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Shutemov" , Michal Hocko , Mike Kravetz , Shuah Khan , Vlastimil Babka , Matthew Wilcox , , , , , , LKML , John Hubbard Subject: [PATCH v4 04/12] mm: introduce page_ref_sub_return() Date: Tue, 4 Feb 2020 15:41:09 -0800 Message-ID: <20200204234117.2974687-5-jhubbard@nvidia.com> X-Mailer: git-send-email 2.25.0 In-Reply-To: <20200204234117.2974687-1-jhubbard@nvidia.com> References: <20200204234117.2974687-1-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=1580859666; bh=eGaNN16zOGlpqgBYnD+qS5CoX6lMktFz46tjMpWu0K4=; 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=m3DL424ceOUdqPIcEv4fvFteh7CP3YVJXATD1jE4kBe/uqOBlVoeMZJnpG54qLPqi LS4h54t2eUR+P11uvSih3VuwVd8jf/B3Q+TI7dbaEIcsJIx5Kxlxek9hX7M58hkiiw N43uwtFs4tgl/n63rhFntpjRP3ZeMlMhhV67NNMOMpB0SEUf3HKSWTHQWFhdWEXB6+ HQ/jrVmgnB0jGlJ9rU0cDt3U1cux8KoQIFdR0rUDFYkYVppvb1SfSPFVV/eUdzK4TX Zs7wDNjspwR6vj9vWmJaedKN3dBZdkBEI/G/hcY6nprBOuCdgCq7vrZqv1IxOMEb+S mLC9EgDmYvetw== 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. Signed-off-by: John Hubbard Reviewed-by: Jan Kara --- 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..a0e171265b79 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)) + __page_ref_mod_and_return(page, -nr, ret); + return ret; +} + static inline void page_ref_inc(struct page *page) { atomic_inc(&page->_refcount);