Blame SOURCES/kvm-QIOChannelSocket-Fix-zero-copy-flush-returning-code-.patch

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From 905cc8032fc63619efb3f0a8c9754b7190bcc43a Mon Sep 17 00:00:00 2001
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From: Leonardo Bras <leobras@redhat.com>
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Date: Mon, 11 Jul 2022 18:11:11 -0300
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Subject: [PATCH 3/9] QIOChannelSocket: Fix zero-copy flush returning code 1
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 when nothing sent
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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RH-Author: Leonardo Brás <leobras@redhat.com>
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RH-MergeRequest: 201: Zero-copy-send fixes + improvements
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RH-Commit: [3/8] 1ad707702fa26cd4d0fa1870c21f5f26ae93ff97
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RH-Bugzilla: 2110203
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RH-Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
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RH-Acked-by: Peter Xu <peterx@redhat.com>
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RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
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If flush is called when no buffer was sent with MSG_ZEROCOPY, it currently
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returns 1. This return code should be used only when Linux fails to use
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MSG_ZEROCOPY on a lot of sendmsg().
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Fix this by returning early from flush if no sendmsg(...,MSG_ZEROCOPY)
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was attempted.
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Fixes: 2bc58ffc2926 ("QIOChannelSocket: Implement io_writev zero copy flag & io_flush for CONFIG_LINUX")
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Signed-off-by: Leonardo Bras <leobras@redhat.com>
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Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
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Acked-by: Daniel P. Berrangé <berrange@redhat.com>
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Reviewed-by: Juan Quintela <quintela@redhat.com>
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Reviewed-by: Peter Xu <peterx@redhat.com>
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Message-Id: <20220711211112.18951-2-leobras@redhat.com>
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Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
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(cherry picked from commit 927f93e099c4f9184e60a1bc61624ac2d04d0223)
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Signed-off-by: Leonardo Bras <leobras@redhat.com>
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---
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 io/channel-socket.c | 8 +++++++-
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 1 file changed, 7 insertions(+), 1 deletion(-)
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diff --git a/io/channel-socket.c b/io/channel-socket.c
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index df858da924..cf0d67c51b 100644
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--- a/io/channel-socket.c
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+++ b/io/channel-socket.c
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@@ -717,12 +717,18 @@ static int qio_channel_socket_flush(QIOChannel *ioc,
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     struct cmsghdr *cm;
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     char control[CMSG_SPACE(sizeof(*serr))];
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     int received;
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-    int ret = 1;
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+    int ret;
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+
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+    if (sioc->zero_copy_queued == sioc->zero_copy_sent) {
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+        return 0;
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+    }
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     msg.msg_control = control;
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     msg.msg_controllen = sizeof(control);
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     memset(control, 0, sizeof(control));
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+    ret = 1;
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+
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     while (sioc->zero_copy_sent < sioc->zero_copy_queued) {
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         received = recvmsg(sioc->fd, &msg, MSG_ERRQUEUE);
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         if (received < 0) {
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-- 
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2.31.1
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