From: Valerie Aurora <vaurora@redhat.com>
To: Theodore Tso <tytso@MIT.EDU>
Cc: Jamie Lokier <jamie@shareable.org>,
"J. R. Okajima" <hooanon05@yahoo.co.jp>,
linux-fsdevel@vger.kernel.org,
Alexander Viro <viro@zeniv.linux.org.uk>,
Erez Zadok <ezk@cs.sunysb.edu>,
Christoph Hellwig <hch@infradead.org>
Subject: Re: Union mounts and fchown/fchmod/utimensat
Date: Tue, 30 Mar 2010 16:30:35 -0400 [thread overview]
Message-ID: <20100330203035.GA7487@shell> (raw)
In-Reply-To: <DAF97B23-3C67-4776-996E-B9E09D28BD66@mit.edu>
On Tue, Mar 30, 2010 at 07:16:18AM -0400, Theodore Tso wrote:
> Hmmm.... do we also need to worry about read-only fd's of directories, and interaction with the *at() system calls. For example:
>
> int renameat(int olddirfd, const char *oldpath, int newdirfd, const char *newpath)
>
> ... where olddirfd and newdirfd might be r/o file descriptors for directories participating in a Union mount?
>
> This is just one example, of course. There's also openat(), symlinkat(), etc.
Directories are always copied up in this version of union mounts, so
it doesn't matter whether you open a directory O_RDONLY or not, you'll
always have the topmost version and see all the effects of link(),
linkat(), rename(), renameat(), etc. It's only with files that you
can get a stale copy if you open it O_RDONLY and it gets modified
through some other path.
Always copying up directories solves a lot of problems. I managed to
eliminate several hundred lines of code with that change in the
design.
-VAL
next prev parent reply other threads:[~2010-03-30 20:31 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-26 22:45 Union mounts and fchown/fchmod/utimensat Valerie Aurora
2010-03-27 15:43 ` J. R. Okajima
2010-03-29 18:39 ` Valerie Aurora
2010-03-29 23:48 ` Jamie Lokier
2010-03-30 11:16 ` Theodore Tso
2010-03-30 20:30 ` Valerie Aurora [this message]
2010-03-30 21:31 ` Valerie Aurora
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