linux-kernel - Re: [PATCH v1.1 2/5] IMA: define readcount functions

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Message-ID: <20101102004545.GQ2715@dastard>
Date:	Tue, 2 Nov 2010 11:45:45 +1100
From:	Dave Chinner <david@...morbit.com>
To:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
Cc:	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, jmorris@...ei.org,
	akpm@...ux-foundation.org, torvalds@...ux-foundation.org,
	eparis@...hat.com, viro@...iv.linux.org.uk,
	Mimi Zohar <zohar@...ibm.com>
Subject: Re: [PATCH v1.1 2/5] IMA: define readcount functions

On Mon, Nov 01, 2010 at 03:45:36PM -0400, Mimi Zohar wrote:
> Define iget/iput_readcount() functions to be called from the VFS layer.

Can't say I like the function names. i_readcount_{inc,dec} seem more
appropriate, especially so they don't get confused with inode
reference counting...

Cheers,

Dave.

> +void iput_readcount(struct inode *inode)
> +{
> +	spin_lock(&inode->i_lock);
> +	if (unlikely((atomic_read(&inode->i_readcount) == 0)))
> +		printk(KERN_INFO "i_readcount: imbalance ino %ld\n",
> +		       inode->i_ino);
> +	else
> +		atomic_dec(&inode->i_readcount);
> +	spin_unlock(&inode->i_lock);
> +}

No need for the lock just to indicate an imbalance. You could just
use:

	if (atomic_dec_return(&inode->i_readcount) < 0) {
		.....
	}

Given this is an integrity subsystem, I suspect the correct thing to
do here is BUG(), not just issue an informational message that
something is wrong with the integrity tracking....

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com
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