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11 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:
12 - directory indexing - fast file find and list operations
13 - extents - fast big file truncate
14 - journaling transactions & recovery - power loss resistance
16 Lwext4 is an excellent choice for SD/MMC card, USB flash drive or any other wear
17 leveled memory types. However it is not good for raw flash devices.
19 Feel free to contact me:
20 kostka.grzegorz@gmail.com
25 The most of the source code of lwext4 was taken from HelenOS:
28 Some features are based on FreeBSD and Linux implementations.
30 KaHo Ng (https://github.com/ngkaho1234):
31 * advanced extents implementation
33 * metadata checksum support
34 * journal recovery & transactions
35 * many bugfixes & improvements
37 Lwext4 could be used also as fuse internals. Here is a nice project which uses lwext4 as a filesystem base:
38 * https://github.com/ngkaho1234/fuse-lwext4
43 * filetypes: regular, directories, softlinks
44 * support for hardlinks
45 * multiple blocksize supported: 1KB, 2KB, 4KB ... 64KB
46 * little/big endian architectures supported
47 * multiple configurations (ext2/ext3/ext4)
48 * only C standard library dependency
49 * various CPU architectures supported (x86/64, cortex-mX, msp430 ...)
50 * small memory footprint
51 * flexible configurations
56 Advanced ext4 filesystem features, like extents or journaling require some memory.
57 However most of the memory expensive features could be disabled at compile time.
58 Here is a brief summary for cortex-m4 processor:
60 * .text: 20KB - only ext2 fs support , 50KB - full ext4 fs feature set
61 * .data: 8KB - minimum 8 x 1KB block cache, 12KB - when journaling and extents are enabled
62 * .stack: 2KB - is enough (not measured precisely)
64 Blocks are allocated dynamically. Previous versions of library could work without
65 malloc but from 1.0.0 dynamic memory allocation is required. However, block cache
66 should not allocate more than CONFIG_BLOCK_DEV CACHE_SIZE.
68 Supported ext2/3/4 features
72 * filetype, recover, meta_bg, extents, 64bit, flex_bg: **yes**
73 * compression, journal_dev, mmp, ea_inode, dirdata, bg_meta_csum, largedir, inline_data: **no**
77 * has_journal, ext_attr, dir_index: **yes**
78 * dir_prealloc, imagic_inodes, resize_inode: **no**
82 * sparse_super, large_file, huge_file, gdt_csum, dir_nlink, extra_isize, metadata_csum: **yes**
83 * quota, bigalloc, btree_dir: **no**
87 * blockdev - block devices set, supported blockdev
88 * fs_test - test suite, mkfs and demo application
90 * include - header files
91 * toolchain - cmake toolchain files
92 * CMakeLists.txt - CMake config file
93 * ext_images.7z - compressed ext2/3/4 100MB images
94 * fs_test.mk - automatic tests definitions
95 * Makefile - helper makefile to generate cmake and run test suite
96 * README.md - readme file
104 Download MSYS-2: https://sourceforge.net/projects/msys2/
106 Install required packages is MSYS2 Shell package manager:
108 pacman -S make gcc cmake p7zip
113 Package installation (Debian):
115 apt-get install make gcc cmake p7zip
118 Compile & install tools
127 lwext4-generic demo application
129 Simple lwext4 library test application:
130 * load ext2/3/4 images
131 * load linux block device with ext2/3/4 part
132 * load windows volume with ext2/3/4 filesystem
133 * directory speed test
134 * file write/read speed test
136 How to use for images/blockdevices:
138 lwext4-generic -i ext_images/ext2
139 lwext4-generic -i ext_images/ext3
140 lwext4-generic -i ext_images/ext4
143 Show full option set:
145 lwext4-generic --help
151 Execute tests for 100MB unpacked images:
155 Execute tests for autogenerated 1GB images (only on Linux targets) + fsck:
159 Using lwext4-mkfs tool
161 It is possible to create ext2/3/4 partition by internal library tool.
163 Generate empty file (1GB):
165 dd if=/dev/zero of=ext_image bs=1M count=1024
167 Create ext2 partition:
169 lwext4-mkfs -i ext_image -e 2
171 Create ext3 partition:
173 lwext4-mkfs -i ext_image -e 3
175 Create ext4 partition:
177 lwext4-mkfs -i ext_image -e 4
179 Show full option set:
184 Cross compile standalone library
189 Lwext4 could be compiled for many targets. Here are an examples for 8/16/32/64 bit architectures.
190 * generic for x86 or amd64
191 * arm-none-eabi-gcc for ARM cortex-m0/m3/m4 microcontrollers
192 * avr-gcc for AVR xmega microcontrollers
193 * bfin-elf-gcc for blackfin processors
194 * msp430-gcc for msp430 microcontrollers
196 Library has been tested only for generic (amd64) & ARM Cortex M architectures.
197 For other targets compilation passes (with warnings somewhere) but tests are
198 not done yet. Lwext4 code is written with endianes respect. Big endian
199 behavior also hasn't been tested yet.
201 Build avrxmega7 library:
209 Build cortex-m0 library:
217 Build cortex-m3 library:
225 Build cortex-m4 library: