From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:58886) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eFEgW-0001wQ-Lu for qemu-devel@nongnu.org; Thu, 16 Nov 2017 02:34:05 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eFEgV-0003WB-MQ for qemu-devel@nongnu.org; Thu, 16 Nov 2017 02:34:04 -0500 References: <20171113194857.13933-1-eblake@redhat.com> From: Vladimir Sementsov-Ogievskiy Message-ID: Date: Thu, 16 Nov 2017 10:33:49 +0300 MIME-Version: 1.0 In-Reply-To: <20171113194857.13933-1-eblake@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Subject: Re: [Qemu-devel] [PATCH for-2.11] nbd/client: Don't hard-disconnect on ESHUTDOWN from server List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eric Blake , qemu-devel@nongnu.org Cc: qemu-block@nongnu.org, qemu-trivial@nongnu.org, Paolo Bonzini 13.11.2017 22:48, Eric Blake wrote: > 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-trivial@nongnu.org > Signed-off-by: Eric Blake 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); -- Best regards, Vladimir