On 30/05/25 4:17 am, Zi Yan wrote:
On 28 May 2025, at 23:17, Dev Jain wrote:
On 28/05/25 10:42 pm, Zi Yan wrote:
On 28 May 2025, at 7:31, Dev Jain wrote:
Suppose xas is pointing somewhere near the end of the multi-entry batch.
Then it may happen that the computed slot already falls beyond the batch,
thus breaking the loop due to !xa_is_sibling(), and computing the wrong
order. Thus ensure that the caller is aware of this by triggering a BUG
when the entry is a sibling entry.
Is it possible to add a test case in lib/test_xarray.c for this?
You can compile the tests with “make -C tools/testing/radix-tree”
and run “./tools/testing/radix-tree/xarray”.
Sorry forgot to Cc you.
I can surely do that later, but does this patch look fine?
I am not sure the exact situation you are describing, so I asked you
to write a test case to demonstrate the issue. :)
Suppose we have a shift-6 node having an order-9 entry => 8 - 1 = 7 siblings,
so assume the slots are at offset 0 till 7 in this node. If xas->xa_offset is 6,
then the code will compute order as 1 + xas->xa_node->shift = 7. So I mean to
say that the order computation must start from the beginning of the multi-slot
entries, that is, the non-sibling entry.
This patch is motivated by code inspection and not a real bug report.
Signed-off-by: Dev Jain <dev.jain@xxxxxxx>
---
The patch applies on 6.15 kernel.
lib/xarray.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/lib/xarray.c b/lib/xarray.c
index 9644b18af18d..0f699766c24f 100644
--- a/lib/xarray.c
+++ b/lib/xarray.c
@@ -1917,6 +1917,8 @@ int xas_get_order(struct xa_state *xas)
if (!xas->xa_node)
return 0;
+ XA_NODE_BUG_ON(xas->xa_node, xa_is_sibling(xa_entry(xas->xa,
+ xas->xa_node, xas->xa_offset)));
for (;;) {
unsigned int slot = xas->xa_offset + (1 << order);
--
2.30.2
Best Regards,
Yan, Zi
Best Regards,
Yan, Zi
