From 01b05c66a3616d5a4adc39fc90962e9efaf791d1 Mon Sep 17 00:00:00 2001 From: Eric Blake Date: Mon, 13 Nov 2017 13:48:57 -0600 Subject: [PATCH] nbd/client: Don't hard-disconnect on ESHUTDOWN from server The NBD spec says that a server may fail any transmission request with ESHUTDOWN when it is apparent that no further request from the client can be successfully honored. The client is supposed to then initiate a soft shutdown (wait for all remaining in-flight requests to be answered, then send NBD_CMD_DISC). However, since qemu's server never uses ESHUTDOWN errors, this code was mostly untested since its introduction in commit b6f5d3b5. More recently, I learned that nbdkit as the NBD server is able to send ESHUTDOWN errors, so I finally tested this code, and noticed that our client was special-casing ESHUTDOWN to cause a hard shutdown (immediate disconnect, with no NBD_CMD_DISC), but only if the server sends this error as a simple reply. Further investigation found that commit d2febedb introduced a regression where structured replies behave differently than simple replies - but that the structured reply behavior is more in line with the spec (even if we still lack code in nbd-client.c to properly quit sending further requests). So this patch reverts the portion of b6f5d3b5 that introduced an improper hard-disconnect special-case at the lower level, and leaves the future enhancement of a nicer soft-disconnect at the higher level for another day. CC: qemu-stable@nongnu.org Signed-off-by: Eric Blake Message-Id: <20171113194857.13933-1-eblake@redhat.com> Reviewed-by: Vladimir Sementsov-Ogievskiy --- nbd/client.c | 6 ------ 1 file changed, 6 deletions(-) diff --git a/nbd/client.c b/nbd/client.c index 4e15fc484d..eea236ca06 100644 --- a/nbd/client.c +++ b/nbd/client.c @@ -996,15 +996,9 @@ int nbd_receive_reply(QIOChannel *ioc, NBDReply *reply, Error **errp) if (ret < 0) { break; } - trace_nbd_receive_simple_reply(reply->simple.error, nbd_err_lookup(reply->simple.error), reply->handle); - if (reply->simple.error == NBD_ESHUTDOWN) { - /* This works even on mingw which lacks a native ESHUTDOWN */ - error_setg(errp, "server shutting down"); - return -EINVAL; - } break; case NBD_STRUCTURED_REPLY_MAGIC: ret = nbd_receive_structured_reply_chunk(ioc, &reply->structured, errp);