FEC: Error correction happens only on the verity devive

[Riz <mdrizwan827@xxxxxxxxx>]

Hi,
I was working with dm-verity with FEC enabled.

I corrupted an image ( 1bit corruption ) and was able to correct it using FEC after mounting the filesystem using "veritysetup open".

For example:
Suppose there is a text file under /home named myText.txt

In the text file I just replaced a "P" with a "Q", causing a 1 bit corruption.

Now when the filesystem is mounted as read-only after activation using veritysetup open, I just login and do a "cat /home/myText/txt".

I could see that the error has been corrected and the file is proper. ( Q is replaced back by P).

All good, but when I again cross-check the filesystem(ext4) from outside using dd command, I could see that the file still has the corrupted Q, but not the corrected P.

Is this the expected behavior that the correction doesn't happen directly inside the filesystem?
Or Am I missing something here?

Thanks

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