ext4: remove the I_VERSION mount flag and use the super_block flag instead

There's no point to have two bits that are set in parallel; so use the
MS_I_VERSION flag that is needed by the VFS anyway, and that way we
free up a bit in sbi->s_mount_opts.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

fs/ext4/ext4.h

@@ -942,7 +942,6 @@ struct ext4_inode_info {
 #define EXT4_MOUNT_DIOREAD_NOLOCK	0x400000 /* Enable support for dio read nolocking */
 #define EXT4_MOUNT_JOURNAL_CHECKSUM	0x800000 /* Journal checksums */
 #define EXT4_MOUNT_JOURNAL_ASYNC_COMMIT	0x1000000 /* Journal Async Commit */
-#define EXT4_MOUNT_I_VERSION            0x2000000 /* i_version support */
 #define EXT4_MOUNT_MBLK_IO_SUBMIT	0x4000000 /* multi-block io submits */
 #define EXT4_MOUNT_DELALLOC		0x8000000 /* Delalloc support */
 #define EXT4_MOUNT_DATA_ERR_ABORT	0x10000000 /* Abort on file data write */

fs/ext4/inode.c

@@ -4322,7 +4322,7 @@ int ext4_mark_iloc_dirty(handle_t *handle,
 {
 	int err = 0;
 
-	if (test_opt(inode->i_sb, I_VERSION))
+	if (IS_I_VERSION(inode))
 		inode_inc_iversion(inode);
 
 	/* the do_update_inode consumes one bh->b_count */

fs/ext4/super.c

@@ -1125,7 +1125,7 @@ static int ext4_show_options(struct seq_file *seq, struct dentry *root)
 		seq_puts(seq, ",journal_async_commit");
 	else if (test_opt(sb, JOURNAL_CHECKSUM))
 		seq_puts(seq, ",journal_checksum");
-	if (test_opt(sb, I_VERSION))
+	if (sb->s_flags & MS_I_VERSION)
 		seq_puts(seq, ",i_version");
 	if (!test_opt(sb, DELALLOC) &&
 	    !(def_mount_opts & EXT4_DEFM_NODELALLOC))
@@ -1793,7 +1793,6 @@ static int parse_options(char *options, struct super_block *sb,
 				 "Ignoring deprecated bh option");
 			break;
 		case Opt_i_version:
-			set_opt(sb, I_VERSION);
 			sb->s_flags |= MS_I_VERSION;
 			break;
 		case Opt_nodelalloc: