xfs_bmap_util: use swap macro

Make use of the swap macro and remove some unnecessary variables.
This makes the code easier to read and maintain. Also, reduces the
stack usage.

This code was detected with the help of Coccinelle.
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

fs/xfs/xfs_bmap_util.c

@@ -1688,7 +1688,6 @@ xfs_swap_extent_forks(
 	int			*src_log_flags,
 	int			*target_log_flags)
 {
-	struct xfs_ifork	tempifp, *ifp, *tifp;
 	xfs_filblks_t		aforkblks = 0;
 	xfs_filblks_t		taforkblks = 0;
 	xfs_extnum_t		junk;
@@ -1730,11 +1729,7 @@ xfs_swap_extent_forks(
 	/*
 	 * Swap the data forks of the inodes
 	 */
-	ifp = &ip->i_df;
-	tifp = &tip->i_df;
-	tempifp = *ifp;		/* struct copy */
-	*ifp = *tifp;		/* struct copy */
-	*tifp = tempifp;	/* struct copy */
+	swap(ip->i_df, tip->i_df);
 
 	/*
 	 * Fix the on-disk inode values
@@ -1743,13 +1738,8 @@ xfs_swap_extent_forks(
 	ip->i_d.di_nblocks = tip->i_d.di_nblocks - taforkblks + aforkblks;
 	tip->i_d.di_nblocks = tmp + taforkblks - aforkblks;
 
-	tmp = (uint64_t) ip->i_d.di_nextents;
-	ip->i_d.di_nextents = tip->i_d.di_nextents;
-	tip->i_d.di_nextents = tmp;
-
-	tmp = (uint64_t) ip->i_d.di_format;
-	ip->i_d.di_format = tip->i_d.di_format;
-	tip->i_d.di_format = tmp;
+	swap(ip->i_d.di_nextents, tip->i_d.di_nextents);
+	swap(ip->i_d.di_format, tip->i_d.di_format);
 
 	/*
 	 * The extents in the source inode could still contain speculative
@@ -1844,7 +1834,6 @@ xfs_swap_extents(
 	int			src_log_flags, target_log_flags;
 	int			error = 0;
 	int			lock_flags;
-	struct xfs_ifork	*cowfp;
 	uint64_t		f;
 	int			resblks = 0;
 
@@ -1986,18 +1975,11 @@ xfs_swap_extents(
 
 	/* Swap the cow forks. */
 	if (xfs_sb_version_hasreflink(&mp->m_sb)) {
-		xfs_extnum_t	extnum;
-
 		ASSERT(ip->i_cformat == XFS_DINODE_FMT_EXTENTS);
 		ASSERT(tip->i_cformat == XFS_DINODE_FMT_EXTENTS);
 
-		extnum = ip->i_cnextents;
-		ip->i_cnextents = tip->i_cnextents;
-		tip->i_cnextents = extnum;
-
-		cowfp = ip->i_cowfp;
-		ip->i_cowfp = tip->i_cowfp;
-		tip->i_cowfp = cowfp;
+		swap(ip->i_cnextents, tip->i_cnextents);
+		swap(ip->i_cowfp, tip->i_cowfp);
 
 		if (ip->i_cowfp && ip->i_cowfp->if_bytes)
 			xfs_inode_set_cowblocks_tag(ip);