xfs: cleanup xfs_reflink_find_cow_mapping

Use xfs_iext_lookup_extent to look up the extent, drop a useless check,
drop a unneeded return value and clean up the general style a little bit.

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


diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index 35e02ce..e92355a 100644
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -420,44 +420,31 @@ xfs_reflink_allocate_cow_range(
 }
 
 /*
- * Find the CoW reservation (and whether or not it needs block allocation)
- * for a given byte offset of a file.
+ * Find the CoW reservation for a given byte offset of a file.
  */
 bool
 xfs_reflink_find_cow_mapping(
 	struct xfs_inode		*ip,
 	xfs_off_t			offset,
-	struct xfs_bmbt_irec		*imap,
-	bool				*need_alloc)
+	struct xfs_bmbt_irec		*imap)
 {
-	struct xfs_bmbt_irec		irec;
-	struct xfs_ifork		*ifp;
-	struct xfs_bmbt_rec_host	*gotp;
-	xfs_fileoff_t			bno;
+	struct xfs_ifork		*ifp = XFS_IFORK_PTR(ip, XFS_COW_FORK);
+	xfs_fileoff_t			offset_fsb;
+	struct xfs_bmbt_irec		got;
 	xfs_extnum_t			idx;
 
 	ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL | XFS_ILOCK_SHARED));
 	ASSERT(xfs_is_reflink_inode(ip));
 
-	/* Find the extent in the CoW fork. */
-	ifp = XFS_IFORK_PTR(ip, XFS_COW_FORK);
-	bno = XFS_B_TO_FSBT(ip->i_mount, offset);
-	gotp = xfs_iext_bno_to_ext(ifp, bno, &idx);
-	if (!gotp)
+	offset_fsb = XFS_B_TO_FSBT(ip->i_mount, offset);
+	if (!xfs_iext_lookup_extent(ip, ifp, offset_fsb, &idx, &got))
 		return false;
-
-	xfs_bmbt_get_all(gotp, &irec);
-	if (bno >= irec.br_startoff + irec.br_blockcount ||
-	    bno < irec.br_startoff)
+	if (got.br_startoff > offset_fsb)
 		return false;
 
 	trace_xfs_reflink_find_cow_mapping(ip, offset, 1, XFS_IO_OVERWRITE,
-			&irec);
-
-	/* If it's still delalloc, we must allocate later. */
-	*imap = irec;
-	*need_alloc = !!(isnullstartblock(irec.br_startblock));
-
+			&got);
+	*imap = got;
 	return true;
 }