On Thu, Sep 15, 2011 at 1:14 AM, Ted Ts'o <tytso@xxxxxxx> wrote: > On Wed, Sep 14, 2011 at 01:59:06PM -0600, Andreas Dilger wrote: >> >> There is the field that you told Amir he could use for the exception >> bitmap for snapshots, which is using one of the two reserved fields in >> ext2_group_desc, and also one of the 3 reserved fields in ext4_group_desc >> for 64-bit block numbers. That leaves one __u32 in ext2_group_desc, and >> two __u32 in ext4_group_desc for checksums. > > Right, that's what I was forgetting. Thanks for reminding me! > Thanks Andreas for reminding! Here is a patch to reserve the exclude bitmap field, so we won't forget them again... The full patch series for adding exclude bitmap can be found here: https://github.com/amir73il/e2fsprogs-snapshots-patch-queue --- From: Amir Goldstein <amir73il@xxxxxxxxxxxx> Date: Thu, 15 Sep 2011 09:42:38 +0300 Ext4 snapshots require the compatible feature 'exclude_bitmap', meaning that the exclude bitmap was allocated. The allocated exclude bitmap blocks are stored in the block group descriptors. To allow easy migration of existing Next3 installations, I took the liberty of 'burning' the old 'exclude_inode' compatible flag and using a new 'exclude_bitmap' comaptible flag, to state the exclude bitmap blocks are stored in the group descriptors. Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxxxxx> --- lib/ext2fs/ext2_fs.h | 13 +++++++++---- 1 files changed, 9 insertions(+), 4 deletions(-) diff --git a/lib/ext2fs/ext2_fs.h b/lib/ext2fs/ext2_fs.h index 54cb3d4..f1f0e19 100644 --- a/lib/ext2fs/ext2_fs.h +++ b/lib/ext2fs/ext2_fs.h @@ -142,7 +142,8 @@ struct ext2_group_desc __u16 bg_free_inodes_count; /* Free inodes count */ __u16 bg_used_dirs_count; /* Directories count */ __u16 bg_flags; - __u32 bg_reserved[2]; + __u32 bg_exclude_bitmap; /* Exclude bitmap block */ + __u32 bg_reserved[1]; __u16 bg_itable_unused; /* Unused inodes count */ __u16 bg_checksum; /* crc16(s_uuid+grouo_num+group_desc)*/ }; @@ -159,7 +160,8 @@ struct ext4_group_desc __u16 bg_free_inodes_count; /* Free inodes count */ __u16 bg_used_dirs_count; /* Directories count */ __u16 bg_flags; /* EXT4_BG_flags (INODE_UNINIT, etc) */ - __u32 bg_reserved[2]; /* Likely block/inode bitmap checksum */ + __u32 bg_exclude_bitmap; /* Exclude bitmap block */ + __u32 bg_reserved[1]; /* Likely block/inode bitmap checksum */ __u16 bg_itable_unused; /* Unused inodes count */ __u16 bg_checksum; /* crc16(sb_uuid+group+desc) */ __u32 bg_block_bitmap_hi; /* Blocks bitmap block MSB */ @@ -169,12 +171,14 @@ struct ext4_group_desc __u16 bg_free_inodes_count_hi;/* Free inodes count MSB */ __u16 bg_used_dirs_count_hi; /* Directories count MSB */ __u16 bg_itable_unused_hi; /* Unused inodes count MSB */ - __u32 bg_reserved2[3]; + __u32 bg_exclude_bitmap_hi; /* Exclude bitmap block MSB */ + __u32 bg_reserved2[2]; }; #define EXT2_BG_INODE_UNINIT 0x0001 /* Inode table/bitmap not initialized */ #define EXT2_BG_BLOCK_UNINIT 0x0002 /* Block bitmap not initialized */ #define EXT2_BG_INODE_ZEROED 0x0004 /* On-disk itable initialized to zero */ +#define EXT2_BG_EXCLUDE_UNINIT 0x0008 /* Exclude bitmap not initialized */ /* * Data structures used by the directory indexing feature @@ -670,7 +674,8 @@ struct ext2_super_block { #define EXT2_FEATURE_COMPAT_RESIZE_INODE 0x0010 #define EXT2_FEATURE_COMPAT_DIR_INDEX 0x0020 #define EXT2_FEATURE_COMPAT_LAZY_BG 0x0040 -#define EXT2_FEATURE_COMPAT_EXCLUDE_INODE 0x0080 +/* #define EXT2_FEATURE_COMPAT_EXCLUDE_INODE 0x0080 not used */ +#define EXT2_FEATURE_COMPAT_EXCLUDE_BITMAP 0x0100 #define EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER 0x0001 #define EXT2_FEATURE_RO_COMPAT_LARGE_FILE 0x0002 -- 1.7.0.4 -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
