Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757194Ab2HIJDk (ORCPT ); Thu, 9 Aug 2012 05:03:40 -0400 Received: from mx1.redhat.com ([209.132.183.28]:57380 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756982Ab2HIJDj (ORCPT ); Thu, 9 Aug 2012 05:03:39 -0400 Date: Thu, 9 Aug 2012 14:33:12 +0530 From: Amit Shah To: Yoshihiro YUNOMAE Cc: linux-kernel@vger.kernel.org, Anthony Liguori , Arnd Bergmann , Borislav Petkov , "Franch Ch. Eigler" , Frederic Weisbecker , Greg Kroah-Hartman , Herbert Xu , Ingo Molnar , Mathieu Desnoyers , Steven Rostedt , virtualization@lists.linux-foundation.org, qemu-devel@nongnu.org, yrl.pp-manager.tt@hitachi.com, Masami Hiramatsu Subject: Re: [RFC PATCH 2/6] virtio/console: Add a failback for unstealable pipe buffer Message-ID: <20120809090312.GH3280@amit.redhat.com> References: <20120724023657.6600.52706.stgit@ltc189.sdl.hitachi.co.jp> <20120724023718.6600.68836.stgit@ltc189.sdl.hitachi.co.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120724023718.6600.68836.stgit@ltc189.sdl.hitachi.co.jp> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1844 Lines: 49 On (Tue) 24 Jul 2012 [11:37:18], Yoshihiro YUNOMAE wrote: > From: Masami Hiramatsu > > Add a failback memcpy path for unstealable pipe buffer. > If buf->ops->steal() fails, virtio-serial tries to > copy the page contents to an allocated page, instead > of just failing splice(). > > Signed-off-by: Masami Hiramatsu > Cc: Amit Shah > Cc: Arnd Bergmann > Cc: Greg Kroah-Hartman > --- > > drivers/char/virtio_console.c | 28 +++++++++++++++++++++++++--- > 1 files changed, 25 insertions(+), 3 deletions(-) > > diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c > index fe31b2f..911cb3e 100644 > --- a/drivers/char/virtio_console.c > +++ b/drivers/char/virtio_console.c > @@ -794,7 +794,7 @@ static int pipe_to_sg(struct pipe_inode_info *pipe, struct pipe_buffer *buf, > struct splice_desc *sd) > { > struct sg_list *sgl = sd->u.data; > - unsigned int len = 0; > + unsigned int offset, len; > > if (sgl->n == MAX_SPLICE_PAGES) > return 0; > @@ -807,9 +807,31 @@ static int pipe_to_sg(struct pipe_inode_info *pipe, struct pipe_buffer *buf, > > len = min(buf->len, sd->len); > sg_set_page(&(sgl->sg[sgl->n]), buf->page, len, buf->offset); > - sgl->n++; > - sgl->len += len; > + } else { > + /* Failback to copying a page */ > + struct page *page = alloc_page(GFP_KERNEL); I prefer zeroing out the page. If there's not enough data to be filled in the page, the remaining data can be leaked to the host. Amit -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/