On Thu, Mar 06, 2025 at 03:42:29PM +1100, Balbir Singh wrote:
> Add routines to support allocation of large order zone device folios
> and helper functions for zone device folios, to check if a folio is
> device private and helpers for setting zone device data.
>
> When large folios are used, the existing page_free() callback in
> pgmap is called when the folio is freed, this is true for both
> PAGE_SIZE and higher order pages.
>
> Signed-off-by: Balbir Singh <balbirs@xxxxxxxxxx>
> ---
> include/linux/memremap.h | 22 +++++++++++++++++-
> mm/memremap.c | 50 +++++++++++++++++++++++++++++-----------
> 2 files changed, 58 insertions(+), 14 deletions(-)
>
> diff --git a/include/linux/memremap.h b/include/linux/memremap.h
> index 4aa151914eab..11d586dd8ef1 100644
> --- a/include/linux/memremap.h
> +++ b/include/linux/memremap.h
> @@ -169,6 +169,18 @@ static inline bool folio_is_device_private(const struct folio *folio)
> return is_device_private_page(&folio->page);
> }
>
> +static inline void *folio_zone_device_data(const struct folio *folio)
> +{
> + VM_BUG_ON_FOLIO(!folio_is_device_private(folio), folio);
> + return folio->page.zone_device_data;
> +}
> +
> +static inline void folio_set_zone_device_data(struct folio *folio, void *data)
> +{
> + VM_BUG_ON_FOLIO(!folio_is_device_private(folio), folio);
> + folio->page.zone_device_data = data;
> +}
> +
> static inline bool is_pci_p2pdma_page(const struct page *page)
> {
> return IS_ENABLED(CONFIG_PCI_P2PDMA) &&
> @@ -199,7 +211,7 @@ static inline bool folio_is_fsdax(const struct folio *folio)
> }
>
> #ifdef CONFIG_ZONE_DEVICE
> -void zone_device_page_init(struct page *page);
> +void init_zone_device_folio(struct folio *folio, 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);
> @@ -209,6 +221,14 @@ struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
> bool pgmap_pfn_valid(struct dev_pagemap *pgmap, unsigned long pfn);
>
> unsigned long memremap_compat_align(void);
> +
> +static inline void zone_device_page_init(struct page *page)
> +{
> + struct folio *folio = page_folio(page);
> +
> + init_zone_device_folio(folio, 0);
> +}
> +
> #else
> static inline void *devm_memremap_pages(struct device *dev,
> struct dev_pagemap *pgmap)
> diff --git a/mm/memremap.c b/mm/memremap.c
> index 2aebc1b192da..7d98d0a4c0cd 100644
> --- a/mm/memremap.c
> +++ b/mm/memremap.c
> @@ -459,20 +459,21 @@ EXPORT_SYMBOL_GPL(get_dev_pagemap);
> void free_zone_device_folio(struct folio *folio)
> {
> struct dev_pagemap *pgmap = folio->pgmap;
> + unsigned int nr = folio_nr_pages(folio);
> + int i;
> + bool anon = folio_test_anon(folio);
> + struct page *page = folio_page(folio, 0);
>
> if (WARN_ON_ONCE(!pgmap))
> return;
>
> mem_cgroup_uncharge(folio);
>
> - /*
> - * Note: we don't expect anonymous compound pages yet. Once supported
> - * and we could PTE-map them similar to THP, we'd have to clear
> - * PG_anon_exclusive on all tail pages.
> - */
> - if (folio_test_anon(folio)) {
> - VM_BUG_ON_FOLIO(folio_test_large(folio), folio);
> - __ClearPageAnonExclusive(folio_page(folio, 0));
> + WARN_ON_ONCE(folio_test_large(folio) && !anon);
> +
> + for (i = 0; i < nr; i++) {
> + if (anon)
> + __ClearPageAnonExclusive(folio_page(folio, i));
> }
>
> /*
> @@ -496,10 +497,19 @@ void free_zone_device_folio(struct folio *folio)
>
> switch (pgmap->type) {
> case MEMORY_DEVICE_PRIVATE:
> + if (folio_test_large(folio)) {
> + folio_unqueue_deferred_split(folio);
> +
> + percpu_ref_put_many(&folio->pgmap->ref, nr - 1);
> + }
> + pgmap->ops->page_free(page);
It seems to me this would be a good time to finally convert page_free() to
folio_free() and have it take a folio instead.
> + put_dev_pagemap(pgmap);
> + page->mapping = NULL;
> + break;
> case MEMORY_DEVICE_COHERENT:
> if (WARN_ON_ONCE(!pgmap->ops || !pgmap->ops->page_free))
> break;
> - pgmap->ops->page_free(folio_page(folio, 0));
> + pgmap->ops->page_free(page);
Ditto.
> put_dev_pagemap(pgmap);
> break;
>
> @@ -523,14 +533,28 @@ void free_zone_device_folio(struct folio *folio)
> }
> }
>
> -void zone_device_page_init(struct page *page)
> +void init_zone_device_folio(struct folio *folio, unsigned int order)
Is this supposed to deal with taking any arbitrary zone_device folio and
initialising it to the given order? If so I'd expect to see things like
clear_compound_head() to cope with initialising a previously higher order folio
to a 0-order folio.
> {
> + struct page *page = folio_page(folio, 0);
> +
> + VM_BUG_ON(order > MAX_ORDER_NR_PAGES);
> +
> + WARN_ON_ONCE(order && order != HPAGE_PMD_ORDER);
> +
> /*
> * Drivers shouldn't be allocating pages after calling
> * memunmap_pages().
> */
> - WARN_ON_ONCE(!percpu_ref_tryget_live(&page_pgmap(page)->ref));
> - set_page_count(page, 1);
> + WARN_ON_ONCE(!percpu_ref_tryget_many(&page_pgmap(page)->ref, 1 << order));
> + folio_set_count(folio, 1);
> lock_page(page);
> +
> + /*
> + * Only PMD level migration is supported for THP migration
> + */
> + if (order > 1) {
> + prep_compound_page(page, order);
> + folio_set_large_rmappable(folio);
> + }
> }
> -EXPORT_SYMBOL_GPL(zone_device_page_init);
> +EXPORT_SYMBOL_GPL(init_zone_device_folio);
> --
> 2.48.1
>
