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Diffstat (limited to 'include/linux/page_ref.h')
-rw-r--r-- | include/linux/page_ref.h | 344 |
1 files changed, 344 insertions, 0 deletions
diff --git a/include/linux/page_ref.h b/include/linux/page_ref.h new file mode 100644 index 000000000..2e677e6ad --- /dev/null +++ b/include/linux/page_ref.h @@ -0,0 +1,344 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _LINUX_PAGE_REF_H +#define _LINUX_PAGE_REF_H + +#include <linux/atomic.h> +#include <linux/mm_types.h> +#include <linux/page-flags.h> +#include <linux/tracepoint-defs.h> + +DECLARE_TRACEPOINT(page_ref_set); +DECLARE_TRACEPOINT(page_ref_mod); +DECLARE_TRACEPOINT(page_ref_mod_and_test); +DECLARE_TRACEPOINT(page_ref_mod_and_return); +DECLARE_TRACEPOINT(page_ref_mod_unless); +DECLARE_TRACEPOINT(page_ref_freeze); +DECLARE_TRACEPOINT(page_ref_unfreeze); + +#ifdef CONFIG_DEBUG_PAGE_REF + +/* + * Ideally we would want to use the trace_<tracepoint>_enabled() helper + * functions. But due to include header file issues, that is not + * feasible. Instead we have to open code the static key functions. + * + * See trace_##name##_enabled(void) in include/linux/tracepoint.h + */ +#define page_ref_tracepoint_active(t) tracepoint_enabled(t) + +extern void __page_ref_set(struct page *page, int v); +extern void __page_ref_mod(struct page *page, int v); +extern void __page_ref_mod_and_test(struct page *page, int v, int ret); +extern void __page_ref_mod_and_return(struct page *page, int v, int ret); +extern void __page_ref_mod_unless(struct page *page, int v, int u); +extern void __page_ref_freeze(struct page *page, int v, int ret); +extern void __page_ref_unfreeze(struct page *page, int v); + +#else + +#define page_ref_tracepoint_active(t) false + +static inline void __page_ref_set(struct page *page, int v) +{ +} +static inline void __page_ref_mod(struct page *page, int v) +{ +} +static inline void __page_ref_mod_and_test(struct page *page, int v, int ret) +{ +} +static inline void __page_ref_mod_and_return(struct page *page, int v, int ret) +{ +} +static inline void __page_ref_mod_unless(struct page *page, int v, int u) +{ +} +static inline void __page_ref_freeze(struct page *page, int v, int ret) +{ +} +static inline void __page_ref_unfreeze(struct page *page, int v) +{ +} + +#endif + +static inline int page_ref_count(const struct page *page) +{ + return atomic_read(&page->_refcount); +} + +/** + * folio_ref_count - The reference count on this folio. + * @folio: The folio. + * + * The refcount is usually incremented by calls to folio_get() and + * decremented by calls to folio_put(). Some typical users of the + * folio refcount: + * + * - Each reference from a page table + * - The page cache + * - Filesystem private data + * - The LRU list + * - Pipes + * - Direct IO which references this page in the process address space + * + * Return: The number of references to this folio. + */ +static inline int folio_ref_count(const struct folio *folio) +{ + return page_ref_count(&folio->page); +} + +static inline int page_count(const struct page *page) +{ + return folio_ref_count(page_folio(page)); +} + +static inline void set_page_count(struct page *page, int v) +{ + atomic_set(&page->_refcount, v); + if (page_ref_tracepoint_active(page_ref_set)) + __page_ref_set(page, v); +} + +static inline void folio_set_count(struct folio *folio, int v) +{ + set_page_count(&folio->page, v); +} + +/* + * Setup the page count before being freed into the page allocator for + * the first time (boot or memory hotplug) + */ +static inline void init_page_count(struct page *page) +{ + set_page_count(page, 1); +} + +static inline void page_ref_add(struct page *page, int nr) +{ + atomic_add(nr, &page->_refcount); + if (page_ref_tracepoint_active(page_ref_mod)) + __page_ref_mod(page, nr); +} + +static inline void folio_ref_add(struct folio *folio, int nr) +{ + page_ref_add(&folio->page, nr); +} + +static inline void page_ref_sub(struct page *page, int nr) +{ + atomic_sub(nr, &page->_refcount); + if (page_ref_tracepoint_active(page_ref_mod)) + __page_ref_mod(page, -nr); +} + +static inline void folio_ref_sub(struct folio *folio, int nr) +{ + page_ref_sub(&folio->page, nr); +} + +static inline int page_ref_sub_return(struct page *page, int nr) +{ + int ret = atomic_sub_return(nr, &page->_refcount); + + if (page_ref_tracepoint_active(page_ref_mod_and_return)) + __page_ref_mod_and_return(page, -nr, ret); + return ret; +} + +static inline int folio_ref_sub_return(struct folio *folio, int nr) +{ + return page_ref_sub_return(&folio->page, nr); +} + +static inline void page_ref_inc(struct page *page) +{ + atomic_inc(&page->_refcount); + if (page_ref_tracepoint_active(page_ref_mod)) + __page_ref_mod(page, 1); +} + +static inline void folio_ref_inc(struct folio *folio) +{ + page_ref_inc(&folio->page); +} + +static inline void page_ref_dec(struct page *page) +{ + atomic_dec(&page->_refcount); + if (page_ref_tracepoint_active(page_ref_mod)) + __page_ref_mod(page, -1); +} + +static inline void folio_ref_dec(struct folio *folio) +{ + page_ref_dec(&folio->page); +} + +static inline int page_ref_sub_and_test(struct page *page, int nr) +{ + int ret = atomic_sub_and_test(nr, &page->_refcount); + + if (page_ref_tracepoint_active(page_ref_mod_and_test)) + __page_ref_mod_and_test(page, -nr, ret); + return ret; +} + +static inline int folio_ref_sub_and_test(struct folio *folio, int nr) +{ + return page_ref_sub_and_test(&folio->page, nr); +} + +static inline int page_ref_inc_return(struct page *page) +{ + int ret = atomic_inc_return(&page->_refcount); + + if (page_ref_tracepoint_active(page_ref_mod_and_return)) + __page_ref_mod_and_return(page, 1, ret); + return ret; +} + +static inline int folio_ref_inc_return(struct folio *folio) +{ + return page_ref_inc_return(&folio->page); +} + +static inline int page_ref_dec_and_test(struct page *page) +{ + int ret = atomic_dec_and_test(&page->_refcount); + + if (page_ref_tracepoint_active(page_ref_mod_and_test)) + __page_ref_mod_and_test(page, -1, ret); + return ret; +} + +static inline int folio_ref_dec_and_test(struct folio *folio) +{ + return page_ref_dec_and_test(&folio->page); +} + +static inline int page_ref_dec_return(struct page *page) +{ + int ret = atomic_dec_return(&page->_refcount); + + if (page_ref_tracepoint_active(page_ref_mod_and_return)) + __page_ref_mod_and_return(page, -1, ret); + return ret; +} + +static inline int folio_ref_dec_return(struct folio *folio) +{ + return page_ref_dec_return(&folio->page); +} + +static inline bool page_ref_add_unless(struct page *page, int nr, int u) +{ + bool ret = atomic_add_unless(&page->_refcount, nr, u); + + if (page_ref_tracepoint_active(page_ref_mod_unless)) + __page_ref_mod_unless(page, nr, ret); + return ret; +} + +static inline bool folio_ref_add_unless(struct folio *folio, int nr, int u) +{ + return page_ref_add_unless(&folio->page, nr, u); +} + +/** + * folio_try_get - Attempt to increase the refcount on a folio. + * @folio: The folio. + * + * If you do not already have a reference to a folio, you can attempt to + * get one using this function. It may fail if, for example, the folio + * has been freed since you found a pointer to it, or it is frozen for + * the purposes of splitting or migration. + * + * Return: True if the reference count was successfully incremented. + */ +static inline bool folio_try_get(struct folio *folio) +{ + return folio_ref_add_unless(folio, 1, 0); +} + +static inline bool folio_ref_try_add_rcu(struct folio *folio, int count) +{ +#ifdef CONFIG_TINY_RCU + /* + * The caller guarantees the folio will not be freed from interrupt + * context, so (on !SMP) we only need preemption to be disabled + * and TINY_RCU does that for us. + */ +# ifdef CONFIG_PREEMPT_COUNT + VM_BUG_ON(!in_atomic() && !irqs_disabled()); +# endif + VM_BUG_ON_FOLIO(folio_ref_count(folio) == 0, folio); + folio_ref_add(folio, count); +#else + if (unlikely(!folio_ref_add_unless(folio, count, 0))) { + /* Either the folio has been freed, or will be freed. */ + return false; + } +#endif + return true; +} + +/** + * folio_try_get_rcu - Attempt to increase the refcount on a folio. + * @folio: The folio. + * + * This is a version of folio_try_get() optimised for non-SMP kernels. + * If you are still holding the rcu_read_lock() after looking up the + * page and know that the page cannot have its refcount decreased to + * zero in interrupt context, you can use this instead of folio_try_get(). + * + * Example users include get_user_pages_fast() (as pages are not unmapped + * from interrupt context) and the page cache lookups (as pages are not + * truncated from interrupt context). We also know that pages are not + * frozen in interrupt context for the purposes of splitting or migration. + * + * You can also use this function if you're holding a lock that prevents + * pages being frozen & removed; eg the i_pages lock for the page cache + * or the mmap_sem or page table lock for page tables. In this case, + * it will always succeed, and you could have used a plain folio_get(), + * but it's sometimes more convenient to have a common function called + * from both locked and RCU-protected contexts. + * + * Return: True if the reference count was successfully incremented. + */ +static inline bool folio_try_get_rcu(struct folio *folio) +{ + return folio_ref_try_add_rcu(folio, 1); +} + +static inline int page_ref_freeze(struct page *page, int count) +{ + int ret = likely(atomic_cmpxchg(&page->_refcount, count, 0) == count); + + if (page_ref_tracepoint_active(page_ref_freeze)) + __page_ref_freeze(page, count, ret); + return ret; +} + +static inline int folio_ref_freeze(struct folio *folio, int count) +{ + return page_ref_freeze(&folio->page, count); +} + +static inline void page_ref_unfreeze(struct page *page, int count) +{ + VM_BUG_ON_PAGE(page_count(page) != 0, page); + VM_BUG_ON(count == 0); + + atomic_set_release(&page->_refcount, count); + if (page_ref_tracepoint_active(page_ref_unfreeze)) + __page_ref_unfreeze(page, count); +} + +static inline void folio_ref_unfreeze(struct folio *folio, int count) +{ + page_ref_unfreeze(&folio->page, count); +} +#endif |