XFS: handle hole punching via fallocate properly

This patch simply allows XFS to handle the hole punching flag in fallocate
properly.  I've tested this with a little program that does a bunch of random
hole punching with FL_KEEP_SIZE and without it to make sure it does the right
thing.  Thanks,

Signed-off-by: Josef Bacik <josef@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/xfs/linux-2.6/xfs_iops.c

@@ -516,6 +516,7 @@ xfs_vn_fallocate(
 	loff_t		new_size = 0;
 	xfs_flock64_t	bf;
 	xfs_inode_t	*ip = XFS_I(inode);
+	int		cmd = XFS_IOC_RESVSP;
 
 	/* preallocation on directories not yet supported */
 	error = -ENODEV;
@@ -528,6 +529,9 @@ xfs_vn_fallocate(
 
 	xfs_ilock(ip, XFS_IOLOCK_EXCL);
 
+	if (mode & FALLOC_FL_PUNCH_HOLE)
+		cmd = XFS_IOC_UNRESVSP;
+
 	/* check the new inode size is valid before allocating */
 	if (!(mode & FALLOC_FL_KEEP_SIZE) &&
 	    offset + len > i_size_read(inode)) {
@@ -537,8 +541,7 @@ xfs_vn_fallocate(
 			goto out_unlock;
 	}
 
-	error = -xfs_change_file_space(ip, XFS_IOC_RESVSP, &bf,
-				       0, XFS_ATTR_NOLOCK);
+	error = -xfs_change_file_space(ip, cmd, &bf, 0, XFS_ATTR_NOLOCK);
 	if (error)
 		goto out_unlock;