Re: [PATCH 25/30] mm/vma: update vmg_adjust_set_range() to offset pgoff instead

On Mon, Jun 29, 2026 at 01:23:36PM +0100, Lorenzo Stoakes wrote:
> We are calculating the pgoff as an offset, since we have vma_add_pgoff()
> and vma_sub_pgoff() available, just offset this value directly and use
> __vma_set_range() for vma->vm_[start, end] values.
> 
> We take care to update the range before offsetting the page offset, so the
> adjusted VMA's vm_start and vm_pgoff are mutually consistent at the point
> the page offset helpers operate - this matters once vma_set_pgoff() comes
> to assert invariants which relate the two.
> 

Given the prior code just did it in 3 lines of code with no special
dance, there's a presumption here that this is done in a critical
section and no external actor can see the inconsistent state?

(i.e. range is updated but offset is not)

Just think about this from a bisection/debugging standpoint.

> Doing so lays the foundation for future work which allows for use of
> virtual page offsets for MAP_PRIVATE-file backed mappings.
> 
> No functional change intended.
> 
> Signed-off-by: Lorenzo Stoakes <[email protected]>

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