samples/subsys/fs/littlefs does not work with native_posix board on WSL2

[ivan2angelov]

samples/subsys/fs/littlefs is not working with native_posix board.
file system mounting fails with error -19.

branch main at

Build environment: WSL2 with Ubuntu 20.04

To Reproduce
west build -p auto samples/subsys/fs/littlefs -b native_posix

that build produces zephyr.elf.
Running zephyr.elf in WSL2 produces following output:

./build/zephyr/zephyr.elf
Failed to get status of flash device file flash.bin: Value too large for defined data type
*** Booting Zephyr OS build v3.0.0-rc3-48-gd353e5516079 ***
Area 4 at 0xfc000 on flash_ctrl for 16384 bytes
[00:00:00.000,000] littlefs: LittleFS version 2.4, disk version 2.0
[00:00:00.000,000] littlefs: can't get flash device: flash_ctrl
[00:00:00.000,000] fs: fs mount error (-19)
FAIL: mount id 4 at /lfs: -19

Expected behavior
I expected application example to run to completion without any errors (mounting fs, open dir, close dir, unmount fs).

Impact
Not sure what is the correct way to configure and use littlefs on native_posix.

Environment (please complete the following information):

• OS: (e.g. Linux, MacOS, Windows) - Win 10 + WSL2
• Toolchain (e.g Zephyr SDK, ...) zephyr SDK
• Commit SHA or Version used: d353e55

Additional context
samples/subsys/fs/fat_fs/ does not work with native_posix - it produces different error code on mounting though.

[Laczen]

@ivan2angelov, I just tested this and cannot reproduce it. Could you delete the build folder and try again ?

[ivan2angelov]

Sure. I did that.
I am at commit d353e55

git status reports no "dirty" files.

Here is build output:
`
zephyrproject/zephyr (main) $ west build -p always -b native_posix samples/subsys/fs/littlefs
-- west build: generating a build system
Including boilerplate (Zephyr base): /mnt/c/work/zephyrproject/zephyr/cmake/app/boilerplate.cmake
-- Application: /mnt/c/work/zephyrproject/zephyr/samples/subsys/fs/littlefs
-- Zephyr version: 3.0.0-rc3 (/mnt/c/work/zephyrproject/zephyr)
-- Found Python3: /usr/bin/python3.8 (found suitable exact version "3.8.10") found components: Interpreter
-- Found west (found suitable version "0.12.0", minimum required is "0.7.1")
-- Board: native_posix
-- Cache files will be written to: /home/iangelov/.cache/zephyr
-- Found dtc: /usr/bin/dtc (found suitable version "1.5.0", minimum required is "1.4.6")
-- Found toolchain: host (gcc/ld)
-- Found BOARD.dts: /mnt/c/work/zephyrproject/zephyr/boards/posix/native_posix/native_posix.dts
-- Generated zephyr.dts: /mnt/c/work/zephyrproject/zephyr/build/zephyr/zephyr.dts
-- Generated devicetree_unfixed.h: /mnt/c/work/zephyrproject/zephyr/build/zephyr/include/generated/devicetree_unfixed.h
-- Generated device_extern.h: /mnt/c/work/zephyrproject/zephyr/build/zephyr/include/generated/device_extern.h
-- Including generated dts.cmake file: /mnt/c/work/zephyrproject/zephyr/build/zephyr/dts.cmake
Parsing /mnt/c/work/zephyrproject/zephyr/samples/subsys/fs/littlefs/Kconfig
Loaded configuration '/mnt/c/work/zephyrproject/zephyr/boards/posix/native_posix/native_posix_defconfig'
Merged configuration '/mnt/c/work/zephyrproject/zephyr/samples/subsys/fs/littlefs/prj.conf'
Configuration saved to '/mnt/c/work/zephyrproject/zephyr/build/zephyr/.config'
Kconfig header saved to '/mnt/c/work/zephyrproject/zephyr/build/zephyr/include/generated/autoconf.h'
-- The C compiler identification is GNU 9.3.0
-- The CXX compiler identification is GNU 9.3.0
-- The ASM compiler identification is GNU
-- Found assembler: /usr/bin/gcc
-- Configuring done
-- Generating done
-- Build files have been written to: /mnt/c/work/zephyrproject/zephyr/build
-- west build: building application
[1/118] Preparing syscall dependency handling

[2/118] Generating include/generated/version.h
-- Zephyr version: 3.0.0-rc3 (/mnt/c/work/zephyrproject/zephyr), build: v3.0.0-rc3-48-gd353e5516079
[114/118] Linking C executable zephyr/zephyr_pre0.elf

[118/118] Linking C executable zephyr/zephyr.elf
`

And here is the output of executing the binary:
`
./build/zephyr/zephyr.elf

Failed to get status of flash device file flash.bin: Value too large for defined data type

*** Booting Zephyr OS build v3.0.0-rc3-48-gd353e5516079 ***

Area 4 at 0xfc000 on flash_ctrl for 16384 bytes

[00:00:00.000,000] littlefs: LittleFS version 2.4, disk version 2.0

[00:00:00.000,000] littlefs: can't get flash device: flash_ctrl

[00:00:00.000,000] fs: fs mount error (-19)

FAIL: mount id 4 at /lfs: -19
`

[Laczen]

@ivan2angelov, it seems like wsl2 has a problem with the created flash.bin file to support flash simulation on native-posix. Have you changed something in the native-posix dts file? Normally a 2MB file (2048kB) is created for the flash emulation, but wsl is reporting that this file is to large. Could you check the size of flash.bin in the build folder.

[ivan2angelov]

@Laczen thank you for the hints.
this is what I have:
zephyrproject/zephyr (main) $ find . -name flash.bin
./flash.bin
####@### /mnt/c/work/zephyrproject/zephyr (main) $ ll ./flash.bin
-rw------- 1 ##### #### 0 Feb 22 09:38 ./flash.bin

it seems like flash.bin is created in zephyr folder and it has zero bytes size.

[Laczen]

@ivan2angelov, I think this is because you are trying to create the flash.bin file on /mnt/c and it might be that this doesn't work. Could you try the same thing in your wsl2 home folder. I don't have this problem but I am using zephyr on wsl2 and installed zephyr on the ubuntu disk. There might be a wsl2 problem with calling fstat on windows folders.

[ivan2angelov]

@Laczen Great thank you for the tip!

Indeed, it was "user error".

I created flash.bin under my linux home directory and pass that to the example with -flash=<path-to-linux-folder/flash.bin>.
After that the example "formatted" flash.bin and second run mounted/unmounted without problems:

./build/zephyr/zephyr.elf -flash=/home/######/zephyr_flash/flash.bin
*** Booting Zephyr OS build v3.0.0-rc3-48-gd353e5516079 ***
Area 4 at 0xfc000 on flash_ctrl for 16384 bytes
[00:00:00.000,000] littlefs: LittleFS version 2.4, disk version 2.0
[00:00:00.000,000] littlefs: FS at flash_ctrl:0xfc000 is 4 0x1000-byte blocks with 512 cycle
[00:00:00.000,000] littlefs: sizes: rd 16 ; pr 16 ; ca 64 ; la 32
[00:00:00.000,000] littlefs: /lfs mounted
/lfs mount: 0
/lfs: bsize = 16 ; frsize = 4096 ; blocks = 4 ; bfree = 2
/lfs/boot_count stat: 0
fn 'boot_count' size 4
/lfs/boot_count read count 1: 4
/lfs/boot_count seek start: 0
/lfs/boot_count write new boot count 2: 4
/lfs/boot_count close: 0
/lfs opendir: 0
F 4 boot_count
End of files
[00:00:00.000,000] littlefs: /lfs unmounted
/lfs unmount: 0