xfs: make the start pointer passed to btree update_lastrec functions const

This btree function is called when updating a record in the rightmost
block of a btree so that we can update the AGF's longest free extent
length field.  Neither parameter is supposed to be updated, so mark them
both const.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

fs/xfs/libxfs/xfs_alloc_btree.c

@@ -103,11 +103,11 @@ xfs_allocbt_free_block(
  */
 STATIC void
 xfs_allocbt_update_lastrec(
-	struct xfs_btree_cur	*cur,
-	struct xfs_btree_block	*block,
-	union xfs_btree_rec	*rec,
-	int			ptr,
-	int			reason)
+	struct xfs_btree_cur		*cur,
+	const struct xfs_btree_block	*block,
+	const union xfs_btree_rec	*rec,
+	int				ptr,
+	int				reason)
 {
 	struct xfs_agf		*agf = cur->bc_ag.agbp->b_addr;
 	struct xfs_perag	*pag;

fs/xfs/libxfs/xfs_btree.h

@@ -117,8 +117,8 @@ struct xfs_btree_ops {
 
 	/* update last record information */
 	void	(*update_lastrec)(struct xfs_btree_cur *cur,
-				  struct xfs_btree_block *block,
-				  union xfs_btree_rec *rec,
+				  const struct xfs_btree_block *block,
+				  const union xfs_btree_rec *rec,
 				  int ptr, int reason);
 
 	/* records in block/level */
@@ -423,7 +423,7 @@ void xfs_btree_log_recs(struct xfs_btree_cur *, struct xfs_buf *, int, int);
 /*
  * Helpers.
  */
-static inline int xfs_btree_get_numrecs(struct xfs_btree_block *block)
+static inline int xfs_btree_get_numrecs(const struct xfs_btree_block *block)
 {
 	return be16_to_cpu(block->bb_numrecs);
 }
@@ -434,7 +434,7 @@ static inline void xfs_btree_set_numrecs(struct xfs_btree_block *block,
 	block->bb_numrecs = cpu_to_be16(numrecs);
 }
 
-static inline int xfs_btree_get_level(struct xfs_btree_block *block)
+static inline int xfs_btree_get_level(const struct xfs_btree_block *block)
 {
 	return be16_to_cpu(block->bb_level);
 }