Re: [PATCH v2] ceph: fix posix ACL hooks

[Christoph Hellwig <hch@infradead.org>]

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.