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