jbd2: reduce journal_head size
Remove unused t_cow_tid field (ext4 copy-on-write support doesn't seem
to be happening) and change b_modified and b_jlist to bitfields thus
saving 8 bytes in the structure.
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: Zheng Liu <wenqing.lz@taobao.com>
diff --git a/include/linux/journal-head.h b/include/linux/journal-head.h
index c18b46f..13a3da2 100644
--- a/include/linux/journal-head.h
+++ b/include/linux/journal-head.h
@@ -31,21 +31,14 @@
/*
* Journalling list for this buffer [jbd_lock_bh_state()]
*/
- unsigned b_jlist;
+ unsigned b_jlist:4;
/*
* This flag signals the buffer has been modified by
* the currently running transaction
* [jbd_lock_bh_state()]
*/
- unsigned b_modified;
-
- /*
- * This feild tracks the last transaction id in which this buffer
- * has been cowed
- * [jbd_lock_bh_state()]
- */
- tid_t b_cow_tid;
+ unsigned b_modified:1;
/*
* Copy of the buffer data frozen for writing to the log.