linux-ext4 - Re: Block allocation in EXT4

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Date:	Mon, 26 Aug 2013 12:54:31 -0500
From:	Eric Sandeen <sandeen@...hat.com>
To:	Subranshu Patel <spatel.ml@...il.com>
CC:	linux-ext4@...r.kernel.org
Subject: Re: Block allocation in EXT4

On 8/26/13 10:55 AM, Subranshu Patel wrote:
>  In EXT4 it seems that both direct/indirect and extent tree based
> block allocation is used. I used debugfs and it seems that the root
> inode uses the direct/indirect block allocation. The other files and
> direcyories used extent based allocation.
> 
> Do all the EXT4 reserved inode (0 -11) use the direct/indirect
> allocation scheme?

Nope; looks like a leftover oddity from old mkfs.

mkfs-time created dirs weren't created w/ the extents flag until:

commit 1afb468b9a80031b39eab37272709f45727fb221
Author: Theodore Ts'o <tytso@....edu>
Date:   Fri Jun 10 13:58:18 2011 -0400

    libext2fs: create extent-based directories if the extents feature is enabled
    
    This allows mke2fs to create the root and lost+found directories using
    extents.
    
    Signed-off-by: "Theodore Ts'o" <tytso@....edu>

so newly mkfs'd filesystems w/ newer e2fsprogs shouldn't exhibit
what you see.

-Eric

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