From: "Darrick J. Wong" <darrick.wong@oracle.com>
To: Dave Chinner <david@fromorbit.com>
Cc: Wang Shilong <wangshilong1991@gmail.com>,
linux-ext4@vger.kernel.org, linux-fs@vger.kernel.org,
linux-xfs@vger.kernel.org, Wang Shilong <wshilong@ddn.com>,
Andreas Dilger <adilger@dilger.ca>, Li Xi <lixi@ddn.com>
Subject: Re: [RFC PATCH] ext4: add link file support for {GET,SET}XATTR ioctl
Date: Thu, 31 Jan 2019 09:40:59 -0800 [thread overview]
Message-ID: <20190131174059.GA10211@magnolia> (raw)
In-Reply-To: <20190131034106.GJ4205@dastard>
On Thu, Jan 31, 2019 at 02:41:06PM +1100, Dave Chinner wrote:
> On Thu, Jan 31, 2019 at 10:47:12AM +0900, Wang Shilong wrote:
> > From: Wang Shilong <wshilong@ddn.com>
> >
> > Currently there is no way to change project ID of
> > symlink file itself, this is important to implement
> > Directory quota for an existed directory.
>
> This seems like something open(O_PATH|O_NOFOLLOW) should allow.
> from open(2):
...but I thought O_PATH|O_NOFOLLOW file descriptions didn't allow ioctl
calls?
$ ln -sf urk /mnt/cow
$ xfs_io -c 'open -PL /mnt/cow' -c 'chproj 6'
setprojid: Bad file descriptor
$ ls -la /mnt/
lrwxrwxrwx 1 root root 3 Jan 31 09:30 /mnt/cow -> moo
> If pathname is a symbolic link and the O_NOFOLLOW flag is
> also specified, then the call returns a file descriptor
> referring to the symbolic link. This file descriptor
> can be used as the dirfd argument in calls to fchownat(2),
> fstatat(2), linkat(2), and read¿ linkat(2) with an empty
> pathname to have the calls operate on the symbolic link.
>
> Changing the project id is the equivalent of fchownat().....
/me & others wonder (on the ext4 call) if maybe we should promote
project id to a vfs level concept? i.e. store project id in struct
inode instead of the fs-specific inode structures. Then we can use the
existing setattr infrastructure to persist those changes.
As for fchownat, how about a new flag that means "use the value in the
gid field to set the project id"?
--D
> Cheers,
>
> Dave.
> --
> Dave Chinner
> david@fromorbit.com
next prev parent reply other threads:[~2019-01-31 17:41 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-31 1:47 [RFC PATCH] ext4: add link file support for {GET,SET}XATTR ioctl Wang Shilong
2019-01-31 3:41 ` Dave Chinner
2019-01-31 17:40 ` Darrick J. Wong [this message]
2019-01-31 20:43 ` Dave Chinner
2019-02-14 8:14 ` 答复: " Wang Shilong
2019-02-14 15:54 ` Darrick J. Wong
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