[PATCH 38/47] mke2fs: Warn if not enabling all the features that metadata_csum wants

["Darrick J. Wong" <djwong@us.ibm.com>]

There are some features (gdt_csum, 64bit, bg_use_meta_csum) that help
metadata_csum to work optimally.  Print a warning if the user tries to create a
filesystem without those features.

Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
---
 misc/mke2fs.c |   35 ++++++++++++++++++++++++++++++++++-
 1 files changed, 34 insertions(+), 1 deletions(-)


diff --git a/misc/mke2fs.c b/misc/mke2fs.c
index 45bab5c..fc57372 100644
--- a/misc/mke2fs.c
+++ b/misc/mke2fs.c
@@ -865,7 +865,8 @@ static __u32 ok_features[3] = {
 		EXT2_FEATURE_INCOMPAT_META_BG|
 		EXT4_FEATURE_INCOMPAT_FLEX_BG|
 		EXT4_FEATURE_INCOMPAT_MMP |
-		EXT4_FEATURE_INCOMPAT_64BIT,
+		EXT4_FEATURE_INCOMPAT_64BIT |
+		EXT4_FEATURE_INCOMPAT_BG_USE_META_CSUM,
 	/* R/O compat */
 	EXT2_FEATURE_RO_COMPAT_LARGE_FILE|
 		EXT4_FEATURE_RO_COMPAT_HUGE_FILE|
@@ -2278,6 +2279,38 @@ int main (int argc, char *argv[])
 		exit(1);
 	}
 
+	/* Check the user's mkfs options for metadata checksumming */
+	if (!quiet &&
+	    EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
+				       EXT4_FEATURE_RO_COMPAT_METADATA_CSUM)) {
+		if (!EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
+				EXT4_FEATURE_RO_COMPAT_GDT_CSUM))
+			printf(_("Group descriptor checksums "
+				 "are not enabled.  This reduces the "
+				 "coverage of metadata checksumming.  "
+				 "Pass -O uninit_bg to rectify.\n"));
+		if (EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
+				EXT4_FEATURE_RO_COMPAT_GDT_CSUM) &&
+		    !EXT2_HAS_INCOMPAT_FEATURE(fs->super,
+				EXT4_FEATURE_INCOMPAT_BG_USE_META_CSUM))
+			printf(_("Group descriptor checksums will not use "
+				 "the faster metadata_checksum algorithm.  "
+				 "Pass -O bg_use_meta_csum to rectify.\n"));
+		if (!EXT2_HAS_INCOMPAT_FEATURE(fs->super,
+				EXT3_FEATURE_INCOMPAT_EXTENTS))
+			printf(_("Extents are not enabled.  The file extent "
+				 "tree can be checksummed, whereas block maps "
+				 "cannot.  Not enabling extents reduces the "
+				 "coverage of metadata checksumming.  "
+				 "Pass -O extents to rectify.\n"));
+		if (!EXT2_HAS_INCOMPAT_FEATURE(fs->super,
+				EXT4_FEATURE_INCOMPAT_64BIT))
+			printf(_("64-bit filesystem support is not "
+				 "enabled.  The larger fields afforded by "
+				 "this feature enable full-strength "
+				 "checksumming.  Pass -O 64bit to rectify.\n"));
+	}
+
 	/* Can't undo discard ... */
 	if (!noaction && discard && (io_ptr != undo_io_manager)) {
 		retval = mke2fs_discard_device(fs);