jbd2: remove bh_state lock from checkpointing code

All accesses to checkpointing entries in journal_head are protected
by j_list_lock. Thus __jbd2_journal_remove_checkpoint() doesn't really
need bh_state lock.

Also the only part of journal head that the rest of checkpointing code
needs to check is jh->b_transaction which is safe to read under
j_list_lock.

So we can safely remove bh_state lock from all of checkpointing code which
makes it considerably prettier.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/linux/journal-head.h b/include/linux/journal-head.h
index 423cb6d78ee0..c18b46f8aeeb 100644
--- a/include/linux/journal-head.h
+++ b/include/linux/journal-head.h
@@ -66,6 +66,8 @@ struct journal_head {
 	 * transaction (if there is one).  Only applies to buffers on a
 	 * transaction's data or metadata journaling list.
 	 * [j_list_lock] [jbd_lock_bh_state()]
+	 * Either of these locks is enough for reading, both are needed for
+	 * changes.
 	 */
 	transaction_t *b_transaction;