netdev - Re: [PATCH v3 15/18] vhost: switch vhost get_indirect() to iov_iter, kill memcpy

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Message-ID: <20150204085225.GA9920@redhat.com>
Date:	Wed, 4 Feb 2015 09:52:25 +0100
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH v3 15/18] vhost: switch vhost get_indirect() to iov_iter,
 kill memcpy_fromiovec()

On Wed, Feb 04, 2015 at 06:40:06AM +0000, Al Viro wrote:
> From: Al Viro <viro@...iv.linux.org.uk>
> 
> Cc: Michael S. Tsirkin <mst@...hat.com>
> Cc: kvm@...r.kernel.org
> Cc: virtualization@...ts.linux-foundation.org
> Signed-off-by: Al Viro <viro@...iv.linux.org.uk>

Acked-by: Michael S. Tsirkin <mst@...hat.com>

> ---
>  drivers/vhost/vhost.c |  6 ++++--
>  include/linux/uio.h   |  1 -
>  lib/iovec.c           | 25 -------------------------
>  3 files changed, 4 insertions(+), 28 deletions(-)
> 
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index cb807d0..2ee2826 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -1125,6 +1125,7 @@ static int get_indirect(struct vhost_virtqueue *vq,
>  	struct vring_desc desc;
>  	unsigned int i = 0, count, found = 0;
>  	u32 len = vhost32_to_cpu(vq, indirect->len);
> +	struct iov_iter from;
>  	int ret;
>  
>  	/* Sanity check */
> @@ -1142,6 +1143,7 @@ static int get_indirect(struct vhost_virtqueue *vq,
>  		vq_err(vq, "Translation failure %d in indirect.\n", ret);
>  		return ret;
>  	}
> +	iov_iter_init(&from, READ, vq->indirect, ret, len);
>  
>  	/* We will use the result as an address to read from, so most
>  	 * architectures only need a compiler barrier here. */
> @@ -1164,8 +1166,8 @@ static int get_indirect(struct vhost_virtqueue *vq,
>  			       i, count);
>  			return -EINVAL;
>  		}
> -		if (unlikely(memcpy_fromiovec((unsigned char *)&desc,
> -					      vq->indirect, sizeof desc))) {
> +		if (unlikely(copy_from_iter(&desc, sizeof(desc), &from) !=
> +			     sizeof(desc))) {
>  			vq_err(vq, "Failed indirect descriptor: idx %d, %zx\n",
>  			       i, (size_t)vhost64_to_cpu(vq, indirect->addr) + i * sizeof desc);
>  			return -EINVAL;
> diff --git a/include/linux/uio.h b/include/linux/uio.h
> index 1c5e453..af3439f 100644
> --- a/include/linux/uio.h
> +++ b/include/linux/uio.h
> @@ -135,7 +135,6 @@ static inline void iov_iter_reexpand(struct iov_iter *i, size_t count)
>  size_t csum_and_copy_to_iter(void *addr, size_t bytes, __wsum *csum, struct iov_iter *i);
>  size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum, struct iov_iter *i);
>  
> -int memcpy_fromiovec(unsigned char *kdata, struct iovec *iov, int len);
>  int memcpy_fromiovecend(unsigned char *kdata, const struct iovec *iov,
>  			int offset, int len);
>  int memcpy_toiovecend(const struct iovec *v, unsigned char *kdata,
> diff --git a/lib/iovec.c b/lib/iovec.c
> index 2d99cb4..4a90875 100644
> --- a/lib/iovec.c
> +++ b/lib/iovec.c
> @@ -3,31 +3,6 @@
>  #include <linux/uio.h>
>  
>  /*
> - *	Copy iovec to kernel. Returns -EFAULT on error.
> - *
> - *	Note: this modifies the original iovec.
> - */
> -
> -int memcpy_fromiovec(unsigned char *kdata, struct iovec *iov, int len)
> -{
> -	while (len > 0) {
> -		if (iov->iov_len) {
> -			int copy = min_t(unsigned int, len, iov->iov_len);
> -			if (copy_from_user(kdata, iov->iov_base, copy))
> -				return -EFAULT;
> -			len -= copy;
> -			kdata += copy;
> -			iov->iov_base += copy;
> -			iov->iov_len -= copy;
> -		}
> -		iov++;
> -	}
> -
> -	return 0;
> -}
> -EXPORT_SYMBOL(memcpy_fromiovec);
> -
> -/*
>   *	Copy kernel to iovec. Returns -EFAULT on error.
>   */
>  
> -- 
> 2.1.4
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