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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 +++++++++++++++++++++++++++++ include/linux/mm.h | 1 + lib/test_hmm.c | 35 +++++++++++++++++++++++++++++++++++ mm/huge_memory.c | 2 +- 4 files changed, 66 insertions(+), 1 deletion(-) diff --git a/include/linux/memremap.h b/include/linux/memremap.h index 75987a8cfc6b..ba95c31a7251 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_page_init(struct page *= page) zone_device_folio_init(folio, 0); } =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/include/linux/mm.h b/include/linux/mm.h index a6bfa46937a8..f9c8983c2055 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1250,6 +1250,7 @@ static inline struct folio *virt_to_folio(const void = *x) void __folio_put(struct folio *folio); =20 void split_page(struct page *page, unsigned int order); +void prep_compound_page(struct page *page, unsigned int order); void folio_copy(struct folio *dst, struct folio *src); int folio_mc_copy(struct folio *dst, struct folio *src); =20 diff --git a/lib/test_hmm.c b/lib/test_hmm.c index 50e175edc58a..41092c065c2d 100644 --- a/lib/test_hmm.c +++ b/lib/test_hmm.c @@ -1653,9 +1653,44 @@ 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 { .page_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) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index d634b2157a56..e38482e6e5c0 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -3907,7 +3907,6 @@ static int __folio_split(struct folio *folio, unsigne= d int new_order, =20 ret =3D __split_unmapped_folio(folio, new_order, split_at, &xas, mapping, uniform_split); - /* * Unfreeze after-split folios and put them back to the right * list. @folio should be kept frozon until page cache @@ -3958,6 +3957,7 @@ static int __folio_split(struct folio *folio, unsigne= d int new_order, __filemap_remove_folio(new_folio, NULL); folio_put_refs(new_folio, nr_pages); } + /* * Unfreeze @folio only after all page cache entries, which * used to point to it, have been updated with new folios. --=20 2.50.1