linux-ext4 - [PATCH 01/02] ext2: reserve INCOMPAT

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Date:	Tue, 6 Dec 2011 17:13:51 -0700
From:	Andreas Dilger <adilger@...mcloud.com>
To:	Andreas Dilger <adilger@...mcloud.com>
Cc:	Theodore Ts'o <tytso@....edu>,
	ext4 development <linux-ext4@...r.kernel.org>,
	Liang Zhen <liang@...mcloud.com>, Tao Ma <tm@....ma>
Subject: [PATCH 01/02] ext2: reserve INCOMPAT_INLINEDATA feature flag

Reserve the EXT4_FEATURE_INCOMPAT_INLINEDATA feature flag for use
with storing small file data in the i_blocks field (up to 60 bytes)
and/or the large xattr space (after i_extra_isize, up to the large
inode size).  On typical filesystems this can save 1-3% of the space,
and more importantly it also avoids seeking to read the data block.

This will become increasingly important with bigalloc filesystems,
since they consume a full cluster of blocks for each file, including
small directories that could easily fit into the inode itself.

Signed-off-by: Andreas Dilger <adilger@...mcloud.com>
Originally-by: Tao Ma <tm@....ma>
---
 lib/ext2fs/ext2_fs.h |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/lib/ext2fs/ext2_fs.h b/lib/ext2fs/ext2_fs.h
index 0f8cde8..6cf47f9 100644
--- a/lib/ext2fs/ext2_fs.h
+++ b/lib/ext2fs/ext2_fs.h
@@ -719,6 +719,7 @@ struct ext2_super_block {
 #define EXT4_FEATURE_INCOMPAT_FLEX_BG		0x0200
 #define EXT4_FEATURE_INCOMPAT_EA_INODE		0x0400
 #define EXT4_FEATURE_INCOMPAT_DIRDATA		0x1000
+#define EXT4_FEATURE_INCOMPAT_INLINEDATA	0x2000 /* data in inode */

 #define EXT2_FEATURE_COMPAT_SUPP	0
 #define EXT2_FEATURE_INCOMPAT_SUPP    (EXT2_FEATURE_INCOMPAT_FILETYPE| \
-- 
1.7.2

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