linux-kernel - Re: [PATCH 0/4 v3] fs: Remove i

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Message-ID: <20141104201620.GL7996@ZenIV.linux.org.uk>
Date:	Tue, 4 Nov 2014 20:16:21 +0000
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Jan Kara <jack@...e.cz>, Christoph Hellwig <hch@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux FS Devel <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH 0/4 v3] fs: Remove i_devices from struct inode

On Tue, Nov 04, 2014 at 11:52:22AM -0800, Andy Lutomirski wrote:

> Let me try again, though: what if a chardev inode replaced i_cdev with
> NULL and dropped its kobj reference in iput_final?  This would add a
> bit over overhead to things that repeatedly open and close the same
> device node, but I doubt this matters much.

How is it different from what Jan proposed?  The whole problem is that
iput_final() is too late.  We could clean the reference on close, all
right, and have it looked up again on every open, but I'm not at all sure
that situation with opening/closing cdev is never a hot path, especially with
udev playing silly buggers, etc.
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