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Date: Thu, 09 Aug 2012 21:30:50 +0900 From: Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@...achi.com> To: linux-kernel@...r.kernel.org Cc: Amit Shah <amit.shah@...hat.com>, Anthony Liguori <anthony@...emonkey.ws>, Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...64.org>, "Franch Ch. Eigler" <fche@...hat.com>, Frederic Weisbecker <fweisbec@...il.com>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Herbert Xu <herbert@...dor.apana.org.au>, Ingo Molnar <mingo@...hat.com>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>, Rusty Russell <rusty@...tcorp.com.au>, Steven Rostedt <rostedt@...dmis.org>, virtualization@...ts.linux-foundation.org, qemu-devel@...gnu.org, yrl.pp-manager.tt@...achi.com, Masami Hiramatsu <masami.hiramatsu.pt@...achi.com> Subject: [PATCH V2 2/6] virtio/console: Add a failback for unstealable pipe buffer From: Masami Hiramatsu <masami.hiramatsu.pt@...achi.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.pt@...achi.com> --- 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 730816c..22b7373 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); + 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; } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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