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12 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:
13 - directory indexing - fast file find and list operations
14 - extents - fast big file truncate
15 - journaling transactions & recovery - power loss resistance
17 Lwext4 is an excellent choice for SD/MMC card, USB flash drive or any other wear
18 leveled memory types. However it is not good for raw flash devices.
20 Feel free to contact me:
21 kostka.grzegorz@gmail.com
26 The most of the source code of lwext4 was taken from HelenOS:
29 Some features are based on FreeBSD and Linux implementations.
31 KaHo Ng (https://github.com/ngkaho1234):
32 * advanced extents implementation
34 * metadata checksum support
35 * journal recovery & transactions
36 * many bugfixes & improvements
38 Lwext4 could be used also as fuse internals. Here is a nice project which uses lwext4 as a filesystem base:
39 * https://github.com/ngkaho1234/fuse-lwext4
44 * filetypes: regular, directories, softlinks
45 * support for hardlinks
46 * multiple blocksize supported: 1KB, 2KB, 4KB ... 64KB
47 * little/big endian architectures supported
48 * multiple configurations (ext2/ext3/ext4)
49 * only C standard library dependency
50 * various CPU architectures supported (x86/64, cortex-mX, msp430 ...)
51 * small memory footprint
52 * flexible configurations
57 Advanced ext4 filesystem features, like extents or journaling require some memory.
58 However most of the memory expensive features could be disabled at compile time.
59 Here is a brief summary for cortex-m4 processor:
61 * .text: 20KB - only ext2 fs support , 50KB - full ext4 fs feature set
62 * .data: 8KB - minimum 8 x 1KB block cache, 12KB - when journaling and extents are enabled
63 * .stack: 2KB - is enough (not measured precisely)
65 Blocks are allocated dynamically. Previous versions of library could work without
66 malloc but from 1.0.0 dynamic memory allocation is required. However, block cache
67 should not allocate more than CONFIG_BLOCK_DEV CACHE_SIZE.
69 Supported ext2/3/4 features
73 * filetype, recover, meta_bg, extents, 64bit, flex_bg: **yes**
74 * compression, journal_dev, mmp, ea_inode, dirdata, bg_meta_csum, largedir, inline_data: **no**
78 * has_journal, ext_attr, dir_index: **yes**
79 * dir_prealloc, imagic_inodes, resize_inode: **no**
83 * sparse_super, large_file, huge_file, gdt_csum, dir_nlink, extra_isize, metadata_csum: **yes**
84 * quota, bigalloc, btree_dir: **no**
88 * blockdev - block devices set, supported blockdev
89 * fs_test - test suite, mkfs and demo application
91 * include - header files
92 * toolchain - cmake toolchain files
93 * CMakeLists.txt - CMake config file
94 * ext_images.7z - compressed ext2/3/4 100MB images
95 * fs_test.mk - automatic tests definitions
96 * Makefile - helper makefile to generate cmake and run test suite
97 * README.md - readme file
105 Download MSYS-2: https://sourceforge.net/projects/msys2/
107 Install required packages is MSYS2 Shell package manager:
109 pacman -S make gcc cmake p7zip
114 Package installation (Debian):
116 apt-get install make gcc cmake p7zip
119 Compile & install tools
128 lwext4-generic demo application
130 Simple lwext4 library test application:
131 * load ext2/3/4 images
132 * load linux block device with ext2/3/4 part
133 * load windows volume with ext2/3/4 filesystem
134 * directory speed test
135 * file write/read speed test
137 How to use for images/blockdevices:
139 lwext4-generic -i ext_images/ext2
140 lwext4-generic -i ext_images/ext3
141 lwext4-generic -i ext_images/ext4
144 Show full option set:
146 lwext4-generic --help
152 Execute tests for 100MB unpacked images:
156 Execute tests for autogenerated 1GB images (only on Linux targets) + fsck:
160 Using lwext4-mkfs tool
162 It is possible to create ext2/3/4 partition by internal library tool.
164 Generate empty file (1GB):
166 dd if=/dev/zero of=ext_image bs=1M count=1024
168 Create ext2 partition:
170 lwext4-mkfs -i ext_image -e 2
172 Create ext3 partition:
174 lwext4-mkfs -i ext_image -e 3
176 Create ext4 partition:
178 lwext4-mkfs -i ext_image -e 4
180 Show full option set:
185 Cross compile standalone library
190 Lwext4 could be compiled for many targets. Here are an examples for 8/16/32/64 bit architectures.
191 * generic for x86 or amd64
192 * arm-none-eabi-gcc for ARM cortex-m0/m3/m4 microcontrollers
193 * avr-gcc for AVR xmega microcontrollers
194 * bfin-elf-gcc for blackfin processors
195 * msp430-gcc for msp430 microcontrollers
197 Library has been tested only for generic (amd64) & ARM Cortex M architectures.
198 For other targets compilation passes (with warnings somewhere) but tests are
199 not done yet. Lwext4 code is written with endianes respect. Big endian
200 behavior also hasn't been tested yet.
202 Build avrxmega7 library:
210 Build cortex-m0 library:
218 Build cortex-m3 library:
226 Build cortex-m4 library: