From: Eric Blake Date: Mon, 13 Nov 2017 19:48:57 +0000 (-0600) Subject: nbd/client: Don't hard-disconnect on ESHUTDOWN from server X-Git-Tag: qemu-xen-4.10.1^2~7 X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=b81833fe7d0dd56bec6f4066adec5859af01fdd6;p=qemu-xen.git 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 (cherry picked from commit 01b05c66a3616d5a4adc39fc90962e9efaf791d1) Conflicts: nbd/client.c *drop dep on d2febedb Signed-off-by: Michael Roth --- diff --git a/nbd/client.c b/nbd/client.c index 4caff77119..f04e95542f 100644 --- a/nbd/client.c +++ b/nbd/client.c @@ -945,12 +945,6 @@ ssize_t nbd_receive_reply(QIOChannel *ioc, NBDReply *reply, Error **errp) reply->handle = ldq_be_p(buf + 8); reply->error = nbd_errno_to_system_errno(reply->error); - - if (reply->error == ESHUTDOWN) { - /* This works even on mingw which lacks a native ESHUTDOWN */ - error_setg(errp, "server shutting down"); - return -EINVAL; - } trace_nbd_receive_reply(magic, reply->error, reply->handle); if (magic != NBD_REPLY_MAGIC) {