[v12,10/69] mmap: use the VMA iterator in count_vma_pages_range()

Commit Message

Liam R. Howlett July 20, 2022, 2:17 a.m. UTC

From: "Matthew Wilcox (Oracle)" <[e-mail]>

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

Link: https://lkml.kernel.org/r/[e-mail]
Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Matthew Wilcox (Oracle) <[e-mail]>
Signed-off-by: Liam R. Howlett <[e-mail]>
Acked-by: Vlastimil Babka <[e-mail]>
Reviewed-by: David Hildenbrand <[e-mail]>
Cc: Catalin Marinas <[e-mail]>
Cc: David Howells <[e-mail]>
Cc: SeongJae Park <[e-mail]>
Cc: Will Deacon <[e-mail]>
Cc: Davidlohr Bueso <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---
 mm/mmap.c | 24 +++++++-----------------
 1 file changed, 7 insertions(+), 17 deletions(-)

Patch

diff --git a/mm/mmap.c b/mm/mmap.c
index ba754a3cfbd8..1a209b61896f 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -676,29 +676,19 @@  munmap_vma_range(struct mm_struct *mm, unsigned long start, unsigned long len,
 
 	return 0;
 }
+
 static unsigned long count_vma_pages_range(struct mm_struct *mm,
 		unsigned long addr, unsigned long end)
 {
-	unsigned long nr_pages = 0;
+	VMA_ITERATOR(vmi, mm, addr);
 	struct vm_area_struct *vma;
+	unsigned long nr_pages = 0;
 
-	/* Find first overlapping mapping */
-	vma = find_vma_intersection(mm, addr, end);
-	if (!vma)
-		return 0;
-
-	nr_pages = (min(end, vma->vm_end) -
-		max(addr, vma->vm_start)) >> PAGE_SHIFT;
-
-	/* Iterate over the rest of the overlaps */
-	for (vma = vma->vm_next; vma; vma = vma->vm_next) {
-		unsigned long overlap_len;
-
-		if (vma->vm_start > end)
-			break;
+	for_each_vma_range(vmi, vma, end) {
+		unsigned long vm_start = max(addr, vma->vm_start);
+		unsigned long vm_end = min(end, vma->vm_end);
 
-		overlap_len = min(end, vma->vm_end) - vma->vm_start;
-		nr_pages += overlap_len >> PAGE_SHIFT;
+		nr_pages += PHYS_PFN(vm_end - vm_start);
 	}
 
 	return nr_pages;