ext4: use ext4_write_inode() when fsyncing w/o a journal

In no-journal mode, we previously used __generic_file_fsync() in
no-journal mode.  This triggers a lockdep warning, and in addition,
it's not safe to depend on the inode writeback mechanism in the case
ext4.  We can solve both problems by calling ext4_write_inode()
directly.
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org

fs/ext4/fsync.c

@@ -116,8 +116,16 @@ int ext4_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
 		goto out;
 	}
 
+	ret = file_write_and_wait_range(file, start, end);
+	if (ret)
+		return ret;
+
 	if (!journal) {
-		ret = __generic_file_fsync(file, start, end, datasync);
+		struct writeback_control wbc = {
+			.sync_mode = WB_SYNC_ALL
+		};
+
+		ret = ext4_write_inode(inode, &wbc);
 		if (!ret)
 			ret = ext4_sync_parent(inode);
 		if (test_opt(inode->i_sb, BARRIER))
@@ -125,9 +133,6 @@ int ext4_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
 		goto out;
 	}
 
-	ret = file_write_and_wait_range(file, start, end);
-	if (ret)
-		return ret;
 	/*
 	 * data=writeback,ordered:
 	 *  The caller's filemap_fdatawrite()/wait will sync the data.