ext2: avoid printk floods in the face of directory corruption
A very large directory with many read failures (either due to storage
problems, or due to invalid size & blocks from corruption) will generate a
printk storm as the filesystem continues to try to read all the blocks.
This flood of messages can tie up the box until it is complete - which may
be a very long time, especially for very large corrupted values.
This is fixed by only reporting the corruption once each time we try to
read the directory.