lkml.org 
[lkml]   [2006]   [Dec]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: radix-tree.c:__lookup_slot() dead code removal
    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    So, the patch is no longer valid.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/

    \
     
     \ /
      Last update: 2006-12-04 11:39    [W:0.024 / U:3.312 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site