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Date:      Sun, 29 Dec 2002 18:45:42 -0500 (EST)
From:      Robert Watson <rwatson@FreeBSD.org>
To:        Garrett Wollman <wollman@lcs.mit.edu>
Cc:        cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org
Subject:   Re: cvs commit: src/sys/kern syscalls.master
Message-ID:  <Pine.NEB.3.96L.1021229184046.36992I-100000@fledge.watson.org>
In-Reply-To: <200212292217.gBTMHLpV009761@khavrinen.lcs.mit.edu>

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On Sun, 29 Dec 2002, Garrett Wollman wrote:

> >   These calls are similar in spirit to lstat(), lchown(), lchmod(), etc,
> 
> ...except for the extreme verbosity in their names.

Yeah.  They're derived from the POSIX1e-D17 naming scheme, and that naming
scheme sucks. :-)

> There should probably be a file mode bit that is returned by stat() to
> indicate that additional attributes exist that are not in struct stat. 

When I first did the ACL stuff, I noticed the ls(1) extension described in
the draft spec and implemented on a number of platforms, which essentially
prints a '+' after the ls -l mode display if there are extended
protections.  At that point, we didn't have any obviously spare and
appropriate bits in struct stat.  If/when we upgrade all these structures
for 64-bit extensions, we should be sure to look at this.  I'm not sure we
want to generally signify the presence of extended attributes -- probably
just the ones with recognizably useful semantics.  With UFS2, we added
more flag bits to the inode, with the intent of using some of the spare
bits to cache extended attribute information so we could avoid reading in
extended attributes unnecessarily.  For example, adding a flag indicating
whether an access ACL or a default ACL is present would allow us to avoid
reading in those EAs during ufs_access().  For soft updates reasons,
they'd be hints with appropriate failure modes (if the hint is wrong, it
indicates the EA is present rather than not). 

Robert N M Watson             FreeBSD Core Team, TrustedBSD Projects
robert@fledge.watson.org      Network Associates Laboratories




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