From e339ad31f59925b48a92ee3947692fdf9758b8c7 Mon Sep 17 00:00:00 2001 From: Ryusuke Konishi Date: Mon, 6 Apr 2009 19:01:59 -0700 Subject: nilfs2: introduce secondary super block The former versions didn't have extra super blocks. This improves the weak point by introducing another super block at unused region in tail of the partition. This doesn't break disk format compatibility; older versions just ingore the secondary super block, and new versions just recover it if it doesn't exist. The partition created by an old mkfs may not have unused region, but in that case, the secondary super block will not be added. This doesn't make more redundant copies of the super block; it is a future work. Signed-off-by: Ryusuke Konishi Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/nilfs2_fs.h | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'include/linux') diff --git a/include/linux/nilfs2_fs.h b/include/linux/nilfs2_fs.h index cbce6647f7f..1275b309953 100644 --- a/include/linux/nilfs2_fs.h +++ b/include/linux/nilfs2_fs.h @@ -252,6 +252,10 @@ struct nilfs_super_block { #define NILFS_MIN_NRSVSEGS 8 /* Minimum number of reserved segments */ +/* + * bytes offset of secondary super block + */ +#define NILFS_SB2_OFFSET_BYTES(devsize) ((((devsize) >> 12) - 1) << 12) /* * Maximal count of links to a file -- cgit v1.2.3