linux-kernel - Re: [PATCH 15/41] whiteout: ext2 whiteout support

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Message-ID: <20091027021426.GA14574@shell>
Date:	Mon, 26 Oct 2009 22:14:26 -0400
From:	Valerie Aurora <vaurora@...hat.com>
To:	Andreas Dilger <adilger@....com>
Cc:	Jan Blunck <jblunck@...e.de>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Christoph Hellwig <hch@...radead.org>,
	Andy Whitcroft <apw@...onical.com>,
	Scott James Remnant <scott@...onical.com>,
	Sandu Popa Marius <sandupopamarius@...il.com>,
	Jan Rekorajski <baggins@...h.mimuw.edu.pl>,
	"J. R. Okajima" <hooanon05@...oo.co.jp>,
	Arnd Bergmann <arnd@...db.de>,
	Vladimir Dronnikov <dronnikov@...il.com>,
	Felix Fietkau <nbd@...nwrt.org>, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org, Theodore Tso <tytso@....edu>,
	linux-ext4@...r.kernel.org
Subject: Re: [PATCH 15/41] whiteout: ext2 whiteout support

On Wed, Oct 21, 2009 at 03:17:38PM -0600, Andreas Dilger wrote:
> On 2009-10-21, at 13:19, Valerie Aurora wrote:
> >This patch adds whiteout support to EXT2. A whiteout is an empty  
> >directory
> >entry (inode == 0) with the file type set to EXT2_FT_WHT. Therefore it
> >allocates space in directories. Due to being implemented as a  
> >filetype it is
> >necessary to have the EXT2_FEATURE_INCOMPAT_FILETYPE flag set.
> >
> >diff --git a/include/linux/ext2_fs.h b/include/linux/ext2_fs.h
> >index 121720d..bd10826 100644
> >--- a/include/linux/ext2_fs.h
> >+++ b/include/linux/ext2_fs.h
> >@@ -189,6 +189,7 @@ struct ext2_group_desc
> >+#define EXT2_OPAQUE_FL			0x00040000
> 
> Please check in the upstream e2fsprogs ext2_fs.h before defining new  
> flag
> values for ext2/3/4.  In this case, 0x40000 conflicts with  
> EXT4_HUGE_FILE_FL,
> which is of course bad.
> 
> 
> >@@ -503,10 +504,12 @@ struct ext2_super_block {
> >#define EXT2_FEATURE_INCOMPAT_META_BG		0x0010
> >+#define EXT2_FEATURE_INCOMPAT_WHITEOUT		0x0020
> 
> This one doesn't conflict, probably due to luck, because 0x0040-0x0200  
> are
> already in use for other features.  I'm not sure if 0x0020 was  
> reserved for
> some other use, or just skipped to avoid potential conflicts.

Thanks for reviewing!  I'll fix that in the next rev.

-VAL
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