linux-ext4 - [PATCH] e2fsck: update j_tail

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Date:	Mon, 25 Apr 2016 13:43:32 +0900
From:	Daeho Jeong <daeho.jeong@...sung.com>
To:	tytso@....edu, linux-ext4@...r.kernel.org
Cc:	Daeho Jeong <daeho.jeong@...sung.com>,
	Youngjin Gil <youngjin.gil@...sung.com>
Subject: [PATCH] e2fsck: update j_tail_sequence after recovery

When journal is released, s_sequence is set to j_tail_sequence.
But, currently, even if the recovery process is successfully completed,
the j_tail_sequence and, finally, s_sequence are never changed. By this,
when we repeat doing power-off the device suddenly and executing e2fsck
without full scan before mount, the s_sequence number will never change
and, in a very rare case, newly generated journal logs will be
surprisingly grafted to the old journal logs. In this case, out-of-date
metadata log can be replayed on the filesystem area and the filesystem
can be crashed unintentionally by journal recovery process. Therefore,
we need to update j_tail_sequence after recovery process is successfully
completed in e2fsck.

Youngjin had repeated this test and found the problem. With our test,
the filesystem crash occurred within 4 hours.

Signed-off-by: Youngjin Gil <youngjin.gil@...sung.com>
Signed-off-by: Daeho Jeong <daeho.jeong@...sung.com>
---
 e2fsck/journal.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/e2fsck/journal.c b/e2fsck/journal.c
index c8ac57d..83256d8 100644
--- a/e2fsck/journal.c
+++ b/e2fsck/journal.c
@@ -948,6 +948,8 @@ static errcode_t recover_ext3_journal(e2fsck_t ctx)
 		mark_buffer_dirty(journal->j_sb_buffer);
 	}

+	journal->j_tail_sequence = journal->j_transaction_sequence;
+
 errout:
 	journal_destroy_revoke(journal);
 	journal_destroy_revoke_caches();
-- 
1.7.9.5

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