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