On (Tue) 24 Jul 2012 [11:37:18], Yoshihiro YUNOMAE wrote:
> From: Masami Hiramatsu <masami.hiramatsu...@hitachi.com>
>
> 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 <masami.hiramatsu...@hitachi.com>
> Cc: Amit Shah <amit.s...@redhat.com>
> Cc: Arnd Bergmann <a...@arndb.de>
> Cc: Greg Kroah-Hartman <gre...@linuxfoundation.org>
> ---
>
> 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
