Re: [PATCH v3 02/15] mm: introduce linear_anon_page_index()

On Wed, Jul 29, 2026 at 05:48:37PM +0100, Lorenzo Stoakes (ARM) wrote:
> This function provides the anonymous equivalent of linear_page_index(),
> instead offsetting based on the anonymous page offset of the VMA.
> 
> It is valid only for anonymous or MAP_PRIVATE file-backed mappings. It must
> not be called for shared file-backed mappings.
> 
> For pure anon VMAs, this will be equal to linear_page_index().
> 
> Assert that both of these invariants are true In linear_anon_page_index()
> and implement the algorithm in __linear_anon_page_index().
> 
> Note that MAP_PRIVATE-/dev/zero mappings will satisfy vma_is_anonymous()
> but not fulfill this invariant, so when asserting this we check
> vma->vm_file to account for this.
> 
> We do not update callsites yet, so no functional change intended.
> 
> Also const-ify vma_is_anonymous() to make it compatible with the
> const-ified linear_anon_page_index().
> 
> VMA userland tests are also updated accordingly.
> 
> Signed-off-by: Lorenzo Stoakes (ARM) <[email protected]>

Reviewed-by: Gregory Price (Meta) <[email protected]>