Messages in this thread | | | Date | Mon, 4 Dec 2006 18:37:04 +0800 | From | WU Fengguang <> | Subject | Re: radix-tree.c:__lookup_slot() dead code removal |
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On Mon, Dec 04, 2006 at 09:18:40PM +1100, Nick Piggin wrote: > Frank van Maarseveen wrote: > >Most of the code suggests that it is valid to insert a NULL item, > >possibly a zero item with pointer cast. However, in __lookup_slot() > >whether or not the slot is found seems to depend on the actual value > >of the item in one special case. But further on it doesn't make any > >difference so to remove some dead code: > > > >--- a/lib/radix-tree.c 2006-12-03 13:23:00.000000000 +0100 > >+++ b/lib/radix-tree.c 2006-12-03 17:57:03.000000000 +0100 > >@@ -319,9 +319,6 @@ static inline void **__lookup_slot(struc > > if (index > radix_tree_maxindex(height)) > > return NULL; > > > >- if (height == 0 && root->rnode) > >- return (void **)&root->rnode; > >- > > shift = (height-1) * RADIX_TREE_MAP_SHIFT; > > slot = &root->rnode; > > I would say it is not valid to insert a NULL item (because NULL > means an unsuccessful lookup, you may as well just delete the > item). > > Also, I don't see how this is dead code anyway. height == 0 > radix-trees are a special case and do not have a radix_tree_node > at ->rnode.
Sorry.
For linux-2.6.19 it was redundant code:
if (height == 0 && root->rnode) return (void **)&root->rnode;
shift = (height-1) * RADIX_TREE_MAP_SHIFT; slot = &root->rnode;
while (height > 0) { ...... }
return (void **)slot;
I just find out it is no longer the case for -mm: the function has been heavily reworked.
So, the patch is no longer valid.
Fengguang Wu - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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