linux-ext4 - [FOR-STABLE 20/20] ext4: add checksum calculation when clearing UNINIT flag in ext4_new

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Message-Id: <1226851540-8032-21-git-send-email-tytso@mit.edu>
Date:	Sun, 16 Nov 2008 11:05:40 -0500
From:	Theodore Ts'o <tytso@....edu>
To:	stable@...nel.org
Cc:	Ext4 Developers List <linux-ext4@...r.kernel.org>,
	Frederic Bohe <frederic.bohe@...l.net>,
	"Theodore Ts'o" <tytso@....edu>
Subject: [FOR-STABLE 20/20] ext4: add checksum calculation when clearing UNINIT flag in ext4_new_inode

From: Frederic Bohe <frederic.bohe@...l.net>

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 <frederic.bohe@...l.net>
Signed-off-by: "Theodore Ts'o" <tytso@....edu>
(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));
 
-- 
1.6.0.4.8.g36f27.dirty

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