README.md

exfat-linux

This exFAT filesystem module for Linux kernel is based on sdFAT drivers by Samsung, which is used with their smartphone lineups.

The main objective of exfat-linux is to provide the best generic kernel drivers for exFAT. That means Samsung-specific modifications such as fat12/16/32 handlings, defrag and etc has been removed to make the code portable.

This project can be used for everyday Linux users by simply doing make && make install. Ubuntu users can simply add a PPA and start using it, without even downloading the code. This can also be directly dropped-in to an existing Linux kernel source for building the filesystem drivers inline, which should be useful for Android kernel developers.

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exfat-nofuse's development has been stale for more than a year with no clear maintainership. It's also been lacking critical upstream(which is Samsung) changes.

exfat-linux is:

• Based on a totally different and newer base provided by Samsung
• Intended to keep upstream changes constantly merged
• Intended to fix breakage from newer kernels as-soon-as-possible

exfat-linux has been tested with all major LTS kernels ranging from 3.4 to 4.19 and the ones Canonical uses for Ubuntu: 3.4, 3.10, 3.18, 4.1, 4.4, 4.9, 4.14, 4.19 and 4.15, 5.0, 5.2, and 5.3-rc.

It's also been tested with x86(i386), x86_64(amd64), arm32(AArch32) and arm64(AArch64).

Disclaimer

● Original authorship and copyright: Samsung

● Maintainer of exfat-linux: Park Ju Hyung(arter97)

Using exfat-linux

● Ubuntu PPA

If you're an Ubuntu user, you can simply add a PPA repository and start using the exFAT module.

Ubuntu will handle upgrades automatically as well.

1. Add the exfat-linux repository

   sudo add-apt-repository ppa:arter97/exfat-linux
   sudo apt update
   

2. Install the module

   sudo apt install exfat-dkms

This will use DKMS(Dynamic Kernel Module Support) and automatically build exFAT module for your current Ubuntu installation.

● Manually installing the module

1. Download the code

   git clone https://github.com/arter97/exfat-linux
   cd exfat-linux
   

2. Build

   make

3. Install

   sudo make install

This will install the module to your currently running kernel.

1. And finally load

   sudo modprobe exfat

If you upgrade the kernel, you'll have to repeat this process.

If you want to update exfat-linux to the latest version, you'll have to repeat this process.

● Merging the drivers to existing Linux kernel source

If you're using git, using git subtree or git submodule is highly recommended.

1. Add this repository to fs/exfat

2. Modify fs/Kconfig

 menu "DOS/FAT/NT Filesystems"

 source "fs/fat/Kconfig"
+source "fs/exfat/Kconfig"
 source "fs/ntfs/Kconfig"
 endmenu

1. Modify fs/Makefile

 obj-$(CONFIG_FAT_FS)    += fat/
+obj-$(CONFIG_EXFAT_FS)  += exfat/
 obj-$(CONFIG_BFS_FS)    += bfs/

And you're good to go!

Benchmarks

For reference, existing exFAT implementations were tested and compared on a server running Ubuntu 16.04 with Linux kernel 4.14 under a contained virtual machine.

Linux 4.14 was used as higher LTS kernels don't work with exfat-nofuse at the time of testing.

● Ramdisk

fio sequential I/O

Implementation Base Read Write exfat-linux 2.2.0 7042 MB/s 2173 MB/s exfat-nofuse 1.2.9 6849 MB/s 1961 MB/s exfat-fuse N/A 3097 MB/s 1710 MB/s ext4 N/A 7352 MB/s 3333 MB/s

fio random I/O

Implementation Base Read Write exfat-linux 2.2.0 760 MB/s 2222 MB/s exfat-nofuse 1.2.9 760 MB/s 2160 MB/s exfat-fuse N/A 1.7 MB/s 1.6 MB/s ext4 N/A 747 MB/s 2816 MB/s

● NVMe device

fio sequential I/O

Implementation Base Read Write exfat-linux 2.2.0 1283 MB/s 1832 MB/s exfat-nofuse 1.2.9 1285 MB/s 1678 MB/s exfat-fuse N/A 751 MB/s 1464 MB/s ext4 N/A 1283 MB/s 3356 MB/s

fio random I/O

Implementation Base Read Write exfat-linux 2.2.0 26 MB/s 1885 MB/s exfat-nofuse 1.2.9 24 MB/s 1827 MB/s exfat-fuse N/A 1.6 MB/s 1.6 MB/s ext4 N/A 29 MB/s 2821 MB/s

Mount options

• uid

• gid

• umask

• dmask

• fmask

• allow_utime

• codepage

• iocharset

• utf8

• tz

  • Please refer to the vfat's documentation.

• namecase

  • Passing namecase=1 as a mount option will make exFAT operate in a case-sensitive mode.

  • Default is insensitive mode.

• symlink

  • Allow a symlink to be created under exFAT.

• errors=continue

  • Keep going on a filesystem error.

• errors=panic

  • Panic and halt the machine if an error occurs.

• errors=remount-ro

  • Remount the filesystem read-only on an error.

• discard

  • Enable the use of discard/TRIM commands to ensure flash storage doesn't run out of free blocks. This option may introduce latency penalty on file removal operations.

• delayed_meta

  • Delay flushing metadata, hence improving performance.

  • This is enabled by default, please pass nodelayed_meta to disable it.

Enjoy!