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

Liam Howlett
2022-07-20T02:18:44Z

From: "Matthew Wilcox (Oracle)" <willy@infradead.org>

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

Link: https://lkml.kernel.org/r/20220504010716.661115-12-Liam.Howlett@oracle.com
Link: https://lkml.kernel.org/r/20220621204632.3370049-11-Liam.Howlett@oracle.com
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>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Howells <dhowells@redhat.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: Will Deacon <will@kernel.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
mm/mmap.c | 24 +++++++-----------------
1 file changed, 7 insertions(+), 17 deletions(-)

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;
--
2.35.1