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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
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+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]));