir_offset);
 
                 /* inode */
                 if (dn->d_inode) {
diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index b7bda5d9611d..f51ab2627b41 100644
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -2238,8 +2238,7 @@ static void handle_reply(struct ceph_mds_session *session, struct ceph_msg *msg)
         err = ceph_fill_trace(mdsc->fsc->sb, req, req->r_session);
         if (err == 0) {
                 if (result == 0 && (req->r_op == CEPH_MDS_OP_READDIR ||
-                                    req->r_op == CEPH_MDS_OP_LSSNAP) &&
-                    rinfo->dir_nr)
+                                    req->r_op == CEPH_MDS_OP_LSSNAP))
                         ceph_readdir_prepopulate(req, req->r_session);
                 ceph_unreserve_caps(mdsc, &req->r_caps_reservation);
         }