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tcm_vhost: Optimize gup in vhost_scsi_map_to_sgl

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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>
This commit is contained in:
Asias He 2013-01-22 11:20:27 +08:00 committed by Nicholas Bellinger
parent f3158f362c
commit 1810053e8d
1 changed files with 32 additions and 26 deletions
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58
drivers/vhost/tcm_vhost.c
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@ -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;
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 @@ 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]));