Re: [PATCH v5 23/38] mm/mlock: eliminate weird VMA_IO_BIT abuse and simplify

When performing mlock() or munlock() otherwise normal VMAs have VMA_IO_BIT
solely to fix a race with migration which might otherwise double-count
mlock VMAs.

This is unnecessary - at the point of applying folio mlock state, whether
setting or clearing PG_mlocked, we know whether or not we are locking.

Solve this in two ways - thread a boolean through the page table walk
indicating whether a lock or unlock is being performed, and run a locking
walk with VMA_LOCKONFAULT_BIT set and VMA_LOCKED_BIT cleared.

This state never occurs otherwise, as VMA_LOCKONFAULT_BIT always implies
VMA_LOCKED_BIT. These are also always cleared together.

Then, update folio_add_lru_vma() and mlock_folio() to check only for
[ ... ]

While here, also replace some deprecated VMA flag predicates.

Reviewed-by: Zi Yan <ziy@nvidia.com>
Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261009-b4-mmap-prepare-vma-flag-sanify-v5-0-923b70125b1e@kernel.org?part=23