[PATCH] tune2fs: Update overhead when toggling journal feature

[Jan Kara <jack@suse.cz>]

When adding or removing journal from a filesystem, we also need to add /
remove journal blocks from overhead stored in the superblock.  Otherwise
total number of blocks in the filesystem as reported by statfs(2) need
not match reality and could lead to odd results like negative number of
used blocks reported by df(1).

Signed-off-by: Jan Kara <jack@suse.cz>
---
 misc/tune2fs.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/misc/tune2fs.c b/misc/tune2fs.c
index 4d4cf5a13384..2f6858abda32 100644
--- a/misc/tune2fs.c
+++ b/misc/tune2fs.c
@@ -396,6 +396,8 @@ static errcode_t remove_journal_inode(ext2_filsys fs)
 				_("while clearing journal inode"));
 			return retval;
 		}
+		fs->super->s_overhead_clusters -=
+			EXT2FS_NUM_B2C(fs, EXT2_I_SIZE(&inode) / fs->blocksize);
 		memset(&inode, 0, sizeof(inode));
 		ext2fs_mark_bb_dirty(fs);
 		fs->flags &= ~EXT2_FLAG_SUPER_ONLY;
@@ -1663,8 +1665,12 @@ static int add_journal(ext2_filsys fs)
 			com_err(program_name, retval, "%s",
 				_("\n\twhile trying to create journal file"));
 			return retval;
-		} else
-			fputs(_("done\n"), stdout);
+		}
+		fs->super->s_overhead_clusters += EXT2FS_NUM_B2C(fs,
+			jparams.num_journal_blocks + jparams.num_fc_blocks);
+		ext2fs_mark_super_dirty(fs);
+		fputs(_("done\n"), stdout);
+
 		/*
 		 * If the filesystem wasn't mounted, we need to force
 		 * the block group descriptors out.
-- 
2.26.2