Description of problem: When we detect block size, we create probe file and try to write possible block sizes there. After that, we remove the file. If it fails during this process, we get general exception like "Operation not permitted" (see e.g. BZ #1777726), but it's not clear, where exactly it failed (writing file, deleting file). It would be nice to provide more precise exception (e.g. "Failed to remove file $FILENAME: Operation not permitted"), as that admin can easily determine, where the problem is.
The error message comes from ioprocess so it can be improved only there.
Fixing the exception message is not enough since we delete the file after a successful probing, and we need to know about failing to delete a probe file. The simplest solution is to log detailed warnings in exp_probe_block_size() open_probe() and close_probe(). These logs are written to iprocess stderr and logged by vdsm. This should provide all the info we need to debug issues. If we want to pass a detailed error message for each of these unlikely errors, we need to pass the GError** err from the API all down to probe_open() use g_set_error(). I would start with logging warnings and spend our time on something which bring more value to users.
ioprocess with this fix was not released yet so we cannot test it yet.
No need for verification, this is only logs addition