Re: [PATCH] mm/huge_memory: fix override of entry in remove_migration_pmd

[David Hildenbrand (Red Hat)]

On 13.11.25 12:56, Lorenzo Stoakes wrote:
> On Thu, Nov 13, 2025 at 04:13:52PM +1100, Balbir Singh wrote:
> > The softleaf changes exposed a BUG in remove_rmap_pmd() where the
> > migration entry was being overridden when the folio is device private.
> >
> > Use scope local entry for creating the device private pmde. Make the
> > pmde writable if the migration entry is writable by moving the check
> > softleaf_is_migration_write() prior to creating the device private entry.
> >
> > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> > Cc: David Hildenbrand <david@xxxxxxxxxx>
> > Cc: Zi Yan <ziy@xxxxxxxxxx>
> > Cc: Joshua Hahn <joshua.hahnjy@xxxxxxxxx>
> > Cc: Rakie Kim <rakie.kim@xxxxxx>
> > Cc: Byungchul Park <byungchul@xxxxxx>
> > Cc: Gregory Price <gourry@xxxxxxxxxx>
> > Cc: Ying Huang <ying.huang@xxxxxxxxxxxxxxxxx>
> > Cc: Alistair Popple <apopple@xxxxxxxxxx>
> > Cc: Oscar Salvador <osalvador@xxxxxxx>
> > Cc: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
> > Cc: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
> > Cc: "Liam R. Howlett" <Liam.Howlett@xxxxxxxxxx>
> > Cc: Nico Pache <npache@xxxxxxxxxx>
> > Cc: Ryan Roberts <ryan.roberts@xxxxxxx>
> > Cc: Dev Jain <dev.jain@xxxxxxx>
> > Cc: Barry Song <baohua@xxxxxxxxxx>
> > Cc: Lyude Paul <lyude@xxxxxxxxxx>
> > Cc: Danilo Krummrich <dakr@xxxxxxxxxx>
> > Cc: David Airlie <airlied@xxxxxxxxx>
> > Cc: Simona Vetter <simona@xxxxxxxx>
> > Cc: Ralph Campbell <rcampbell@xxxxxxxxxx>
> > Cc: Mika Penttilä <mpenttil@xxxxxxxxxx>
> > Cc: Matthew Brost <matthew.brost@xxxxxxxxx>
> > Cc: Francois Dugast <francois.dugast@xxxxxxxxx>
> >
> > Signed-off-by: Balbir Singh <balbirs@xxxxxxxxxx>
>
> THe logic LGTM but we don't want to have a bisect hazard here by having the bug
> introduced earlier then resolved here.

Exactly.

--
Cheers

David