On Tue, 2013-01-22 at 11:20 +0800, Asias He wrote:
> We can get all the pages in one time instead of calling
> gup N times.
>
> Signed-off-by: Asias He <as...@redhat.com>
> ---
Everything looks fine after initial testing, so also applied to
target-pending/for-next.
Nice optimization. :)
--nab
> drivers/vhost/tcm_vhost.c | 54
> ++++++++++++++++++++++++++---------------------
> 1 file changed, 30 insertions(+), 24 deletions(-)
>
> diff --git a/drivers/vhost/tcm_vhost.c b/drivers/vhost/tcm_vhost.c
> index 796a6b0..c994f00 100644
> --- a/drivers/vhost/tcm_vhost.c
> +++ b/drivers/vhost/tcm_vhost.c
> @@ -430,40 +430,47 @@ static struct tcm_vhost_cmd *vhost_scsi_allocate_cmd(
> * Returns the number of scatterlist entries used or -errno on error.
> */
> static int vhost_scsi_map_to_sgl(struct scatterlist *sgl,
> - unsigned int sgl_count, void __user *ptr, size_t len, int write)
> + unsigned int sgl_count, struct iovec *iov, int write)
> {
> + unsigned int npages = 0, pages_nr, offset, nbytes;
> struct scatterlist *sg = sgl;
> - unsigned int npages = 0;
> - int ret;
> + void __user *ptr = iov->iov_base;
> + size_t len = iov->iov_len;
> + struct page **pages;
> + int ret, i;
>
> - while (len > 0) {
> - struct page *page;
> - unsigned int offset = (uintptr_t)ptr & ~PAGE_MASK;
> - unsigned int nbytes = min_t(unsigned int,
> - PAGE_SIZE - offset, len);
> + pages_nr = iov_num_pages(iov);
> + if (pages_nr > sgl_count)
> + return -ENOBUFS;
>
> - if (npages == sgl_count) {
> - ret = -ENOBUFS;
> - goto err;
> - }
> + pages = kmalloc(pages_nr * sizeof(struct page *), GFP_KERNEL);
> + if (!pages)
> + return -ENOMEM;
>
> - ret = get_user_pages_fast((unsigned long)ptr, 1, write, &page);
> - BUG_ON(ret == 0); /* we should either get our page or fail */
> - if (ret < 0)
> - goto err;
> + ret = get_user_pages_fast((unsigned long)ptr, pages_nr, write, pages);
> + /* No pages were pinned */
> + if (ret < 0)
> + goto out;
> + /* Less pages pinned than wanted */
> + if (ret != pages_nr) {
> + for (i = 0; i < ret; i++)
> + put_page(pages[i]);
> + ret = -EFAULT;
> + goto out;
> + }
>
> - sg_set_page(sg, page, nbytes, offset);
> + while (len > 0) {
> + offset = (uintptr_t)ptr & ~PAGE_MASK;
> + nbytes = min_t(unsigned int, PAGE_SIZE - offset, len);
> + sg_set_page(sg, pages[npages], nbytes, offset);
> ptr += nbytes;
> len -= nbytes;
> sg++;
> npages++;
> }
> - return npages;
>
> -err:
> - /* Put pages that we hold */
> - for (sg = sgl; sg != &sgl[npages]; sg++)
> - put_page(sg_page(sg));
> +out:
> + kfree(pages);
> return ret;
> }
>
> @@ -496,8 +503,7 @@ static int vhost_scsi_map_iov_to_sgl(struct tcm_vhost_cmd
> *tv_cmd,
>
> pr_debug("Mapping %u iovecs for %u pages\n", niov, sgl_count);
> for (i = 0; i < niov; i++) {
> - ret = vhost_scsi_map_to_sgl(sg, sgl_count, iov[i].iov_base,
> - iov[i].iov_len, write);
> + ret = vhost_scsi_map_to_sgl(sg, sgl_count, &iov[i], write);
> if (ret < 0) {
> for (i = 0; i < tv_cmd->tvc_sgl_count; i++)
> put_page(sg_page(&tv_cmd->tvc_sgl[i]));
--
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