> Make it clear what we're blocking in MADV_DOFORK. Previously we simply
> disallowed VM_SPECIAL i.e. mappings not managed by core mm, fixed mappings
> and
> VMA_IO_BIT.
>
> Now the invariant is established that mm-managed mappings may not set
> VMA_IO_BIT, the VMA_IO_BIT check is redundant.
>
> The rest is equivalent to testing for a fixed or non-mm-managed 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.
>
> Acked-by: Zi Yan <[email protected]>
> Signed-off-by: Lorenzo Stoakes (ARM) <[email protected]>
Sashiko has reviewed this patch and found no issues. It looks great!
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Sashiko AI review ยท
https://sashiko.dev/#/patchset/20261003-b4-mmap-prepare-vma-flag-sanify-v4-0-a1f052500...@kernel.org?part=32
