xfs: consolidate extent swap code

So we don't need xfs_dfrag.h in userspace anymore, move the extent
swap ioctl structure definition to xfs_fs.h where most of the other
ioctl structure definitions are.

Now that we don't need separate files for extent swapping, separate
the basic file descriptor checking code to xfs_ioctl.c, and the code
that does the extent swap operation to xfs_bmap_util.c.  This
cleanly separates the user interface code from the physical
mechanism used to do the extent swap.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Mark Tinguely <tinguely@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

diff --git a/fs/xfs/xfs_fs.h b/fs/xfs/xfs_fs.h
index 68c2e18..74b24b2 100644
--- a/fs/xfs/xfs_fs.h
+++ b/fs/xfs/xfs_fs.h
@@ -461,6 +461,21 @@
 				 + (handle).ha_fid.fid_len)
 
 /*
+ * Structure passed to XFS_IOC_SWAPEXT
+ */
+typedef struct xfs_swapext
+{
+	__int64_t	sx_version;	/* version */
+#define XFS_SX_VERSION		0
+	__int64_t	sx_fdtarget;	/* fd of target file */
+	__int64_t	sx_fdtmp;	/* fd of tmp file */
+	xfs_off_t	sx_offset;	/* offset into file */
+	xfs_off_t	sx_length;	/* leng from offset */
+	char		sx_pad[16];	/* pad space, unused */
+	xfs_bstat_t	sx_stat;	/* stat of target b4 copy */
+} xfs_swapext_t;
+
+/*
  * Flags for going down operation
  */
 #define XFS_FSOP_GOING_FLAGS_DEFAULT		0x0	/* going down */