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ext3_extents.h
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/* * 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 */