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[2003:dc:6f01:900:230:64ff:fe74:809]) by smtp.gmail.com with ESMTPSA id co18-20020a0560000a1200b0033d4c3b0beesm15044920wrb.19.2024.02.22.03.51.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 22 Feb 2024 03:51:09 -0800 (PST) From: Max Kellermann To: akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: willy@infradead.org, Max Kellermann Subject: [PATCH v2 09/14] linux/mm.h: move usage count functions to mm/folio_usage.h Date: Thu, 22 Feb 2024 12:50:50 +0100 Message-Id: <20240222115055.1172877-10-max.kellermann@ionos.com> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20240222115055.1172877-1-max.kellermann@ionos.com> References: <20240222115055.1172877-1-max.kellermann@ionos.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1791599949910308855 X-GMAIL-MSGID: 1791599949910308855 Prepare to reduce dependencies on linux/mm.h. This new header contains wrappers for the low-level functions from page_ref.h. By having those higher-level functions in a separate header, we can avoid their additional dependencies in the page_ref.h. Having these in a separate header will allow eliminating the dependency on linux/mm.h from these headers: - linux/skbuff.h - linux/swap.h Signed-off-by: Max Kellermann --- include/linux/mm.h | 168 +------------------------------ include/linux/mm/folio_usage.h | 177 +++++++++++++++++++++++++++++++++ 2 files changed, 178 insertions(+), 167 deletions(-) create mode 100644 include/linux/mm/folio_usage.h diff --git a/include/linux/mm.h b/include/linux/mm.h index 7a302da7de24..0dc38017e134 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -4,6 +4,7 @@ #include #include +#include #include #include #include @@ -1058,51 +1059,6 @@ struct inode; #include -/* - * Methods to modify the page usage count. - * - * What counts for a page usage: - * - cache mapping (page->mapping) - * - private data (page->private) - * - page mapped in a task's page tables, each mapping - * is counted separately - * - * Also, many kernel routines increase the page count before a critical - * routine so they can be sure the page doesn't go away from under them. - */ - -/* - * Drop a ref, return true if the refcount fell to zero (the page has no users) - */ -static inline int put_page_testzero(struct page *page) -{ - VM_BUG_ON_PAGE(page_ref_count(page) == 0, page); - return page_ref_dec_and_test(page); -} - -static inline int folio_put_testzero(struct folio *folio) -{ - return put_page_testzero(&folio->page); -} - -/* - * Try to grab a ref unless the page has a refcount of zero, return false if - * that is the case. - * This can be called when MMU is off so it must not access - * any of the virtual mappings. - */ -static inline bool get_page_unless_zero(struct page *page) -{ - return page_ref_add_unless(page, 1, 0); -} - -static inline struct folio *folio_get_nontail_page(struct page *page) -{ - if (unlikely(!get_page_unless_zero(page))) - return NULL; - return (struct folio *)page; -} - extern int page_is_ram(unsigned long pfn); enum { @@ -1258,8 +1214,6 @@ static inline struct folio *virt_to_folio(const void *x) return page_folio(page); } -void __folio_put(struct folio *folio); - void put_pages_list(struct list_head *pages); void split_page(struct page *page, unsigned int order); @@ -1350,126 +1304,6 @@ vm_fault_t finish_fault(struct vm_fault *vmf); * back into memory. */ -/* 127: arbitrary random number, small enough to assemble well */ -#define folio_ref_zero_or_close_to_overflow(folio) \ - ((unsigned int) folio_ref_count(folio) + 127u <= 127u) - -/** - * folio_get - Increment the reference count on a folio. - * @folio: The folio. - * - * Context: May be called in any context, as long as you know that - * you have a refcount on the folio. If you do not already have one, - * folio_try_get() may be the right interface for you to use. - */ -static inline void folio_get(struct folio *folio) -{ - VM_BUG_ON_FOLIO(folio_ref_zero_or_close_to_overflow(folio), folio); - folio_ref_inc(folio); -} - -static inline void get_page(struct page *page) -{ - folio_get(page_folio(page)); -} - -static inline __must_check bool try_get_page(struct page *page) -{ - page = compound_head(page); - if (WARN_ON_ONCE(page_ref_count(page) <= 0)) - return false; - page_ref_inc(page); - return true; -} - -/** - * folio_put - Decrement the reference count on a folio. - * @folio: The folio. - * - * If the folio's reference count reaches zero, the memory will be - * released back to the page allocator and may be used by another - * allocation immediately. Do not access the memory or the struct folio - * after calling folio_put() unless you can be sure that it wasn't the - * last reference. - * - * Context: May be called in process or interrupt context, but not in NMI - * context. May be called while holding a spinlock. - */ -static inline void folio_put(struct folio *folio) -{ - if (folio_put_testzero(folio)) - __folio_put(folio); -} - -/** - * folio_put_refs - Reduce the reference count on a folio. - * @folio: The folio. - * @refs: The amount to subtract from the folio's reference count. - * - * If the folio's reference count reaches zero, the memory will be - * released back to the page allocator and may be used by another - * allocation immediately. Do not access the memory or the struct folio - * after calling folio_put_refs() unless you can be sure that these weren't - * the last references. - * - * Context: May be called in process or interrupt context, but not in NMI - * context. May be called while holding a spinlock. - */ -static inline void folio_put_refs(struct folio *folio, int refs) -{ - if (folio_ref_sub_and_test(folio, refs)) - __folio_put(folio); -} - -/* - * union release_pages_arg - an array of pages or folios - * - * release_pages() releases a simple array of multiple pages, and - * accepts various different forms of said page array: either - * a regular old boring array of pages, an array of folios, or - * an array of encoded page pointers. - * - * The transparent union syntax for this kind of "any of these - * argument types" is all kinds of ugly, so look away. - */ -typedef union { - struct page **pages; - struct folio **folios; - struct encoded_page **encoded_pages; -} release_pages_arg __attribute__ ((__transparent_union__)); - -void release_pages(release_pages_arg, int nr); - -/** - * folios_put - Decrement the reference count on an array of folios. - * @folios: The folios. - * @nr: How many folios there are. - * - * Like folio_put(), but for an array of folios. This is more efficient - * than writing the loop yourself as it will optimise the locks which - * need to be taken if the folios are freed. - * - * Context: May be called in process or interrupt context, but not in NMI - * context. May be called while holding a spinlock. - */ -static inline void folios_put(struct folio **folios, unsigned int nr) -{ - release_pages(folios, nr); -} - -static inline void put_page(struct page *page) -{ - struct folio *folio = page_folio(page); - - /* - * For some devmap managed pages we need to catch refcount transition - * from 2 to 1: - */ - if (put_devmap_managed_page(&folio->page)) - return; - folio_put(folio); -} - /* * GUP_PIN_COUNTING_BIAS, and the associated functions that use it, overload * the page's refcount so that two separate items are tracked: the original page diff --git a/include/linux/mm/folio_usage.h b/include/linux/mm/folio_usage.h new file mode 100644 index 000000000000..2700e2ec4d78 --- /dev/null +++ b/include/linux/mm/folio_usage.h @@ -0,0 +1,177 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _LINUX_MM_FOLIO_USAGE_H +#define _LINUX_MM_FOLIO_USAGE_H + +#include // for put_devmap_managed_page() +#include // for VM_BUG_ON_PAGE() +#include // for struct folio +#include + +/* + * Methods to modify the page usage count. + * + * What counts for a page usage: + * - cache mapping (page->mapping) + * - private data (page->private) + * - page mapped in a task's page tables, each mapping + * is counted separately + * + * Also, many kernel routines increase the page count before a critical + * routine so they can be sure the page doesn't go away from under them. + */ + +/* + * Drop a ref, return true if the refcount fell to zero (the page has no users) + */ +static inline int put_page_testzero(struct page *page) +{ + VM_BUG_ON_PAGE(page_ref_count(page) == 0, page); + return page_ref_dec_and_test(page); +} + +static inline int folio_put_testzero(struct folio *folio) +{ + return put_page_testzero(&folio->page); +} + +/* + * Try to grab a ref unless the page has a refcount of zero, return false if + * that is the case. + * This can be called when MMU is off so it must not access + * any of the virtual mappings. + */ +static inline bool get_page_unless_zero(struct page *page) +{ + return page_ref_add_unless(page, 1, 0); +} + +static inline struct folio *folio_get_nontail_page(struct page *page) +{ + if (unlikely(!get_page_unless_zero(page))) + return NULL; + return (struct folio *)page; +} + +void __folio_put(struct folio *folio); + +/* 127: arbitrary random number, small enough to assemble well */ +#define folio_ref_zero_or_close_to_overflow(folio) \ + ((unsigned int) folio_ref_count(folio) + 127u <= 127u) + +/** + * folio_get - Increment the reference count on a folio. + * @folio: The folio. + * + * Context: May be called in any context, as long as you know that + * you have a refcount on the folio. If you do not already have one, + * folio_try_get() may be the right interface for you to use. + */ +static inline void folio_get(struct folio *folio) +{ + VM_BUG_ON_FOLIO(folio_ref_zero_or_close_to_overflow(folio), folio); + folio_ref_inc(folio); +} + +static inline void get_page(struct page *page) +{ + folio_get(page_folio(page)); +} + +static inline __must_check bool try_get_page(struct page *page) +{ + page = compound_head(page); + if (WARN_ON_ONCE(page_ref_count(page) <= 0)) + return false; + page_ref_inc(page); + return true; +} + +/** + * folio_put - Decrement the reference count on a folio. + * @folio: The folio. + * + * If the folio's reference count reaches zero, the memory will be + * released back to the page allocator and may be used by another + * allocation immediately. Do not access the memory or the struct folio + * after calling folio_put() unless you can be sure that it wasn't the + * last reference. + * + * Context: May be called in process or interrupt context, but not in NMI + * context. May be called while holding a spinlock. + */ +static inline void folio_put(struct folio *folio) +{ + if (folio_put_testzero(folio)) + __folio_put(folio); +} + +/** + * folio_put_refs - Reduce the reference count on a folio. + * @folio: The folio. + * @refs: The amount to subtract from the folio's reference count. + * + * If the folio's reference count reaches zero, the memory will be + * released back to the page allocator and may be used by another + * allocation immediately. Do not access the memory or the struct folio + * after calling folio_put_refs() unless you can be sure that these weren't + * the last references. + * + * Context: May be called in process or interrupt context, but not in NMI + * context. May be called while holding a spinlock. + */ +static inline void folio_put_refs(struct folio *folio, int refs) +{ + if (folio_ref_sub_and_test(folio, refs)) + __folio_put(folio); +} + +/* + * union release_pages_arg - an array of pages or folios + * + * release_pages() releases a simple array of multiple pages, and + * accepts various different forms of said page array: either + * a regular old boring array of pages, an array of folios, or + * an array of encoded page pointers. + * + * The transparent union syntax for this kind of "any of these + * argument types" is all kinds of ugly, so look away. + */ +typedef union { + struct page **pages; + struct folio **folios; + struct encoded_page **encoded_pages; +} release_pages_arg __attribute__ ((__transparent_union__)); + +void release_pages(release_pages_arg, int nr); + +/** + * folios_put - Decrement the reference count on an array of folios. + * @folios: The folios. + * @nr: How many folios there are. + * + * Like folio_put(), but for an array of folios. This is more efficient + * than writing the loop yourself as it will optimise the locks which + * need to be taken if the folios are freed. + * + * Context: May be called in process or interrupt context, but not in NMI + * context. May be called while holding a spinlock. + */ +static inline void folios_put(struct folio **folios, unsigned int nr) +{ + release_pages(folios, nr); +} + +static inline void put_page(struct page *page) +{ + struct folio *folio = page_folio(page); + + /* + * For some devmap managed pages we need to catch refcount transition + * from 2 to 1: + */ + if (put_devmap_managed_page(&folio->page)) + return; + folio_put(folio); +} + +#endif /* _LINUX_MM_FOLIO_USAGE_H */