linux-kernel - Re: [PATCH 12/15] VFS: Add owner-filesystem positive/negative dentry checks

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Date:	Fri, 27 Mar 2015 14:42:37 +0000
From:	David Howells <dhowells@...hat.com>
To:	Miklos Szeredi <miklos@...redi.hu>
Cc:	dhowells@...hat.com, viro@....linux.org.uk,
	"linux-unionfs@...r.kernel.org" <linux-unionfs@...r.kernel.org>,
	Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 12/15] VFS: Add owner-filesystem positive/negative dentry checks

Miklos Szeredi <miklos@...redi.hu> wrote:

> I think this is confusing as hell, there needs to be more consistency
> in the naming.  E.g. d_backing_is_positive() vs. d_is_positive().   I
> know it's the other way round now, but only with a few users.

Yeah.  The problem is that all of:

	__d_entry_type()
	d_is_miss()
	d_is_whiteout()
	d_can_lookup()
	d_is_autodir()
	d_is_dir()
	d_is_symlink()
	d_is_reg()
	d_is_special()
	d_is_file()
	d_is_negative()
	d_is_positive()

refer to the 'backing' inode (if there is one) in the case that you have a
unionmount and the top dentry's ->d_inode is NULL.  (Well, technically, that
doesn't happen in the case of directories)

Of course, if we decide we aren't going to do unionmount, certain things
become simpler.

> Also a separate include file might help, that needs explicit including to
> get the "backing" variants

I would like to see a 'for fs implementer' header and a 'for fs user' header
but Al didn't like that last time I suggested it.

However, it doesn't help with the naming since there are situations where you
need *both* - eg. overlayfs.

> and which would have big fat warnings all over.

Well, we could argue about which side should have the warnings.

David
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