[lustre-devel] [PATCH 3/8] lustre: fld: resend seq lookup RPC if it is on LWP

[James Simmons <jsimmons@infradead.org>]

From: wang di <di.wang@intel.com>

Because Light Weight connection might be evicted after
restart, then cause inflight RPC fails, to avoid this,
we need resend seq lookup RPC.

remove "-f" from "stop mdt" in sanity 17m, so umount can
keep the the connection, and otherwise the OSP might be
evicted.

WC-bug-id: https://jira.whamcloud.com/browse/LU-4571
Lustre-commit: cf7f66d87e52293535cde6e8cc7386e6c1bdfa46
Signed-off-by: wang di <di.wang@intel.com>
Reviewed-on: http://review.whamcloud.com/9106
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Jinshan Xiong <jinshan.xiong@gmail.com>
Reviewed-by: Niu Yawei <yawei.niu@intel.com>
---
 fs/lustre/fld/fld_request.c | 23 +++++++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/fs/lustre/fld/fld_request.c b/fs/lustre/fld/fld_request.c
index 248fffa..ec45ea6 100644
--- a/fs/lustre/fld/fld_request.c
+++ b/fs/lustre/fld/fld_request.c
@@ -314,6 +314,7 @@ int fld_client_rpc(struct obd_export *exp,
 
 	LASSERT(exp);
 
+again:
 	imp = class_exp2cliimp(exp);
 	switch (fld_op) {
 	case FLD_QUERY:
@@ -329,8 +330,15 @@ int fld_client_rpc(struct obd_export *exp,
 		op = req_capsule_client_get(&req->rq_pill, &RMF_FLD_OPC);
 		*op = FLD_LOOKUP;
 
-		if (imp->imp_connect_flags_orig & OBD_CONNECT_MDS_MDS)
+		/* For MDS_MDS seq lookup, it will always use LWP connection,
+		 * but LWP will be evicted after restart, so cause the error.
+		 * so we will set no_delay for seq lookup request, once the
+		 * request fails because of the eviction. always retry here
+		 */
+		if (imp->imp_connect_flags_orig & OBD_CONNECT_MDS_MDS) {
 			req->rq_allow_replay = 1;
+			req->rq_no_delay = 1;
+		}
 		break;
 	case FLD_READ:
 		req = ptlrpc_request_alloc_pack(imp, &RQF_FLD_READ,
@@ -358,8 +366,19 @@ int fld_client_rpc(struct obd_export *exp,
 	obd_get_request_slot(&exp->exp_obd->u.cli);
 	rc = ptlrpc_queue_wait(req);
 	obd_put_request_slot(&exp->exp_obd->u.cli);
-	if (rc)
+	if (rc != 0) {
+		if (rc == -EWOULDBLOCK) {
+			/* For no_delay req(see above), EWOULDBLOCK means the
+			 * connection is being evicted, but this seq lookup
+			 * should not return error, since it would cause
+			 * unecessary failure of the application, instead
+			 * it should retry here
+			 */
+			ptlrpc_req_finished(req);
+			goto again;
+		}
 		goto out_req;
+	}
 
 	if (fld_op == FLD_QUERY) {
 		prange = req_capsule_server_get(&req->rq_pill, &RMF_FLD_MDFLD);
-- 
1.8.3.1