Subject: Re: [Ext2-devel] Re: [RFC] [PATCH] Reducing average ext2 fsck time
	through fs-wide dirty bit]
From: Mingming Cao <cmm@us.ibm.com>
Reply-To: cmm@us.ibm.com
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Valerie Henson <val_henson@linux.intel.com>, linux-kernel@vger.kernel.org,
       ext2-devel@lists.sourceforge.net,
       Arjan van de Ven <arjan@linux.intel.com>,
       "Theodore Ts'o" <tytso@mit.edu>, Zach Brown <zach.brown@oracle.com>
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References: <20060322011034.GP12571@goober>
	 <1143032930.3584.5.camel@localhost.localdomain>
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Organization: IBM LTC
Date: Wed, 22 Mar 2006 10:18:45 -0800
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On Wed, 2006-03-22 at 13:08 +0000, Alan Cox wrote:
> On Maw, 2006-03-21 at 17:10 -0800, Valerie Henson wrote:
> > The combination of the orphan inode and preallocation blocks problem
> > led me to another idea: create in-memory-only allocation bitmaps for
> > both inodes and blocks.  
> 
> This was actually done by Interactive Unix long ago to get sane
> performance of System 5 file systems which didnt directly use bitmaps.
> 
> I suspect you don't need a complete in memory bitmap list however, you
> just need an exceptions table of extents that are preallocated.
> Furthermore you can bound this by either releasing oldest preallocations
> or refusing new ones when you hit some kind of resource bound.
> 

This is pretty much what ext3 block reservation does, every inode has a
range of disk blocks(or call it extent) that are reserved (or call it
preallocated). 

> Similarly for inodes, except that you actually have the in memory
> exception list in the ext2 inodes in memory already (no inode is orphan
> unless open) so you may only need another list pointer to walk the
> orphans
> 
> Alan
> 
> 
> 
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