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>

1 files changed, 2 insertions, 9 deletions

diff --git a/include/linux/journal-head.h b/include/linux/journal-head.h
index c18b46f8aeeb..13a3da25ff07 100644
--- a/include/linux/journal-head.h
+++ b/include/linux/journal-head.h
@@ -31,21 +31,14 @@ struct journal_head {
         /*
          * 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.