linux-kernel - Re: *at syscalls for xattrs?

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Date:	Mon, 16 Jul 2007 02:33:39 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Miklos Szeredi <miklos@...redi.hu>
CC:	jeremy@...p.org, jengelh@...putergmbh.de, viro@....linux.org.uk,
	nmiell@...cast.net, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: *at syscalls for xattrs?

Miklos Szeredi wrote:
> 
> The *at() thing basically gives you the advantages of a CWD without
> the disadvantages.
> 
> For example it could be useful to implement the functionality of
> find(1) as a library interface.
> 

What the *at() interfaces really do is fix/paper over a longstanding
wart in Unix: the cwd really should have been a standard file descriptor
(like stdin/stdout/stderr) instead of a magic piece of state maintained
in kernel space.

If they had been designed-in from the beginning I suspect we wouldn't
have had, say, stat() and fstat(), but simply statat() -- the "normal"
ones would simply be statat(stddir, path) and statat(fd, NULL)
respectively.  Now it isn't quite so clean.

You can do some of that stuff with fchdir(), but *at() is much nicer,
minus the oddball Solaris naming with random presence and absence of f-
prefixes.

	-hpa
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