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jbd2: reduce journal_head size

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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>
This commit is contained in:
Jan Kara 2013-04-12 00:03:42 -04:00 • committed by Theodore Ts'o
commit ae4647fb76
1 changed files with 2 additions and 9 deletions
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11
include/linux/journal-head.h
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@ -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.