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=-7.2 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS 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 22D86C43219 for ; Mon, 29 Apr 2019 14:14:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E225620675 for ; Mon, 29 Apr 2019 14:14:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1556547244; bh=xf6NipygRwz8sNGT+uqf5PgnOsEKfKT1vm3IZ3bunjM=; h=Subject:To:Cc:References:From:Date:In-Reply-To:List-ID:From; b=m/ZhZKTSGh68dX3Jp+EnA/BUvsoyWB2F7tgQBUUHfVatZl7DodbArqUUbGboDAcgP qhS+lH97RhX0Wmyji2v2K8wq6nUBlJFqOpjK4sTzAUtQbWdZ8hUp6g3pHWSv3Tls/S sTkV35ctBEFTdjEDFxkSnunluL/WFjoyNCU+kvyg= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728311AbfD2OOC (ORCPT ); Mon, 29 Apr 2019 10:14:02 -0400 Received: from mail.kernel.org ([198.145.29.99]:33018 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728196AbfD2OOC (ORCPT ); Mon, 29 Apr 2019 10:14:02 -0400 Received: from [192.168.0.101] (unknown [58.212.133.185]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 75D6320652; Mon, 29 Apr 2019 14:14:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1556547241; bh=xf6NipygRwz8sNGT+uqf5PgnOsEKfKT1vm3IZ3bunjM=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=dso4WA3f9LnwH+OyLKzx9gjPszb+OcJsevJ1VxlQW5cC4aDph7RORwuDlkB86eNA8 q/XDB8hJuEdwfD5rG8Fs5+ks4fTIp4o4MBiK1yNfIwPHETyf9GmAKyiUVj84nByrBk 2x5gEM1+/soBwQiUPiA+Nykh6NB86t3bieQfx24c= Subject: Re: [PATCH 1/2] f2fs: fix to avoid potential negative .f_bfree To: Jaegeuk Kim , Chao Yu Cc: linux-f2fs-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, drosen@google.com References: <20190426095754.85784-1-yuchao0@huawei.com> <20190428134722.GC37346@jaegeuk-macbookpro.roam.corp.google.com> From: Chao Yu Message-ID: Date: Mon, 29 Apr 2019 22:13:55 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20190428134722.GC37346@jaegeuk-macbookpro.roam.corp.google.com> 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 2019-4-28 21:47, Jaegeuk Kim wrote: > On 04/26, Chao Yu wrote: >> When calculating .f_bfree value in f2fs_statfs(), sbi->unusable_block_count >> can be increased after the judgment condition, result in overflow of >> .f_bfree in later calculation. This patch fixes to use a temporary signed >> variable to save the calculation result of .f_bfree. >> >> if (unlikely(buf->f_bfree <= sbi->unusable_block_count)) >> buf->f_bfree = 0; >> else >> buf->f_bfree -= sbi->unusable_block_count; > > Do we just need stat_lock for this? Like we access other stat value in statfs(), we just need the instantaneous value of .unusable_block_count, so we don't need additional stat_lock, right? Thanks, > >> >> Signed-off-by: Chao Yu >> --- >> fs/f2fs/super.c | 7 +++++-- >> 1 file changed, 5 insertions(+), 2 deletions(-) >> >> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c >> index 2376bb01b5c4..fcc9793dbc2c 100644 >> --- a/fs/f2fs/super.c >> +++ b/fs/f2fs/super.c >> @@ -1216,6 +1216,7 @@ static int f2fs_statfs(struct dentry *dentry, struct kstatfs *buf) >> u64 id = huge_encode_dev(sb->s_bdev->bd_dev); >> block_t total_count, user_block_count, start_count; >> u64 avail_node_count; >> + long long bfree; >> >> total_count = le64_to_cpu(sbi->raw_super->block_count); >> user_block_count = sbi->user_block_count; >> @@ -1226,10 +1227,12 @@ static int f2fs_statfs(struct dentry *dentry, struct kstatfs *buf) >> buf->f_blocks = total_count - start_count; >> buf->f_bfree = user_block_count - valid_user_blocks(sbi) - >> sbi->current_reserved_blocks; >> - if (unlikely(buf->f_bfree <= sbi->unusable_block_count)) >> + >> + bfree = buf->f_bfree - sbi->unusable_block_count; >> + if (unlikely(bfree < 0)) >> buf->f_bfree = 0; >> else >> - buf->f_bfree -= sbi->unusable_block_count; >> + buf->f_bfree = bfree; >> >> if (buf->f_bfree > F2FS_OPTION(sbi).root_reserved_blocks) >> buf->f_bavail = buf->f_bfree - >> -- >> 2.18.0.rc1