Enable exFAT filesystem

arch/arm64/configs/k63v2_64_bsp_defconfig

@@ -443,6 +443,7 @@ CONFIG_JOLIET=y
 CONFIG_ZISOFS=y
 CONFIG_MSDOS_FS=y
 CONFIG_VFAT_FS=y
+CONFIG_EXFAT_FS=y
 CONFIG_TMPFS=y
 CONFIG_TMPFS_POSIX_ACL=y
 CONFIG_SDCARD_FS=y

fs/Kconfig

@@ -103,6 +103,7 @@ if BLOCK
 menu "DOS/FAT/NT Filesystems"
 
 source "fs/fat/Kconfig"
+source "fs/exfat/Kconfig"
 source "fs/ntfs/Kconfig"
 
 endmenu

fs/Makefile

@@ -78,6 +78,7 @@ obj-$(CONFIG_HUGETLBFS)		+= hugetlbfs/
 obj-$(CONFIG_CODA_FS)		+= coda/
 obj-$(CONFIG_MINIX_FS)		+= minix/
 obj-$(CONFIG_FAT_FS)		+= fat/
+obj-$(CONFIG_EXFAT_FS)		+= exfat/
 obj-$(CONFIG_BFS_FS)		+= bfs/
 obj-$(CONFIG_ISO9660_FS)	+= isofs/
 obj-$(CONFIG_HFSPLUS_FS)	+= hfsplus/ # Before hfs to find wrapped HFS+

fs/exfat/Kconfig

@@ -0,0 +1,66 @@
+config EXFAT_FS
+	tristate "exFAT fs support"
+	depends on BLOCK
+	select NLS
+	select NLS_UTF8
+	select NLS_CODEPAGE_437
+	select NLS_ISO8859_1
+	help
+	  If you want to use the exFAT file system, then you must say Y or M
+	  here to inlucde exFAT support. exFAT supports winnt short-name rule.
+	  (winnt: emulate the Windows NT rule for display/create.)
+
+	  To compile this as a module, choose M here: the module will be called
+	  exfat.
+
+if EXFAT_FS
+config EXFAT_DEFAULT_CODEPAGE
+	int "Default codepage for exFAT"
+	default 437
+	help
+	  This option should be set to the codepage of your exFAT filesystems.
+
+config EXFAT_DEFAULT_IOCHARSET
+	string "Default iocharset for exFAT"
+	default "utf8"
+	help
+	  Set this to the default input/output character set you'd
+	  like exFAT to use. It should probably match the character set
+	  that most of your exFAT filesystems use, and can be overridden
+	  with the "iocharset" mount option for exFAT filesystems.
+
+config EXFAT_VIRTUAL_XATTR
+	bool "Virtual xattr support for exFAT"
+	default y
+	help
+	  To support virtual xattr.
+
+config EXFAT_VIRTUAL_XATTR_SELINUX_LABEL
+	string "Default string for SELinux label"
+	default "u:object_r:exfat:s0"
+	depends on EXFAT_VIRTUAL_XATTR
+	help
+	  Set this to the default string for SELinux label.
+	  Support for "u:object_r:exfat:s0" was added in Android Pie,
+	  if you're running Oreo or lower, use "u:object_r:vfat:s0" instead.
+
+config EXFAT_DEBUG
+	bool "enable debug features"
+
+if EXFAT_DEBUG
+
+config EXFAT_DBG_MSG
+	bool "enable debug messages"
+
+config EXFAT_DBG_BUGON
+	bool "enable strict BUG_ON() for debugging"
+
+config EXFAT_DBG_WARNON
+	bool "enable strict WARN_ON() for debugging"
+
+endif # if EXFAT_DEBUG
+
+config EXFAT_UEVENT
+	bool "enable uevent"
+
+endif # if EXFAT_FS

fs/exfat/Makefile

@@ -0,0 +1,42 @@
+#
+# Makefile for the linux FAT12/16/32(VFAT)/64(exFAT) filesystem driver.
+#
+
+ifneq ($(KERNELRELEASE),)
+# Called from inline kernel build
+# DKMS_DEFINE
+obj-$(CONFIG_EXFAT_FS) += exfat.o
+
+exfat-objs	:= super.o core.o core_exfat.o blkdev.o fatent.o cache.o \
+		   nls.o misc.o extent.o xattr.o
+else
+# Called from external kernel module build
+
+KERNELRELEASE	?= $(shell uname -r)
+KDIR	?= /lib/modules/${KERNELRELEASE}/build
+MDIR	?= /lib/modules/${KERNELRELEASE}
+PWD	:= $(shell pwd)
+
+export CONFIG_EXFAT_FS := m
+
+all:
+	$(MAKE) -C $(KDIR) M=$(PWD) modules
+
+clean:
+	$(MAKE) -C $(KDIR) M=$(PWD) clean
+
+help:
+	$(MAKE) -C $(KDIR) M=$(PWD) help
+
+install: exfat.ko
+	rm -f ${MDIR}/kernel/fs/exfat/exfat.ko
+	install -m644 -b -D exfat.ko ${MDIR}/kernel/fs/exfat/exfat.ko
+	depmod -aq
+
+uninstall:
+	rm -rf ${MDIR}/kernel/fs/exfat
+	depmod -aq
+
+endif
+
+.PHONY : all clean install uninstall

fs/exfat/README.md

@@ -0,0 +1,202 @@
+# 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.
+
+---------------------------------------
+
+[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-nofuse]: https://github.com/dorimanx/exfat-nofuse
+
+**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](https://twitter.com/arter97))
+
+## Using exfat-linux
+
+### ● Ubuntu PPA
+
+If you're an Ubuntu user, you can simply add a [PPA repository](https://launchpad.net/~arter97/+archive/ubuntu/exfat-linux) 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__.
+
+4. 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
+```
+
+3. 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 |
+
+[exfat-fuse]: https://github.com/relan/exfat
+
+## Mount options
+
+* uid
+* gid
+* umask
+* dmask
+* fmask
+* allow_utime
+* codepage
+* iocharset
+* quiet
+* utf8
+* tz
+
+  * Please refer to the [vfat](https://github.com/torvalds/linux/blob/master/Documentation/filesystems/vfat.txt)'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!