nilfs2: treat missing cpfile header block as metadata corruption

nilfs2: treat missing cpfile header block as metadata corruption

The cpfile, a metadata file that holds metadata for checkpoint management,
also has statistical information in its first block, and if reading this
block fails, it receives the internal code -ENOENT and returns that code
to the callers.

As with sufile, to prevent this -ENOENT from being propagated to system
calls, return -EIO instead when reading the header block fails.

Link: https://lkml.kernel.org/r/20240821154627.11848-3-konishi.ryusuke@gmail.com
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>