Messages in this thread | | | Subject | Re: [PATCH] mm: remove extra ZONE_DEVICE struct page refcount | From | Ralph Campbell <> | Date | Wed, 16 Sep 2020 17:34:17 -0700 |
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On 9/15/20 11:09 PM, Christoph Hellwig wrote: >> diff --git a/include/linux/mm.h b/include/linux/mm.h >> index 517751310dd2..5a82037a4b26 100644 >> --- a/include/linux/mm.h >> +++ b/include/linux/mm.h >> @@ -1093,34 +1093,6 @@ static inline bool is_zone_device_page(const struct page *page) >> #ifdef CONFIG_DEV_PAGEMAP_OPS >> void free_devmap_managed_page(struct page *page); >> DECLARE_STATIC_KEY_FALSE(devmap_managed_key); > > The export for devmap_managed_key can be dropped now. In fact I think > we can remove devmap_managed_key entirely now - it is only checked in > the actual page free path instead of for each refcount manipulation, > so a good old unlikely is probably enough. > > Also free_devmap_managed_page can move to mm/internal.h.
Good suggestion.
>> +#ifdef CONFIG_DEV_PAGEMAP_OPS >> +static void __put_devmap_managed_page(struct page *page) >> +{ >> + if (!static_branch_unlikely(&devmap_managed_key)) >> + return; >> + >> + switch (page->pgmap->type) { >> + case MEMORY_DEVICE_PRIVATE: >> + case MEMORY_DEVICE_FS_DAX: >> + free_devmap_managed_page(page); >> + break; >> + default: >> + break; >> + } >> +} >> +#else >> +static inline void __put_devmap_managed_page(struct page *page) >> +{ >> +} >> +#endif > > I think this should be moved to mm/memremap.c or even better > actually be folded into free_devmap_managed_page, which would need > a new name like free_zone_device_page(). > > Something like this incremental patch: > > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 7bb9e93cf86cde..29350dc27cd0cd 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -1090,11 +1090,6 @@ static inline bool is_zone_device_page(const struct page *page) > } > #endif > > -#ifdef CONFIG_DEV_PAGEMAP_OPS > -void free_devmap_managed_page(struct page *page); > -DECLARE_STATIC_KEY_FALSE(devmap_managed_key); > -#endif /* CONFIG_DEV_PAGEMAP_OPS */ > - > static inline bool is_device_private_page(const struct page *page) > { > return IS_ENABLED(CONFIG_DEV_PAGEMAP_OPS) && > diff --git a/mm/internal.h b/mm/internal.h > index 6345b08ce86ccf..629959a6f26d7c 100644 > --- a/mm/internal.h > +++ b/mm/internal.h > @@ -618,4 +618,12 @@ struct migration_target_control { > gfp_t gfp_mask; > }; > > +#ifdef CONFIG_DEV_PAGEMAP_OPS > +void free_zone_device_page(struct page *page); > +#else > +static inline void free_zone_device_page(struct page *page) > +{ > +} > +#endif > + > #endif /* __MM_INTERNAL_H */ > diff --git a/mm/memremap.c b/mm/memremap.c > index d549e3733f4098..b15ad2264a4f1c 100644 > --- a/mm/memremap.c > +++ b/mm/memremap.c > @@ -12,6 +12,7 @@ > #include <linux/types.h> > #include <linux/wait_bit.h> > #include <linux/xarray.h> > +#include "internal.h" > > static DEFINE_XARRAY(pgmap_array); > > @@ -37,36 +38,6 @@ unsigned long memremap_compat_align(void) > EXPORT_SYMBOL_GPL(memremap_compat_align); > #endif > > -#ifdef CONFIG_DEV_PAGEMAP_OPS > -DEFINE_STATIC_KEY_FALSE(devmap_managed_key); > -EXPORT_SYMBOL(devmap_managed_key); > - > -static void devmap_managed_enable_put(void) > -{ > - static_branch_dec(&devmap_managed_key); > -} > - > -static int devmap_managed_enable_get(struct dev_pagemap *pgmap) > -{ > - if (pgmap->type == MEMORY_DEVICE_PRIVATE && > - (!pgmap->ops || !pgmap->ops->page_free)) { > - WARN(1, "Missing page_free method\n"); > - return -EINVAL; > - } > - > - static_branch_inc(&devmap_managed_key); > - return 0; > -} > -#else > -static int devmap_managed_enable_get(struct dev_pagemap *pgmap) > -{ > - return -EINVAL; > -} > -static void devmap_managed_enable_put(void) > -{ > -} > -#endif /* CONFIG_DEV_PAGEMAP_OPS */ > - > static void pgmap_array_delete(struct range *range) > { > xa_store_range(&pgmap_array, PHYS_PFN(range->start), PHYS_PFN(range->end), > @@ -181,7 +152,6 @@ void memunmap_pages(struct dev_pagemap *pgmap) > pageunmap_range(pgmap, i); > > WARN_ONCE(pgmap->altmap.alloc, "failed to free all reserved pages\n"); > - devmap_managed_enable_put(); > } > EXPORT_SYMBOL_GPL(memunmap_pages); > > @@ -319,7 +289,6 @@ void *memremap_pages(struct dev_pagemap *pgmap, int nid) > .pgprot = PAGE_KERNEL, > }; > const int nr_range = pgmap->nr_range; > - bool need_devmap_managed = true; > int error, i; > > if (WARN_ONCE(!nr_range, "nr_range must be specified\n")) > @@ -331,8 +300,9 @@ void *memremap_pages(struct dev_pagemap *pgmap, int nid) > WARN(1, "Device private memory not supported\n"); > return ERR_PTR(-EINVAL); > } > - if (!pgmap->ops || !pgmap->ops->migrate_to_ram) { > - WARN(1, "Missing migrate_to_ram method\n"); > + if (!pgmap->ops || > + !pgmap->ops->migrate_to_ram || !pgmap->ops->page_free) { > + WARN(1, "Missing ops\n"); > return ERR_PTR(-EINVAL); > } > if (!pgmap->owner) { > @@ -348,11 +318,9 @@ void *memremap_pages(struct dev_pagemap *pgmap, int nid) > } > break; > case MEMORY_DEVICE_GENERIC: > - need_devmap_managed = false; > break; > case MEMORY_DEVICE_PCI_P2PDMA: > params.pgprot = pgprot_noncached(params.pgprot); > - need_devmap_managed = false; > break; > default: > WARN(1, "Invalid pgmap type %d\n", pgmap->type); > @@ -376,12 +344,6 @@ void *memremap_pages(struct dev_pagemap *pgmap, int nid) > } > } > > - if (need_devmap_managed) { > - error = devmap_managed_enable_get(pgmap); > - if (error) > - return ERR_PTR(error); > - } > - > /* > * Clear the pgmap nr_range as it will be incremented for each > * successfully processed range. This communicates how many > @@ -496,16 +458,9 @@ struct dev_pagemap *get_dev_pagemap(unsigned long pfn, > EXPORT_SYMBOL_GPL(get_dev_pagemap); > > #ifdef CONFIG_DEV_PAGEMAP_OPS > -void free_devmap_managed_page(struct page *page) > +static void free_device_private_page(struct page *page) > { > - /* notify page idle for dax */ > - if (!is_device_private_page(page)) { > - wake_up_var(&page->_refcount); > - return; > - } > - > __ClearPageWaiters(page); > - > mem_cgroup_uncharge(page); > > /* > @@ -540,4 +495,19 @@ void free_devmap_managed_page(struct page *page) > page->mapping = NULL; > page->pgmap->ops->page_free(page); > } > + > +void free_zone_device_page(struct page *page) > +{ > + switch (page->pgmap->type) { > + case MEMORY_DEVICE_FS_DAX: > + /* notify page idle */ > + wake_up_var(&page->_refcount); > + return; > + case MEMORY_DEVICE_PRIVATE: > + free_device_private_page(page); > + return; > + default: > + return; > + } > +} > #endif /* CONFIG_DEV_PAGEMAP_OPS */ > diff --git a/mm/swap.c b/mm/swap.c > index bcab5db351184a..83451ac70d0f05 100644 > --- a/mm/swap.c > +++ b/mm/swap.c > @@ -113,36 +113,14 @@ static void __put_compound_page(struct page *page) > destroy_compound_page(page); > } > > -#ifdef CONFIG_DEV_PAGEMAP_OPS > -static void __put_devmap_managed_page(struct page *page) > -{ > - if (!static_branch_unlikely(&devmap_managed_key)) > - return; > - > - switch (page->pgmap->type) { > - case MEMORY_DEVICE_PRIVATE: > - case MEMORY_DEVICE_FS_DAX: > - free_devmap_managed_page(page); > - break; > - default: > - break; > - } > -} > -#else > -static inline void __put_devmap_managed_page(struct page *page) > -{ > -} > -#endif > - > void __put_page(struct page *page) > { > if (is_zone_device_page(page)) { > - __put_devmap_managed_page(page); > - > /* > * The page belongs to the device that created pgmap. Do > * not return it to page allocator. > */ > + free_zone_device_page(page); > return; > } > > @@ -923,7 +901,7 @@ void release_pages(struct page **pages, int nr) > flags); > locked_pgdat = NULL; > } > - __put_devmap_managed_page(page); > + free_zone_device_page(page); > return; > } > >
Thanks for the review! I will apply the above in v2. I found a couple of more reference count checks in fs/dax.c so I need to run fstests with dax before sending v2 out.
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