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1.. SPDX-License-Identifier: GPL-2.0
2
3Block and inode Bitmaps
4-----------------------
5
6The data block bitmap tracks the usage of data blocks within the block
7group.
8
9The inode bitmap records which entries in the inode table are in use.
10
11As with most bitmaps, one bit represents the usage status of one data
12block or inode table entry. This implies a block group size of 8 *
13number_of_bytes_in_a_logical_block.
14
15NOTE: If ``BLOCK_UNINIT`` is set for a given block group, various parts
16of the kernel and e2fsprogs code pretends that the block bitmap contains
17zeros (i.e. all blocks in the group are free). However, it is not
18necessarily the case that no blocks are in use -- if ``meta_bg`` is set,
19the bitmaps and group descriptor live inside the group. Unfortunately,
20ext2fs_test_block_bitmap2() will return '0' for those locations,
21which produces confusing debugfs output.