The metadata_csum feature works best when two features are enabled. These
features are "extents" (because the block map has no space for checksums) and
"64bit" (this enables storage of full 32-bit checksums in certain fields).
Print a warning if the user tries to create a filesystem without those
features.
Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx>
---
misc/mke2fs.c | 19 +++++++++++++++++++
1 files changed, 19 insertions(+), 0 deletions(-)
diff --git a/misc/mke2fs.c b/misc/mke2fs.c
index 61b332a..e8c60ca 100644
--- a/misc/mke2fs.c
+++ b/misc/mke2fs.c
@@ -2309,6 +2309,25 @@ 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_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);
--
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