linux-kernel - Re: [PATCH] Memory shortage can result in inconsistent flocks state

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Message-ID: <20070912190653.GA13792@fieldses.org>
Date:	Wed, 12 Sep 2007 15:06:53 -0400
From:	"J. Bruce Fields" <bfields@...ldses.org>
To:	Pavel Emelyanov <xemul@...nvz.org>
Cc:	Trond Myklebust <trond.myklebust@....uio.no>,
	Andrew Morton <akpm@...l.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	devel@...nvz.org
Subject: Re: [PATCH] Memory shortage can result in inconsistent flocks state

On Tue, Sep 11, 2007 at 04:38:13PM +0400, Pavel Emelyanov wrote:
> This is a known feature that such "re-locking" is not atomic,
> but in the racy case the file should stay locked (although by
> some other process), but in this case the file will be unlocked.

That's a little subtle (I assume you've never seen this actually
happen?), but it makes sense to me.

> The proposal is to prepare the lock in advance keeping no chance
> to fail in the future code.

And the patch certainly looks correct.

I can add it to my (trivial) lock patches, if that's helpful--it'll
get folded into the branch -mm pulls from and I can pass it along to
Linus for 2.6.24.

What I don't have that I wish I did is good regression tests for the
flock or lease code (for posix locks I've been using connectathon,
though that misses some important things too).

--b.
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