Re: [PATCH 4/8] vhost/scsi: Change vhost_scsi_map_to_sgl to accept iov ptr + len

["Michael S. Tsirkin" <mst@redhat.com>]

On Fri, Jan 30, 2015 at 08:12:28AM +0000, Nicholas A. Bellinger wrote:
> From: Nicholas Bellinger <nab@linux-iscsi.org>
> 
> This patch changes vhost_scsi_map_to_sgl() parameters to accept virtio
> iovec ptr + len when determing pages_nr.
> 
> This is currently done with iov_num_pages() -> PAGE_ALIGN, so allow
> the same parameters as well.
> 
> Cc: Michael S. Tsirkin <mst@redhat.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
> ---
>  drivers/vhost/scsi.c | 37 +++++++++++++++----------------------
>  1 file changed, 15 insertions(+), 22 deletions(-)
> 
> diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
> index 9c5ac23..049e603 100644
> --- a/drivers/vhost/scsi.c
> +++ b/drivers/vhost/scsi.c
> @@ -220,10 +220,10 @@ static struct workqueue_struct *tcm_vhost_workqueue;
>  static DEFINE_MUTEX(tcm_vhost_mutex);
>  static LIST_HEAD(tcm_vhost_list);
>  
> -static int iov_num_pages(struct iovec *iov)
> +static int iov_num_pages(void __user *iov_base, size_t iov_len)
>  {
> -	return (PAGE_ALIGN((unsigned long)iov->iov_base + iov->iov_len) -
> -	       ((unsigned long)iov->iov_base & PAGE_MASK)) >> PAGE_SHIFT;
> +	return (PAGE_ALIGN((unsigned long)iov_base + iov_len) -
> +	       ((unsigned long)iov_base & PAGE_MASK)) >> PAGE_SHIFT;
>  }
>  
>  static void tcm_vhost_done_inflight(struct kref *kref)
> @@ -777,25 +777,18 @@ vhost_scsi_get_tag(struct vhost_virtqueue *vq, struct tcm_vhost_tpg *tpg,
>   * Returns the number of scatterlist entries used or -errno on error.
>   */
>  static int
> -vhost_scsi_map_to_sgl(struct tcm_vhost_cmd *tv_cmd,
> +vhost_scsi_map_to_sgl(struct tcm_vhost_cmd *cmd,
> +		      void __user *ptr,
> +		      size_t len,
>  		      struct scatterlist *sgl,
> -		      unsigned int sgl_count,
> -		      struct iovec *iov,
> -		      struct page **pages,
>  		      bool write)
>  {
> -	unsigned int npages = 0, pages_nr, offset, nbytes;
> +	unsigned int npages = 0, offset, nbytes;
> +	unsigned int pages_nr = iov_num_pages(ptr, len);
>  	struct scatterlist *sg = sgl;
> -	void __user *ptr = iov->iov_base;
> -	size_t len = iov->iov_len;
> +	struct page **pages = cmd->tvc_upages;
>  	int ret, i;
>  
> -	pages_nr = iov_num_pages(iov);
> -	if (pages_nr > sgl_count) {
> -		pr_err("vhost_scsi_map_to_sgl() pages_nr: %u greater than"
> -		       " sgl_count: %u\n", pages_nr, sgl_count);
> -		return -ENOBUFS;
> -	}
>  	if (pages_nr > TCM_VHOST_PREALLOC_UPAGES) {
>  		pr_err("vhost_scsi_map_to_sgl() pages_nr: %u greater than"
>  		       " preallocated TCM_VHOST_PREALLOC_UPAGES: %u\n",
> @@ -840,7 +833,7 @@ vhost_scsi_map_iov_to_sgl(struct tcm_vhost_cmd *cmd,
>  	int ret, i;
>  
>  	for (i = 0; i < niov; i++)
> -		sgl_count += iov_num_pages(&iov[i]);
> +		sgl_count += iov_num_pages(iov[i].iov_base, iov[i].iov_len);
>  

A helper function for this loop seems in order as well?


>  	if (sgl_count > TCM_VHOST_PREALLOC_SGLS) {
>  		pr_err("vhost_scsi_map_iov_to_sgl() sgl_count: %u greater than"
> @@ -856,8 +849,8 @@ vhost_scsi_map_iov_to_sgl(struct tcm_vhost_cmd *cmd,
>  	pr_debug("Mapping iovec %p for %u pages\n", &iov[0], sgl_count);
>  
>  	for (i = 0; i < niov; i++) {
> -		ret = vhost_scsi_map_to_sgl(cmd, sg, sgl_count, &iov[i],
> -					    cmd->tvc_upages, write);
> +		ret = vhost_scsi_map_to_sgl(cmd, iov[i].iov_base, iov[i].iov_len,
> +					    sg, write);
>  		if (ret < 0) {
>  			for (i = 0; i < cmd->tvc_sgl_count; i++) {
>  				struct page *page = sg_page(&cmd->tvc_sgl[i]);
> @@ -884,7 +877,7 @@ vhost_scsi_map_iov_to_prot(struct tcm_vhost_cmd *cmd,
>  	int ret, i;
>  
>  	for (i = 0; i < niov; i++)
> -		prot_sgl_count += iov_num_pages(&iov[i]);
> +		prot_sgl_count += iov_num_pages(iov[i].iov_base, iov[i].iov_len);
>  
>  	if (prot_sgl_count > TCM_VHOST_PREALLOC_PROT_SGLS) {
>  		pr_err("vhost_scsi_map_iov_to_prot() sgl_count: %u greater than"
> @@ -899,8 +892,8 @@ vhost_scsi_map_iov_to_prot(struct tcm_vhost_cmd *cmd,
>  	cmd->tvc_prot_sgl_count = prot_sgl_count;
>  
>  	for (i = 0; i < niov; i++) {
> -		ret = vhost_scsi_map_to_sgl(cmd, prot_sg, prot_sgl_count, &iov[i],
> -					    cmd->tvc_upages, write);
> +		ret = vhost_scsi_map_to_sgl(cmd, iov[i].iov_base, iov[i].iov_len,
> +					    prot_sg, write);
>  		if (ret < 0) {
>  			for (i = 0; i < cmd->tvc_prot_sgl_count; i++) {
>  				struct page *page = sg_page(&cmd->tvc_prot_sgl[i]);
> -- 
> 1.9.1