ext4: add support for filesystems without JOURNAL

JOURNAL is optional for EXT4 (and EXT3) filesystems, so add support for
skipping it. This fixes corrupting EXT4 volumes without JOURNAL after
using uboot's 'ext4write' command.
Signed-off-by: NMarek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: NLukasz Majewski <lukma@denx.de>

fs/ext4/ext4_journal.c

@@ -645,6 +645,10 @@ void ext4fs_update_journal(void)
 	struct ext_filesystem *fs = get_fs();
 	long int blknr;
 	int i;
+
+	if (!(fs->sb->feature_compatibility & EXT4_FEATURE_COMPAT_HAS_JOURNAL))
+		return;
+
 	ext4fs_read_inode(ext4fs_root, EXT2_JOURNAL_INO, &inode_journal);
 	blknr = read_allocated_block(&inode_journal, jrnl_blk_idx++, NULL);
 	update_descriptor_block(blknr);

fs/ext4/ext4_journal.h

@@ -17,6 +17,8 @@
 #ifndef __EXT4_JRNL__
 #define __EXT4_JRNL__
 
+#define EXT4_FEATURE_COMPAT_HAS_JOURNAL		0x0004
+
 #define EXT2_JOURNAL_INO		8	/* Journal inode */
 #define EXT2_JOURNAL_SUPERBLOCK	0	/* Journal  Superblock number */