xfs: encode the max btree height in the cursor

Encode the maximum btree height in the cursor, since we're soon going to
allow smaller cursors for AG btrees and larger cursors for file btrees.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

fs/xfs/libxfs/xfs_bmap.c

@@ -239,7 +239,7 @@ xfs_bmap_get_bp(
 	if (!cur)
 		return NULL;
 
-	for (i = 0; i < XFS_BTREE_MAXLEVELS; i++) {
+	for (i = 0; i < cur->bc_maxlevels; i++) {
 		if (!cur->bc_levels[i].bp)
 			break;
 		if (xfs_buf_daddr(cur->bc_levels[i].bp) == bno)

fs/xfs/libxfs/xfs_btree.c

@@ -2933,7 +2933,7 @@ xfs_btree_new_iroot(
 	be16_add_cpu(&block->bb_level, 1);
 	xfs_btree_set_numrecs(block, 1);
 	cur->bc_nlevels++;
-	ASSERT(cur->bc_nlevels <= XFS_BTREE_MAXLEVELS);
+	ASSERT(cur->bc_nlevels <= cur->bc_maxlevels);
 	cur->bc_levels[level + 1].ptr = 1;
 
 	kp = xfs_btree_key_addr(cur, 1, block);
@@ -3097,7 +3097,7 @@ xfs_btree_new_root(
 	xfs_btree_setbuf(cur, cur->bc_nlevels, nbp);
 	cur->bc_levels[cur->bc_nlevels].ptr = nptr;
 	cur->bc_nlevels++;
-	ASSERT(cur->bc_nlevels <= XFS_BTREE_MAXLEVELS);
+	ASSERT(cur->bc_nlevels <= cur->bc_maxlevels);
 	*stat = 1;
 	return 0;
 error0:

fs/xfs/libxfs/xfs_btree.h

@@ -238,6 +238,7 @@ struct xfs_btree_cur
 	xfs_btnum_t		bc_btnum; /* identifies which btree type */
 	union xfs_btree_irec	bc_rec;	/* current insert/search record value */
 	uint8_t			bc_nlevels; /* number of levels in the tree */
+	uint8_t			bc_maxlevels; /* maximum levels for this btree type */
 	int			bc_statoff; /* offset of btree stats array */
 
 	/*
@@ -590,6 +591,7 @@ xfs_btree_alloc_cursor(
 	cur->bc_tp = tp;
 	cur->bc_mp = mp;
 	cur->bc_btnum = btnum;
+	cur->bc_maxlevels = XFS_BTREE_MAXLEVELS;
 
 	return cur;
 }

fs/xfs/libxfs/xfs_btree_staging.c

@@ -657,12 +657,12 @@ xfs_btree_bload_compute_geometry(
 	 * checking levels 0 and 1 here, so set bc_nlevels such that the btree
 	 * code doesn't interpret either as the root level.
 	 */
-	cur->bc_nlevels = XFS_BTREE_MAXLEVELS - 1;
+	cur->bc_nlevels = cur->bc_maxlevels - 1;
 	xfs_btree_bload_ensure_slack(cur, &bbl->leaf_slack, 0);
 	xfs_btree_bload_ensure_slack(cur, &bbl->node_slack, 1);
 
 	bbl->nr_records = nr_this_level = nr_records;
-	for (cur->bc_nlevels = 1; cur->bc_nlevels <= XFS_BTREE_MAXLEVELS;) {
+	for (cur->bc_nlevels = 1; cur->bc_nlevels <= cur->bc_maxlevels;) {
 		uint64_t	level_blocks;
 		uint64_t	dontcare64;
 		unsigned int	level = cur->bc_nlevels - 1;
@@ -703,7 +703,7 @@ xfs_btree_bload_compute_geometry(
 			 * block-based btree level.
 			 */
 			cur->bc_nlevels++;
-			ASSERT(cur->bc_nlevels <= XFS_BTREE_MAXLEVELS);
+			ASSERT(cur->bc_nlevels <= cur->bc_maxlevels);
 			xfs_btree_bload_level_geometry(cur, bbl, level,
 					nr_this_level, &avg_per_block,
 					&level_blocks, &dontcare64);
@@ -719,14 +719,14 @@ xfs_btree_bload_compute_geometry(
 
 			/* Otherwise, we need another level of btree. */
 			cur->bc_nlevels++;
-			ASSERT(cur->bc_nlevels <= XFS_BTREE_MAXLEVELS);
+			ASSERT(cur->bc_nlevels <= cur->bc_maxlevels);
 		}
 
 		nr_blocks += level_blocks;
 		nr_this_level = level_blocks;
 	}
 
-	if (cur->bc_nlevels > XFS_BTREE_MAXLEVELS)
+	if (cur->bc_nlevels > cur->bc_maxlevels)
 		return -EOVERFLOW;
 
 	bbl->btree_height = cur->bc_nlevels;