From 7b2d55d2c8961ae9d456d3133f4ae2f0fbd3e14f Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?J=C3=A9r=C3=B4me=20Glisse?= Date: Fri, 8 Sep 2017 16:11:46 -0700 Subject: [PATCH] mm/ZONE_DEVICE: special case put_page() for device private pages MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit A ZONE_DEVICE page that reach a refcount of 1 is free ie no longer have any user. For device private pages this is important to catch and thus we need to special case put_page() for this. Link: http://lkml.kernel.org/r/20170817000548.32038-9-jglisse@redhat.com Signed-off-by: Jérôme Glisse Cc: Kirill A. Shutemov Cc: Dan Williams Cc: Ross Zwisler Cc: Aneesh Kumar Cc: Balbir Singh Cc: Benjamin Herrenschmidt Cc: David Nellans Cc: Evgeny Baskakov Cc: Johannes Weiner Cc: John Hubbard Cc: Mark Hairgrove Cc: Michal Hocko Cc: Paul E. McKenney Cc: Sherry Cheung Cc: Subhash Gutti Cc: Vladimir Davydov Cc: Bob Liu Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/memremap.h | 13 +++++++++++++ include/linux/mm.h | 31 ++++++++++++++++++++++--------- kernel/memremap.c | 25 ++++++++++++++++++++++++- mm/hmm.c | 8 ++++++++ 4 files changed, 67 insertions(+), 10 deletions(-) diff --git a/include/linux/memremap.h b/include/linux/memremap.h index 8e164ec9eed0..8aa6b82679e2 100644 --- a/include/linux/memremap.h +++ b/include/linux/memremap.h @@ -126,6 +126,14 @@ struct dev_pagemap { void *devm_memremap_pages(struct device *dev, struct resource *res, struct percpu_ref *ref, struct vmem_altmap *altmap); struct dev_pagemap *find_dev_pagemap(resource_size_t phys); + +static inline bool is_zone_device_page(const struct page *page); + +static inline bool is_device_private_page(const struct page *page) +{ + return is_zone_device_page(page) && + page->pgmap->type == MEMORY_DEVICE_PRIVATE; +} #else static inline void *devm_memremap_pages(struct device *dev, struct resource *res, struct percpu_ref *ref, @@ -144,6 +152,11 @@ static inline struct dev_pagemap *find_dev_pagemap(resource_size_t phys) { return NULL; } + +static inline bool is_device_private_page(const struct page *page) +{ + return false; +} #endif /** diff --git a/include/linux/mm.h b/include/linux/mm.h index a74c4e954352..eccdab4bb44a 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -23,6 +23,7 @@ #include #include #include +#include struct mempolicy; struct anon_vma; @@ -792,25 +793,25 @@ static inline bool is_zone_device_page(const struct page *page) { return page_zonenum(page) == ZONE_DEVICE; } - -static inline bool is_device_private_page(const struct page *page) -{ - /* See MEMORY_DEVICE_PRIVATE in include/linux/memory_hotplug.h */ - return ((page_zonenum(page) == ZONE_DEVICE) && - (page->pgmap->type == MEMORY_DEVICE_PRIVATE)); -} #else static inline bool is_zone_device_page(const struct page *page) { return false; } +#endif -static inline bool is_device_private_page(const struct page *page) +#ifdef CONFIG_DEVICE_PRIVATE +void put_zone_device_private_page(struct page *page); +#else +static inline void put_zone_device_private_page(struct page *page) { - return false; } #endif +static inline bool is_device_private_page(const struct page *page); + +DECLARE_STATIC_KEY_FALSE(device_private_key); + static inline void get_page(struct page *page) { page = compound_head(page); @@ -826,6 +827,18 @@ static inline void put_page(struct page *page) { page = compound_head(page); + /* + * For private device pages we need to catch refcount transition from + * 2 to 1, when refcount reach one it means the private device page is + * free and we need to inform the device driver through callback. See + * include/linux/memremap.h and HMM for details. + */ + if (static_branch_unlikely(&device_private_key) && + unlikely(is_device_private_page(page))) { + put_zone_device_private_page(page); + return; + } + if (put_page_testzero(page)) __put_page(page); } diff --git a/kernel/memremap.c b/kernel/memremap.c index f1d1e0dfe8b4..1403cf16fa61 100644 --- a/kernel/memremap.c +++ b/kernel/memremap.c @@ -11,7 +11,6 @@ * General Public License for more details. */ #include -#include #include #include #include @@ -500,3 +499,27 @@ struct vmem_altmap *to_vmem_altmap(unsigned long memmap_start) return pgmap ? pgmap->altmap : NULL; } #endif /* CONFIG_ZONE_DEVICE */ + + +#ifdef CONFIG_DEVICE_PRIVATE +void put_zone_device_private_page(struct page *page) +{ + int count = page_ref_dec_return(page); + + /* + * If refcount is 1 then page is freed and refcount is stable as nobody + * holds a reference on the page. + */ + if (count == 1) { + /* Clear Active bit in case of parallel mark_page_accessed */ + __ClearPageActive(page); + __ClearPageWaiters(page); + + page->mapping = NULL; + + page->pgmap->page_free(page, page->pgmap->data); + } else if (!count) + __put_page(page); +} +EXPORT_SYMBOL(put_zone_device_private_page); +#endif /* CONFIG_DEVICE_PRIVATE */ diff --git a/mm/hmm.c b/mm/hmm.c index f6c745b9a25a..3c6265d4254b 100644 --- a/mm/hmm.c +++ b/mm/hmm.c @@ -25,9 +25,17 @@ #include #include #include +#include #include +/* + * Device private memory see HMM (Documentation/vm/hmm.txt) or hmm.h + */ +DEFINE_STATIC_KEY_FALSE(device_private_key); +EXPORT_SYMBOL(device_private_key); + + #ifdef CONFIG_HMM static const struct mmu_notifier_ops hmm_mmu_notifier_ops;