From mboxrd@z Thu Jan 1 00:00:00 1970 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=-8.5 required=3.0 tests=INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham 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 7F760C433FF for ; Tue, 6 Aug 2019 08:36:10 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 3FBD5206A2 for ; Tue, 6 Aug 2019 08:36:10 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3FBD5206A2 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id C648F6B0003; Tue, 6 Aug 2019 04:36:09 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id C15CD6B0006; Tue, 6 Aug 2019 04:36:09 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B042F6B0269; Tue, 6 Aug 2019 04:36:09 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from mail-ed1-f69.google.com (mail-ed1-f69.google.com [209.85.208.69]) by kanga.kvack.org (Postfix) with ESMTP id 5D84B6B0003 for ; Tue, 6 Aug 2019 04:36:09 -0400 (EDT) Received: by mail-ed1-f69.google.com with SMTP id i9so53323101edr.13 for ; Tue, 06 Aug 2019 01:36:09 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-original-authentication-results:x-gm-message-state:date:from:to :cc:subject:message-id:references:mime-version:content-disposition :in-reply-to:user-agent; bh=usHodNDDdHnrrq29Ie86wdnv1GycZfA8HH8x6PHNn/I=; b=Dymw8c92XLRmAVh8t960vLRwhodeS6YtXYgv9uIcbEGbIcl1XPZOMFqKRWQPe0NY0E hhHk2xDlpKzMTQl6zjGpL0oW1K0yJFajXvrME0/7Dv3PrYKZ2YYzEmuQ49gkinMAWUHh POnNBwi0dVqh8cKymGzV9ikNbgtsVRWCF3gI+1t3AtyHN/ZZFr/6iOFfFqWQRQZy1c8G B7y7g7t27+ENpK0+8evUPVJTWMeKNMUIuefeS+Qnhdv+w7PpnarGKqNDAvb+hvyJxlCe pIRDmeufsj3QO3bMjEgeYDhOuZP7NQ3NR468eXdxZIbSN/ok8Xl2gxCrpYEB1M9/6ekQ lO1g== X-Original-Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) smtp.mailfrom=mhocko@kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=kernel.org X-Gm-Message-State: APjAAAWhbIjBuca7YHjA5NyCSqBfrgN1UiNmHcAhlJw5Yi/GW25Us97d DOxO2BF7t7TjBT8CH0BfgTUmYPu45K/DruYvpBD+ORTKRt5bZAUvE5i+fG52SIs5sLhkVf4Yb7Z NjN9OriKBxjfN82a4qLVO+YTzDKzfDlCTmdPgn7x3OIfTeMBiakxOwjB4P/65blk= X-Received: by 2002:a17:906:1916:: with SMTP id a22mr1938878eje.271.1565080568926; Tue, 06 Aug 2019 01:36:08 -0700 (PDT) X-Google-Smtp-Source: APXvYqzcbDuLYAVtcw3YnV0iWKbhvZLl/Usl2TIb9lL7sR/X1SGWP7mI589gJ7DXVIQAFoPyB9M9 X-Received: by 2002:a17:906:1916:: with SMTP id a22mr1938826eje.271.1565080568105; Tue, 06 Aug 2019 01:36:08 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1565080568; cv=none; d=google.com; s=arc-20160816; b=gDsN22uSJiNRu7HoPpyGIoLwqUCFAaETm+WPChv6Qa61/GvH5gr5vEnclpqhDbdpqd FOK/6eVtFiqHRN/rDsxlff9uLQBYnJeVeitWBR9wTuASOcY+pX9Iaa0+kdeP3oDgPQck tFD35lInHhFB2AFOpZByKu4ulAFnBBfUxn/I9cU35RNGBZT7OzYNwkRPQe/qObc/K8z2 S8zC9544/bOTb/R0DAR5pnZwsnRHJOlQkZsVCEx5BdB/Yi8fn0loIeTWnZyYM1GCcImj EMmoFkj0Lh02LlXDCWH4sX3Jz6wVp8H76kj+dA71XaTEXING8N7xb/B574mi/nAQ4qjV sy2g== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=user-agent:in-reply-to:content-disposition:mime-version:references :message-id:subject:cc:to:from:date; bh=usHodNDDdHnrrq29Ie86wdnv1GycZfA8HH8x6PHNn/I=; b=P4Gh2sYk0GkWCzyjHK1QL9Fkcx6szuQV/uOstCF5g17JwalefigjWzw3LRfRlKixTu 7zjzRO4Sd/OJHj5MHqWxJ4LTCOS79BIjiYudwbRVYvi66kjt92yC6IbneKv5DAxasyUe rrt09e4GGaD1qjCF27kFztTUcrFGnX2Jjig9l96/qMj7i8F6ct197HWppQksJMi7tpgf 4LPxGzYU8Ry0snKmBbXqg3JRr6vdVQbbeiBLQtSWWjzT49gI/hETaE3x9W9zwPuxsNu5 nRnJaFXfiQE0bov1JXosNDpF+MOKwJ95mo4KwLjuaGnTRa12Xnw9PFWIoZckpH0om9ZC t+sQ== ARC-Authentication-Results: i=1; mx.google.com; spf=softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) smtp.mailfrom=mhocko@kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=kernel.org Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id c45si31426833eda.303.2019.08.06.01.36.07 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 06 Aug 2019 01:36:08 -0700 (PDT) Received-SPF: softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) client-ip=195.135.220.15; Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) smtp.mailfrom=mhocko@kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=kernel.org X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 3ACB5ABC7; Tue, 6 Aug 2019 08:36:07 +0000 (UTC) Date: Tue, 6 Aug 2019 10:36:05 +0200 From: Michal Hocko To: Sai Praneeth Prakhya Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, dave.hansen@intel.com, Ingo Molnar , Vlastimil Babka , Peter Zijlstra , Andrew Morton , Anshuman Khandual Subject: Re: [PATCH V2] fork: Improve error message for corrupted page tables Message-ID: <20190806083605.GA19060@dhcp22.suse.cz> References: <3ef8a340deb1c87b725d44edb163073e2b6eca5a.1565059496.git.sai.praneeth.prakhya@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3ef8a340deb1c87b725d44edb163073e2b6eca5a.1565059496.git.sai.praneeth.prakhya@intel.com> User-Agent: Mutt/1.10.1 (2018-07-13) 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: On Mon 05-08-19 20:05:27, Sai Praneeth Prakhya wrote: > When a user process exits, the kernel cleans up the mm_struct of the user > process and during cleanup, check_mm() checks the page tables of the user > process for corruption (E.g: unexpected page flags set/cleared). For > corrupted page tables, the error message printed by check_mm() isn't very > clear as it prints the loop index instead of page table type (E.g: Resident > file mapping pages vs Resident shared memory pages). The loop index in > check_mm() is used to index rss_stat[] which represents individual memory > type stats. Hence, instead of printing index, print memory type, thereby > improving error message. > > Without patch: > -------------- > [ 204.836425] mm/pgtable-generic.c:29: bad p4d 0000000089eb4e92(800000025f941467) > [ 204.836544] BUG: Bad rss-counter state mm:00000000f75895ea idx:0 val:2 > [ 204.836615] BUG: Bad rss-counter state mm:00000000f75895ea idx:1 val:5 > [ 204.836685] BUG: non-zero pgtables_bytes on freeing mm: 20480 > > With patch: > ----------- > [ 69.815453] mm/pgtable-generic.c:29: bad p4d 0000000084653642(800000025ca37467) > [ 69.815872] BUG: Bad rss-counter state mm:00000000014a6c03 type:MM_FILEPAGES val:2 > [ 69.815962] BUG: Bad rss-counter state mm:00000000014a6c03 type:MM_ANONPAGES val:5 > [ 69.816050] BUG: non-zero pgtables_bytes on freeing mm: 20480 I like this. On any occasion I am investigating an issue with an rss inbalance I have to go back to kernel sources to see which pte type that is. > Also, change print function (from printk(KERN_ALERT, ..) to pr_alert()) so > that it matches the other print statement. good change as well. Maybe we should also lower the loglevel (in a separate patch) as well. While this is not nice because we are apparently leaking memory behind it shouldn't be really critical enough to jump on normal consoles. > Cc: Ingo Molnar > Cc: Vlastimil Babka > Cc: Peter Zijlstra > Cc: Andrew Morton > Cc: Anshuman Khandual > Acked-by: Dave Hansen > Suggested-by: Dave Hansen > Signed-off-by: Sai Praneeth Prakhya Acked-by: Michal Hocko > --- > > Changes from V1 to V2: > ---------------------- > 1. Move struct definition from header file to fork.c file, so that it won't be > included in every compilation unit. As this struct is used *only* in fork.c, > include the definition in fork.c itself. > 2. Index the struct to match respective macros. > 3. Mention about print function change in commit message. > > kernel/fork.c | 11 +++++++++-- > 1 file changed, 9 insertions(+), 2 deletions(-) > > diff --git a/kernel/fork.c b/kernel/fork.c > index d8ae0f1b4148..f34f441c50c0 100644 > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -125,6 +125,13 @@ int nr_threads; /* The idle threads do not count.. */ > > static int max_threads; /* tunable limit on nr_threads */ > > +static const char * const resident_page_types[NR_MM_COUNTERS] = { > + [MM_FILEPAGES] = "MM_FILEPAGES", > + [MM_ANONPAGES] = "MM_ANONPAGES", > + [MM_SWAPENTS] = "MM_SWAPENTS", > + [MM_SHMEMPAGES] = "MM_SHMEMPAGES", > +}; > + > DEFINE_PER_CPU(unsigned long, process_counts) = 0; > > __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ > @@ -649,8 +656,8 @@ static void check_mm(struct mm_struct *mm) > long x = atomic_long_read(&mm->rss_stat.count[i]); > > if (unlikely(x)) > - printk(KERN_ALERT "BUG: Bad rss-counter state " > - "mm:%p idx:%d val:%ld\n", mm, i, x); > + pr_alert("BUG: Bad rss-counter state mm:%p type:%s val:%ld\n", > + mm, resident_page_types[i], x); > } > > if (mm_pgtables_bytes(mm)) > -- > 2.7.4 -- Michal Hocko SUSE Labs