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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 60186C32771 for ; Wed, 28 Sep 2022 05:16:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229846AbiI1FQu (ORCPT ); Wed, 28 Sep 2022 01:16:50 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48186 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231642AbiI1FQq (ORCPT ); Wed, 28 Sep 2022 01:16:46 -0400 Received: from mail-oa1-x33.google.com (mail-oa1-x33.google.com [IPv6:2001:4860:4864:20::33]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BAEBA127C9C for ; Tue, 27 Sep 2022 22:16:45 -0700 (PDT) Received: by mail-oa1-x33.google.com with SMTP id 586e51a60fabf-131a17bf7fdso1323637fac.3 for ; Tue, 27 Sep 2022 22:16:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=mime-version:message-id:subject:cc:to:from:date:from:to:cc:subject :date; bh=RRxMxuisd8lNkNGWBlf9ZKEk1omHCIF/OzgSnFJx1kM=; b=rp3aMO0gAAhK0s2GVDrsTX/gwBmv9vZ3TFYoRHevkUoy9MkVX+I1yOVHL2U+wScbD3 a4Iu0r7SxbTXEQwzbBoZotEQ4SXYXNn9iUmyFlUxqyCmRZN4Kbm2xqd6f6dFNjiPuyB3 jdUvgYFtYBIDqfDNZgg4N/aFo2WUQzp96+1+1PTKz7p9Qa9H86j2OxuffAhEqyzPvh3J I+BvstOwG6UAnBYqKE2CW9ZXw42ycTphdbRCqVp8/lewnvDIwfOHR1LyGlrrnA8Noqr7 KDmEIYBn6ZmUCKQBmbNp8Pczg76HqN9FdijVfr11GfCtPvQthYMEEnTlZ2ohWkIOiJ3C OXmQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=mime-version:message-id:subject:cc:to:from:date:x-gm-message-state :from:to:cc:subject:date; bh=RRxMxuisd8lNkNGWBlf9ZKEk1omHCIF/OzgSnFJx1kM=; b=Z6mvlyzbEBwIeK/M18fFYDAKS+sbluaey2sDCM7a1WAxM9/p5xVRSfnvVuNx22kRIR HlJ3a4pB0NTXgNHxnLZRtwhxMWVw3gZOV6EkWDFxwUkPQoPgEafh5TCUTCOCfumbQ9gN jfPLNTtB/EnykUXKi/SxAyLPqFXhg7bigVooTy3JVm5Cs4TZ/T9OMVrvN0YnK2zS+yHz 9atYcYu8dQumzbEUaGubGSZFqyn2a3uyRmv4IGJoglLZdf1ioGFOSe3wkeEXktdbuN06 JFGmwtxpiy9dJyBBVGsBQ4XZ4cBfeEedEumKZuNdXQhgjCD1GB4qhkfxRy/F8k9HbFVX t1qw== X-Gm-Message-State: ACrzQf3Mvl/RNGqdNTD49Ja1LIvb5+x8D+sqY7HOSh8vYn2aOLQ4peYq DpA4WofFHLHhNErRNk4wqmZsj3sJcoC1Sw== X-Google-Smtp-Source: AMsMyM4PZ3D1UYkxS5n08OIECJI0ht8TLoWou8MHGKLjkqkXvqmfbdICMQDwIMHH775ucD9gOnhgSg== X-Received: by 2002:a05:6870:80d3:b0:126:1e6c:f01c with SMTP id r19-20020a05687080d300b001261e6cf01cmr4613620oab.17.1664342204582; Tue, 27 Sep 2022 22:16:44 -0700 (PDT) Received: from ripple.attlocal.net (172-10-233-147.lightspeed.sntcca.sbcglobal.net. [172.10.233.147]) by smtp.gmail.com with ESMTPSA id q5-20020acac005000000b0034fddfc5922sm1466958oif.36.2022.09.27.22.16.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 27 Sep 2022 22:16:44 -0700 (PDT) Date: Tue, 27 Sep 2022 22:16:35 -0700 (PDT) From: Hugh Dickins X-X-Sender: hugh@ripple.attlocal.net To: Matthew Wilcox , Vlastimil Babka cc: Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: amusing SLUB compaction bug when CC_OPTIMIZE_FOR_SIZE Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org It's a bug in linux-next, but taking me too long to identify which commit is "to blame", so let me throw it over to you without more delay: I think __PageMovable() now needs to check !PageSlab(). I had made a small experimental change somewhere, rebuilt and rebooted, was not surprised to crash once swapping and compaction came in, but was surprised to find the crash in isolate_movable_page(), called by compaction's isolate_migratepages_block(). page->mapping was ffffffff811303aa, which qualifies as __PageMovable(), which expects struct movable_operations at page->mapping minus low bits. But ffffffff811303aa was the address of SLUB's rcu_free_slab(): I have CONFIG_CC_OPTIMIZE_FOR_SIZE=y, so function addresses may have low bits set. Over to you! Thanks, Hugh