From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Subject: Re: [PATCH] introduce range check for extent pblock references
Date: Sat, 7 Feb 2009 23:02:39 +0530
Message-ID: <20090207173239.GA25942@skywalker>
References: <498DAA9A.8030309@ph.tum.de>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Cc: Theodore Tso <tytso@mit.edu>,
	Ext4 Developers List <linux-ext4@vger.kernel.org>
To: Thiemo Nagel <thiemo.nagel@ph.tum.de>
Content-Disposition: inline
In-Reply-To: <498DAA9A.8030309@ph.tum.de>
Sender: linux-ext4-owner@vger.kernel.org

On Sat, Feb 07, 2009 at 04:36:58PM +0100, Thiemo Nagel wrote:
> This time I have aimed to catch all cases in which an invalid physical  
> block might be used and implemented checks directly in ext_pblock() and  
> idx_pblock() following the assumption that most of the times one of  
> these functions is called a device access to that address will follow.  
> If you think this is too heavy, I could also split the check from the  
> pblock calculation, but in that case I could only guess at which of the  
> several accesses to *_pblock() in extents.c a check would be necessary  
> and where it wouldn't and there would be the possibility of missing  
> something.


Do we want to check for validity every time we look at the physical
block of the extent. I guess that would be bad performance wise. I guess
we should check only once when we read the extent from the disk. ??

-aneesh