linux-ext4 - Re: [PATCH] introduce range check for extent pblock references

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Date:	Sat, 7 Feb 2009 23:02:39 +0530
From:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:	Thiemo Nagel <thiemo.nagel@...tum.de>
Cc:	Theodore Tso <tytso@....edu>,
	Ext4 Developers List <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] introduce range check for extent pblock references

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
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