From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dongsheng Yang Subject: Re: [PATCH v3 11/39] fs: quota: replace opened calling of ->sync_fs with sync_filesystem Date: Fri, 18 Sep 2015 13:49:25 +0800 Message-ID: <55FBA5E5.1040201@cn.fujitsu.com> References: <1442307754-13233-1-git-send-email-yangds.fnst@cn.fujitsu.com> <1442307754-13233-12-git-send-email-yangds.fnst@cn.fujitsu.com> <20150916101402.GE13325@quack.suse.cz> <55FA5D8A.9030108@cn.fujitsu.com> <20150917110547.GB32280@quack.suse.cz> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="------------050809040201020305030500" Cc: , , , , To: Jan Kara Return-path: Received: from cn.fujitsu.com ([59.151.112.132]:12028 "EHLO heian.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1751614AbbIRFz6 (ORCPT ); Fri, 18 Sep 2015 01:55:58 -0400 In-Reply-To: <20150917110547.GB32280@quack.suse.cz> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: --------------050809040201020305030500 Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit On 09/17/2015 07:05 PM, Jan Kara wrote: > On Thu 17-09-15 14:28:26, Dongsheng Yang wrote: >> On 09/16/2015 06:14 PM, Jan Kara wrote: >>> On Tue 15-09-15 17:02:06, Dongsheng Yang wrote: >>>> There are only two places in whole kernel to call ->sync_fs directly. It >>>> will sync fs even in read-only mode. It's not a good idea and some filesystem >>>> would warn out if you are syncing in read-only mode. But sync_filesystem() >>>> does filter this case out. Let's call sync_filesystem() here instead. >>>> >>>> Signed-off-by: Dongsheng Yang >>> >>> So I'd prefer ubifs used hidden system inodes for quota files, set >>> DQUOT_QUOTA_SYS_FILE flag and so this code calling sync_fs() could be >>> completely avoided. >> >> Hmmm, I think it's a good idea to make quota files SYS_FILEs. But how >> about quota-tools? E.g, if quotacheck do some modification >> on quota files, we would not read them without a sync_fs(). >> >> Could you help explain how quota works in this case? > > So tools like quota(1) or setquota(1) work using quotactl so they don't > need access to quota files. When quota files are system files, quotacheck > functionality belongs into the fsck - so fsck.ubifs is responsible for > checking consistency of quota files. How e.g. e2fsck does it is that when > scanning inodes, it computes usage for each user / group, loads limits > information from old quota files and then just creates new quota files with > updated information if there's any difference to the old quota files. About quotacheck, I think just call fsync() in it sounds good to me. Maybe something like the attachment. OKEY, but I found repquota is still using read() to access quota files. Please consider that case: 1.we read quota file and there is a pagecache for it. 2. Then kernel did some modification on quota files. But if the files is SYS_FILES marked, dquot_quota_sync() would not drop the pagecache, then 3. repquota would get an outdated data from pagecache. I am not sure why ext4 works well in this case. There must be something I am missing. Maybe we can introduce a Q_GETBLK for quotactl() to make all quota tools getting informations from ioctl. > > Another advantage of the checking functionality being in fsck is that > fs-specific fsck can gather usage information much more efficiently (and > fsck has to do full fs scan anyway) and there's no need to propagate quota > usage information to userspace using FIQSIZE ioctl() and similar stuff... So, let me try to summary the my opinions about it. Pros: (1). Security. quota files shouldn't be accessible to usespace. (2). Efficiency. No need for quotacheck, just do it in fsck. (3). No need FIOQSIZE any more. Cons: (1). Incompatibility: If I set DQUOT_QUOTA_SYS_FILE currently, there are at least two commands would not work: quotacheck and repquota. Actually that means the whole quota is not usable to user. So, I think the compatibility is important to me. Then what about setting quota files as regular files at first. After all tools (quota tools, quotacheck, repquota, fsck) prepared, setting the DQUOT_QUOTA_SYS_FILE seems better. Yang > > Honza > --------------050809040201020305030500 Content-Type: text/x-patch; name="0001-quotacheck-sync-files-in-quotacheck.patch" Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="0001-quotacheck-sync-files-in-quotacheck.patch" >>From 1cf9d072cdd4d17c620834864f79ec5a0765d2bf Mon Sep 17 00:00:00 2001 From: Dongsheng Yang Date: Fri, 18 Sep 2015 08:40:49 -0400 Subject: [PATCH] quotacheck: sync files in quotacheck. After a quotacheck, we need to make kernel to see the modification. Compared with syncing quota files in kernel, we would rather sync it in quotacheck command. Signed-off-by: Dongsheng Yang --- quotacheck.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/quotacheck.c b/quotacheck.c index 6f34cff..e4b184d 100644 --- a/quotacheck.c +++ b/quotacheck.c @@ -768,6 +768,20 @@ rename_new: close(fd); } #endif + + /* Do a syncing for the quota file */ + if ((fd = open(filename, O_RDWR)) < 0) { + errstr(_("Cannot open new quota file %s: %s\n"), filename, strerror(errno)); + free(filename); + return -1; + } + if (fsync(fd)) { + errstr(_("Cannot sync quota file %s: %s\n"), filename, strerror(errno)); + free(filename); + return -1; + } + close(fd); + free(filename); return 0; } -- 1.8.3.1 --------------050809040201020305030500--