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| Current File : //usr/include/ext2fs/ext3_extents.h |
/*
* 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 on-disk structure
* it's used at the bottom of the tree
*/
struct ext3_extent {
__u32 ee_block; /* first logical block extent covers */
__u16 ee_len; /* number of blocks covered by extent */
__u16 ee_start_hi; /* high 16 bits of physical block */
__u32 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 {
__u32 ei_block; /* index covers logical blocks from 'block' */
__u32 ei_leaf; /* pointer to the physical block of the next *
* level. leaf or next index could bet here */
__u16 ei_leaf_hi; /* high 16 bits of physical block */
__u16 ei_unused;
};
/*
* each block (leaves and indexes), even inode-stored has header
*/
struct ext3_extent_header {
__u16 eh_magic; /* probably will support different formats */
__u16 eh_entries; /* number of valid entries */
__u16 eh_max; /* capacity of store in entries */
__u16 eh_depth; /* has tree real underlaying blocks? */
__u32 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_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 */