tune2fs: warn if extents are not enabled when turning on metadata_csum

Warn the user if we're trying to enable metadata_csum on a FS that
doesn't support extents (since block maps cannot contain checksums).

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/misc/tune2fs.c b/misc/tune2fs.c
index 34d2cd9..31fbe55 100644 (file)
--- a/misc/tune2fs.c
+++ b/misc/tune2fs.c
@@ -1113,6 +1113,14 @@ mmp_error:
                if (mount_flags & EXT2_MF_MOUNTED)
                        fputs(_("Cannot enable metadata_csum on a mounted "
                                "filesystem!\n"), stderr);
+               if (!EXT2_HAS_INCOMPAT_FEATURE(fs->super,
+                               EXT3_FEATURE_INCOMPAT_EXTENTS))
+                       printf("%s",
+                              _("Extents are not enabled.  The file extent "
+                                "tree can be checksummed, whereas block maps "
+                                "cannot.  Not enabling extents reduces the "
+                                "coverage of metadata checksumming.  "
+                                "Re-run with -O extent to rectify.\n"));
                rewrite_checksums = 1;
                /* metadata_csum supersedes uninit_bg */
                fs->super->s_feature_ro_compat &=