On 7/16/26 11:27, Lorenzo Stoakes (ARM) wrote:
> On Wed, Jul 15, 2026 at 05:23:09PM +0200, Vlastimil Babka (SUSE) wrote:
>> On 7/10/26 22:16, Lorenzo Stoakes wrote:
>> > 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 <[email protected]>
>> > Reviewed-by: SJ Park <[email protected]>
>> > Reviewed-by: Pedro Falcato <[email protected]>
>> > Signed-off-by: Lorenzo Stoakes <[email protected]>
>>
>> Reviewed-by: Vlastimil Babka (SUSE) <[email protected]>
>
> Thanks!
>
>>
>> Nit:
>>
>> > 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.
Right, thanks. Didn't consider it would be actually working with unaligned
addresses but seems like it can.
>>
>> >
>> > for (i = 0; i < dests->nr_dests; i++)
>> > weight_total += dests->weight_arr[i];
>>
>> > 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) <<
Thanks for pretending you didn't notice this one, which was even more
obviously incorrect :)
>> > vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, addr, &vmf->ptl);
>> > if (!vmf->pte) {
>> > folio_unlock(folio);
>>
>> > --- 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.
>
>>
>> > }
>> > return pol;
>> > }
>>
>> > --- 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 :)
And a later patch removes the other occurence.
>>
>> > + 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
