Re: [PATCH v5 1/5] mm/zone_device: Reinitialize large zone device private folios

Fri, 16 Jan 2026 10:08:32 -0800 


On 2026-01-16 11:43, Rodrigo Vivi wrote:

On Wed, Jan 14, 2026 at 08:19:52PM +0100, Francois Dugast 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.

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 +-

AMD folks, ack to get this patch through drm-misc-next or even perhaps some mm
related tree?



The kfd_migrate change looks straight-forward enough for me. We don't 
use large device pages yet, so I guess the changes in 
zone_device_page_init should be safe for us. Feel free to add  my


Acked-by: Felix Kuehling <[email protected]>


I have no objections to merging this through drm-misc-next. @Alex, how 
will this flow back into our amd-staging-drm-next branch? I guess we'll 
get it on the next branch rebase. There should be no rush as I don't 
think we're affected by the bug being fixed here.


Thanks,
  Felix





  drivers/gpu/drm/drm_pagemap.c            |  2 +-
  drivers/gpu/drm/nouveau/nouveau_dmem.c   |  2 +-

Nouveau folks, ack as well?


  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 */
+#ifdef NR_PAGES_IN_LARGE_FOLIO
+               ((struct folio *)(new_page - 1))->_nr_pages = 0;
+#endif
+               new_folio->mapping = NULL;
+               new_folio->pgmap = pgmap;    /* Also clear compound head */
+               new_folio->share = 0;   /* fsdax only, unused for device 
private */
+               VM_WARN_ON_FOLIO(folio_ref_count(new_folio), new_folio);
+               VM_WARN_ON_FOLIO(!folio_is_zone_device(new_folio), new_folio);
+       }
+
        /*
         * Drivers shouldn't be allocating pages after calling
         * memunmap_pages().
--
2.43.0



























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