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Commit 1810053e authored by Asias He's avatar Asias He Committed by Nicholas Bellinger
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tcm_vhost: Optimize gup in vhost_scsi_map_to_sgl 



We can get all the pages in one time instead of calling
gup N times.

Signed-off-by: default avatarAsias He <asias@redhat.com>
Signed-off-by: default avatarNicholas Bellinger <nab@linux-iscsi.org>
parent f3158f36

drivers/vhost/tcm_vhost.c

+30 −24
Original line number Diff line number Diff line
@@ -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 */

	ret = get_user_pages_fast((unsigned long)ptr, pages_nr, write, pages);

	/* No pages were pinned */

	if (ret < 0)

			goto err;

		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]));