From c2cc7028e41c76e44b6e247c4b495c7523b23c87 Mon Sep 17 00:00:00 2001 From: Amir Goldstein Date: Sun, 20 Mar 2011 20:08:48 -0400 Subject: [PATCH] jbd2: add the b_cow_tid field to journal_head struct The b_cow_tid field will be used by the ext4 snapshots code to store the transaction id when the buffer was last cowed. Merging this patch to mainline will allow users to test ext4 snapshots as a standalone module, without the need to patch and install a development kernel. On 64bit machines this field uses fills in a padding "hole" and does not increase the size of the struct. On a 32bit machine this patch increases the size of the struct from 60 to 64 bytes. Signed-off-by: Amir Goldstein Signed-off-by: "Theodore Ts'o" --- include/linux/journal-head.h | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/include/linux/journal-head.h b/include/linux/journal-head.h index 525aac3c97df..44e95d0a721f 100644 --- a/include/linux/journal-head.h +++ b/include/linux/journal-head.h @@ -40,6 +40,13 @@ struct journal_head { */ unsigned b_modified; + /* + * This feild tracks the last transaction id in which this buffer + * has been cowed + * [jbd_lock_bh_state()] + */ + unsigned b_cow_tid; + /* * Copy of the buffer data frozen for writing to the log. * [jbd_lock_bh_state()]