From 0fc0a6c7d5492e109a852542ec665567eeefbf34 Mon Sep 17 00:00:00 2001 From: Eric Blake Date: Wed, 19 Jul 2017 18:01:59 +0200 Subject: [PATCH 02/17] nbd: strict nbd_wr_syncv RH-Author: Eric Blake Message-id: <20170719180202.23329-2-eblake@redhat.com> Patchwork-id: 75817 O-Subject: [RHEV-7.4.z qemu-kvm-rhev PATCH 1/4] nbd: strict nbd_wr_syncv Bugzilla: 1473638 RH-Acked-by: Stefan Hajnoczi RH-Acked-by: Paolo Bonzini RH-Acked-by: Jeffrey Cody From: Vladimir Sementsov-Ogievskiy nbd_wr_syncv is called either from coroutine or from client negotiation code, when socket is in blocking mode. So, -EAGAIN is impossible. Furthermore, EAGAIN is confusing, as, what to read/write again? With EAGAIN as a return code we don't know how much data is already read or written by the function, so in case of EAGAIN the whole communication is broken. Signed-off-by: Vladimir Sementsov-Ogievskiy Message-Id: <20170516094533.6160-2-vsementsov@virtuozzo.com> Signed-off-by: Paolo Bonzini (cherry picked from commit f250a42ddaee042ad2eb02022a3ebd18fcf987de) Signed-off-by: Eric Blake Signed-off-by: Miroslav Rezanina --- nbd/common.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) diff --git a/nbd/common.c b/nbd/common.c index dccbb8e..4db45b3 100644 --- a/nbd/common.c +++ b/nbd/common.c @@ -20,6 +20,10 @@ #include "qapi/error.h" #include "nbd-internal.h" +/* nbd_wr_syncv + * The function may be called from coroutine or from non-coroutine context. + * When called from non-coroutine context @ioc must be in blocking mode. + */ ssize_t nbd_wr_syncv(QIOChannel *ioc, struct iovec *iov, size_t niov, @@ -42,11 +46,8 @@ ssize_t nbd_wr_syncv(QIOChannel *ioc, len = qio_channel_writev(ioc, local_iov, nlocal_iov, &local_err); } if (len == QIO_CHANNEL_ERR_BLOCK) { - if (qemu_in_coroutine()) { - qio_channel_yield(ioc, do_read ? G_IO_IN : G_IO_OUT); - } else { - return -EAGAIN; - } + assert(qemu_in_coroutine()); + qio_channel_yield(ioc, do_read ? G_IO_IN : G_IO_OUT); continue; } if (len < 0) { -- 1.8.3.1