xfs: introduce a new xfs_inode_has_cow_data helper

We have a few places that already check if an inode has actual data in
the COW fork to avoid work on reflink inodes that do not actually have
outstanding COW blocks.  There are a few more places that can avoid
working if doing the same check, so add a documented helper for this
condition and use it in all places where it makes sense.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index f4d3252..814100d 100644
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -338,7 +338,7 @@ xfs_map_blocks(
 	imap_valid = offset_fsb >= wpc->imap.br_startoff &&
 		     offset_fsb < wpc->imap.br_startoff + wpc->imap.br_blockcount;
 	if (imap_valid &&
-	    (!xfs_is_reflink_inode(ip) || wpc->io_type == XFS_IO_COW))
+	    (!xfs_inode_has_cow_data(ip) || wpc->io_type == XFS_IO_COW))
 		return 0;
 
 	if (XFS_FORCED_SHUTDOWN(mp))
@@ -363,7 +363,7 @@ xfs_map_blocks(
 	 * Check if this is offset is covered by a COW extents, and if yes use
 	 * it directly instead of looking up anything in the data fork.
 	 */
-	if (xfs_is_reflink_inode(ip) &&
+	if (xfs_inode_has_cow_data(ip) &&
 	    xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb, &icur, &imap) &&
 	    imap.br_startoff <= offset_fsb) {
 		xfs_iunlock(ip, XFS_ILOCK_SHARED);