From: Al Viro <viro@ZenIV.linux.org.uk>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: David Miller <davem@davemloft.net>,
netdev@vger.kernel.org, kvm@vger.kernel.org
Subject: Re: [PATCH v2 17/18] vhost: don't bother copying iovecs in handle_rx(), kill memcpy_toiovecend()
Date: Tue, 3 Feb 2015 22:13:11 +0000 [thread overview]
Message-ID: <20150203221311.GD29656@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20150203152154.GA9072@redhat.com>
On Tue, Feb 03, 2015 at 04:21:54PM +0100, Michael S. Tsirkin wrote:
> > Hmm having second thoughts here.
> > Will this modify the iov in vq->iov?
> > If yes, how will recvmsg fill it?
>
> OK that was just me misunderstanding what the
> function does. As it doesn't modify the iovec itself,
> I think there's no issue, my ack stands.
That, BTW, was the point of switching ->sendmsg() and ->recvmsg() to
iov_iter primitives - not only do memcpy_toiovec() et.al. change the
iovec, the way it's done was protocol-dependent, up to and including
the things like "have sent 60 caller-supplied bytes, iovec modified
with only 6 bytes consumed". What's worse, on TCP sendmsg we usually
left iovec unchanged, but sometimes it got drained. Granted, that
happened only after setsockopt() playing caller with TCP_REPAIR (i.e.
checkpoint/restart stuff), but...
next prev parent reply other threads:[~2015-02-03 22:13 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20150131035513.GK29656@ZenIV.linux.org.uk>
2015-02-02 7:59 ` [PATCH v2 15/18] vhost: switch vhost get_indirect() to iov_iter, kill memcpy_fromiovec() Al Viro
2015-02-03 9:01 ` Michael S. Tsirkin
2015-02-02 7:59 ` [PATCH v2 16/18] vhost: don't bother with copying iovec in handle_tx() Al Viro
2015-02-03 9:14 ` Michael S. Tsirkin
2015-02-02 7:59 ` [PATCH v2 17/18] vhost: don't bother copying iovecs in handle_rx(), kill memcpy_toiovecend() Al Viro
2015-02-03 9:13 ` Michael S. Tsirkin
2015-02-03 10:04 ` Michael S. Tsirkin
2015-02-03 15:21 ` Michael S. Tsirkin
2015-02-03 22:13 ` Al Viro [this message]
2015-02-02 7:59 ` [PATCH v2 18/18] vhost: vhost_scsi_handle_vq() should just use copy_from_user() Al Viro
2015-02-03 0:42 ` Nicholas A. Bellinger
2015-02-03 9:05 ` Michael S. Tsirkin
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