ocfs2: Write support for inline data

This fixes up write, truncate, mmap, and RESVSP/UNRESVP to understand inline
inode data.

For the most part, the changes to the core write code can be relied on to do
the heavy lifting. Any code calling ocfs2_write_begin (including shared
writeable mmap) can count on it doing the right thing with respect to
growing inline data to an extent tree.

Size reducing truncates, including UNRESVP can simply zero that portion of
the inode block being removed. Size increasing truncatesm, including RESVP
have to be a little bit smarter and grow the inode to an extent tree if
necessary.

Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>
Reviewed-by: Joel Becker <joel.becker@oracle.com>

fs/ocfs2/inode.c

@@ -514,6 +514,10 @@ static int ocfs2_truncate_for_delete(struct ocfs2_super *osb,
 
 	fe = (struct ocfs2_dinode *) fe_bh->b_data;
 
+	/*
+	 * This check will also skip truncate of inodes with inline
+	 * data and fast symlinks.
+	 */
 	if (fe->i_clusters) {
 		handle = ocfs2_start_trans(osb, OCFS2_INODE_UPDATE_CREDITS);
 		if (IS_ERR(handle)) {