linux-ext4 - [patch 19/35] jbd2: correctly unescape journal data blocks

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Message-Id: <200803200000.m2K00s63011848@imap1.linux-foundation.org>
Date:	Wed, 19 Mar 2008 17:00:54 -0700
From:	akpm@...ux-foundation.org
To:	torvalds@...ux-foundation.org
Cc:	akpm@...ux-foundation.org, duaneg@...da.com, jack@...e.cz,
	linux-ext4@...r.kernel.org, stable@...nel.org
Subject: [patch 19/35] jbd2: correctly unescape journal data blocks

From: "Duane Griffin" <duaneg@...da.com>

Fix a long-standing typo (predating git) that will cause data corruption if a
journal data block needs unescaping.  At the moment the wrong buffer head's
data is being unescaped.

To test this case mount a filesystem with data=journal, start creating and
deleting a bunch of files containing only JBD2_MAGIC_NUMBER (0xc03b3998), then
pull the plug on the device.  Without this patch the files will contain zeros
instead of the correct data after recovery.

Signed-off-by: Duane Griffin <duaneg@...da.com>
Acked-by: Jan Kara <jack@...e.cz>
Cc: <linux-ext4@...r.kernel.org>
Cc: <stable@...nel.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
---

 fs/jbd2/recovery.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff -puN fs/jbd2/recovery.c~jbd2-correctly-unescape-journal-data-blocks fs/jbd2/recovery.c
--- a/fs/jbd2/recovery.c~jbd2-correctly-unescape-journal-data-blocks
+++ a/fs/jbd2/recovery.c
@@ -535,7 +535,7 @@ static int do_one_pass(journal_t *journa
 					memcpy(nbh->b_data, obh->b_data,
 							journal->j_blocksize);
 					if (flags & JBD2_FLAG_ESCAPE) {
-						*((__be32 *)bh->b_data) =
+						*((__be32 *)nbh->b_data) =
 						cpu_to_be32(JBD2_MAGIC_NUMBER);
 					}
 
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