debian/patches/extra/0037-nbd-strict-nbd_wr_syncv.patch

   1 From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
   2 From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
   3 Date: Tue, 16 May 2017 12:45:29 +0300
   4 Subject: [PATCH] nbd: strict nbd_wr_syncv
   5
   6 nbd_wr_syncv is called either from coroutine or from client negotiation
   7 code, when socket is in blocking mode. So, -EAGAIN is impossible.
   8
   9 Furthermore, EAGAIN is confusing, as, what to read/write again? With
  10 EAGAIN as a return code we don't know how much data is already
  11 read or written by the function, so in case of EAGAIN the whole
  12 communication is broken.
  13
  14 Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
  15 Message-Id: <20170516094533.6160-2-vsementsov@virtuozzo.com>
  16 Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
  17 ---
  18  nbd/common.c | 11 ++++++-----
  19  1 file changed, 6 insertions(+), 5 deletions(-)
  20
  21 diff --git a/nbd/common.c b/nbd/common.c
  22 index dccbb8e9de..4db45b3ede 100644
  23 --- a/nbd/common.c
  24 +++ b/nbd/common.c
  25 @@ -20,6 +20,10 @@
  26  #include "qapi/error.h"
  27  #include "nbd-internal.h"
  28
  29 +/* nbd_wr_syncv
  30 + * The function may be called from coroutine or from non-coroutine context.
  31 + * When called from non-coroutine context @ioc must be in blocking mode.
  32 + */
  33  ssize_t nbd_wr_syncv(QIOChannel *ioc,
  34                       struct iovec *iov,
  35                       size_t niov,
  36 @@ -42,11 +46,8 @@ ssize_t nbd_wr_syncv(QIOChannel *ioc,
  37              len = qio_channel_writev(ioc, local_iov, nlocal_iov, &local_err);
  38          }
  39          if (len == QIO_CHANNEL_ERR_BLOCK) {
  40 -            if (qemu_in_coroutine()) {
  41 -                qio_channel_yield(ioc, do_read ? G_IO_IN : G_IO_OUT);
  42 -            } else {
  43 -                return -EAGAIN;
  44 -            }
  45 +            assert(qemu_in_coroutine());
  46 +            qio_channel_yield(ioc, do_read ? G_IO_IN : G_IO_OUT);
  47              continue;
  48          }
  49          if (len < 0) {
  50 --
  51 2.11.0
  52