> Make it clear what we're blocking in MADV_DOFORK. Previously we simply
> disallowed VM_SPECIAL i.e. kernel-owned mappings, fixed mappings and
> VMA_IO_BIT.
>
> Now the invariant is established that only kernel-owned mappings can set
> VMA_IO_BIT, the VMA_IO_BIT check is redundant.
>
> The rest is equivalent to testing for a kernel-owned or fixed mapping,
> i.e. exactly the same check as whether the VMA is permitted to be merged.
>
> This was established by commit 0b2758f48f22 ("Require (reasonably) normal
> mappings for MADV_DOFORK") containing my hands-down favourite call out of
> all time.
>
> Express the same thing differently - if we wouldn't be allowed to merge it,
> then we aren't allowed to manipulate CoW behaviour on fork.
>
> No functional change intended.
>
> Signed-off-by: Lorenzo Stoakes (ARM) <[email protected]>
Sashiko has reviewed this patch and found no issues. It looks great!
--
Sashiko AI review ยท
https://sashiko.dev/#/patchset/20260914-b4-mmap-prepare-vma-flag-sanify-v2-0-7d9781ed5...@kernel.org?part=33
