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: Asias He <asias@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
diff --git a/drivers/vhost/tcm_vhost.c b/drivers/vhost/tcm_vhost.c
index 62058d7..704e4f6 100644
--- a/drivers/vhost/tcm_vhost.c
+++ b/drivers/vhost/tcm_vhost.c
@@ -430,40 +430,47 @@
* 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;
+
+ pages_nr = iov_num_pages(iov);
+ if (pages_nr > sgl_count)
+ return -ENOBUFS;
+
+ pages = kmalloc(pages_nr * sizeof(struct page *), GFP_KERNEL);
+ if (!pages)
+ return -ENOMEM;
+
+ 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;
+ }
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);
-
- if (npages == sgl_count) {
- ret = -ENOBUFS;
- goto err;
- }
-
- 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;
-
- sg_set_page(sg, page, nbytes, offset);
+ 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 @@
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]));
