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From:   Liam Howlett <liam.howlett@oracle.com>
To:     "maple-tree@lists.infradead.org" <maple-tree@lists.infradead.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>
Subject: [PATCH v5 11/70] mmap: Use the VMA iterator in
 count_vma_pages_range()
Thread-Topic: [PATCH v5 11/70] mmap: Use the VMA iterator in
 count_vma_pages_range()
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Date:   Wed, 2 Feb 2022 02:42:01 +0000
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From: "Matthew Wilcox (Oracle)" <willy@infradead.org>

This simplifies the implementation and is faster than using the linked
list.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
---
 mm/mmap.c | 24 +++++++-----------------
 1 file changed, 7 insertions(+), 17 deletions(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index 1007e55f472c..15d7363b0c63 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -670,29 +670,19 @@ munmap_vma_range(struct mm_struct *mm, unsigned long =
start, unsigned long len,
=20
 	return 0;
 }
+
 static unsigned long count_vma_pages_range(struct mm_struct *mm,
 		unsigned long addr, unsigned long end)
 {
-	unsigned long nr_pages =3D 0;
+	VMA_ITERATOR(vmi, mm, addr);
 	struct vm_area_struct *vma;
+	unsigned long nr_pages =3D 0;
=20
-	/* Find first overlapping mapping */
-	vma =3D find_vma_intersection(mm, addr, end);
-	if (!vma)
-		return 0;
-
-	nr_pages =3D (min(end, vma->vm_end) -
-		max(addr, vma->vm_start)) >> PAGE_SHIFT;
-
-	/* Iterate over the rest of the overlaps */
-	for (vma =3D vma->vm_next; vma; vma =3D vma->vm_next) {
-		unsigned long overlap_len;
-
-		if (vma->vm_start > end)
-			break;
+	for_each_vma_range(vmi, vma, end) {
+		unsigned long vm_start =3D max(addr, vma->vm_start);
+		unsigned long vm_end =3D min(end, vma->vm_end);
=20
-		overlap_len =3D min(end, vma->vm_end) - vma->vm_start;
-		nr_pages +=3D overlap_len >> PAGE_SHIFT;
+		nr_pages +=3D (vm_end - vm_start) / PAGE_SIZE;
 	}
=20
 	return nr_pages;
--=20
2.34.1