huven
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2 years ago | |
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blockdev | 8 years ago | |
fs_test | 2 years ago | |
include | 2 years ago | |
src | 2 years ago | |
toolchain | 8 years ago | |
.clang-format | 9 years ago | |
.gitignore | 9 years ago | |
.travis.yml | 9 years ago | |
CHANGELOG | 9 years ago | |
CMakeLists.txt | 6 years ago | |
LICENSE | 8 years ago | |
Makefile | 8 years ago | |
README.md | 6 years ago | |
_config.yml | 8 years ago | |
fs_test.mk | 8 years ago |
README.md
About
The main goal of the lwext4 project is to provide ext2/3/4 filesystem for microcontrollers. It may be an interesting alternative for traditional MCU filesystem libraries (mostly based on FAT32). Library has some cool and unique features in microcontrollers world:
- directory indexing - fast file find and list operations
- extents - fast big file truncate
- journaling transactions & recovery - power loss resistance
Lwext4 is an excellent choice for SD/MMC card, USB flash drive or any other wear leveled memory types. However it is not good for raw flash devices.
Feel free to contact me: kostka.grzegorz@gmail.com
Credits
The most of the source code of lwext4 was taken from HelenOS:
Some features are based on FreeBSD and Linux implementations.
KaHo Ng (https://github.com/ngkaho1234):
- advanced extents implementation
- xattr support
- metadata checksum support
- journal recovery & transactions
- many bugfixes & improvements
Lwext4 could be used also as fuse internals. Here is a nice project which uses lwext4 as a filesystem base:
Some of the source files are licensed under GPLv2. It makes whole lwext4 GPLv2 licensed. To use library as a BSD3, GPLv2 licensed source files must be removed first. At this point there are two files licensed under GPLv2:
- ext4_xattr.c
- ext4_extents.c
All other modules and headers are BSD-3-Clause licensed code.
Features
- filetypes: regular, directories, softlinks
- support for hardlinks
- multiple blocksize supported: 1KB, 2KB, 4KB ... 64KB
- little/big endian architectures supported
- multiple configurations (ext2/ext3/ext4)
- only C standard library dependency
- various CPU architectures supported (x86/64, cortex-mX, msp430 ...)
- small memory footprint
- flexible configurations
Memory footprint
Advanced ext4 filesystem features, like extents or journaling require some memory. However most of the memory expensive features could be disabled at compile time. Here is a brief summary for cortex-m4 processor:
- .text: 20KB - only ext2 fs support , 50KB - full ext4 fs feature set
- .data: 8KB - minimum 8 x 1KB block cache, 12KB - when journaling and extents are enabled
- .stack: 2KB - is enough (not measured precisely)
Blocks are allocated dynamically. Previous versions of library could work without malloc but from 1.0.0 dynamic memory allocation is required. However, block cache should not allocate more than CONFIG_BLOCK_DEV CACHE_SIZE.
Supported ext2/3/4 features
incompatible:
- filetype, recover, meta_bg, extents, 64bit, flex_bg: yes
- compression, journal_dev, mmp, ea_inode, dirdata, bg_meta_csum, largedir, inline_data: no
compatible:
- has_journal, ext_attr, dir_index: yes
- dir_prealloc, imagic_inodes, resize_inode: no
read-only:
- sparse_super, large_file, huge_file, gdt_csum, dir_nlink, extra_isize, metadata_csum: yes
- quota, bigalloc, btree_dir: no
Project tree
- blockdev - block devices set, supported blockdev
- fs_test - test suite, mkfs and demo application
- src - source files
- include - header files
- toolchain - cmake toolchain files
- CMakeLists.txt - CMake config file
- ext_images.7z - compressed ext2/3/4 100MB images
- fs_test.mk - automatic tests definitions
- Makefile - helper makefile to generate cmake and run test suite
- README.md - readme file
Compile
Dependencies
- Windows
Download MSYS-2: https://sourceforge.net/projects/msys2/
Install required packages is MSYS2 Shell package manager:
pacman -S make gcc cmake p7zip
- Linux
Package installation (Debian):
apt-get install make gcc cmake p7zip
Compile & install tools
make generic
cd build_generic
make
sudo make install
lwext4-generic demo application
Simple lwext4 library test application:
- load ext2/3/4 images
- load linux block device with ext2/3/4 part
- load windows volume with ext2/3/4 filesystem
- directory speed test
- file write/read speed test
How to use for images/blockdevices:
lwext4-generic -i ext_images/ext2
lwext4-generic -i ext_images/ext3
lwext4-generic -i ext_images/ext4
Show full option set:
lwext4-generic --help
Run automatic tests
Execute tests for 100MB unpacked images:
make test
Execute tests for autogenerated 1GB images (only on Linux targets) + fsck:
make test_all
Using lwext4-mkfs tool
It is possible to create ext2/3/4 partition by internal library tool.
Generate empty file (1GB):
dd if=/dev/zero of=ext_image bs=1M count=1024
Create ext2 partition:
lwext4-mkfs -i ext_image -e 2
Create ext3 partition:
lwext4-mkfs -i ext_image -e 3
Create ext4 partition:
lwext4-mkfs -i ext_image -e 4
Show full option set:
lwext4-mkfs --help
Cross compile standalone library
Toolchains needed:
Lwext4 could be compiled for many targets. Here are an examples for 8/16/32/64 bit architectures.
- generic for x86 or amd64
- arm-none-eabi-gcc for ARM cortex-m0/m3/m4 microcontrollers
- avr-gcc for AVR xmega microcontrollers
- bfin-elf-gcc for blackfin processors
- msp430-gcc for msp430 microcontrollers
Library has been tested only for generic (amd64) & ARM Cortex M architectures. For other targets compilation passes (with warnings somewhere) but tests are not done yet. Lwext4 code is written with endianes respect. Big endian behavior also hasn't been tested yet.
Build avrxmega7 library:
make avrxmega7
cd build_avrxmega7
make lwext4
Build cortex-m0 library:
make cortex-m0
cd build_cortex-m0
make lwext4
Build cortex-m3 library:
make cortex-m3
cd build_cortex-m3
make lwext4
Build cortex-m4 library:
make cortex-m4
cd build_cortex-m4
make lwext4