On 1/15/26 07:18, Matthew Brost wrote: > On Wed, Jan 14, 2026 at 09:57:31PM -0800, Matthew Brost wrote: >> On Thu, Jan 15, 2026 at 04:27:26PM +1100, Alistair Popple wrote: >> > On 2026-01-15 at 06:19 +1100, Francois Dugast <[email protected]> >> > wrote... >> > > From: Matthew Brost <[email protected]> >> > > >> > > Reinitialize metadata for large zone device private folios in >> > > zone_device_page_init prior to creating a higher-order zone device >> > > private folio. This step is necessary when the folio’s order changes >> > > dynamically between zone_device_page_init calls to avoid building a >> > > corrupt folio. As part of the metadata reinitialization, the dev_pagemap >> > > must be passed in from the caller because the pgmap stored in the folio >> > > page may have been overwritten with a compound head. >> > >> > Thanks for fixing, a couple of minor comments below. >> > >> > > Cc: Zi Yan <[email protected]> >> > > Cc: Alistair Popple <[email protected]> >> > > Cc: adhavan Srinivasan <[email protected]> >> > > Cc: Nicholas Piggin <[email protected]> >> > > Cc: Michael Ellerman <[email protected]> >> > > Cc: "Christophe Leroy (CS GROUP)" <[email protected]> >> > > Cc: Felix Kuehling <[email protected]> >> > > Cc: Alex Deucher <[email protected]> >> > > Cc: "Christian König" <[email protected]> >> > > Cc: David Airlie <[email protected]> >> > > Cc: Simona Vetter <[email protected]> >> > > Cc: Maarten Lankhorst <[email protected]> >> > > Cc: Maxime Ripard <[email protected]> >> > > Cc: Thomas Zimmermann <[email protected]> >> > > Cc: Lyude Paul <[email protected]> >> > > Cc: Danilo Krummrich <[email protected]> >> > > Cc: David Hildenbrand <[email protected]> >> > > Cc: Oscar Salvador <[email protected]> >> > > Cc: Andrew Morton <[email protected]> >> > > Cc: Jason Gunthorpe <[email protected]> >> > > Cc: Leon Romanovsky <[email protected]> >> > > Cc: Lorenzo Stoakes <[email protected]> >> > > Cc: Liam R. Howlett <[email protected]> >> > > Cc: Vlastimil Babka <[email protected]> >> > > Cc: Mike Rapoport <[email protected]> >> > > Cc: Suren Baghdasaryan <[email protected]> >> > > Cc: Michal Hocko <[email protected]> >> > > Cc: Balbir Singh <[email protected]> >> > > Cc: [email protected] >> > > Cc: [email protected] >> > > Cc: [email protected] >> > > Cc: [email protected] >> > > Cc: [email protected] >> > > Cc: [email protected] >> > > Cc: [email protected] >> > > Cc: [email protected] >> > > Fixes: d245f9b4ab80 ("mm/zone_device: support large zone device private >> > > folios") >> > > Signed-off-by: Matthew Brost <[email protected]> >> > > Signed-off-by: Francois Dugast <[email protected]> >> > > --- >> > > arch/powerpc/kvm/book3s_hv_uvmem.c | 2 +- >> > > drivers/gpu/drm/amd/amdkfd/kfd_migrate.c | 2 +- >> > > drivers/gpu/drm/drm_pagemap.c | 2 +- >> > > drivers/gpu/drm/nouveau/nouveau_dmem.c | 2 +- >> > > include/linux/memremap.h | 9 ++++++--- >> > > lib/test_hmm.c | 4 +++- >> > > mm/memremap.c | 20 +++++++++++++++++++- >> > > 7 files changed, 32 insertions(+), 9 deletions(-) >> > > >> > > diff --git a/arch/powerpc/kvm/book3s_hv_uvmem.c >> > > b/arch/powerpc/kvm/book3s_hv_uvmem.c >> > > index e5000bef90f2..7cf9310de0ec 100644 >> > > --- a/arch/powerpc/kvm/book3s_hv_uvmem.c >> > > +++ b/arch/powerpc/kvm/book3s_hv_uvmem.c >> > > @@ -723,7 +723,7 @@ static struct page *kvmppc_uvmem_get_page(unsigned >> > > long gpa, struct kvm *kvm) >> > > >> > > dpage = pfn_to_page(uvmem_pfn); >> > > dpage->zone_device_data = pvt; >> > > - zone_device_page_init(dpage, 0); >> > > + zone_device_page_init(dpage, &kvmppc_uvmem_pgmap, 0); >> > > return dpage; >> > > out_clear: >> > > spin_lock(&kvmppc_uvmem_bitmap_lock); >> > > diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c >> > > b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c >> > > index af53e796ea1b..6ada7b4af7c6 100644 >> > > --- a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c >> > > +++ b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c >> > > @@ -217,7 +217,7 @@ svm_migrate_get_vram_page(struct svm_range *prange, >> > > unsigned long pfn) >> > > page = pfn_to_page(pfn); >> > > svm_range_bo_ref(prange->svm_bo); >> > > page->zone_device_data = prange->svm_bo; >> > > - zone_device_page_init(page, 0); >> > > + zone_device_page_init(page, page_pgmap(page), 0); >> > > } >> > > >> > > static void >> > > diff --git a/drivers/gpu/drm/drm_pagemap.c >> > > b/drivers/gpu/drm/drm_pagemap.c >> > > index 03ee39a761a4..c497726b0147 100644 >> > > --- a/drivers/gpu/drm/drm_pagemap.c >> > > +++ b/drivers/gpu/drm/drm_pagemap.c >> > > @@ -201,7 +201,7 @@ static void drm_pagemap_get_devmem_page(struct page >> > > *page, >> > > struct drm_pagemap_zdd *zdd) >> > > { >> > > page->zone_device_data = drm_pagemap_zdd_get(zdd); >> > > - zone_device_page_init(page, 0); >> > > + zone_device_page_init(page, zdd->dpagemap->pagemap, 0); >> > > } >> > > >> > > /** >> > > diff --git a/drivers/gpu/drm/nouveau/nouveau_dmem.c >> > > b/drivers/gpu/drm/nouveau/nouveau_dmem.c >> > > index 58071652679d..3d8031296eed 100644 >> > > --- a/drivers/gpu/drm/nouveau/nouveau_dmem.c >> > > +++ b/drivers/gpu/drm/nouveau/nouveau_dmem.c >> > > @@ -425,7 +425,7 @@ nouveau_dmem_page_alloc_locked(struct nouveau_drm >> > > *drm, bool is_large) >> > > order = ilog2(DMEM_CHUNK_NPAGES); >> > > } >> > > >> > > - zone_device_folio_init(folio, order); >> > > + zone_device_folio_init(folio, page_pgmap(folio_page(folio, 0)), >> > > order); >> > > return page; >> > > } >> > > >> > > diff --git a/include/linux/memremap.h b/include/linux/memremap.h >> > > index 713ec0435b48..e3c2ccf872a8 100644 >> > > --- a/include/linux/memremap.h >> > > +++ b/include/linux/memremap.h >> > > @@ -224,7 +224,8 @@ static inline bool is_fsdax_page(const struct page >> > > *page) >> > > } >> > > >> > > #ifdef CONFIG_ZONE_DEVICE >> > > -void zone_device_page_init(struct page *page, unsigned int order); >> > > +void zone_device_page_init(struct page *page, struct dev_pagemap *pgmap, >> > > + unsigned int order); >> > > void *memremap_pages(struct dev_pagemap *pgmap, int nid); >> > > void memunmap_pages(struct dev_pagemap *pgmap); >> > > void *devm_memremap_pages(struct device *dev, struct dev_pagemap >> > > *pgmap); >> > > @@ -234,9 +235,11 @@ bool pgmap_pfn_valid(struct dev_pagemap *pgmap, >> > > unsigned long pfn); >> > > >> > > unsigned long memremap_compat_align(void); >> > > >> > > -static inline void zone_device_folio_init(struct folio *folio, unsigned >> > > int order) >> > > +static inline void zone_device_folio_init(struct folio *folio, >> > > + struct dev_pagemap *pgmap, >> > > + unsigned int order) >> > > { >> > > - zone_device_page_init(&folio->page, order); >> > > + zone_device_page_init(&folio->page, pgmap, order); >> > > if (order) >> > > folio_set_large_rmappable(folio); >> > > } >> > > diff --git a/lib/test_hmm.c b/lib/test_hmm.c >> > > index 8af169d3873a..455a6862ae50 100644 >> > > --- a/lib/test_hmm.c >> > > +++ b/lib/test_hmm.c >> > > @@ -662,7 +662,9 @@ static struct page *dmirror_devmem_alloc_page(struct >> > > dmirror *dmirror, >> > > goto error; >> > > } >> > > >> > > - zone_device_folio_init(page_folio(dpage), order); >> > > + zone_device_folio_init(page_folio(dpage), >> > > + page_pgmap(folio_page(page_folio(dpage), >> > > 0)), >> > > + order); >> > > dpage->zone_device_data = rpage; >> > > return dpage; >> > > >> > > diff --git a/mm/memremap.c b/mm/memremap.c >> > > index 63c6ab4fdf08..6f46ab14662b 100644 >> > > --- a/mm/memremap.c >> > > +++ b/mm/memremap.c >> > > @@ -477,10 +477,28 @@ void free_zone_device_folio(struct folio *folio) >> > > } >> > > } >> > > >> > > -void zone_device_page_init(struct page *page, unsigned int order) >> > > +void zone_device_page_init(struct page *page, struct dev_pagemap *pgmap, >> > > + unsigned int order) >> > > { >> > > + struct page *new_page = page; >> > > + unsigned int i; >> > > + >> > > VM_WARN_ON_ONCE(order > MAX_ORDER_NR_PAGES); >> > > >> > > + for (i = 0; i < (1UL << order); ++i, ++new_page) { >> > > + struct folio *new_folio = (struct folio *)new_page; >> > > + >> > > + new_page->flags.f &= ~0xffUL; /* Clear possible >> > > order, page head */ >> > >> > This seems odd to me, mainly due to the "magic" number. Why not just clear >> > the flags entirely? Or at least explicitly just clear the flags you care >> > about >> > which would remove the need for the comment and should let you use the >> > proper >> > PageFlag functions. >> > >> >> I'm copying this from folio_reset_order [1]. My paranoia about touching >> anything related to struct page is high, so I did the same thing >> folio_reset_order does here. >> >> [1] https://elixir.bootlin.com/linux/v6.18.5/source/include/linux/mm.h#L1075 >> > > This immediately hangs my first SVM test... > > diff --git a/mm/memremap.c b/mm/memremap.c > index 6f46ab14662b..ef8c56876cf5 100644 > --- a/mm/memremap.c > +++ b/mm/memremap.c > @@ -488,7 +488,7 @@ void zone_device_page_init(struct page *page, struct > dev_pagemap *pgmap, > for (i = 0; i < (1UL << order); ++i, ++new_page) { > struct folio *new_folio = (struct folio *)new_page; > > - new_page->flags.f &= ~0xffUL; /* Clear possible order, page > head */ > + new_page->flags.f = 0; > #ifdef NR_PAGES_IN_LARGE_FOLIO > ((struct folio *)(new_page - 1))->_nr_pages = 0; > #endif
the flags field includes also zone and node id, so clearing that will break the pages's node+zone association, that's probably why...
