1*8a98ec7cSDarrick J. Wong.. SPDX-License-Identifier: GPL-2.0 2*8a98ec7cSDarrick J. Wong 3*8a98ec7cSDarrick J. WongBlock and inode Bitmaps 4*8a98ec7cSDarrick J. Wong----------------------- 5*8a98ec7cSDarrick J. Wong 6*8a98ec7cSDarrick J. WongThe data block bitmap tracks the usage of data blocks within the block 7*8a98ec7cSDarrick J. Wonggroup. 8*8a98ec7cSDarrick J. Wong 9*8a98ec7cSDarrick J. WongThe inode bitmap records which entries in the inode table are in use. 10*8a98ec7cSDarrick J. Wong 11*8a98ec7cSDarrick J. WongAs with most bitmaps, one bit represents the usage status of one data 12*8a98ec7cSDarrick J. Wongblock or inode table entry. This implies a block group size of 8 \* 13*8a98ec7cSDarrick J. Wongnumber\_of\_bytes\_in\_a\_logical\_block. 14*8a98ec7cSDarrick J. Wong 15*8a98ec7cSDarrick J. WongNOTE: If ``BLOCK_UNINIT`` is set for a given block group, various parts 16*8a98ec7cSDarrick J. Wongof the kernel and e2fsprogs code pretends that the block bitmap contains 17*8a98ec7cSDarrick J. Wongzeros (i.e. all blocks in the group are free). However, it is not 18*8a98ec7cSDarrick J. Wongnecessarily the case that no blocks are in use -- if ``meta_bg`` is set, 19*8a98ec7cSDarrick J. Wongthe bitmaps and group descriptor live inside the group. Unfortunately, 20*8a98ec7cSDarrick J. Wongext2fs\_test\_block\_bitmap2() will return '0' for those locations, 21*8a98ec7cSDarrick J. Wongwhich produces confusing debugfs output. 22*8a98ec7cSDarrick J. Wong 23*8a98ec7cSDarrick J. WongInode Table 24*8a98ec7cSDarrick J. Wong----------- 25*8a98ec7cSDarrick J. WongInode tables are statically allocated at mkfs time. Each block group 26*8a98ec7cSDarrick J. Wongdescriptor points to the start of the table, and the superblock records 27*8a98ec7cSDarrick J. Wongthe number of inodes per group. See the section on inodes for more 28*8a98ec7cSDarrick J. Wonginformation. 29