[PATCH] Fix over-zealous tag clearing in radix_tree_delete

[PATCH] Fix over-zealous tag clearing in radix_tree_delete

[NeilBrown]

Against 2.6.16-rc2-mm1.  For inclusion in 2.6.16 please.

### Comments for Changeset

If a tag is set for a node being deleted from a radix_tree,
then that tag gets cleared from the parent of the node, even
if it is set for some siblings of the node begin deleted.

This patch changes the logic to include a test for any_tag_set similar
to the logic a little futher down.  Care is taken to ensure that
'nr_cleared_tags' remains equals to the number of entries in the
'tags' array which are set to '0' (which means that this tag is not
set in the tree below pathp->node, and should be cleared at
pathp->node and possibly above.

Acked-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Neil Brown <neilb@suse.de>

### Diffstat output
 ./lib/radix-tree.c |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff ./lib/radix-tree.c~current~ ./lib/radix-tree.c
--- ./lib/radix-tree.c~current~	2006-02-16 13:22:28.000000000 +1100
+++ ./lib/radix-tree.c	2006-02-16 14:31:21.000000000 +1100
@@ -753,12 +753,14 @@ void *radix_tree_delete(struct radix_tre
 	 */
 	nr_cleared_tags = 0;
 	for (tag = 0; tag < RADIX_TREE_TAGS; tag++) {
+		tags[tag] = 1;
 		if (tag_get(pathp->node, tag, pathp->offset)) {
 			tag_clear(pathp->node, tag, pathp->offset);
-			tags[tag] = 0;
-			nr_cleared_tags++;
-		} else
-			tags[tag] = 1;
+			if (!any_tag_set(pathp->node, tag)) {
+				tags[tag] = 0;
+				nr_cleared_tags++;
+			}
+		}
 	}
 
 	for (pathp--; nr_cleared_tags && pathp->node; pathp--) {

Re: [PATCH] Fix over-zealous tag clearing in radix_tree_delete

[Nick Piggin]

NeilBrown wrote:
> Against 2.6.16-rc2-mm1.  For inclusion in 2.6.16 please.
> 
> ### Comments for Changeset
> 
> If a tag is set for a node being deleted from a radix_tree,
> then that tag gets cleared from the parent of the node, even
> if it is set for some siblings of the node begin deleted.
> 
> This patch changes the logic to include a test for any_tag_set similar
> to the logic a little futher down.  Care is taken to ensure that
> 'nr_cleared_tags' remains equals to the number of entries in the
> 'tags' array which are set to '0' (which means that this tag is not
> set in the tree below pathp->node, and should be cleared at
> pathp->node and possibly above.
> 
> Acked-by: Nick Piggin <npiggin@suse.de>
> Signed-off-by: Neil Brown <neilb@suse.de>
> 

Linus FYI, I was able to modify the radix tree test harness to catch
the bug and can no longer trigger it after the fix. Resulting code
passes all other harness tests as well of course.

Should be applied ASAP. However, unlike Andrew I don't think this is
a filesystem corrupting bug (maybe he was talking about NFS?).

-- 
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