radix-tree: tidy up next_chunk

Convert radix_tree_next_chunk to use 'child' instead of 'slot' as the
name of the child node.  Also use node_maxindex() where it makes sense.

The 'rnode' variable was unnecessary; it doesn't overlap in usage with
'node', so we can just use 'node' the whole way through the function.

Improve the testcase to start the walk from every index in the carefully
constructed tree, and to accept any index within the range covered by
the entry.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jan Kara <jack@suse.com>
Cc: Neil Brown <neilb@suse.de>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 19 insertions, 34 deletions

diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 4b4a2a20a3d1..c42867a1769a 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -876,7 +876,7 @@ void **radix_tree_next_chunk(struct radix_tree_root *root,
 			     struct radix_tree_iter *iter, unsigned flags)
 {
 	unsigned shift, tag = flags & RADIX_TREE_ITER_TAG_MASK;
-	struct radix_tree_node *rnode, *node;
+	struct radix_tree_node *node, *child;
 	unsigned long index, offset, maxindex;
 
 	if ((flags & RADIX_TREE_ITER_TAGGED) && !root_tag_get(root, tag))
@@ -896,38 +896,29 @@ void **radix_tree_next_chunk(struct radix_tree_root *root,
 		return NULL;
 
  restart:
-	shift = radix_tree_load_root(root, &rnode, &maxindex);
+	shift = radix_tree_load_root(root, &child, &maxindex);
 	if (index > maxindex)
 		return NULL;
+	if (!child)
+		return NULL;
 
-	if (radix_tree_is_internal_node(rnode)) {
-		rnode = entry_to_node(rnode);
-	} else if (rnode) {
+	if (!radix_tree_is_internal_node(child)) {
 		/* Single-slot tree */
 		iter->index = index;
 		iter->next_index = maxindex + 1;
 		iter->tags = 1;
-		__set_iter_shift(iter, shift);
+		__set_iter_shift(iter, 0);
 		return (void **)&root->rnode;
-	} else
-		return NULL;
-
-	shift -= RADIX_TREE_MAP_SHIFT;
-	offset = index >> shift;
-
-	node = rnode;
-	while (1) {
-		struct radix_tree_node *slot;
-		unsigned new_off = radix_tree_descend(node, &slot, offset);
+	}
 
-		if (new_off < offset) {
-			offset = new_off;
-			index &= ~((RADIX_TREE_MAP_SIZE << shift) - 1);
-			index |= offset << shift;
-		}
+	do {
+		node = entry_to_node(child);
+		shift -= RADIX_TREE_MAP_SHIFT;
+		offset = (index >> shift) & RADIX_TREE_MAP_MASK;
+		offset = radix_tree_descend(node, &child, offset);
 
 		if ((flags & RADIX_TREE_ITER_TAGGED) ?
-				!tag_get(node, tag, offset) : !slot) {
+				!tag_get(node, tag, offset) : !child) {
 			/* Hole detected */
 			if (flags & RADIX_TREE_ITER_CONTIG)
 				return NULL;
@@ -945,29 +936,23 @@ void **radix_tree_next_chunk(struct radix_tree_root *root,
 					if (slot)
 						break;
 				}
-			index &= ~((RADIX_TREE_MAP_SIZE << shift) - 1);
+			index &= ~node_maxindex(node);
 			index += offset << shift;
 			/* Overflow after ~0UL */
 			if (!index)
 				return NULL;
 			if (offset == RADIX_TREE_MAP_SIZE)
 				goto restart;
-			slot = rcu_dereference_raw(node->slots[offset]);
+			child = rcu_dereference_raw(node->slots[offset]);
 		}
 
-		if ((slot == NULL) || (slot == RADIX_TREE_RETRY))
+		if ((child == NULL) || (child == RADIX_TREE_RETRY))
 			goto restart;
-		if (!radix_tree_is_internal_node(slot))
-			break;
-
-		node = entry_to_node(slot);
-		shift -= RADIX_TREE_MAP_SHIFT;
-		offset = (index >> shift) & RADIX_TREE_MAP_MASK;
-	}
+	} while (radix_tree_is_internal_node(child));
 
 	/* Update the iterator state */
-	iter->index = index & ~((1 << shift) - 1);
-	iter->next_index = (index | ((RADIX_TREE_MAP_SIZE << shift) - 1)) + 1;
+	iter->index = (index &~ node_maxindex(node)) | (offset << node->shift);
+	iter->next_index = (index | node_maxindex(node)) + 1;
 	__set_iter_shift(iter, shift);
 
 	/* Construct iter->tags bit-mask from node->tags[tag] array */