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=-13.6 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, NICE_REPLY_A,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 19D0DC433E2 for ; Mon, 31 Aug 2020 15:22:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D58E020767 for ; Mon, 31 Aug 2020 15:22:21 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=kernel-dk.20150623.gappssmtp.com header.i=@kernel-dk.20150623.gappssmtp.com header.b="kpvTUnxi" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728223AbgHaPWU (ORCPT ); Mon, 31 Aug 2020 11:22:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54040 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726755AbgHaPWS (ORCPT ); Mon, 31 Aug 2020 11:22:18 -0400 Received: from mail-io1-xd44.google.com (mail-io1-xd44.google.com [IPv6:2607:f8b0:4864:20::d44]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B0006C061573 for ; Mon, 31 Aug 2020 08:22:17 -0700 (PDT) Received: by mail-io1-xd44.google.com with SMTP id h10so6332443ioq.6 for ; Mon, 31 Aug 2020 08:22:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20150623.gappssmtp.com; s=20150623; h=from:subject:to:cc:references:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=v6aATz1DrVzTsNm6cohCGLPYmM1JDr9u4o7wfl1KrmQ=; b=kpvTUnxia+Vb6v+2T62Y1tzsvRiUWtVSiYS8bxwIgN+SjgF7L1liSKiLaaoKbbqJso 9SPZVUN5K3oaoyI7rEAOsAgh9o7gV/yXCgF+5srCxYXCHpF4WuTl/ElWZtu6YLhSCg60 Pzu62ZNUGtY4niWkO/jRXwatOwWCKX6zAeW6q7+SjjomqfpYfr+1ETFayYIJAqfNZ4G+ qHNe8QjTj+pZjvHt/z/KzTqZx6L/2K7SgrBekZjb57pJ6xB0LYFrRW4EUeDWbf4lMZJ6 93/xr1CVxvjJmyZhwEkSAAdiSeAcr6lfw+RsmoWqkZhas3cbbgY8xkYxcf3SD7ofLm/F kFog== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:subject:to:cc:references:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=v6aATz1DrVzTsNm6cohCGLPYmM1JDr9u4o7wfl1KrmQ=; b=MVauvNZUj9T8/S+AJobMd+uSWmwhWsA2Cvd7O7TftB+akGBK6PcXhRUjtzLl8MzJjz haEuxpc2gAHfdLijiX21Fado4jA4TZn0a4foK7AzcaYfJQbSRjODI253byuFSRtRl2gy lScONBZdcTaSYK6ZGuaVCmFzx6yQLBD2RSjWKuH4lgSRI6nYBcsds8iisBRpY76xfZeb HSZQhWegyCDccwfObQO0E3dHcBUGra6urtl4+B+IYl9GWtDA+YUTBV1f5oqn7wLQNqjM Dsa4le3WL03H04wRKyTS8fQBz+/kjcw3o6BagVrHf991jSujIb32NTmFRGmWiuefPB54 EdgA== X-Gm-Message-State: AOAM530IMFzkeIMyTH/ykui9FWt8wOs/BaFBy0PlXHILLHZyJbmqfmAc RqfEPYg+U1lLw0DV393MVOvwKlmCysHJiW9L X-Google-Smtp-Source: ABdhPJyAgM2GlRZVCWCkUnBO1XNUnkD9OMa7NSlRGQqHiZ2S//nbyzT3RwaPgka2CDaZG5IjCJjVhw== X-Received: by 2002:a02:c8c8:: with SMTP id q8mr1642061jao.46.1598887336702; Mon, 31 Aug 2020 08:22:16 -0700 (PDT) Received: from [192.168.1.58] ([65.144.74.34]) by smtp.gmail.com with ESMTPSA id m3sm4704997ill.57.2020.08.31.08.22.15 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 31 Aug 2020 08:22:16 -0700 (PDT) From: Jens Axboe Subject: Re: [PATCH] fat: Avoid oops when bdi->io_pages==0 To: OGAWA Hirofumi Cc: Andrew Morton , linux-kernel , fsdevel References: <87ft85osn6.fsf@mail.parknet.co.jp> Message-ID: Date: Mon, 31 Aug 2020 09:22:15 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <87ft85osn6.fsf@mail.parknet.co.jp> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Aug 29, 2020 at 7:08 PM OGAWA Hirofumi wrote: > > On one system, there was bdi->io_pages==0. This seems to be the bug of > a driver somewhere, and should fix it though. Anyway, it is better to > avoid the divide-by-zero Oops. > > So this check it. > > Signed-off-by: OGAWA Hirofumi > Cc: > --- > fs/fat/fatent.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/fat/fatent.c b/fs/fat/fatent.c > index f7e3304..98a1c4f 100644 > --- a/fs/fat/fatent.c 2020-08-30 06:52:47.251564566 +0900 > +++ b/fs/fat/fatent.c 2020-08-30 06:54:05.838319213 +0900 > @@ -660,7 +660,7 @@ static void fat_ra_init(struct super_blo > if (fatent->entry >= ent_limit) > return; > > - if (ra_pages > sb->s_bdi->io_pages) > + if (sb->s_bdi->io_pages && ra_pages > sb->s_bdi->io_pages) > ra_pages = rounddown(ra_pages, sb->s_bdi->io_pages); > reada_blocks = ra_pages << (PAGE_SHIFT - sb->s_blocksize_bits + 1); I don't think we should work-around this here. What device is this on? Something like the below may help. diff --git a/block/blk-core.c b/block/blk-core.c index d9d632639bd1..10c08ac50697 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -539,6 +539,7 @@ struct request_queue *blk_alloc_queue(int node_id) goto fail_stats; q->backing_dev_info->ra_pages = VM_READAHEAD_PAGES; + q->backing_dev_info->io_pages = VM_READAHEAD_PAGES; q->backing_dev_info->capabilities = BDI_CAP_CGROUP_WRITEBACK; q->node = node_id; -- Jens Axboe