Re: [PATCH v1 1/2] mm/migrate: remove MIGRATEPAGE_UNMAP

On 11 Aug 2025, at 10:39, David Hildenbrand wrote:

> migrate_folio_unmap() is the only user of MIGRATEPAGE_UNMAP. We want to
> remove MIGRATEPAGE_* completely.
>
> It's rather weird to have a generic MIGRATEPAGE_UNMAP, documented to be
> returned from address-space callbacks, when it's only used for an
> internal helper.
>
> Let's start by having only a single "success" return value for
> migrate_folio_unmap() -- 0 -- by moving the "folio was already freed"
> check into the single caller.
>
> There is a remaining comment for PG_isolated, which we renamed to
> PG_movable_ops_isolated recently and forgot to update.
>
> While we might still run into that case with zsmalloc, it's something we
> want to get rid of soon. So let's just focus that optimization on real
> folios only for now by excluding movable_ops pages. Note that concurrent
> freeing can happen at any time and this "already freed" check is not
> relevant for correctness.
>
> Signed-off-by: David Hildenbrand <[email protected]>
> ---
>  include/linux/migrate.h |  1 -
>  mm/migrate.c            | 40 ++++++++++++++++++++--------------------
>  2 files changed, 20 insertions(+), 21 deletions(-)
>
LGTM. Reviewed-by: Zi Yan <[email protected]>

Best Regards,
Yan, Zi

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