On Fri, Nov 25, 2016 at 05:57:20PM +0530, Anshuman Khandual wrote:

On 11/08/2016 05:01 AM, Naoya Horiguchi wrote:

...

quoted

@@ -497,30 +541,15 @@ static int queue_pages_pte_range(pmd_t *pmd, unsigned long addr,
 	struct page *page;
 	struct queue_pages *qp = walk->private;
 	unsigned long flags = qp->flags;
-	int nid, ret;
+	int ret;
 	pte_t *pte;
 	spinlock_t *ptl;
 
-	if (pmd_trans_huge(*pmd)) {
-		ptl = pmd_lock(walk->mm, pmd);
-		if (pmd_trans_huge(*pmd)) {
-			page = pmd_page(*pmd);
-			if (is_huge_zero_page(page)) {
-				spin_unlock(ptl);
-				__split_huge_pmd(vma, pmd, addr, false, NULL);
-			} else {
-				get_page(page);
-				spin_unlock(ptl);
-				lock_page(page);
-				ret = split_huge_page(page);
-				unlock_page(page);
-				put_page(page);
-				if (ret)
-					return 0;
-			}
-		} else {
-			spin_unlock(ptl);
-		}
+	ptl = pmd_trans_huge_lock(pmd, vma);
+	if (ptl) {
+		ret = queue_pages_pmd(pmd, ptl, addr, end, walk);
+		if (ret)
+			return 0;
 	}

I wonder if we should introduce pte_entry function along with pmd_entry
function as we are first looking for trans huge PMDs either for direct
addition into the migration list or splitting it before looking for PTEs.

Most of pagewalk users don't define pte_entry because of performance reason
(to avoid the overhead of PTRS_PER_PMD function calls).
But that could be a nice cleanup if we have a workaround.

Thanks,
Naoya Horiguchi
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