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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4FCF1C43334 for ; Tue, 26 Jul 2022 02:02:00 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 7478D8E0002; Mon, 25 Jul 2022 22:01:59 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 6F70C8E0001; Mon, 25 Jul 2022 22:01:59 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5BED48E0002; Mon, 25 Jul 2022 22:01:59 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 4B1958E0001 for ; Mon, 25 Jul 2022 22:01:59 -0400 (EDT) Received: from smtpin04.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id B8F6712062F for ; Tue, 26 Jul 2022 02:01:58 +0000 (UTC) X-FDA: 79727600316.04.6214C51 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by imf08.hostedemail.com (Postfix) with ESMTP id 6ADB61600A3 for ; Tue, 26 Jul 2022 02:01:57 +0000 (UTC) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.54]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4LsKpg03KwzkXF6; Tue, 26 Jul 2022 09:59:23 +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; Tue, 26 Jul 2022 10:01:53 +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: Tue, 26 Jul 2022 10:01:53 +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 ARC-Authentication-Results: i=1; imf08.hostedemail.com; dkim=none; dmarc=pass (policy=quarantine) header.from=huawei.com; spf=pass (imf08.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.188 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1658800918; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=5Q9pPQjvFKxYvgjN9leosNPjWAuXg+XgHR6GxIT7e1k=; b=EEGmVkJfkFoHM8sSYXroYnsChDFcmiP/VqT/hmEz/Q37nLY40CNjJceFrLQk25arfUKm1w ROINpvoPruMfnH75RRGTJEchvzljuEUHzxKglhfhS+iQSt/tjAB2DEsiMqwfEFrXe1TZv/ FYL1EM427tR0CHpMLLkQcFL3EeFEajM= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1658800918; a=rsa-sha256; cv=none; b=qYNsbF4xLPskrct0A5Go3YvXjmQptEQCrkditlydJAIuQHEOGiN+30QGS0CC3tBHzKZDTw 1mgihTJOlTv+VT19XW745lgiZr6+3CB5SmqsgMv0UV8HHKUEsT7I46Yu08IOWudXZdiibv W5U/TMcd7gUSejxD+Ee2LRj2rfuqvnU= X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 6ADB61600A3 X-Rspam-User: Authentication-Results: imf08.hostedemail.com; dkim=none; dmarc=pass (policy=quarantine) header.from=huawei.com; spf=pass (imf08.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.188 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com X-Stat-Signature: pohrbmot3f35w5nwrjt8b4xueokh7ck7 X-HE-Tag: 1658800917-832295 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 2022/7/26 7:40, Mike Kravetz wrote: > On 07/23/22 10:56, Miaohe Lin wrote: >> 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. > > I agree that 0 as a max value makes little sense. However, it is allowed > today and from what I can tell it is file system specific. So, there is no > defined behavior. So it might be better to keep the code as is. > >> >>> >>> 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. >> > > Agree that this is inconsistent and confusing. > > In the case where min_size and size is not specified, -1 for size still may > make sense. min_size specifies how many pages are reserved for use by the > filesystem. The only required relation between min_size and size is that if > size is specified, then min_size must be smaller. Otherwise, it makes no > sense to reserve pages (min_size) that can not be used. > >>> 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. :) >> > > I am fine with the comment change. Thanks for reading through the code and > trying to make sense of it! I will do it in next version. Many thanks for your time. >