On Wed, Jul 15, 2026 at 05:23:09PM +0200, Vlastimil Babka (SUSE) wrote:

On 7/10/26 22:16, Lorenzo Stoakes wrote:

quoted

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.

Reviewed-by: Gregory Price <gourry@gourry.net>
Reviewed-by: SJ Park <sj@kernel.org>
Reviewed-by: Pedro Falcato <pfalcato@suse.de>
Signed-off-by: Lorenzo Stoakes <ljs@kernel.org>

Reviewed-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>

Thanks!

Nit:

quoted

diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c
index 2058db9c01d5..d10b8042adb5 100644
--- a/mm/damon/vaddr.c
+++ b/mm/damon/vaddr.c

@@ -10,6 +10,7 @@
 #include <linux/mman.h>
 #include <linux/mmu_notifier.h>
 #include <linux/page_idle.h>
+#include <linux/pagemap.h>
 #include <linux/pagewalk.h>
 #include <linux/sched/mm.h>

@@ -623,8 +624,8 @@ static void damos_va_migrate_dests_add(struct folio *folio,
 	}

 	order = folio_order(folio);
-	ilx = vma->vm_pgoff >> order;
-	ilx += (addr - vma->vm_start) >> (PAGE_SHIFT + order);
+	ilx = vma_start_pgoff(vma) >> order;
+	ilx += linear_page_delta(vma, addr) >> order;

Could these be combined to linear_page_index(vma, addr) >> order?

So this is:

	(x >> order) + (y >> order)

And linear_page_index(vma, addr) >> order is:

	(x + y) >> order

Consider:

	order = 1, x = 0b11, y = 0b01

	(x    >> order) + (y    >> order) =
	(0b11 >> 1    ) + (0b01 >> 1    ) =
	0b1             + 0               =
	1

	(x    + y   ) >> order =
	(0b11 + 0b01) >> 1     =
	(0b100      ) >> 1     =
	2

They are not equivalent - the carry bit changes the result.

quoted

 	for (i = 0; i < dests->nr_dests; i++)
 		weight_total += dests->weight_arr[i];

quoted

diff --git a/mm/filemap.c b/mm/filemap.c
index b39111abdc4b..1dbb4c6f824e 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c

@@ -3411,8 +3411,8 @@ static struct file *do_sync_mmap_readahead(struct vm_fault *vmf)
 		 * of memory.
 		 */
 		struct vm_area_struct *vma = vmf->vma;
-		unsigned long start = vma->vm_pgoff;
-		unsigned long end = start + vma_pages(vma);
+		const unsigned long start = vma_start_pgoff(vma);
+		const unsigned long end = vma_end_pgoff(vma);
 		unsigned long ra_end;

 		ra->order = exec_folio_order();

@@ -3930,7 +3930,8 @@ vm_fault_t filemap_map_pages(struct vm_fault *vmf,
 		goto out;
 	}

-	addr = vma->vm_start + ((start_pgoff - vma->vm_pgoff) << PAGE_SHIFT);
+	addr = vma->vm_start +
+		((start_pgoff - vma_start_pgoff(vma)) << PAGE_SHIFT);

This could be linear_page_index(vma, start_pgoff) <<

quoted

 	vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, addr, &vmf->ptl);
 	if (!vmf->pte) {
 		folio_unlock(folio);

quoted

--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c

@@ -2049,8 +2049,8 @@ struct mempolicy *get_vma_policy(struct vm_area_struct *vma,
 		pol = get_task_policy(current);
 	if (pol->mode == MPOL_INTERLEAVE ||
 	    pol->mode == MPOL_WEIGHTED_INTERLEAVE) {
-		*ilx += vma->vm_pgoff >> order;
-		*ilx += (addr - vma->vm_start) >> (PAGE_SHIFT + order);
+		*ilx += vma_start_pgoff(vma) >> order;
+		*ilx += linear_page_delta(vma, addr) >> order;

Also?

See above.

quoted

 	}
 	return pol;
 }

quoted

--- a/mm/nommu.c
+++ b/mm/nommu.c

@@ -975,7 +975,7 @@ static int do_mmap_private(struct vm_area_struct *vma,
 		/* read the contents of a file into the copy */
 		loff_t fpos;

-		fpos = vma->vm_pgoff;
+		fpos = vma_start_pgoff(vma);
 		fpos <<= PAGE_SHIFT;

 		ret = kernel_read(vma->vm_file, base, len, &fpos);

@@ -1378,7 +1378,8 @@ static int split_vma(struct vma_iterator *vmi, struct vm_area_struct *vma,
 	delete_nommu_region(vma->vm_region);
 	if (new_below) {
 		vma->vm_region->vm_start = vma->vm_start = addr;
-		vma->vm_region->vm_pgoff = vma->vm_pgoff += npages;

yuck, good to remove that ugly construct
it's not the only occurence in this function
oh well

Yup at least improved it here :)

quoted

+		vma->vm_pgoff += npages;
+		vma->vm_region->vm_pgoff = vma_start_pgoff(vma);
 	} else {
 		vma->vm_region->vm_end = vma->vm_end = addr;
 		vma->vm_region->vm_top = addr;

Cheers, Lorenzo