mm/vma: use vma_start_pgoff(), linear_page_index() in mm code

There are many instances in which linear_page_index() (as well as
linear_page_delta()) is open-coded, which is confusing and inconsistent.

Additionally, vma->vm_pgoff doesn't necessarily make it clear that this is
the page offset of the start of the VMA range.

Doing so also aids greppability.

So use vma_start_pgoff() in favour of directly accessing vma->vm_pgoff, and
linear_page_index() where we can.

This also lays the ground for future changes which will add an anonymous
page offset in order to be able to index MAP_PRIVATE-file backed anon
folios in terms of their virtual page offset.

No functional change intended.

Link: https://lore.kernel.org/20260710-b4-pre-scalable-cow-v2-18-2a5aa403d977@kernel.org
Signed-off-by: Lorenzo Stoakes <ljs@kernel.org>
Reviewed-by: Gregory Price <gourry@gourry.net>
Reviewed-by: SJ Park <sj@kernel.org>
Reviewed-by: Pedro Falcato <pfalcato@suse.de>
Reviewed-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
Cc: Ackerley Tng <ackerleytng@google.com>
Cc: David Hildenbrand (Arm) <david@kernel.org>
Cc: Kai Huang <kai.huang@intel.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Liam R. Howlett (Oracle) <liam@infradead.org>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 14 insertions, 10 deletions

diff --git a/mm/internal.h b/mm/internal.h
index e5dcab69eb4f..f950e88fdb52 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -924,26 +924,28 @@ static inline bool
 folio_within_range(struct folio *folio, struct vm_area_struct *vma,
 		unsigned long start, unsigned long end)
 {
-	pgoff_t pgoff, addr;
-	unsigned long vma_pglen = vma_pages(vma);
+	const unsigned long vma_pglen = vma_pages(vma);
+	pgoff_t pgoff_folio, pgoff_vma_start;
+	unsigned long addr;
 
 	VM_WARN_ON_FOLIO(folio_test_ksm(folio), folio);
 	if (start > end)
 		return false;
 
+	pgoff_folio = folio_pgoff(folio);
+	pgoff_vma_start = vma_start_pgoff(vma);
+
 	if (start < vma->vm_start)
 		start = vma->vm_start;
 
 	if (end > vma->vm_end)
 		end = vma->vm_end;
 
-	pgoff = folio_pgoff(folio);
-
 	/* if folio start address is not in vma range */
-	if (!in_range(pgoff, vma->vm_pgoff, vma_pglen))
+	if (!in_range(pgoff_folio, pgoff_vma_start, vma_pglen))
 		return false;
 
-	addr = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
+	addr = vma->vm_start + ((pgoff_folio - pgoff_vma_start) << PAGE_SHIFT);
 
 	return !(addr < start || end - addr < folio_size(folio));
 }
@@ -1015,15 +1017,16 @@ extern pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma);
 static inline unsigned long vma_address(const struct vm_area_struct *vma,
 		pgoff_t pgoff, unsigned long nr_pages)
 {
+	const pgoff_t pgoff_start = vma_start_pgoff(vma);
 	unsigned long address;
 
-	if (pgoff >= vma->vm_pgoff) {
+	if (pgoff >= pgoff_start) {
 		address = vma->vm_start +
-			((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
+			((pgoff - pgoff_start) << PAGE_SHIFT);
 		/* Check for address beyond vma (or wrapped through 0?) */
 		if (address < vma->vm_start || address >= vma->vm_end)
 			address = -EFAULT;
-	} else if (pgoff + nr_pages - 1 >= vma->vm_pgoff) {
+	} else if (pgoff + nr_pages - 1 >= pgoff_start) {
 		/* Test above avoids possibility of wrap to 0 on 32-bit */
 		address = vma->vm_start;
 	} else {
@@ -1047,7 +1050,8 @@ static inline unsigned long vma_address_end(struct page_vma_mapped_walk *pvmw)
 		return pvmw->address + PAGE_SIZE;
 
 	pgoff = pvmw->pgoff + pvmw->nr_pages;
-	address = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
+	address = vma->vm_start +
+		((pgoff - vma_start_pgoff(vma)) << PAGE_SHIFT);
 	/* Check for address beyond vma (or wrapped through 0?) */
 	if (address < vma->vm_start || address > vma->vm_end)
 		address = vma->vm_end;