linux-kernel - Re: [GIT PULL] overlay filesystem v25

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Message-ID: <CAJfpegt-X_Cd8B5H65keshhhuwH2-HPpaBC30atKeS3QjaariA@mail.gmail.com>
Date:	Fri, 24 Oct 2014 09:24:45 +0200
From:	Miklos Szeredi <miklos@...redi.hu>
To:	Al Viro <viro@...iv.linux.org.uk>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux-Fsdevel <linux-fsdevel@...r.kernel.org>,
	Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-unionfs@...r.kernel.org
Subject: Re: [GIT PULL] overlay filesystem v25

On Fri, Oct 24, 2014 at 5:24 AM, Al Viro <viro@...iv.linux.org.uk> wrote:
> On Fri, Oct 24, 2014 at 03:20:55AM +0100, Al Viro wrote:
>> Why the hell do you hold ->i_mutex across the entire opening of underlying
>> directory?  All you need is to serialize one assignment; the side that loses
>> the race will simply fput() what it opened...

The reason I didn't do your "fix" is that it

 - adds more lines than it takes,

 - I wasn't sure at all if the lockless access is actually correct
without the ACCESS_ONCE and all the memory barrier magic that might be
necessary on weird architectures.

The rest of the changes look OK.

Thanks,
Miklos
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