tune2fs: allow user to turn on saving the checksum seed

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 c63ead6..f1a0514 100644 (file)
--- a/misc/tune2fs.c
+++ b/misc/tune2fs.c
@@ -149,7 +149,8 @@ static __u32 ok_features[3] = {
                EXT4_FEATURE_INCOMPAT_FLEX_BG |
                EXT4_FEATURE_INCOMPAT_MMP |
                EXT4_FEATURE_INCOMPAT_64BIT |
-               EXT4_FEATURE_INCOMPAT_ENCRYPT,
+               EXT4_FEATURE_INCOMPAT_ENCRYPT |
+               EXT4_FEATURE_INCOMPAT_CSUM_SEED,
        /* R/O compat */
        EXT2_FEATURE_RO_COMPAT_LARGE_FILE |
                EXT4_FEATURE_RO_COMPAT_HUGE_FILE|
@@ -172,7 +173,8 @@ static __u32 clear_ok_features[3] = {
        EXT2_FEATURE_INCOMPAT_FILETYPE |
                EXT4_FEATURE_INCOMPAT_FLEX_BG |
                EXT4_FEATURE_INCOMPAT_MMP |
-               EXT4_FEATURE_INCOMPAT_64BIT,
+               EXT4_FEATURE_INCOMPAT_64BIT |
+               EXT4_FEATURE_INCOMPAT_CSUM_SEED,
        /* R/O compat */
        EXT2_FEATURE_RO_COMPAT_LARGE_FILE |
                EXT4_FEATURE_RO_COMPAT_HUGE_FILE|
@@ -949,6 +951,15 @@ static errcode_t disable_uninit_bg(ext2_filsys fs, __u32 csum_feature_flag)
        return 0;
 }
 
+static void
+try_confirm_csum_seed_support(void)
+{
+       if (access("/sys/fs/ext4/features/metadata_csum_seed", R_OK))
+               fputs(_("WARNING: Could not confirm kernel support for "
+                       "metadata_csum_seed.\n  This requires Linux >= "
+                       "v4.4.\n"), stderr);
+}
+
 /*
  * Update the feature set as provided by the user.
  */
@@ -1214,6 +1225,8 @@ mmp_error:
                         */
                        old_features[E2P_FEATURE_RO_INCOMPAT] |=
                                EXT4_FEATURE_RO_COMPAT_GDT_CSUM;
+               fs->super->s_checksum_seed = 0;
+               ext2fs_clear_feature_csum_seed(fs->super);
        }
 
        if (FEATURE_ON(E2P_FEATURE_RO_INCOMPAT,
@@ -1309,6 +1322,37 @@ mmp_error:
                        EXT4_ENCRYPTION_MODE_AES_256_CTS;
        }
 
+       if (FEATURE_ON(E2P_FEATURE_INCOMPAT,
+               EXT4_FEATURE_INCOMPAT_CSUM_SEED)) {
+               if (!ext2fs_has_feature_metadata_csum(sb)) {
+                       fputs(_("Setting feature 'metadata_csum_seed' "
+                               "is only supported\non filesystems with "
+                               "the metadata_csum feature enabled.\n"),
+                               stderr);
+                       return 1;
+               }
+               try_confirm_csum_seed_support();
+               fs->super->s_checksum_seed = fs->csum_seed;
+       }
+
+       if (FEATURE_OFF(E2P_FEATURE_INCOMPAT,
+               EXT4_FEATURE_INCOMPAT_CSUM_SEED)) {
+               __le32 uuid_seed;
+
+               uuid_seed = ext2fs_crc32c_le(~0, fs->super->s_uuid,
+                                       sizeof(fs->super->s_uuid));
+               if (fs->super->s_checksum_seed != uuid_seed &&
+                   (mount_flags & EXT2_MF_MOUNTED)) {
+                       fputs(_("UUID has changed since enabling "
+                               "metadata_csum.  Filesystem must be unmounted "
+                               "\nto safely rewrite all metadata to "
+                               "match the new UUID.\n"), stderr);
+                       return 1;
+               }
+
+               rewrite_checksums = 1;
+       }
+
        if (sb->s_rev_level == EXT2_GOOD_OLD_REV &&
            (sb->s_feature_compat || sb->s_feature_ro_compat ||
             sb->s_feature_incompat))
@@ -2950,13 +2994,22 @@ retry_open:
 
                if (ext2fs_has_group_desc_csum(fs)) {
                        /*
-                        * Changing the UUID requires rewriting all metadata,
-                        * which can race with a mounted fs.  Don't allow that.
+                        * Changing the UUID on a metadata_csum FS requires
+                        * rewriting all metadata, which can race with a
+                        * mounted fs.  Don't allow that unless we're saving
+                        * the checksum seed.
                         */
-                       if ((mount_flags & EXT2_MF_MOUNTED) && !f_flag) {
+                       if ((mount_flags & EXT2_MF_MOUNTED) &&
+                           !ext2fs_has_feature_csum_seed(fs->super) &&
+                           ext2fs_has_feature_metadata_csum(fs->super)) {
                                fputs(_("The UUID may only be "
                                        "changed when the filesystem is "
                                        "unmounted.\n"), stderr);
+                               fputs(_("If you only use kernels newer than "
+                                       "v4.4, run 'tune2fs -O "
+                                       "metadata_csum_seed' and re-run this "
+                                       "command.\n"), stderr);
+                               try_confirm_csum_seed_support();
                                exit(1);
                        }
                        if (check_fsck_needed(fs))
@@ -3018,7 +3071,8 @@ retry_open:
                }
 
                ext2fs_mark_super_dirty(fs);
-               if (ext2fs_has_feature_metadata_csum(fs->super))
+               if (ext2fs_has_feature_metadata_csum(fs->super) &&
+                   !ext2fs_has_feature_csum_seed(fs->super))
                        rewrite_checksums = 1;
        }