linux-ext4 - [PATCH 04/29] jbd2: Reduce journal

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Date:	Mon,  8 Apr 2013 23:32:09 +0200
From:	Jan Kara <jack@...e.cz>
To:	Ted Tso <tytso@....edu>
Cc:	linux-ext4@...r.kernel.org, Jan Kara <jack@...e.cz>
Subject: [PATCH 04/29] 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@...e.cz>
---
 include/linux/journal-head.h |   11 ++---------
 1 files changed, 2 insertions(+), 9 deletions(-)

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 @@ 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.
-- 
1.7.1

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