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Commit ec8fc870 authored by Masami Hiramatsu's avatar Masami Hiramatsu Committed by Rusty Russell
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virtio/console: Add a failback for unstealable pipe buffer 



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: default avatarMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Acked-by: default avatarAmit Shah <amit.shah@redhat.com>
Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
parent eb5e89fc

drivers/char/virtio_console.c

+25 −3
Original line number Diff line number Diff line
@@ -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);

	} else {

		/* Failback to copying a page */

		struct page *page = alloc_page(GFP_KERNEL);

		char *src = buf->ops->map(pipe, buf, 1);

		char *dst;



		if (!page)

			return -ENOMEM;

		dst = kmap(page);



		offset = sd->pos & ~PAGE_MASK;



		len = sd->len;

		if (len + offset > PAGE_SIZE)

			len = PAGE_SIZE - offset;



		memcpy(dst + offset, src + buf->offset, len);



		kunmap(page);

		buf->ops->unmap(pipe, buf, src);



		sg_set_page(&(sgl->sg[sgl->n]), page, len, offset);

	}

	sgl->n++;

	sgl->len += len;

	}



	return len;

}