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Diffstat (limited to 'lib/ext2fs/ext3_extents.h')
| -rw-r--r-- | lib/ext2fs/ext3_extents.h | 127 |
1 files changed, 127 insertions, 0 deletions
diff --git a/lib/ext2fs/ext3_extents.h b/lib/ext2fs/ext3_extents.h new file mode 100644 index 0000000..309fbc8 --- /dev/null +++ b/lib/ext2fs/ext3_extents.h @@ -0,0 +1,127 @@ +/* + * Copyright (c) 2003,2004 Cluster File Systems, Inc, info@clusterfs.com + * Written by Alex Tomas <alex@clusterfs.com> + * + * %Begin-Header% + * This file may be redistributed under the terms of the GNU Library + * General Public License, version 2. + * %End-Header% + */ + +#ifndef _LINUX_EXT3_EXTENTS +#define _LINUX_EXT3_EXTENTS + +/* + * ext3_inode has i_block array (total 60 bytes) + * first 4 bytes are used to store: + * - tree depth (0 mean there is no tree yet. all extents in the inode) + * - number of alive extents in the inode + */ + +/* + * This is 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 ext3_extent_tail { + __le32 et_checksum; /* crc32c(uuid+inum+extent_block) */ +}; + +/* + * this is extent on-disk structure + * it's used at the bottom of the tree + */ +struct ext3_extent { + __le32 ee_block; /* first logical block extent covers */ + __le16 ee_len; /* number of blocks covered by extent */ + __le16 ee_start_hi; /* high 16 bits of physical block */ + __le32 ee_start; /* low 32 bigs of physical block */ +}; + +/* + * this is index on-disk structure + * it's used at all the levels, but the bottom + */ +struct ext3_extent_idx { + __le32 ei_block; /* index covers logical blocks from 'block' */ + __le32 ei_leaf; /* pointer to the physical block of the next * + * level. leaf or next index could bet here */ + __le16 ei_leaf_hi; /* high 16 bits of physical block */ + __le16 ei_unused; +}; + +/* + * each block (leaves and indexes), even inode-stored has header + */ +struct ext3_extent_header { + __le16 eh_magic; /* probably will support different formats */ + __le16 eh_entries; /* number of valid entries */ + __le16 eh_max; /* capacity of store in entries */ + __le16 eh_depth; /* has tree real underlying blocks? */ + __le32 eh_generation; /* generation of the tree */ +}; + +#define EXT3_EXT_MAGIC 0xf30a + +/* + * array of ext3_ext_path contains path to some extent + * creation/lookup routines use it for traversal/splitting/etc + * truncate uses it to simulate recursive walking + */ +struct ext3_ext_path { + __u32 p_block; + __u16 p_depth; + struct ext3_extent *p_ext; + struct ext3_extent_idx *p_idx; + struct ext3_extent_header *p_hdr; + struct buffer_head *p_bh; +}; + +/* + * EXT_INIT_MAX_LEN is the maximum number of blocks we can have in an + * initialized extent. This is 2^15 and not (2^16 - 1), since we use the + * MSB of ee_len field in the extent datastructure to signify if this + * particular extent is an initialized extent or an uninitialized (i.e. + * preallocated). + * EXT_UNINIT_MAX_LEN is the maximum number of blocks we can have in an + * uninitialized extent. + * If ee_len is <= 0x8000, it is an initialized extent. Otherwise, it is an + * uninitialized one. In other words, if MSB of ee_len is set, it is an + * uninitialized extent with only one special scenario when ee_len = 0x8000. + * In this case we can not have an uninitialized extent of zero length and + * thus we make it as a special case of initialized extent with 0x8000 length. + * This way we get better extent-to-group alignment for initialized extents. + * Hence, the maximum number of blocks we can have in an *initialized* + * extent is 2^15 (32768) and in an *uninitialized* extent is 2^15-1 (32767). + */ +#define EXT_INIT_MAX_LEN (1UL << 15) +#define EXT_UNINIT_MAX_LEN (EXT_INIT_MAX_LEN - 1) +#define EXT_MAX_EXTENT_LBLK (((__u64) 1 << 32) - 1) +#define EXT_MAX_EXTENT_PBLK (((__u64) 1 << 48) - 1) + +#define EXT_FIRST_EXTENT(__hdr__) \ + ((struct ext3_extent *) (((char *) (__hdr__)) + \ + sizeof(struct ext3_extent_header))) +#define EXT_FIRST_INDEX(__hdr__) \ + ((struct ext3_extent_idx *) (((char *) (__hdr__)) + \ + sizeof(struct ext3_extent_header))) +#define EXT_HAS_FREE_INDEX(__path__) \ + (ext2fs_le16_to_cpu((__path__)->p_hdr->eh_entries) < \ + ext2fs_le16_to_cpu((__path__)->p_hdr->eh_max)) +#define EXT_LAST_EXTENT(__hdr__) \ + (EXT_FIRST_EXTENT((__hdr__)) + \ + ext2fs_le16_to_cpu((__hdr__)->eh_entries) - 1) +#define EXT_LAST_INDEX(__hdr__) \ + (EXT_FIRST_INDEX((__hdr__)) + \ + ext2fs_le16_to_cpu((__hdr__)->eh_entries) - 1) +#define EXT_MAX_EXTENT(__hdr__) \ + (EXT_FIRST_EXTENT((__hdr__)) + \ + ext2fs_le16_to_cpu((__hdr__)->eh_max) - 1) +#define EXT_MAX_INDEX(__hdr__) \ + (EXT_FIRST_INDEX((__hdr__)) + \ + ext2fs_le16_to_cpu((__hdr__)->eh_max) - 1) + +#endif /* _LINUX_EXT3_EXTENTS */ + |