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 <redacted>
---
 include/linux/migrate.h |  1 -
 mm/migrate.c            | 40 ++++++++++++++++++++--------------------
 2 files changed, 20 insertions(+), 21 deletions(-)

LGTM. Reviewed-by: Zi Yan [off-list ref]

Best Regards,
Yan, Zi