Some folios, such as hugetlb folios and zone device folios, require special handling when the folio's reference count reaches 0, before being freed. Moreover, guest_memfd folios will likely require special handling to notify it once a folio's reference count reaches 0, to facilitate shared to private folio conversion [*]. Currently, each usecase has a dedicated callback when the folio refcount reaches 0 to that effect. Adding yet more callbacks is not ideal. This patch series introduces struct folio_owner_ops and uses it as a generic way to handle callbacks on freeing a folio. It also applies the callbacks to hugetlb and zone device folios. A pointer to struct folio_owner_ops is overlaid on struct page compound_page, struct page/folio lru. To indicate that the folio uses the callback, this patch series sets bit 1 of the new field, similar to how bit 0 indicates a compound page. Patches 1 to 6 rework the hugetlb code to allow us to reuse folio->lru for the owner ops as long as they are not isolated. Patches 7 to 10 introduce struct folio_owner_ops, and apply the callbacks to zone device and hugetlb folios. Cheers, /fuad [*] https://lore.kernel.org/all/CAGtprH_JP2w-4rq02h_Ugvq5KuHX7TUvegOS7xUs_iy5hriE7g@xxxxxxxxxxxxxx/ David Hildenbrand (6): mm/hugetlb: rename isolate_hugetlb() to folio_isolate_hugetlb() mm/migrate: don't call folio_putback_active_hugetlb() on dst hugetlb folio mm/hugetlb: rename "folio_putback_active_hugetlb()" to "folio_putback_hugetlb()" mm/hugetlb-cgroup: convert hugetlb_cgroup_css_offline() to work on folios mm/hugetlb: use folio->lru int demote_free_hugetlb_folios() mm/hugetlb: use separate folio->_hugetlb_list for hugetlb-internals Fuad Tabba (4): mm: Introduce struct folio_owner_ops mm: Use getters and setters to access page pgmap mm: Use owner_ops on folio_put for zone device pages mm: hugetlb: Use owner_ops on folio_put for hugetlb drivers/gpu/drm/nouveau/nouveau_dmem.c | 4 +- drivers/pci/p2pdma.c | 8 +- include/linux/hugetlb.h | 10 +- include/linux/memremap.h | 14 +- include/linux/mm_types.h | 107 ++++++++++++++- lib/test_hmm.c | 2 +- mm/gup.c | 2 +- mm/hmm.c | 2 +- mm/hugetlb.c | 179 ++++++++++++++++++------- mm/hugetlb_cgroup.c | 19 ++- mm/hugetlb_vmemmap.c | 8 +- mm/internal.h | 1 - mm/memory.c | 2 +- mm/mempolicy.c | 2 +- mm/memremap.c | 49 +------ mm/migrate.c | 20 +-- mm/migrate_device.c | 4 +- mm/mm_init.c | 48 ++++++- mm/swap.c | 25 ++-- 19 files changed, 342 insertions(+), 164 deletions(-) base-commit: beb2622b970047000fa3cae64c23585669b01fca -- 2.47.0.277.g8800431eea-goog
