linux-kernel - Re: [PATCH v2] ceph: fix posix ACL hooks

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Date:	Mon, 3 Feb 2014 13:23:36 -0800
From:	Christoph Hellwig <hch@...radead.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Christoph Hellwig <hch@...radead.org>,
	Ilya Dryomov <ilya.dryomov@...tank.com>,
	Sage Weil <sage@...tank.com>, Dave Jones <davej@...hat.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	ceph-devel@...r.kernel.org,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	Guangliang Zhao <lucienchao@...il.com>,
	Li Wang <li.wang@...ntykylin.com>, zheng.z.yan@...el.com,
	Steven Whitehouse <swhiteho@...hat.com>,
	cluster-devel@...hat.com
Subject: Re: [PATCH v2] ceph: fix posix ACL hooks

On Mon, Feb 03, 2014 at 01:03:32PM -0800, Linus Torvalds wrote:
> Now, to be honest, pushing it down one more level (to
> generic_permission()) will actually start causing some trouble. In
> particular, gfs2_permission() fundamentally does not have a dentry for
> several of the callers.

Looking over the gfs2 code the problem seems to be that it duplicates
permissions checks from the may_{lookup,create,linkat,delete}, most
likely because it needs cluster locking in place for them.  The right
fix seems to be to optionally call the filesystem from those.  That
being said I wonder how ocfs2 or network filesystems get away without
that.

> What do you think? I guess this patch could be split up into two: one
> that does the "vfs_xyz()" helper functions, and another that does the
> inode_permission() change. I tied them together mainly because I
> started with the inode_permission() change, and that required the
> vfs_xyz() change.

The changes look good to me, and yes I think they should be split.
I'll see if I can take this further, but doing something non-hacky
in GFS2 would be the first step here.

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