linux-kernel - Re: [PATCH v2] vfs: Don't exchange "short" filenames unconditionally.

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Message-ID: <CA+55aFxZDsD94CSDYfyw9g3WWNkVApZDKxHVhK2zy0ycRsjcmA@mail.gmail.com>
Date:	Mon, 29 Sep 2014 08:15:51 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Al Viro <viro@...iv.linux.org.uk>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Mikhail Efremov <sem@...linux.org>
Subject: Re: [PATCH v2] vfs: Don't exchange "short" filenames unconditionally.

On Sun, Sep 28, 2014 at 11:05 AM, Al Viro <viro@...iv.linux.org.uk> wrote:
>
> Folks, care to review and test the following?

No testing, but having thought about this some more, I'm personally
getting quite convinced that doing the RCU delaying of the external
name freeing in the __d_free() path is entirely pointless.

So I think the *only* rcu_free() you need is for just the "free old
name" case in copy_name().

In __d_free(), the name pointer has gone through the same grace period
that the dentry pointer itself went through. If it's not safe to free
the external name, then it damn well wouldn't be safe to free the
dentry itself either.

IOW, I think your games in __d_free() are totally unnecessary.

Now you can tell me why I'm wrong.

              Linus
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