xfs: rename xfs_ilock_map_shared

Make it clear that we're only locking against the extent map on the data
fork.  Also clean the function up a little bit.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 349bfa2..e001215 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -912,7 +912,7 @@
 	 * If there are any blocks, read-ahead block 0 as we're almost
 	 * certain to have the next operation be a read there.
 	 */
-	mode = xfs_ilock_map_shared(ip);
+	mode = xfs_ilock_data_map_shared(ip);
 	if (ip->i_d.di_nextents > 0)
 		xfs_dir3_data_readahead(NULL, ip, 0, -1);
 	xfs_iunlock(ip, mode);
@@ -1215,7 +1215,7 @@
 	uint			lock;
 	int			error;
 
-	lock = xfs_ilock_map_shared(ip);
+	lock = xfs_ilock_data_map_shared(ip);
 
 	isize = i_size_read(inode);
 	if (start >= isize) {
@@ -1319,7 +1319,7 @@
 	if (XFS_FORCED_SHUTDOWN(mp))
 		return -XFS_ERROR(EIO);
 
-	lock = xfs_ilock_map_shared(ip);
+	lock = xfs_ilock_data_map_shared(ip);
 
 	isize = i_size_read(inode);
 	if (start >= isize) {