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authorJan Kara <jack@suse.cz>2007-12-04 23:45:27 -0800
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-12-05 09:21:20 -0800
commitd4beaf4ab5f89496f2bcf67db62ad95d99bfeff6 (patch)
treeae6d005199017e9a0ade169fd69cb73d6c0ac88f /include/linux/jbd.h
parent369b8f5a70402d9fe77006cd0044c8a3fcd08430 (diff)
jbd: Fix assertion failure in fs/jbd/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> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/jbd.h')
-rw-r--r--include/linux/jbd.h2
1 files changed, 2 insertions, 0 deletions
diff --git a/include/linux/jbd.h b/include/linux/jbd.h
index 16e7ed855a18..d9ecd13393b0 100644
--- a/include/linux/jbd.h
+++ b/include/linux/jbd.h
@@ -439,6 +439,8 @@ struct transaction_s
/*
* Transaction's current state
* [no locking - only kjournald alters this]
+ * [j_list_lock] guards transition of a transaction into T_FINISHED
+ * state and subsequent call of __journal_drop_transaction()
* FIXME: needs barriers
* KLUDGE: [use j_state_lock]
*/