The DEVICE_PRIVATE/COHERENT changes look good to me so feel free to add:
Reviewed-by: Alistair Popple <[email protected]> Dan Williams <[email protected]> writes: > The initial memremap_pages() implementation inherited the > __init_single_page() default of pages starting life with an elevated > reference count. This originally allowed for the page->pgmap pointer to > alias with the storage for page->lru since a page was only allowed to be > on an lru list when its reference count was zero. > > Since then, 'struct page' definition cleanups have arranged for > dedicated space for the ZONE_DEVICE page metadata, the > MEMORY_DEVICE_{PRIVATE,COHERENT} work has arranged for the 1 -> 0 > page->_refcount transition to route the page to free_zone_device_page() > and not the core-mm page-free, and MEMORY_DEVICE_{PRIVATE,COHERENT} now > arranges for its ZONE_DEVICE pages to start at _refcount 0. With those > cleanups in place and with filesystem-dax and device-dax now converted > to take and drop references at map and truncate time, it is possible to > start MEMORY_DEVICE_FS_DAX and MEMORY_DEVICE_GENERIC reference counts at > 0 as well. > > This conversion also unifies all @pgmap accounting to be relative to > pgmap_request_folio() and the paired folio_put() calls for those > requested folios. This allows pgmap_release_folios() to be simplified to > just a folio_put() helper. > > Cc: Matthew Wilcox <[email protected]> > Cc: Jan Kara <[email protected]> > Cc: "Darrick J. Wong" <[email protected]> > Cc: Christoph Hellwig <[email protected]> > Cc: John Hubbard <[email protected]> > Cc: Alistair Popple <[email protected]> > Cc: Jason Gunthorpe <[email protected]> > Signed-off-by: Dan Williams <[email protected]> > --- > drivers/dax/mapping.c | 2 +- > include/linux/dax.h | 2 +- > include/linux/memremap.h | 6 ++---- > mm/memremap.c | 36 ++++++++++++++++-------------------- > mm/page_alloc.c | 9 +-------- > 5 files changed, 21 insertions(+), 34 deletions(-) > > diff --git a/drivers/dax/mapping.c b/drivers/dax/mapping.c > index 07caaa23d476..ca06f2515644 100644 > --- a/drivers/dax/mapping.c > +++ b/drivers/dax/mapping.c > @@ -691,7 +691,7 @@ static struct page *dax_zap_pages(struct xa_state *xas, > void *entry) > > dax_for_each_folio(entry, folio, i) { > if (zap) > - pgmap_release_folios(folio_pgmap(folio), folio, 1); > + pgmap_release_folios(folio, 1); > if (!ret && !dax_folio_idle(folio)) > ret = folio_page(folio, 0); > } > diff --git a/include/linux/dax.h b/include/linux/dax.h > index f2fbb5746ffa..f4fc37933fc2 100644 > --- a/include/linux/dax.h > +++ b/include/linux/dax.h > @@ -235,7 +235,7 @@ static inline void dax_unlock_mapping_entry(struct > address_space *mapping, > */ > static inline bool dax_page_idle(struct page *page) > { > - return page_ref_count(page) == 1; > + return page_ref_count(page) == 0; > } > > static inline bool dax_folio_idle(struct folio *folio) > diff --git a/include/linux/memremap.h b/include/linux/memremap.h > index 3fb3809d71f3..ddb196ae0696 100644 > --- a/include/linux/memremap.h > +++ b/include/linux/memremap.h > @@ -195,8 +195,7 @@ struct dev_pagemap *get_dev_pagemap(unsigned long pfn, > struct dev_pagemap *pgmap); > bool pgmap_request_folios(struct dev_pagemap *pgmap, struct folio *folio, > int nr_folios); > -void pgmap_release_folios(struct dev_pagemap *pgmap, struct folio *folio, > - int nr_folios); > +void pgmap_release_folios(struct folio *folio, int nr_folios); > bool pgmap_pfn_valid(struct dev_pagemap *pgmap, unsigned long pfn); > > unsigned long vmem_altmap_offset(struct vmem_altmap *altmap); > @@ -238,8 +237,7 @@ static inline bool pgmap_request_folios(struct > dev_pagemap *pgmap, > return false; > } > > -static inline void pgmap_release_folios(struct dev_pagemap *pgmap, > - struct folio *folio, int nr_folios) > +static inline void pgmap_release_folios(struct folio *folio, int nr_folios) > { > } > > diff --git a/mm/memremap.c b/mm/memremap.c > index c46e700f5245..368ff41c560b 100644 > --- a/mm/memremap.c > +++ b/mm/memremap.c > @@ -469,8 +469,10 @@ EXPORT_SYMBOL_GPL(get_dev_pagemap); > > void free_zone_device_page(struct page *page) > { > - if (WARN_ON_ONCE(!page->pgmap->ops || !page->pgmap->ops->page_free)) > - return; > + struct dev_pagemap *pgmap = page->pgmap; > + > + /* wake filesystem 'break dax layouts' waiters */ > + wake_up_var(page); > > mem_cgroup_uncharge(page_folio(page)); > > @@ -505,17 +507,9 @@ void free_zone_device_page(struct page *page) > * to clear page->mapping. > */ > page->mapping = NULL; > - page->pgmap->ops->page_free(page); > - > - if (page->pgmap->type != MEMORY_DEVICE_PRIVATE && > - page->pgmap->type != MEMORY_DEVICE_COHERENT) > - /* > - * Reset the page count to 1 to prepare for handing out the page > - * again. > - */ > - set_page_count(page, 1); > - else > - put_dev_pagemap(page->pgmap); > + if (pgmap->ops && pgmap->ops->page_free) > + pgmap->ops->page_free(page); > + put_dev_pagemap(page->pgmap); > } > > static bool folio_span_valid(struct dev_pagemap *pgmap, struct folio *folio, > @@ -576,17 +570,19 @@ bool pgmap_request_folios(struct dev_pagemap *pgmap, > struct folio *folio, > } > EXPORT_SYMBOL_GPL(pgmap_request_folios); > > -void pgmap_release_folios(struct dev_pagemap *pgmap, struct folio *folio, > int nr_folios) > +/* > + * A symmetric helper to undo the page references acquired by > + * pgmap_request_folios(), but the caller can also just arrange > + * folio_put() on all the folios it acquired previously for the same > + * effect. > + */ > +void pgmap_release_folios(struct folio *folio, int nr_folios) > { > struct folio *iter; > int i; > > - for (iter = folio, i = 0; i < nr_folios; iter = folio_next(iter), i++) { > - if (!put_devmap_managed_page(&iter->page)) > - folio_put(iter); > - if (!folio_ref_count(iter)) > - put_dev_pagemap(pgmap); > - } > + for (iter = folio, i = 0; i < nr_folios; iter = folio_next(folio), i++) > + folio_put(iter); > } > > #ifdef CONFIG_FS_DAX > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 8e9b7f08a32c..e35d1eb3308d 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -6787,6 +6787,7 @@ static void __ref __init_zone_device_page(struct page > *page, unsigned long pfn, > { > > __init_single_page(page, pfn, zone_idx, nid); > + set_page_count(page, 0); > > /* > * Mark page reserved as it will need to wait for onlining > @@ -6819,14 +6820,6 @@ static void __ref __init_zone_device_page(struct page > *page, unsigned long pfn, > set_pageblock_migratetype(page, MIGRATE_MOVABLE); > cond_resched(); > } > - > - /* > - * ZONE_DEVICE pages are released directly to the driver page allocator > - * which will set the page count to 1 when allocating the page. > - */ > - if (pgmap->type == MEMORY_DEVICE_PRIVATE || > - pgmap->type == MEMORY_DEVICE_COHERENT) > - set_page_count(page, 0); > } > > /*
