The V4 filesystem format lacks certain features that are supported
by the V5 format, such as metadata checksumming, strengthened
metadata verification, and the ability to store timestamps past the
year 2038. Because of this, the V4 format is deprecated. All users
should upgrade by backing up their files, reformatting, and restoring
from the backup.

Administrators and users can detect a V4 filesystem by running
xfs_info against a filesystem mountpoint and checking for a string
beginning with "crc=". If the string "crc=0" is found, the
filesystem is a V4 filesystem. If no such string is found, please
upgrade xfsprogs to the latest version and try again.

This option will become default N in September 2025. Support for the
V4 format will be removed entirely in September 2030. Distributors
can say N here to withdraw support earlier.

To continue supporting the old V4 format (crc=0), say Y.
To close off an attack surface, say N.