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

The @start pointer passed to each per-AG btree type's ->alloc_block
function isn't supposed to be modified, since it's a hint about the
location of the btree block being split that is to be fed to the
allocator, so mark the parameter const.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

fs/xfs/libxfs/xfs_alloc_btree.c

@@ -50,10 +50,10 @@ xfs_allocbt_set_root(
 
 STATIC int
 xfs_allocbt_alloc_block(
-	struct xfs_btree_cur	*cur,
-	union xfs_btree_ptr	*start,
-	union xfs_btree_ptr	*new,
-	int			*stat)
+	struct xfs_btree_cur		*cur,
+	const union xfs_btree_ptr	*start,
+	union xfs_btree_ptr		*new,
+	int				*stat)
 {
 	int			error;
 	xfs_agblock_t		bno;

fs/xfs/libxfs/xfs_bmap_btree.c

@@ -193,10 +193,10 @@ xfs_bmbt_update_cursor(
 
 STATIC int
 xfs_bmbt_alloc_block(
-	struct xfs_btree_cur	*cur,
-	union xfs_btree_ptr	*start,
-	union xfs_btree_ptr	*new,
-	int			*stat)
+	struct xfs_btree_cur		*cur,
+	const union xfs_btree_ptr	*start,
+	union xfs_btree_ptr		*new,
+	int				*stat)
 {
 	xfs_alloc_arg_t		args;		/* block allocation args */
 	int			error;		/* error return value */

fs/xfs/libxfs/xfs_btree.h

@@ -110,7 +110,7 @@ struct xfs_btree_ops {
 
 	/* block allocation / freeing */
 	int	(*alloc_block)(struct xfs_btree_cur *cur,
-			       union xfs_btree_ptr *start_bno,
+			       const union xfs_btree_ptr *start_bno,
 			       union xfs_btree_ptr *new_bno,
 			       int *stat);
 	int	(*free_block)(struct xfs_btree_cur *cur, struct xfs_buf *bp);

fs/xfs/libxfs/xfs_btree_staging.c

@@ -59,10 +59,10 @@ xfs_btree_fakeroot_dup_cursor(
  */
 STATIC int
 xfs_btree_fakeroot_alloc_block(
-	struct xfs_btree_cur	*cur,
-	union xfs_btree_ptr	*start_bno,
-	union xfs_btree_ptr	*new_bno,
-	int			*stat)
+	struct xfs_btree_cur		*cur,
+	const union xfs_btree_ptr	*start_bno,
+	union xfs_btree_ptr		*new_bno,
+	int				*stat)
 {
 	ASSERT(0);
 	return -EFSCORRUPTED;

fs/xfs/libxfs/xfs_ialloc_btree.c

@@ -88,11 +88,11 @@ xfs_inobt_mod_blockcount(
 
 STATIC int
 __xfs_inobt_alloc_block(
-	struct xfs_btree_cur	*cur,
-	union xfs_btree_ptr	*start,
-	union xfs_btree_ptr	*new,
-	int			*stat,
-	enum xfs_ag_resv_type	resv)
+	struct xfs_btree_cur		*cur,
+	const union xfs_btree_ptr	*start,
+	union xfs_btree_ptr		*new,
+	int				*stat,
+	enum xfs_ag_resv_type		resv)
 {
 	xfs_alloc_arg_t		args;		/* block allocation args */
 	int			error;		/* error return value */
@@ -127,20 +127,20 @@ __xfs_inobt_alloc_block(
 
 STATIC int
 xfs_inobt_alloc_block(
-	struct xfs_btree_cur	*cur,
-	union xfs_btree_ptr	*start,
-	union xfs_btree_ptr	*new,
-	int			*stat)
+	struct xfs_btree_cur		*cur,
+	const union xfs_btree_ptr	*start,
+	union xfs_btree_ptr		*new,
+	int				*stat)
 {
 	return __xfs_inobt_alloc_block(cur, start, new, stat, XFS_AG_RESV_NONE);
 }
 
 STATIC int
 xfs_finobt_alloc_block(
-	struct xfs_btree_cur	*cur,
-	union xfs_btree_ptr	*start,
-	union xfs_btree_ptr	*new,
-	int			*stat)
+	struct xfs_btree_cur		*cur,
+	const union xfs_btree_ptr	*start,
+	union xfs_btree_ptr		*new,
+	int				*stat)
 {
 	if (cur->bc_mp->m_finobt_nores)
 		return xfs_inobt_alloc_block(cur, start, new, stat);

fs/xfs/libxfs/xfs_refcount_btree.c

@@ -51,10 +51,10 @@ xfs_refcountbt_set_root(
 
 STATIC int
 xfs_refcountbt_alloc_block(
-	struct xfs_btree_cur	*cur,
-	union xfs_btree_ptr	*start,
-	union xfs_btree_ptr	*new,
-	int			*stat)
+	struct xfs_btree_cur		*cur,
+	const union xfs_btree_ptr	*start,
+	union xfs_btree_ptr		*new,
+	int				*stat)
 {
 	struct xfs_buf		*agbp = cur->bc_ag.agbp;
 	struct xfs_agf		*agf = agbp->b_addr;

fs/xfs/libxfs/xfs_rmap_btree.c

@@ -76,10 +76,10 @@ xfs_rmapbt_set_root(
 
 STATIC int
 xfs_rmapbt_alloc_block(
-	struct xfs_btree_cur	*cur,
-	union xfs_btree_ptr	*start,
-	union xfs_btree_ptr	*new,
-	int			*stat)
+	struct xfs_btree_cur		*cur,
+	const union xfs_btree_ptr	*start,
+	union xfs_btree_ptr		*new,
+	int				*stat)
 {
 	struct xfs_buf		*agbp = cur->bc_ag.agbp;
 	struct xfs_agf		*agf = agbp->b_addr;