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authorJan Kara <jack@suse.cz>2008-01-28 23:58:27 -0500
committerTheodore Ts'o <tytso@mit.edu>2008-01-28 23:58:27 -0500
commitf5a7a6b0d9b6af7d46124ed3f6b3995225cb62d0 (patch)
treecbb2bc79a488461bf3bec9b60d15e21717dc8360 /include/linux/jbd2.h
parent36df53f4a3e445175fc1e9d7f433599482ec6d7f (diff)
jbd2: Fix assertion failure in fs/jbd2/checkpoint.c
Before we start committing a transaction, we call __journal_clean_checkpoint_list() to cleanup transaction's written-back buffers. If this call happens to remove all of them (and there were already some buffers), __journal_remove_checkpoint() will decide to free the transaction because it isn't (yet) a committing transaction and soon we fail some assertion - the transaction really isn't ready to be freed :). We change the check in __journal_remove_checkpoint() to free only a transaction in T_FINISHED state. The locking there is subtle though (as everywhere in JBD ;(). We use j_list_lock to protect the check and a subsequent call to __journal_drop_transaction() and do the same in the end of journal_commit_transaction() which is the only place where a transaction can get to T_FINISHED state. Probably I'm too paranoid here and such locking is not really necessary - checkpoint lists are processed only from log_do_checkpoint() where a transaction must be already committed to be processed or from __journal_clean_checkpoint_list() where kjournald itself calls it and thus transaction cannot change state either. Better be safe if something changes in future... Signed-off-by: Jan Kara <jack@suse.cz> Cc: <linux-ext4@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'include/linux/jbd2.h')
-rw-r--r--include/linux/jbd2.h2
1 files changed, 2 insertions, 0 deletions
diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
index d5f7cff4cb2..d861ffd4982 100644
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h
@@ -442,6 +442,8 @@ struct transaction_s
/*
* Transaction's current state
* [no locking - only kjournald2 alters this]
+ * [j_list_lock] guards transition of a transaction into T_FINISHED
+ * state and subsequent call of __jbd2_journal_drop_transaction()
* FIXME: needs barriers
* KLUDGE: [use j_state_lock]
*/