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 AEED9C43334 for ; Sat, 23 Jul 2022 02:56:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233544AbiGWC4K (ORCPT ); Fri, 22 Jul 2022 22:56:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53642 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229572AbiGWC4I (ORCPT ); Fri, 22 Jul 2022 22:56:08 -0400 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E9DDFDEC4 for ; Fri, 22 Jul 2022 19:56:05 -0700 (PDT) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.53]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4LqW8908tszjWx1; Sat, 23 Jul 2022 10:53:13 +0800 (CST) Received: from [10.174.177.76] (10.174.177.76) by canpemm500002.china.huawei.com (7.192.104.244) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Sat, 23 Jul 2022 10:56:00 +0800 Subject: Re: [PATCH 5/5] hugetlbfs: fix confusing hugetlbfs stat To: Mike Kravetz CC: , , , References: <20220721131637.6306-1-linmiaohe@huawei.com> <20220721131637.6306-6-linmiaohe@huawei.com> From: Miaohe Lin Message-ID: Date: Sat, 23 Jul 2022 10:56:00 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.76] X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022/7/23 6:55, Mike Kravetz wrote: > On 07/22/22 14:38, Miaohe Lin wrote: >> On 2022/7/22 8:28, Mike Kravetz wrote: >>> On 07/21/22 21:16, Miaohe Lin wrote: >>>> When size option is not specified, f_blocks, f_bavail and f_bfree will be >>>> set to -1 instead of 0. Likewise, when nr_inodes is not specified, f_files >>>> and f_ffree will be set to -1 too. Check max_hpages and max_inodes against >>>> -1 first to make sure 0 is reported for max/free/used when no limit is set >>>> as the comment states. >>> >>> Just curious, where are you seeing values reported as -1? The check >> >> From the standard statvfs() function. >> >>> for sbinfo->spool was supposed to handle these cases. Seems like it >> >> sbinfo->spool could be created when ctx->max_hpages == -1 while >> ctx->min_hpages != -1 in hugetlbfs_fill_super. >> >>> should handle the max_hpages == -1 case. But, it doesn't look like it >>> considers the max_inodes == -1 case. >>> >>> If I create/mount a hugetlb filesystem without specifying size or nr_inodes, >>> df seems to report zero instead of -1. >>> >>> Just want to understand the reasoning behind the change. > > Thanks for the additional information (and test program)! > >>>From the hugetlbfs documentation: > "If the ``size``, ``min_size`` or ``nr_inodes`` option is not provided on > command line then no limits are set." > > So, having those values set to -1 indicates there is no limit set. > > With this change, 0 is reported for the case where there is no limit set as > well as the case where the max value is 0. IMHO, 0 should not be a valid max value otherwise there will be no hugetlb pages to use. It should mean there's no limit. But maybe I'm wrong. > > There may be some value in reporting -1 as is done today. There still be a inconsistency: If the ``size`` and ``min_size`` isn't specified, then reported max value is 0. But if ``min_size`` is specified while ``size`` isn't specified, the reported max value is -1. > > To be honest, I am not sure what is the correct behavior here. Unless > there is a user visible issue/problem, I am hesitant to change. Other > opinions are welcome. Yes, it might be better to keep it as is. Maybe we could change the comment to reflect what the current behavior is like below? diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c index 44da9828e171..f03b1a019cc0 100644 --- a/fs/hugetlbfs/inode.c +++ b/fs/hugetlbfs/inode.c @@ -1080,7 +1080,7 @@ static int hugetlbfs_statfs(struct dentry *dentry, struct kstatfs *buf) buf->f_bsize = huge_page_size(h); if (sbinfo) { spin_lock(&sbinfo->stat_lock); - /* If no limits set, just report 0 for max/free/used + /* If no limits set, just report 0 or -1 for max/free/used * blocks, like simple_statfs() */ if (sbinfo->spool) { spin_lock_irq(&sbinfo->spool->lock); > No strong opinion to keep this patch or above change. Many thanks for your comment and reply. :)