[sheepdog] [PATCH] sheep: fix handling of too old epoch in check_request

[Christoph Hellwig]

If we hit a too old epoch in check_request (which can only happen
when resume_pending_requests) we currently try to use io_op_done
to decide what to do.  For objects that are store locally on a node
that also acts as a gateway this is currently fatal:

 (a) io_op_done tries to remove the request from a list it has never
     been added to
 (b) io_op_done completes the request despite adding it to the
     wait_rw_queue list

In addition it seems that

 (c) io_op_done was checking for a too large epoch, not a too small one

If that last one was intentional it should at least be documented in there,
but I can't come up with a good explanation for it.

Fix these issues by opencoding the action we want in check_request.

Signed-off-by: Christoph Hellwig <hch at lst.de>

diff --git a/sheep/sdnet.c b/sheep/sdnet.c
index 7fcff4b..7f501aa 100644
--- a/sheep/sdnet.c
+++ b/sheep/sdnet.c
@@ -188,10 +188,18 @@ static int check_request(struct request *req)
 	if (before(req->rq.epoch, sys->epoch)) {
 		eprintf("old node version %u, %u, %x\n",
 			sys->epoch, req->rq.epoch, req->rq.opcode);
-		/* ask gateway to retry. */
+
+		/* ask gateway to retry unless this is a local object */
+		if (req->rq.flags & SD_FLAG_CMD_IO_LOCAL) {
+			req->rp.result = SD_RES_OLD_NODE_VER;
+			req->rp.epoch = sys->epoch;
+			req_done(req);
+			return -1;
+		}
+
 		req->rp.result = SD_RES_OLD_NODE_VER;
-		req->rp.epoch = sys->epoch;
-		req->work.done(&req->work);
+		list_add_tail(&req->request_list,
+				&sys->wait_rw_queue);
 		return -1;
 	} else if (after(req->rq.epoch, sys->epoch)) {
 		eprintf("new node version %u, %u, %x\n",