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Date: Wed, 6 Nov 2019 10:49:24 +0100
From: Jan Kara <jack@...e.cz>
To: Chengguang Xu <cgxu519@...ernel.net>
Cc: Jan Kara <jack@...e.cz>,
"adilger.kernel" <adilger.kernel@...ger.ca>, tytso <tytso@....edu>,
Jan Kara <jack@...e.com>,
linux-ext4 <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH v2] ext4: choose hardlimit when softlimit is larger than
hardlimit in ext4_statfs_project()
On Wed 06-11-19 12:37:35, Chengguang Xu wrote:
> ---- 在 星期二, 2019-10-15 19:25:23 Jan Kara <jack@...e.cz> 撰写 ----
> > On Tue 15-10-19 18:23:27, Chengguang Xu wrote:
> > > Setting softlimit larger than hardlimit seems meaningless
> > > for disk quota but currently it is allowed. In this case,
> > > there may be a bit of comfusion for users when they run
> > > df comamnd to directory which has project quota.
> > >
> > > For example, we set 20M softlimit and 10M hardlimit of
> > > block usage limit for project quota of test_dir(project id 123).
> > >
> > > [root@...es mnt_ext4]# repquota -P -a
> > > *** Report for project quotas on device /dev/loop0
> > > Block grace time: 7days; Inode grace time: 7days
> > > Block limits File limits
> > > Project used soft hard grace used soft hard grace
> > > ----------------------------------------------------------------------
> > > 0 -- 13 0 0 2 0 0
> > > 123 -- 10237 20480 10240 5 200 100
> > >
> > > The result of df command as below:
> > >
> > > [root@...es mnt_ext4]# df -h test_dir
> > > Filesystem Size Used Avail Use% Mounted on
> > > /dev/loop0 20M 10M 10M 50% /home/cgxu/test/mnt_ext4
> > >
> > > Even though it looks like there is another 10M free space to use,
> > > if we write new data to diretory test_dir(inherit project id),
> > > the write will fail with errno(-EDQUOT).
> > >
> > > After this patch, the df result looks like below.
> > >
> > > [root@...es mnt_ext4]# df -h test_dir
> > > Filesystem Size Used Avail Use% Mounted on
> > > /dev/loop0 10M 10M 3.0K 100% /home/cgxu/test/mnt_ext4
> > >
> > > Signed-off-by: Chengguang Xu <cgxu519@...ernel.net>
> > > ---
> > > - Fix a bug in the limit setting logic.
> >
> > Thanks for the patch! It looks good to me. You can add:
> >
> > Reviewed-by: Jan Kara <jack@...e.cz>
> >
>
> Hi Jan,
>
> I have a proposal for another direction.
> Could we add a check for soft limit in quota layer when setting the value?
> So that we could not bother with specific file systems on statfs().
What do you mean exactly? To not allow softlimit to be larger than
hardlimit? That would make some sense but I don't think the risk of
breaking some user that accidentally depends on current behavior is worth
the few checks we can save...
Honza
--
Jan Kara <jack@...e.com>
SUSE Labs, CR
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