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Date:	Sun, 16 Nov 2008 11:05:40 -0500
From:	Theodore Ts'o <>
Cc:	Ext4 Developers List <>,
	Frederic Bohe <>,
	"Theodore Ts'o" <>
Subject: [FOR-STABLE 20/20] ext4: add checksum calculation when clearing UNINIT flag in ext4_new_inode

From: Frederic Bohe <>

When initializing an uninitialized block group in ext4_new_inode(),
its block group checksum must be re-calculated.  This fixes a race
when several threads try to allocate a new inode in an UNINIT'd group.

There is some question whether we need to be initializing the block
bitmap in ext4_new_inode() at all, but for now, if we are going to
init the block group, let's eliminate the race.

Signed-off-by: Frederic Bohe <>
Signed-off-by: "Theodore Ts'o" <>
(cherry picked from commit 23712a9c28b9f80a8cf70c8490358d5f562d2465)
 fs/ext4/ialloc.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index 84e5bbf..13efb5f 100644
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -717,6 +717,8 @@ got:
 			gdp->bg_flags &= cpu_to_le16(~EXT4_BG_BLOCK_UNINIT);
 			free = ext4_free_blocks_after_init(sb, group, gdp);
 			gdp->bg_free_blocks_count = cpu_to_le16(free);
+			gdp->bg_checksum = ext4_group_desc_csum(sbi, group,
+								gdp);
 		spin_unlock(sb_bgl_lock(sbi, group));

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