xfs: switch remaining xfs_trans_dup users to xfs_trans_roll

We have three remaining callers of xfs_trans_dup:

 - xfs_itruncate_extents which open codes xfs_trans_roll
 - xfs_bmap_finish doesn't have an xfs_inode argument and thus leaves
   attaching them to it's callers, but otherwise is identical to
   xfs_trans_roll
 - xfs_dir_ialloc looks at the log reservations in the old xfs_trans
   structure instead of the log reservation parameters, but otherwise
   is identical to xfs_trans_roll.

By allowing a NULL xfs_inode argument to xfs_trans_roll we can switch
these three remaining users over to xfs_trans_roll and mark xfs_trans_dup
static.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c
index 220ef2c..a2dfb30 100644
--- a/fs/xfs/xfs_trans.c
+++ b/fs/xfs/xfs_trans.c
@@ -113,7 +113,7 @@
  * blocks.  Locks and log items, however, are no inherited.  They must
  * be added to the new transaction explicitly.
  */
-xfs_trans_t *
+STATIC xfs_trans_t *
 xfs_trans_dup(
 	xfs_trans_t	*tp)
 {
@@ -1055,7 +1055,8 @@
 	 * Ensure that the inode is always logged.
 	 */
 	trans = *tpp;
-	xfs_trans_log_inode(trans, dp, XFS_ILOG_CORE);
+	if (dp)
+		xfs_trans_log_inode(trans, dp, XFS_ILOG_CORE);
 
 	/*
 	 * Copy the critical parameters from one trans to the next.
@@ -1100,6 +1101,7 @@
 	if (error)
 		return error;
 
-	xfs_trans_ijoin(trans, dp, 0);
+	if (dp)
+		xfs_trans_ijoin(trans, dp, 0);
 	return 0;
 }