From: Zheng Liu <gnehzuil.liu@gmail.com>
To: linux-ext4@vger.kernel.org
Cc: Theodore Ts'o <tytso@mit.edu>,
xfs@oss.sgi.com, Ben Myers <bpm@sgi.com>,
Dmitry Monakhov <dmonakhov@openvz.org>,
Andreas Dilger <adilger.kernel@dilger.ca>
Subject: [RFC] directory quota survey on xfs
Date: Sun, 22 Dec 2013 17:59:29 +0800 [thread overview]
Message-ID: <20131222095929.GA11444@gmail.com> (raw)
Hi all,
As discussed with ext4 folks, I will try to make ext4 file system support
directory quota (a.k.a., project id in xfs). For keeping consistency
with xfs's implementation, I did some tests on xfs, and I summarized the
result as following. This will help us understand what we can do and
what we can't do. Please correct me if I miss doing some tests or mis-
understand something.
I just do some tests about rename/hardlink because they are the key
issue from our discussion.
+ unaccounted dir
x accounted dir
rename(mv)
==========
+ -> +: ok
+ -> x: ok
I use strace(1) to lookup which syscall is used, and I found that xfs
will return EXDEV when mv(1) tries to use rename(2) to move a dir from
a unaccounted dir to a accounted dir. Then mv uses creat(2)/read(2)/
write(2) syscalls to move this dir.
x -> +: wrong (design by feature?)
If we move a dir from a accounted dir to a unaccounted dir, the quota is
still accounted. It seems that xfs don't remove project id from this
dir and its subdirs/files on this case.
x -> x: ok
Xfs returns EXDEV error when mv(1) uses rename(2) to move a dir from a
accounted dir to another accounted dir (These dirs have different
project ids). Then mv(1) uses creat(1)/read(1)/write(1) syscalls to
move this dir.
summary:
rename + x
+ ok ok (EXDEV)
x wrong ok (EXDEV)
hardlink(ln)
========
+ -> +: ok
+ -> x: error
Xfs also returns EXDEV error to forbid this operation. So that means
that we don't allow users to do a hardlink for a file from a unaccount
dir to a accounted dir.
x -> +: ok
This operation can be executed and no any error is reported. After that
the quota doesn't be changed. When both of two hardlinks are removed,
the quota will be discharged.
x -> x: error
Xfs returns EXDEV error to forbid this operation.
summary:
hardlink + x
+ ok error (EXDEV)
x ok error (EXDEV)
As always, any comment or idea are welcome.
Thanks,
- Zheng
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next reply other threads:[~2013-12-22 9:59 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-22 9:59 Zheng Liu [this message]
2013-12-23 1:42 ` [RFC] directory quota survey on xfs Dave Chinner
2013-12-23 9:12 ` Arkadiusz Miśkiewicz
2013-12-23 23:43 ` Dave Chinner
2014-01-15 8:12 ` Zheng Liu
2014-01-15 18:03 ` Andreas Dilger
2014-01-15 21:32 ` Dave Chinner
2014-01-21 7:07 ` Zheng Liu
2014-01-23 22:32 ` Dave Chinner
2014-01-24 0:06 ` Darrick J. Wong
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