Re: [RFC PATCH 1/2] vmsplice unmap gifted pages for recipient

[Dave Hansen]

On 07/25/2013 10:21 AM, Robert Jennings wrote:
> +static void zap_buf_page(unsigned long useraddr)
> +{
> +     struct vm_area_struct *vma;
> +
> +     down_read(&current->mm->mmap_sem);
> +     vma = find_vma_intersection(current->mm, useraddr,
> +                     useraddr + PAGE_SIZE);
> +     if (!IS_ERR_OR_NULL(vma))
> +             zap_page_range(vma, useraddr, PAGE_SIZE, NULL);
> +     up_read(&current->mm->mmap_sem);
> +}
> +
>  /**
>   * splice_to_pipe - fill passed data into a pipe
>   * @pipe:    pipe to fill
> @@ -212,8 +224,16 @@ ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
>                       buf->len = spd->partial[page_nr].len;
>                       buf->private = spd->partial[page_nr].private;
>                       buf->ops = spd->ops;
> -                     if (spd->flags & SPLICE_F_GIFT)
> +                     if (spd->flags & SPLICE_F_GIFT) {
> +                             unsigned long useraddr =
> +                                             spd->partial[page_nr].useraddr;
> +
> +                             if ((spd->flags & SPLICE_F_MOVE) &&
> +                                 !buf->offset && (buf->len == PAGE_SIZE))
> +                                     /* Can move page aligned buf */
> +                                     zap_buf_page(useraddr);
>                               buf->flags |= PIPE_BUF_FLAG_GIFT;
> +                     }

There isn't quite enough context here, but is it going to do this
zap_buf_page() very often?  Seems a bit wasteful to do the up/down and
find_vma() every trip through the loop.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/