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- .. SPDX-License-Identifier: GPL-2.0
- Block and inode Bitmaps
- -----------------------
- The data block bitmap tracks the usage of data blocks within the block
- group.
- The inode bitmap records which entries in the inode table are in use.
- As with most bitmaps, one bit represents the usage status of one data
- block or inode table entry. This implies a block group size of 8 \*
- number\_of\_bytes\_in\_a\_logical\_block.
- NOTE: If ``BLOCK_UNINIT`` is set for a given block group, various parts
- of the kernel and e2fsprogs code pretends that the block bitmap contains
- zeros (i.e. all blocks in the group are free). However, it is not
- necessarily the case that no blocks are in use -- if ``meta_bg`` is set,
- the bitmaps and group descriptor live inside the group. Unfortunately,
- ext2fs\_test\_block\_bitmap2() will return '0' for those locations,
- which produces confusing debugfs output.
- Inode Table
- -----------
- Inode tables are statically allocated at mkfs time. Each block group
- descriptor points to the start of the table, and the superblock records
- the number of inodes per group. See the section on inodes for more
- information.
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