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Date: Sun, 16 Jan 2022 12:18:11 +0000 From: "Matthew Wilcox (Oracle)" <willy@...radead.org> To: linux-kernel@...r.kernel.org, linux-mm@...ck.org, linux-fsdevel@...r.kernel.org Cc: "Matthew Wilcox (Oracle)" <willy@...radead.org>, Christoph Hellwig <hch@....de>, John Hubbard <jhubbard@...dia.com>, Jason Gunthorpe <jgg@...dia.com>, William Kucharski <william.kucharski@...cle.com> Subject: [PATCH 01/12] mm: Add folio_put_refs() This is like folio_put(), but puts N references at once instead of just one. It's like put_page_refs(), but does one atomic operation instead of two, and is available to more than just gup.c. Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org> Reviewed-by: Christoph Hellwig <hch@....de> Reviewed-by: John Hubbard <jhubbard@...dia.com> Reviewed-by: Jason Gunthorpe <jgg@...dia.com> Reviewed-by: William Kucharski <william.kucharski@...cle.com> --- include/linux/mm.h | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) diff --git a/include/linux/mm.h b/include/linux/mm.h index c768a7c81b0b..cb98f75b245e 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1244,6 +1244,26 @@ static inline void folio_put(struct folio *folio) __put_page(&folio->page); } +/** + * 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)) + __put_page(&folio->page); +} + static inline void put_page(struct page *page) { struct folio *folio = page_folio(page); -- 2.34.1
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