From patchwork Wed Jan 29 03:24:10 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: John Hubbard X-Patchwork-Id: 208868 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.9 required=3.0 tests=DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C755AC35240 for ; Wed, 29 Jan 2020 03:24:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9F9C92468E for ; Wed, 29 Jan 2020 03:24:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=nvidia.com header.i=@nvidia.com header.b="E3c5QEyG" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726823AbgA2DYX (ORCPT ); Tue, 28 Jan 2020 22:24:23 -0500 Received: from hqnvemgate24.nvidia.com ([216.228.121.143]:6362 "EHLO hqnvemgate24.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726820AbgA2DYX (ORCPT ); Tue, 28 Jan 2020 22:24:23 -0500 Received: from hqpgpgate102.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate24.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Tue, 28 Jan 2020 19:23:29 -0800 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate102.nvidia.com (PGP Universal service); Tue, 28 Jan 2020 19:24:19 -0800 X-PGP-Universal: processed; by hqpgpgate102.nvidia.com on Tue, 28 Jan 2020 19:24:19 -0800 Received: from HQMAIL107.nvidia.com (172.20.187.13) by HQMAIL101.nvidia.com (172.20.187.10) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Wed, 29 Jan 2020 03:24:19 +0000 Received: from hqnvemgw03.nvidia.com (10.124.88.68) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1473.3 via Frontend Transport; Wed, 29 Jan 2020 03:24:19 +0000 Received: from blueforge.nvidia.com (Not Verified[10.110.48.28]) by hqnvemgw03.nvidia.com with Trustwave SEG (v7, 5, 8, 10121) id ; Tue, 28 Jan 2020 19:24:18 -0800 From: John Hubbard To: Andrew Morton CC: Al Viro , Christoph Hellwig , Dan Williams , Dave Chinner , Ira Weiny , Jan Kara , Jason Gunthorpe , Jonathan Corbet , =?utf-8?b?SsOpcsO0bWUgR2xp?= =?utf-8?q?sse?= , "Kirill A . Shutemov" , Michal Hocko , Mike Kravetz , Shuah Khan , Vlastimil Babka , , , , , , LKML , John Hubbard Subject: [PATCH v2 1/8] mm: dump_page: print head page's refcount, for compound pages Date: Tue, 28 Jan 2020 19:24:10 -0800 Message-ID: <20200129032417.3085670-2-jhubbard@nvidia.com> X-Mailer: git-send-email 2.25.0 In-Reply-To: <20200129032417.3085670-1-jhubbard@nvidia.com> References: <20200129032417.3085670-1-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=1580268209; bh=P1TeODLKtRur5z7N4mKfBv38jAYvtdOaySoL8r08WIg=; 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=E3c5QEyGx95NN96IE5SjKIfekR44Kiz+3iLIw4qlBA+LpbSooYT0An9LHX6XD6yl4 7lXKNT/kQg8YCcnJmYPOse8qK2L5jU8GMbzDsJ5WhQhpVzoarZvejOPeDSNh67wMcQ hhPTwYPCvGm+OytsPAfw0evq9Lg0XgniczwV2eLW6M6FblnpHUvbCcwtJzhu2nPfuq KZMCTpM8R/TZXtYInxwDY4PQVS0KggBcsXut4esMIK1IpOqrkG0AFWn1oyIHFG6HgV oVgZsqQFU53ImQs7VGD18/+8URzEUhFO6Z663+sFH9Q7FNr95JNFeu5iWQeAs6fJV+ IyukOqyF+pdQg== Sender: linux-kselftest-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org When debugging a problem that involves compound pages, it is extremely helpful if dump_page() reports not only the page->_refcount, but also the refcount of the head page of the compound page. That's because the head page collects refcounts for the entire compound page. Therefore, enhance dump_page() so as to print out the refcount of the head page of a compound page. This approach (printing information about a struct page that is not the struct page that was passed into dump_page()) has a precedent: compound_mapcount is already being printed. Signed-off-by: John Hubbard --- mm/debug.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/mm/debug.c b/mm/debug.c index a90da5337c14..4cc6cad8385d 100644 --- a/mm/debug.c +++ b/mm/debug.c @@ -76,9 +76,11 @@ void __dump_page(struct page *page, const char *reason) mapcount = PageSlab(page) ? 0 : page_mapcount(page); if (PageCompound(page)) - pr_warn("page:%px refcount:%d mapcount:%d mapping:%px " - "index:%#lx compound_mapcount: %d\n", - page, page_ref_count(page), mapcount, + pr_warn("page:%px refcount:%d head refcount:%d " + "mapcount:%d mapping:%px index:%#lx " + "compound_mapcount:%d\n", + page, page_ref_count(page), + page_ref_count(compound_head(page)), mapcount, page->mapping, page_to_pgoff(page), compound_mapcount(page)); else