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[209.85.208.177]) by smtp.gmail.com with ESMTPSA id q3sm1049053ljp.44.2021.07.16.13.12.18 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 16 Jul 2021 13:12:19 -0700 (PDT) Received: by mail-lj1-f177.google.com with SMTP id u25so15600149ljj.11 for ; Fri, 16 Jul 2021 13:12:18 -0700 (PDT) X-Received: by 2002:a2e:9a42:: with SMTP id k2mr10438095ljj.507.1626466338693; Fri, 16 Jul 2021 13:12:18 -0700 (PDT) MIME-Version: 1.0 References: <20210707175950.eceddb86c6c555555d4730e2@linux-foundation.org> <20210708010747.zIP9yxsci%akpm@linux-foundation.org> In-Reply-To: From: Linus Torvalds Date: Fri, 16 Jul 2021 13:12:02 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [patch 07/54] mm/slub: use stackdepot to save stack trace in objects To: Christoph Hellwig Cc: Andrew Morton , Christoph Lameter , glittao@gmail.com, Joonsoo Kim , Linux-MM , mm-commits@vger.kernel.org, Pekka Enberg , Randy Dunlap , David Rientjes , Vlastimil Babka , linux-xfs Content-Type: text/plain; charset="UTF-8" Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org On Fri, Jul 16, 2021 at 12:39 AM Christoph Hellwig wrote: > > This somewhat unexpectedly causes a crash when running the xfs/433 test > in xfstests for me. Reverting the commit fixes the problem: I don't see why that would be the case, but I'm inclined to revert that commit for another reason: the code doesn't seem to match the description of the commit. It used to be that CONFIG_SLUB_DEBUG was a config option that was harmless and that defaulted to 'y' because there was little downside. In fact, it's not just "default y", it doesn't even *ask* the user unless CONFIG_EXPERT is on. Because it was fairly harmless. And then SLOB_DEBUG_ON was that "do you actually want this code _enabled_". But now it basically force-enables that STACKDEPOT support too, and then instead of having an _optional_ CONFIG_STACKTRACE, you basically have that as being forced on you whether you want active debugging or not. Maybe that select STACKDEPOT if STACKTRACE_SUPPORT should have been select STACKDEPOT if STACKTRACE because i\t used to be that CONFIG_STACKTRACE was somewhat unusual, and only enabled for special debug cases (admittedly "CONFIG_TRACING" likely meant that it was fairly widely enabled). In contrast, STACKTRACE_SUPPORT is basically "this architecture supports it". So now it seems STACKDEPOT is enabled basically unconditionally. So I really don't see why it would cause that xfs issue, but I think there are multiple reasons to just go "Hmm" on that commit. Comments? Linus 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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 A89B8C12002 for ; Fri, 16 Jul 2021 20:12:24 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 4D12C613F6 for ; Fri, 16 Jul 2021 20:12:24 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4D12C613F6 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id BE2CB8D00F4; Fri, 16 Jul 2021 16:12:24 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B924A8D00EC; Fri, 16 Jul 2021 16:12:24 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A0C148D00F4; Fri, 16 Jul 2021 16:12:24 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0008.hostedemail.com [216.40.44.8]) by kanga.kvack.org (Postfix) with ESMTP id 7368A8D00EC for ; Fri, 16 Jul 2021 16:12:24 -0400 (EDT) Received: from smtpin21.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 4774E824556B for ; Fri, 16 Jul 2021 20:12:23 +0000 (UTC) X-FDA: 78369548166.21.557F496 Received: from mail-lj1-f181.google.com (mail-lj1-f181.google.com [209.85.208.181]) by imf17.hostedemail.com (Postfix) with ESMTP id EC323F00038D for ; Fri, 16 Jul 2021 20:12:22 +0000 (UTC) Received: by mail-lj1-f181.google.com with SMTP id q4so15589034ljp.13 for ; Fri, 16 Jul 2021 13:12:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=sU8WsVZyZL4hTLOJidVGlj9JhubqHLgGG7TU7feZ63c=; b=CF016SMMHT6vvFztAsO+fMbhe+DuyWrPpQs2mWC/vqeWtktS4fgo/7i0dSC7XnmlAD T83WSGPq/LMVpsuj9Subv0HZxyhc6LtaD8awgXFhmfAyAYCxiA/w7YdMhl8fjw5ZdXQh 2FYCKvmLPvrCnmLNoFYZcIVfpkihSFMaqsCL4= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=sU8WsVZyZL4hTLOJidVGlj9JhubqHLgGG7TU7feZ63c=; b=r5KzUNgZG+DwyaUcl7Od7C+RH4McQzF89LRdLKbj14HHB4OMAgVa7tWxWeVdlLgmaC 73Sv3Mv3CfFW0RcnWiRxjlkMW7IhdQZkBLEA9IuQmEk9+9/i7VCwWWU1pkgHNKq+KwGH zr1bim5EeAoSDKa7AvUjenln5mg32splEC5FNjeJenIlh7JkOz9jnaL726efatff2p6m sDzdeN/DGB3NYq0Y48GSZ+o3kr1oQDT0l5zQkcQ0icy5KeVmZyn0qxmQ6y24LZTVmMOC Rm1MJlsGaRdy/9oxgjSLXnXwayigXpaophoeCHE7xoqzVf4qv6RyfTNL/0dlTMsehFf3 fTRw== X-Gm-Message-State: AOAM532t5SLI7FhwDpRfgUBlwjXmb5yzgtSCV4Q2uctTRIqMxTmzI+uk iV5l9zsogON5lIhehyOKJzp0txRXktl0guv0 X-Google-Smtp-Source: ABdhPJxmvDCHZm84bqObrsTvzl4DETsVGQWXdbf9eRuyNTloUC+7YCe318fvXXM+7qQahPS9FO9xeg== X-Received: by 2002:a2e:9652:: with SMTP id z18mr10204066ljh.413.1626466341083; Fri, 16 Jul 2021 13:12:21 -0700 (PDT) Received: from mail-lj1-f178.google.com (mail-lj1-f178.google.com. [209.85.208.178]) by smtp.gmail.com with ESMTPSA id n5sm718332lft.139.2021.07.16.13.12.18 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 16 Jul 2021 13:12:19 -0700 (PDT) Received: by mail-lj1-f178.google.com with SMTP id e20so15631761ljn.8 for ; Fri, 16 Jul 2021 13:12:18 -0700 (PDT) X-Received: by 2002:a2e:9a42:: with SMTP id k2mr10438095ljj.507.1626466338693; Fri, 16 Jul 2021 13:12:18 -0700 (PDT) MIME-Version: 1.0 References: <20210707175950.eceddb86c6c555555d4730e2@linux-foundation.org> <20210708010747.zIP9yxsci%akpm@linux-foundation.org> In-Reply-To: From: Linus Torvalds Date: Fri, 16 Jul 2021 13:12:02 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [patch 07/54] mm/slub: use stackdepot to save stack trace in objects To: Christoph Hellwig Cc: Andrew Morton , Christoph Lameter , glittao@gmail.com, Joonsoo Kim , Linux-MM , mm-commits@vger.kernel.org, Pekka Enberg , Randy Dunlap , David Rientjes , Vlastimil Babka , linux-xfs Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: EC323F00038D X-Stat-Signature: 5umeywh99ot6dzxhdw3agwuyyur1pht1 Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=google header.b=CF016SMM; spf=pass (imf17.hostedemail.com: domain of torvalds@linuxfoundation.org designates 209.85.208.181 as permitted sender) smtp.mailfrom=torvalds@linuxfoundation.org; dmarc=none X-HE-Tag: 1626466342-338217 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 Fri, Jul 16, 2021 at 12:39 AM Christoph Hellwig wrote: > > This somewhat unexpectedly causes a crash when running the xfs/433 test > in xfstests for me. Reverting the commit fixes the problem: I don't see why that would be the case, but I'm inclined to revert that commit for another reason: the code doesn't seem to match the description of the commit. It used to be that CONFIG_SLUB_DEBUG was a config option that was harmless and that defaulted to 'y' because there was little downside. In fact, it's not just "default y", it doesn't even *ask* the user unless CONFIG_EXPERT is on. Because it was fairly harmless. And then SLOB_DEBUG_ON was that "do you actually want this code _enabled_". But now it basically force-enables that STACKDEPOT support too, and then instead of having an _optional_ CONFIG_STACKTRACE, you basically have that as being forced on you whether you want active debugging or not. Maybe that select STACKDEPOT if STACKTRACE_SUPPORT should have been select STACKDEPOT if STACKTRACE because i\t used to be that CONFIG_STACKTRACE was somewhat unusual, and only enabled for special debug cases (admittedly "CONFIG_TRACING" likely meant that it was fairly widely enabled). In contrast, STACKTRACE_SUPPORT is basically "this architecture supports it". So now it seems STACKDEPOT is enabled basically unconditionally. So I really don't see why it would cause that xfs issue, but I think there are multiple reasons to just go "Hmm" on that commit. Comments? Linus