XArray: Fix xa_find_after with multi-index entries
If the entry is of an order which is a multiple of XA_CHUNK_SIZE,
the current detection of sibling entries does not work. Factor out
an xas_sibling() function to make xa_find_after() a little more
understandable, and write a new implementation that doesn't suffer from
the same bug.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: stable@vger.kernel.org
diff --git a/lib/xarray.c b/lib/xarray.c
index 6ecf35c..03300a0 100644
--- a/lib/xarray.c
+++ b/lib/xarray.c
@@ -1826,6 +1826,17 @@
}
EXPORT_SYMBOL(xa_find);
+static bool xas_sibling(struct xa_state *xas)
+{
+ struct xa_node *node = xas->xa_node;
+ unsigned long mask;
+
+ if (!node)
+ return false;
+ mask = (XA_CHUNK_SIZE << node->shift) - 1;
+ return (xas->xa_index & mask) > (xas->xa_offset << node->shift);
+}
+
/**
* xa_find_after() - Search the XArray for a present entry.
* @xa: XArray.
@@ -1860,13 +1871,8 @@
entry = xas_find(&xas, max);
if (xas.xa_node == XAS_BOUNDS)
break;
- if (xas.xa_shift) {
- if (xas.xa_index & ((1UL << xas.xa_shift) - 1))
- continue;
- } else {
- if (xas.xa_offset < (xas.xa_index & XA_CHUNK_MASK))
- continue;
- }
+ if (xas_sibling(&xas))
+ continue;
if (!xas_retry(&xas, entry))
break;
}