linux-ext4 - Re: [Bug 9866] New: chattr sticky behaviour and Orlov block allocator

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Message-Id: <20080201102804.38f61075.akpm@linux-foundation.org>
Date:	Fri, 1 Feb 2008 10:28:04 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>
Cc:	bugme-daemon@...zilla.kernel.org, Joerg-Cyril.Hoehle@...ystems.com
Subject: Re: [Bug 9866] New: chattr sticky behaviour and Orlov block
 allocator

On Fri,  1 Feb 2008 07:25:09 -0800 (PST) bugme-daemon@...zilla.kernel.org wrote:

> http://bugzilla.kernel.org/show_bug.cgi?id=9866
> 
>            Summary: chattr sticky behaviour and Orlov block allocator
>            Product: File System
>            Version: 2.5
>      KernelVersion: 2.6.22
>           Platform: All
>         OS/Version: Linux
>               Tree: Mainline
>             Status: NEW
>           Severity: normal
>           Priority: P1
>          Component: ext3
>         AssignedTo: akpm@...l.org
>         ReportedBy: Joerg-Cyril.Hoehle@...ystems.com
> 
> 
> Latest working kernel version: 2.6.22
> Earliest failing kernel version: 2.6.18 (oldest tested)
> Distribution: Ubuntu Gutsy
> Hardware Environment: Fujitsu Siemens C1110 laptop
> Software Environment: chattr 1.40.2 (12-Jul-2007), mke2fs 1.40.2 (12-Jul-2007)
> Problem Description:
> Some file attributes have sticky behaviour in ext2/3 whereas I believe
> it should not. Namely, a directory marked with chattr +T serves "to be
> the top of directory hierarchies for the purposes of the Orlov block
> allocator", as the manpage says.
> 
> It seems wrong that subdirectories stickily inherit the +T flag: they
> are obviously not top-level! Even files get the T attribute this way,
> even though the chattr manpages only documents it for directories.
> 
> References:
> http://lwn.net/Articles/14633/
> http://lwn.net/Articles/14447/ Theodore Ts'o ext3 patch
> http://en.wikipedia.org/wiki/Orlov_block_allocator
> 
> 
> Steps to reproduce:
> The following shows the sticky behaviour:
> $ mkdir tests
> chattr -V +T tests
> chattr 1.40.2 (12-Jul-2007)
> Flags von tests wie folgt gesetzt: ----------------T-
> $ mkdir tests/src
> $ cp -dp /etc/fstab tests/src
> $ lsattr . tests tests/src
> ----------------T- ./tests
> ----------------T- tests/src
> ----------------T- tests/src/fstab
> 
> I verified (using cp -dpr and ls -lifR) that indeed, the inherited T
> attribute causes all subdirectories to be created in inodes far apart
> (like with mount -o remount,oldalloc), whereas the Orlov allocator
> normally would put the directories next to each other.  My expectation
> is that only e.g. /home/user{1,2,3,4,5,6} should be created spread
> out, whereas each user home's contents would be next each other
> (/home/user1/{foo,bar,etc}).
> 
> The effect of this bug makes chattr +T unusable, because Orlov
> optimization is de facto eliminated.
> 
> Regards,
>  Jörg Höhle
> 
> 
> -- 
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