mke2fs: warn if enabling metadata_csum on a pre-3.18 kernel

The metadata_csum feature (really, the journal checksum disk format)
didn't stabilize until the 3.18 kernel, at which point the companion
journal_csum feature was turned on by default if metadata_csum was
enabled.  Therefore, warn the user if they try to create such a
filesystem on a pre-3.18 kernel.

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

diff --git a/misc/mke2fs.c b/misc/mke2fs.c
index 0f571ad..0a0d2b3 100644 (file)
--- a/misc/mke2fs.c
+++ b/misc/mke2fs.c
@@ -2211,6 +2211,14 @@ profile_error:
                        blocksize, sys_page_size);
        }
 
+       /* Metadata checksumming wasn't totally stable before 3.18. */
+       if (is_before_linux_ver(3, 18, 0) &&
+           (fs_param.s_feature_ro_compat &
+                                       EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
+               fprintf(stderr, _("Suggestion: Use Linux kernel >= 3.18 for "
+                       "improved stability of the metadata and journal "
+                       "checksum features.\n"));
+
        /*
         * On newer kernels we do have lazy_itable_init support. So pick the
         * right default in case ext4 module is not loaded.

diff --git a/tests/filter.sed b/tests/filter.sed
index 59fad4e..6ca6bbc 100644 (file)
--- a/tests/filter.sed
+++ b/tests/filter.sed
@@ -18,6 +18,7 @@ s/\\015//g
 /^Lifetime writes:/d
 /^Maximum mount count:/d
 /^Next check after:/d
+/^Suggestion:/d
 /Reserved blocks uid:/s/ (user .*)//
 /Reserved blocks gid:/s/ (group .*)//
 /whichever comes first/d