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The driver callback for folio_split is invoked to let the device driver know that the folio size has been split into a smaller order. Provide a default implementation for drivers that do not provide this callback that copies the pgmap and mapping fields for the split folios. Update the HMM test driver to handle the split. Cc: Andrew Morton Cc: David Hildenbrand Cc: Zi Yan Cc: Joshua Hahn Cc: Rakie Kim Cc: Byungchul Park Cc: Gregory Price Cc: Ying Huang Cc: Alistair Popple Cc: Oscar Salvador Cc: Lorenzo Stoakes Cc: Baolin Wang Cc: "Liam R. Howlett" Cc: Nico Pache Cc: Ryan Roberts Cc: Dev Jain Cc: Barry Song Cc: Lyude Paul Cc: Danilo Krummrich Cc: David Airlie Cc: Simona Vetter Cc: Ralph Campbell Cc: Mika Penttil=C3=A4 Cc: Matthew Brost Cc: Francois Dugast Signed-off-by: Balbir Singh --- include/linux/memremap.h | 29 +++++++++++++++++++++++++++++ lib/test_hmm.c | 35 +++++++++++++++++++++++++++++++++++ 2 files changed, 64 insertions(+) diff --git a/include/linux/memremap.h b/include/linux/memremap.h index 7df4dd037b69..aca2b16d6889 100644 --- a/include/linux/memremap.h +++ b/include/linux/memremap.h @@ -100,6 +100,13 @@ struct dev_pagemap_ops { */ int (*memory_failure)(struct dev_pagemap *pgmap, unsigned long pfn, unsigned long nr_pages, int mf_flags); + + /* + * Used for private (un-addressable) device memory only. + * This callback is used when a folio is split into + * a smaller folio + */ + void (*folio_split)(struct folio *head, struct folio *tail); }; =20 #define PGMAP_ALTMAP_VALID (1 << 0) @@ -235,6 +242,23 @@ static inline void zone_device_folio_init(struct folio= *folio, unsigned int orde folio_set_large_rmappable(folio); } =20 +static inline void zone_device_private_split_cb(struct folio *original_fol= io, + struct folio *new_folio) +{ + if (folio_is_device_private(original_folio)) { + if (!original_folio->pgmap->ops->folio_split) { + if (new_folio) { + new_folio->pgmap =3D original_folio->pgmap; + new_folio->page.mapping =3D + original_folio->page.mapping; + } + } else { + original_folio->pgmap->ops->folio_split(original_folio, + new_folio); + } + } +} + #else static inline void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap) @@ -268,6 +292,11 @@ static inline unsigned long memremap_compat_align(void) { return PAGE_SIZE; } + +static inline void zone_device_private_split_cb(struct folio *original_fol= io, + struct folio *new_folio) +{ +} #endif /* CONFIG_ZONE_DEVICE */ =20 static inline void put_dev_pagemap(struct dev_pagemap *pgmap) diff --git a/lib/test_hmm.c b/lib/test_hmm.c index 32d402e80bcc..46fa9e200db8 100644 --- a/lib/test_hmm.c +++ b/lib/test_hmm.c @@ -1654,9 +1654,44 @@ static vm_fault_t dmirror_devmem_fault(struct vm_fau= lt *vmf) return ret; } =20 +static void dmirror_devmem_folio_split(struct folio *head, struct folio *t= ail) +{ + struct page *rpage =3D BACKING_PAGE(folio_page(head, 0)); + struct page *rpage_tail; + struct folio *rfolio; + unsigned long offset =3D 0; + + if (!rpage) { + tail->page.zone_device_data =3D NULL; + return; + } + + rfolio =3D page_folio(rpage); + + if (tail =3D=3D NULL) { + folio_reset_order(rfolio); + rfolio->mapping =3D NULL; + folio_set_count(rfolio, 1); + return; + } + + offset =3D folio_pfn(tail) - folio_pfn(head); + + rpage_tail =3D folio_page(rfolio, offset); + tail->page.zone_device_data =3D rpage_tail; + rpage_tail->zone_device_data =3D rpage->zone_device_data; + clear_compound_head(rpage_tail); + rpage_tail->mapping =3D NULL; + + folio_page(tail, 0)->mapping =3D folio_page(head, 0)->mapping; + tail->pgmap =3D head->pgmap; + folio_set_count(page_folio(rpage_tail), 1); +} + static const struct dev_pagemap_ops dmirror_devmem_ops =3D { .folio_free =3D dmirror_devmem_free, .migrate_to_ram =3D dmirror_devmem_fault, + .folio_split =3D dmirror_devmem_folio_split, }; =20 static int dmirror_device_init(struct dmirror_device *mdevice, int id) --=20 2.51.0