LU-4855 fld: refer to MDT0 for fld lookup in some cases

It is possible that when fld client is trying to lookup seq
on one of MDT, but the connection between the client and the MDT
is not being initialized yet, especially during striped dir creation,
because client will only send create req to the master MDT, then
master MDT will distribute the operation to all of other MDT, instead
of client distributing these requests, which will usually trigger
the connection.

In this case, we will send the fld request to MDT0, since it has
all of location information.

Signed-off-by: wang di <di.wang@intel.com>
Change-Id: I577ada2a782ecbdc863d05e8d007c0914a1e7837
Reviewed-on: http://review.whamcloud.com/9877
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-by: Fan Yong <fan.yong@intel.com>
Reviewed-by: Mike Pershin <mike.pershin@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>

diff --git a/lustre/fld/fld_request.c b/lustre/fld/fld_request.c
index 6a4986e..92e47ff 100644 (file)
--- a/lustre/fld/fld_request.c
+++ b/lustre/fld/fld_request.c
@@ -84,11 +84,20 @@ fld_rrb_scan(struct lu_client_fld *fld, seqno_t seq)
        else
                hash = 0;
 
+again:
         cfs_list_for_each_entry(target, &fld->lcf_targets, ft_chain) {
                 if (target->ft_idx == hash)
                         RETURN(target);
         }
 
+       if (hash != 0) {
+               /* It is possible the remote target(MDT) are not connected to
+                * with client yet, so we will refer this to MDT0, which should
+                * be connected during mount */
+               hash = 0;
+               goto again;
+       }
+
         CERROR("%s: Can't find target by hash %d (seq "LPX64"). "
                "Targets (%d):\n", fld->lcf_name, hash, seq,
                fld->lcf_count);