[PATCH] mkfs: warn out the V4 format

[Gao Xiang <hsiangkao@redhat.com>]

Kernel commit b96cb835e37c ("xfs: deprecate the V4 format") started
the process of retiring the old format to close off attack surfaces
and to encourage users to migrate onto V5.

This also prints warning to users when mkfs as well.

Suggested-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@redhat.com>
---
 mkfs/xfs_mkfs.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/mkfs/xfs_mkfs.c b/mkfs/xfs_mkfs.c
index 0eac5336..ef09f8b3 100644
--- a/mkfs/xfs_mkfs.c
+++ b/mkfs/xfs_mkfs.c
@@ -4022,6 +4022,10 @@ main(
 	validate_extsize_hint(mp, &cli);
 	validate_cowextsize_hint(mp, &cli);
 
+	if (!cli.sb_feat.crcs_enabled)
+		fprintf(stderr,
+_("Deprecated V4 format (-mcrc=0) will not be supported after September 2030.\n"));
+
 	/* Print the intended geometry of the fs. */
 	if (!quiet || dry_run) {
 		struct xfs_fsop_geom	geo;
-- 
2.27.0