| .. SPDX-License-Identifier: GPL-2.0 | |
| High Level Design | |
| ================= | |
| An ext4 file system is split into a series of block groups. To reduce | |
| performance difficulties due to fragmentation, the block allocator tries | |
| very hard to keep each file's blocks within the same group, thereby | |
| reducing seek times. The size of a block group is specified in | |
| ``sb.s_blocks_per_group`` blocks, though it can also calculated as 8 \* | |
| ``block_size_in_bytes``. With the default block size of 4KiB, each group | |
| will contain 32,768 blocks, for a length of 128MiB. The number of block | |
| groups is the size of the device divided by the size of a block group. | |
| All fields in ext4 are written to disk in little-endian order. HOWEVER, | |
| all fields in jbd2 (the journal) are written to disk in big-endian | |
| order. | |
| .. include:: blocks.rst | |
| .. include:: blockgroup.rst | |
| .. include:: special_inodes.rst | |
| .. include:: allocators.rst | |
| .. include:: checksums.rst | |
| .. include:: bigalloc.rst | |
| .. include:: inlinedata.rst | |
| .. include:: eainode.rst | |
| .. include:: verity.rst |