xfs: limit xfs_imap_to_bmap to a single mapping

We only call xfs_iomap for single mappings anyway, so remove all
code dealing with multiple mappings from xfs_imap_to_bmap and add
asserts that we never get results that we do not expect.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alex Elder <aelder@sgi.com>

fs/xfs/xfs_iomap.c

@@ -55,22 +55,18 @@
 #define XFS_STRAT_WRITE_IMAPS	2
 #define XFS_WRITE_IMAPS		XFS_BMAP_MAX_NMAP
 
-STATIC int
+STATIC void
 xfs_imap_to_bmap(
 	xfs_inode_t	*ip,
 	xfs_off_t	offset,
 	xfs_bmbt_irec_t *imap,
 	xfs_iomap_t	*iomapp,
 	int		imaps,			/* Number of imap entries */
-	int		iomaps,			/* Number of iomap entries */
 	int		flags)
 {
 	xfs_mount_t	*mp = ip->i_mount;
-	int		pbm;
 	xfs_fsblock_t	start_block;
 
-
-	for (pbm = 0; imaps && pbm < iomaps; imaps--, iomapp++, imap++, pbm++) {
 	iomapp->iomap_offset = XFS_FSB_TO_B(mp, imap->br_startoff);
 	iomapp->iomap_delta = offset - iomapp->iomap_offset;
 	iomapp->iomap_bsize = XFS_FSB_TO_B(mp, imap->br_blockcount);
@@ -94,10 +90,6 @@ xfs_imap_to_bmap(
 		if (ISUNWRITTEN(imap))
 			iomapp->iomap_flags |= IOMAP_UNWRITTEN;
 	}
-
-		offset += iomapp->iomap_bsize - iomapp->iomap_delta;
-	}
-	return pbm;	/* Return the number filled */
 }
 
 int
@@ -119,6 +111,7 @@ xfs_iomap(
 	int		iomap_flags = 0;
 
 	ASSERT((ip->i_d.di_mode & S_IFMT) == S_IFREG);
+	ASSERT(niomaps && *niomaps == 1);
 
 	if (XFS_FORCED_SHUTDOWN(mp))
 		return XFS_ERROR(EIO);
@@ -203,12 +196,11 @@ xfs_iomap(
 		break;
 	}
 
-	if (nimaps) {
-		*niomaps = xfs_imap_to_bmap(ip, offset, &imap,
-					    iomapp, nimaps, *niomaps, iomap_flags);
-	} else if (niomaps) {
-		*niomaps = 0;
-	}
+	ASSERT(nimaps <= 1);
+
+	if (nimaps)
+		xfs_imap_to_bmap(ip, offset, &imap, iomapp, nimaps, iomap_flags);
+	*niomaps = nimaps;
 
 out:
 	if (lockmode)