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=-15.1 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL 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 6B5A8C433E2 for ; Mon, 31 Aug 2020 14:41:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 39A07207EA for ; Mon, 31 Aug 2020 14:41:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="aH/j8WKX" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728079AbgHaOlZ (ORCPT ); Mon, 31 Aug 2020 10:41:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47642 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726489AbgHaOlT (ORCPT ); Mon, 31 Aug 2020 10:41:19 -0400 Received: from mail-lf1-x144.google.com (mail-lf1-x144.google.com [IPv6:2a00:1450:4864:20::144]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 96746C061573 for ; Mon, 31 Aug 2020 07:41:18 -0700 (PDT) Received: by mail-lf1-x144.google.com with SMTP id j15so3624504lfg.7 for ; Mon, 31 Aug 2020 07:41:18 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=5jdf7Yr1a6XX4TRwS1JHRRHr0CFyp0wrlJUOIn8FHr8=; b=aH/j8WKXZPdvikd5WEObfSDw9GR1wJDjg8Q3jQu4nRVY9eQMhZVxWM6/5we9KIEqbG dEL/W1lGnc4l5SckXCn8cshObUaR3qEffqA4aJ1jnqH+OHCZQA0TjM7SyTFMRscUPOqU p9+/ggGI6gxE5rfLwBkj2Pd9U7EfrTXd7A2ff4+FhWHr8PSG+gcNWLoibjGbSQTcHBNt kLxaT7IxEGAYoT1p4dkzBiY9HqNaZ3YL4qctWQ8QDjbfiqLje6MQtdUr0x5L25/dXVDw xx8fbfrVbGopBll7Hf8nNsmdFOuFyWnUA8itQlXufL86bh3cM9BfEEF1jBSp4pnucC7Y 18FA== 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=5jdf7Yr1a6XX4TRwS1JHRRHr0CFyp0wrlJUOIn8FHr8=; b=UgXZYpqgUsAkMWmCSi81yas/STj0N4kLkw+f/O6InAKgp5bnAQB0S5kB/5zTHGZsZX 5kLq3yZYT50uIy0TrWSzDT+jJXi8umMuLMGmR7cp96Oe7CxBrtb3MoGY3E2cxeeUjymC NAPiYqVn+EmKMFFKd74Fi4/4ppXybCI/yMFW+eSpOOcM1+SohSHqjyHdCn602O7FuRER f/NTi+rUB+7SXzPEOUgR6vXdg2TGFWLqPILP+T2+j83xWPnSyyQ0XNdu+0+Lwd6xN2j+ IGbrBDmRPbs0xjrdorKySq/ugYyMW8rVnwtPHAi3QpZI89ViL5dopp6dZD+ZAcuwE+3Z KIEw== X-Gm-Message-State: AOAM53173R4UwAkzk8q4D0g+We2EU/m8M2dnkp+iPKcxxIfO1wbKDYC5 bxeJ6xGqu0jaEp2Mabiq/NNw/RB8/CxXq0xfY5nMCg== X-Google-Smtp-Source: ABdhPJzyliB5lE1nzTQObWc+yrnVQDwbEMzPDyzwKQjR4ExISbfjpW4peJBU8buMyH9dXJeEg+86459vcjM6z2maAYI= X-Received: by 2002:ac2:47ec:: with SMTP id b12mr889283lfp.124.1598884876690; Mon, 31 Aug 2020 07:41:16 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Shakeel Butt Date: Mon, 31 Aug 2020 07:41:05 -0700 Message-ID: Subject: Re: [PATCH 3/5] shmem: shmem_writepage() split unlikely i915 THP To: Hugh Dickins Cc: Andrew Morton , Alex Shi , Johannes Weiner , Michal Hocko , Mike Kravetz , Matthew Wilcox , Qian Cai , Chris Wilson , Kuo-Hsin Yang , LKML , Linux MM Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Aug 30, 2020 at 2:04 PM Hugh Dickins wrote: > > drivers/gpu/drm/i915/gem/i915_gem_shmem.c contains a shmem_writeback() > which calls shmem_writepage() from a shrinker: that usually works well > enough; but if /sys/kernel/mm/transparent_hugepage/shmem_enabled has > been set to "force" (documented as "Force the huge option on for all - > very useful for testing"), shmem_writepage() is surprised to be called > with a huge page, and crashes on the VM_BUG_ON_PAGE(PageCompound) (I > did not find out where the crash happens when CONFIG_DEBUG_VM is off). > > LRU page reclaim always splits the shmem huge page first: I'd prefer not > to demand that of i915, so check and split compound in shmem_writepage(). > > Fixes: 2d6692e642e7 ("drm/i915: Start writeback from the shrinker") > Signed-off-by: Hugh Dickins > Cc: stable@vger.kernel.org # v5.3+ Reviewed-by: Shakeel Butt