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authorRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>2009-04-07 06:01:59 +0400
committerLinus Torvalds <torvalds@linux-foundation.org>2009-04-07 19:31:20 +0400
commite339ad31f59925b48a92ee3947692fdf9758b8c7 (patch)
tree6bb85c43bfd100b0a220c788c654f2f74ca553e4 /include/linux/nilfs2_fs.h
parentcece552074c591970353ad48308d65f110aeaf28 (diff)
downloadlinux-e339ad31f59925b48a92ee3947692fdf9758b8c7.tar.xz
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 <konishi.ryusuke@lab.ntt.co.jp> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/nilfs2_fs.h')
-rw-r--r--include/linux/nilfs2_fs.h4
1 files changed, 4 insertions, 0 deletions
diff --git a/include/linux/nilfs2_fs.h b/include/linux/nilfs2_fs.h
index cbce6647f7fd..1275b3099535 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