From e615391896064eb5a0c760d086b8e1c6ecfffeab Mon Sep 17 00:00:00 2001 From: "Darrick J. Wong" Date: Sun, 29 Apr 2012 18:23:10 -0400 Subject: ext4: change on-disk layout to support extended metadata checksumming Define flags and change structure definitions to allow checksumming of ext4 metadata. Signed-off-by: Darrick J. Wong Signed-off-by: "Theodore Ts'o" --- fs/ext4/ext4_extents.h | 13 +++++++++++++ 1 file changed, 13 insertions(+) (limited to 'fs/ext4/ext4_extents.h') diff --git a/fs/ext4/ext4_extents.h b/fs/ext4/ext4_extents.h index 0f58b86e3a02..94822e74ef73 100644 --- a/fs/ext4/ext4_extents.h +++ b/fs/ext4/ext4_extents.h @@ -63,8 +63,21 @@ * ext4_inode has i_block array (60 bytes total). * The first 12 bytes store ext4_extent_header; * the remainder stores an array of ext4_extent. + * For non-inode extent blocks, ext4_extent_tail + * follows the array. */ +/* + * This is the extent tail on-disk structure. + * All other extent structures are 12 bytes long. It turns out that + * block_size % 12 >= 4 for at least all powers of 2 greater than 512, which + * covers all valid ext4 block sizes. Therefore, this tail structure can be + * crammed into the end of the block without having to rebalance the tree. + */ +struct ext4_extent_tail { + __le32 et_checksum; /* crc32c(uuid+inum+extent_block) */ +}; + /* * This is the extent on-disk structure. * It's used at the bottom of the tree. -- cgit v1.2.1