Re: [PATCH 20/30] mm/vma: introduce vma_assert_can_modify()

On Mon, Jun 29, 2026 at 01:23:31PM +0100, Lorenzo Stoakes wrote:

vma_assert_write_locked() and vma_assert_attached() are useful for their
own purposes, however VMA code absolutely does allow the modification of
non-write locked VMAs if they are at that point detached (i.e. unreachable
from anywhere).

curiosity: I presume this happens mostly during init and/or teardown of
a vma?

It's therefore useful to be able to assert that a VMA is either
detached (modification doesn't matter) or write locked (you're explicitly
locked for modification).

Therefore introduce vma_assert_can_modify() for this purpose.

While we're here, make vma_is_attached() available generally - if
!CONFIG_PER_VMA_LOCKS, then there's no sense in which a VMA is
detached (vma_mark_detached() is a noop), so have this default to true in
this case.

Signed-off-by: Lorenzo Stoakes <ljs@kernel.org>

Reviewed-by: Gregory Price <gourry@gourry.net>