Getting "Corrupted dir pair at {0x0, 0x1} ..." error if I do nrfjprog --eraseall then flash the application

[Omid]

Hello my friends,

I have been working with the LittleFS, and I have realized if I do "nrfjprog --eraseall" and then flash a simple application that writes a few bytes into flash memory via fs_write and related FS APIs, I get the following error although the the application proceeds anyways and actually writes on the flash. Here is the complete error:

littlefs:lfs_dir_fetchmatch: WEST_TOPDIR/modules/fs/littlefs/lfs.c:1234: Corrupted dir pair at {0x0, 0x1}

I was wondering what might be the possible root cause(s) and how I can fix it.

Thanks,
Omid

[Sigurd Hellesvik]

Hi,

Do you get the same error when on every reset, or only first time after you flash the application?

Try to erase external flash:

nrfjprog --family NRF52 --qspieraseall

Also, I googled the error and got this: https://github.com/littlefs-project/littlefs/issues/476. I did not read it, but maybe it can help you?

Regards,
Sigurd Hellesvik

[Omid]

Sigurd Hellesvik said:

Try to erase external flash:

could you tell me about this a bit more?

I do not have any external flash connected to my devkit

At any rate, I tired "nrfjprog --family NRF52 --qspieraseall" and then flashed the application and the issue didn't occur.

[Sigurd Hellesvik]

Omid said:

could you tell me about this a bit more?

I do not have any external flash connected to my devkit

At any rate, I tired "nrfjprog --family NRF52 --qspieraseall" and then flashed the application and the issue didn't occur.

Since you do not use external flash,  I doubt this command will affect anything.

If the error message is only after the first flash, I suggest that you ignore it that time, knowing that when littlefs flash has been initialized, the error will disappear. Does this solution work for you?

[Omid]

Yes, it works for now, but the error still exists, I am more curious to know why this happens. Thanks.

[Sigurd Hellesvik]

The reason for the error is in littlefs_mount().

First, this tries to mount the device. 

Then if that fails, the driver will format the device.
The fail will still print any error logs from lfs_mount()

Then it is mounted again.

[Omid]

I see thanks, could you please tell me why that error in mounting happens? 
I also have SYS_INIT( fs_init, APPLICATION, 0) for initialization. Could the timing be the issue?

[Sigurd Hellesvik]

It happens because when you erase flash the flash is no longer formattet for littlefs. From what I see the error is not a problem, as the file system is will format the flash and then init again.

In short, I do not think that this is an error you can fix.