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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1FD3EEE4996 for ; Mon, 21 Aug 2023 14:26:11 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id AAD558E0010; Mon, 21 Aug 2023 10:26:10 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A5DF18E0006; Mon, 21 Aug 2023 10:26:10 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 925618E0010; Mon, 21 Aug 2023 10:26:10 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 831138E0006 for ; Mon, 21 Aug 2023 10:26:10 -0400 (EDT) Received: from smtpin26.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 414D9140C7F for ; Mon, 21 Aug 2023 14:26:10 +0000 (UTC) X-FDA: 81148336500.26.3C5BCCA Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf29.hostedemail.com (Postfix) with ESMTP id 9ED8C120011 for ; Mon, 21 Aug 2023 14:26:08 +0000 (UTC) Authentication-Results: imf29.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=Ob3wf54j; spf=none (imf29.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1692627968; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=VBLWbhiJ5Y+LfXHbB2wVDfY3nQIzq6btaVbaMioHfUU=; b=y/HqgYqhPBWyk9pT69LzW5W9Lf/rZtp0mRvbIM7uyVLSPjokJd2HRluV1sEQzksYxYTQAS 7Q5rhtPiAtg0CD8+HPkT1lAzLtF4TS0xSq9T6QVUNMCFfGkw1VUTto8I775sV944a76xwP qVN9t/FC686jBaVP0/pgU4OsU4tFhdY= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1692627968; a=rsa-sha256; cv=none; b=LvJNYKa2BFd6IBDaZ0TMnOZl2dW3FTFv7uXsBg2/glzWPX07M/U2KQfPCEMHTF7xF8fwNE vhODrHdNI48nJuj37nlI6X9Q6q6+a6KlEF5zioLdpC4ehobGveffceZsPq7OGT8N5sGZDL +087PWQ1rfYpgUA4fmeaCXVyODi/x1I= ARC-Authentication-Results: i=1; imf29.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=Ob3wf54j; spf=none (imf29.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org; dmarc=none DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=VBLWbhiJ5Y+LfXHbB2wVDfY3nQIzq6btaVbaMioHfUU=; b=Ob3wf54jrst6pqEm8LXcrMnm9m zF7UTAPg+4G/Z5X/gaXsOzPf8/oPTBEWz7UZaZpozdHcPyh6WMpbkSp/NnhWspC2e246EiVEkjRLu d3r7s09NuEB8Dzoy+YQ6SoiraRD8K64+WiEeWNAcaI+BDL6Zjqsfy32mpPbM7Ey+s3JKw4YnuH0rI yxCGVA86DMQPQD/4plE7ar23F5o6tS5xMrhF41ovILa9yv/Ro1TbOpb/vfms/cgwecRF2N8Mt/v0B +JDa9sUH+GMEPdmmz6EU1+XUSOYsC4qneL7wNd5mx3dBA0dplXzyTpv9rJoKsObtBWZB73hH/XH+m LoJI12zg==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1qY5qs-00AgPo-1d; Mon, 21 Aug 2023 14:25:54 +0000 Date: Mon, 21 Aug 2023 15:25:53 +0100 From: Matthew Wilcox To: Anastasia Belova Cc: Johannes Weiner , Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , Andrew Morton , Vladimir Davydov , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, lvc-project@linuxtesting.org Subject: Re: [PATCH] mm: memcomtrol: add warning in case of rtpn = NULL Message-ID: References: <20230821142051.31889-1-abelova@astralinux.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230821142051.31889-1-abelova@astralinux.ru> X-Stat-Signature: ishqsqfhraux5rdrs714ofwxx13s8y73 X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 9ED8C120011 X-Rspam-User: X-HE-Tag: 1692627968-921657 X-HE-Meta: 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 e+pVUq5/ wO8hOEaDzReunWdnvxyxbDoSsvQDQaIQnHp5SMnybBw1lT+u/WWPQj8E1rDkLBMx4usMo1dH980j6C3ToKqkh1r7TH+5HfjI1yMbhTr7oMJII0/cKDvDPu3oI/ldoNFPDekkQlAHiRnp5xVkXfz6C+db7u28mINRuE8Cst095L9d8qKjQHkl6XTpPpkTGxDIr2hIvC3uFukUwglUYbd5mqUCjlw== 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, Aug 21, 2023 at 05:20:51PM +0300, Anastasia Belova wrote: > kzalloc_node may return NULL. So rtpn should be > checked before dereference in mem_cgroup_init. What good will this do? > > rtpn = kzalloc_node(sizeof(*rtpn), GFP_KERNEL, node); > + WARN_ON(!rtpn); > > rtpn->rb_root = RB_ROOT; so you'll get a warning right before you get a crash, which will provide exactly the same information. And you'd already have a warning that the memory allocation had failed (because __GFP_NOWARN wasn't set). So you've increased the amount of data from 2 dumps to 3 without providing any neww information. If you _did_ something to avoid the crash, there might be a point to this, but the fact is that small GFP_KERNEL allocations _don't_ fail. You need to teach your tool that, or you'll be overwhelmed with false positives.