[PATCH v2 4/5] mm: mincore: improve mincore_hugetlb()

[Kefeng Wang <wangkefeng.wang@huawei.com>]

The walk_hugetlb_range() always passes a non-NULL pte, so remove the
dead NULL check. Replace the per-page iteration loop with memset()
for better performance.

Reviewed-by: Pedro Falcato <pfalcato@suse.de>
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
---
 mm/mincore.c | 27 +++++++--------------------
 1 file changed, 7 insertions(+), 20 deletions(-)

diff --git a/mm/mincore.c b/mm/mincore.c
index 8b5e6afefb91..9952bc3edf76 100644
--- a/mm/mincore.c
+++ b/mm/mincore.c
@@ -28,30 +28,17 @@ static int mincore_hugetlb(pte_t *pte, unsigned long hmask, unsigned long addr,
 			unsigned long end, struct mm_walk *walk)
 {
 #ifdef CONFIG_HUGETLB_PAGE
-	unsigned char present;
+	unsigned long nr = (end - addr) >> PAGE_SHIFT;
 	unsigned char *vec = walk->private;
+	unsigned char present;
 	spinlock_t *ptl;
+	pte_t ptep;
 
 	ptl = huge_pte_lock(hstate_vma(walk->vma), walk->mm, pte);
-
-	/*
-	 * Hugepages under user process are always in RAM and never
-	 * swapped out, but theoretically it needs to be checked.
-	 */
-	if (!pte) {
-		present = 0;
-	} else {
-		const pte_t ptep = huge_ptep_get(walk->mm, addr, pte);
-
-		if (huge_pte_none(ptep) || pte_is_marker(ptep))
-			present = 0;
-		else
-			present = 1;
-	}
-
-	for (; addr != end; vec++, addr += PAGE_SIZE)
-		*vec = present;
-	walk->private = vec;
+	ptep = huge_ptep_get(walk->mm, addr, pte);
+	present = !(huge_pte_none(ptep) || pte_is_marker(ptep));
+	memset(vec, present, nr);
+	walk->private += nr;
 	spin_unlock(ptl);
 #else
 	BUG();
-- 
2.55.0