[PATCH v2 03/11] nfs: skip over stale rpc packets

["Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>]

When a former transaction was aborted by hitting Ctrl-C the old reply might
still hang in the ethernet controller making all further transactions fail.

So just skip over old replies.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
---

Notes:
    Changed in v2:
     - use
    	if (rpc_id - ntohl(rpc.id) == 1)
       instead of
    	if (ntohl(rpc.id) < rpc_id)
       to drop at most a single stale reply and handle overflow properly
    
    An alternative would be to drain the ethernet queue before a new request is
    sent. Don't know how that works and I don't see much benefit, so I didn't
    try to find out :-)

 fs/nfs.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/fs/nfs.c b/fs/nfs.c
index 6582bae7db31..76d8c0595db4 100644
--- a/fs/nfs.c
+++ b/fs/nfs.c
@@ -275,8 +275,13 @@ static int rpc_check_reply(unsigned char *pkt, int rpc_prog, unsigned long rpc_i
 
 	memcpy(&rpc, pkt, sizeof(rpc));
 
-	if (ntohl(rpc.id) != rpc_id)
+	if (ntohl(rpc.id) != rpc_id) {
+		if (rpc_id - ntohl(rpc.id) == 1)
+			/* stale packet, wait a bit longer */
+			return 0;
+
 		return -EINVAL;
+	}
 
 	if (rpc.rstatus  ||
 	    rpc.verifier ||
-- 
1.8.5.2


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