linux-ext4 - Re: Motion to nuke FS_DIRECTIO

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Date:	Mon, 25 Jan 2010 09:31:27 +0000
From:	Steven Whitehouse <swhiteho@...hat.com>
To:	tytso@....edu
Cc:	Andreas Dilger <adilger@....com>, linux-ext4@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Subject: Re: Motion to nuke FS_DIRECTIO_FL

Hi,

On Mon, 2010-01-25 at 03:06 -0500, tytso@....edu wrote:
> On Sun, Jan 24, 2010 at 11:18:47PM -0700, Andreas Dilger wrote:
> > 
> > It doesn't seem that ext2/3/4 are using the 0x00100000 value itself,
> > but it seems the VFS is using this value for FS_DIRECTIO_FL.  Should
> > we reserve this in the ext4 flags also, to avoid collisions?  I'm
> > not sure what that flag is for, possibly to force all IO to the file
> > to be uncached?
> 
> Hmm, absolutely nothing seems to use FS_DIRECTIO_FL; it looks like it
> was introduced by GFS2 in commit 128e5eba in 2006 and then dropped in
> commit c9f6a6bb in 2008, but we never killed the FS_DIRECTIO_FL flag
> itself in include/linux/fs.h.
> 
> The summary line for c9f6a6bb is a bit amusing:
> 
>     [GFS2] Remove support for unused and pointless flag
> 
> Heh.
> 
> Sounds like we should just kill it.  Any objections?
> 
> 					- Ted
No. Sounds good to me. It was never used with GFS2 and it a left-over
from GFS1 which had a flag allowing all "normal" I/O to be turned into
O_DIRECT I/O depending on an inode flag. The idea failed due to
alignment restrictions of course and nobody actually used it,

Steve.


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