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Shutemov" , Michal Hocko , "Mike Kravetz" , Shuah Khan , "Vlastimil Babka" , Matthew Wilcox , , , , , , LKML , John Hubbard Subject: [PATCH v5 04/12] mm: introduce page_ref_sub_return() Date: Thu, 6 Feb 2020 19:37:27 -0800 Message-ID: <20200207033735.308000-5-jhubbard@nvidia.com> X-Mailer: git-send-email 2.25.0 In-Reply-To: <20200207033735.308000-1-jhubbard@nvidia.com> References: <20200207033735.308000-1-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=1581046632; bh=DhMMWR0L+su36XhWVkaUTT8AIpyvoaCJ7tCBpQiPc3M=; 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=qCL7wJvyuAIwVgPSCBkxszuO0dlj80eWg/EDbClYxweQTRNHL+GTW+zK5ITf9LNig uRb9r+NQmOvLYXjHpxOGosNBSj7qAFzD1Gp/gXOyn3l/7Eqt4KN7cqUq1efOgufStl 7Bea1KDIgNa9pQWBFdc/LdEPKGUGmPWbDZMoxCXH+5lY5tU5TD64FzekAlyXNuUnXd Myo9xS52/un25I1eAeSv6b3cg81SSkeMiPJec39TyWWzQLsEdozMVBZqphrxjT7MNM jkW3BmWsPJ7q587TT4lIOdnmBBkxgFCDUucq88TsdGmsVVI9cKN0B+bb69YA/DJtdV 8Nhet+MSTrAig== 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 Signed-off-by: John Hubbard Acked-by: Kirill A. Shutemov --- 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);