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Shutemov" , Michal Hocko , Mike Kravetz , Shuah Khan , Vlastimil Babka , Matthew Wilcox , , , , , , LKML , John Hubbard , "Kirill A . Shutemov" Subject: [PATCH v6 03/12] mm: introduce page_ref_sub_return() Date: Mon, 10 Feb 2020 16:15:27 -0800 Message-ID: <20200211001536.1027652-4-jhubbard@nvidia.com> X-Mailer: git-send-email 2.25.0 In-Reply-To: <20200211001536.1027652-1-jhubbard@nvidia.com> References: <20200211001536.1027652-1-jhubbard@nvidia.com> MIME-Version: 1.0 X-NVConfidentiality: public DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1581380075; bh=Q5fLaghgFbabRh4AhaE8eo4PFQNGOCfHUCuIQWHMtww=; h=X-PGP-Universal:From:To:CC:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:X-NVConfidentiality: Content-Transfer-Encoding:Content-Type; b=E4saXd/rsLx1Jd/Hqpfy2VR1S/vr6n2rRE1yCnca9yyLBq3F/vV2Uet6L0Qye+uny KskQcpVdF+AdJ+aBTiA76vt9on1GhUmtZ/Yor21Z4R5H4hlfmezMPLqM7E25P+s671 cmmX3OaOw0WDUhKOEo0U0jtUnUlP6JPfrSXPqGjjTwLdNo90pH6CBuxc2qNtKlsM1X 1m5Pu0ViUqfmn/8U6Vqlw/EnO0zebRmhN7fZrn8sfVJXJv08CjeAEu+RFaEPCVYhLQ XF0F2/tQt6EJyet8TXxIxsHCwyYLKXvCCEyG2wV+VjoRJaF5eKMH3ao9VPkV4HBQNS ZxLBFKa29DTig== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: An upcoming patch requires subtracting a large chunk of refcounts from a page, and checking what the resulting refcount is. This is a little different than the usual "check for zero refcount" that many of the page ref functions already do. However, it is similar to a few other routines that (like this one) are generally useful for things such as 1-based refcounting. Add page_ref_sub_return(), that subtracts a chunk of refcounts atomically, and returns an atomic snapshot of the result. Reviewed-by: Jan Kara Acked-by: Kirill A. Shutemov Signed-off-by: John Hubbard --- include/linux/page_ref.h | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/include/linux/page_ref.h b/include/linux/page_ref.h index 14d14beb1f7f..d27701199a4d 100644 --- a/include/linux/page_ref.h +++ b/include/linux/page_ref.h @@ -102,6 +102,15 @@ static inline void page_ref_sub(struct page *page, int nr) __page_ref_mod(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(__tracepoint_page_ref_mod_and_return)) + __page_ref_mod_and_return(page, -nr, ret); + return ret; +} + static inline void page_ref_inc(struct page *page) { atomic_inc(&page->_refcount);