[PATCH AUTOSEL 5.10 12/22] XArray: Fix splitting to non-zero orders

[Sasha Levin]

From: "Matthew Wilcox (Oracle)" <wi...@infradead.org>

[ Upstream commit 3012110d71f41410932924e1d188f9eb57f1f824 ]

Splitting an order-4 entry into order-2 entries would leave the array
containing pointers to 000040008000c000 instead of 000044448888cccc.
This is a one-character fix, but enhance the test suite to check this
case.

Reported-by: Zi Yan <z...@nvidia.com>
Signed-off-by: Matthew Wilcox (Oracle) <wi...@infradead.org>
Signed-off-by: Sasha Levin <sas...@kernel.org>
---
 lib/test_xarray.c | 26 ++++++++++++++------------
 lib/xarray.c      |  4 ++--
 2 files changed, 16 insertions(+), 14 deletions(-)

diff --git a/lib/test_xarray.c b/lib/test_xarray.c
index 8294f43f4981..8b1c318189ce 100644
--- a/lib/test_xarray.c
+++ b/lib/test_xarray.c
@@ -1530,24 +1530,24 @@ static noinline void check_store_range(struct xarray 
*xa)
 
 #ifdef CONFIG_XARRAY_MULTI
 static void check_split_1(struct xarray *xa, unsigned long index,
-                                                       unsigned int order)
+                               unsigned int order, unsigned int new_order)
 {
-       XA_STATE(xas, xa, index);
-       void *entry;
-       unsigned int i = 0;
+       XA_STATE_ORDER(xas, xa, index, new_order);
+       unsigned int i;
 
        xa_store_order(xa, index, order, xa, GFP_KERNEL);
 
        xas_split_alloc(&xas, xa, order, GFP_KERNEL);
        xas_lock(&xas);
        xas_split(&xas, xa, order);
+       for (i = 0; i < (1 << order); i += (1 << new_order))
+               __xa_store(xa, index + i, xa_mk_index(index + i), 0);
        xas_unlock(&xas);
 
-       xa_for_each(xa, index, entry) {
-               XA_BUG_ON(xa, entry != xa);
-               i++;
+       for (i = 0; i < (1 << order); i++) {
+               unsigned int val = index + (i & ~((1 << new_order) - 1));
+               XA_BUG_ON(xa, xa_load(xa, index + i) != xa_mk_index(val));
        }
-       XA_BUG_ON(xa, i != 1 << order);
 
        xa_set_mark(xa, index, XA_MARK_0);
        XA_BUG_ON(xa, !xa_get_mark(xa, index, XA_MARK_0));
@@ -1557,14 +1557,16 @@ static void check_split_1(struct xarray *xa, unsigned 
long index,
 
 static noinline void check_split(struct xarray *xa)
 {
-       unsigned int order;
+       unsigned int order, new_order;
 
        XA_BUG_ON(xa, !xa_empty(xa));
 
        for (order = 1; order < 2 * XA_CHUNK_SHIFT; order++) {
-               check_split_1(xa, 0, order);
-               check_split_1(xa, 1UL << order, order);
-               check_split_1(xa, 3UL << order, order);
+               for (new_order = 0; new_order < order; new_order++) {
+                       check_split_1(xa, 0, order, new_order);
+                       check_split_1(xa, 1UL << order, order, new_order);
+                       check_split_1(xa, 3UL << order, order, new_order);
+               }
        }
 }
 #else
diff --git a/lib/xarray.c b/lib/xarray.c
index 5fa51614802a..ed775dee1074 100644
--- a/lib/xarray.c
+++ b/lib/xarray.c
@@ -1011,7 +1011,7 @@ void xas_split_alloc(struct xa_state *xas, void *entry, 
unsigned int order,
 
        do {
                unsigned int i;
-               void *sibling;
+               void *sibling = NULL;
                struct xa_node *node;
 
                node = kmem_cache_alloc(radix_tree_node_cachep, gfp);
@@ -1021,7 +1021,7 @@ void xas_split_alloc(struct xa_state *xas, void *entry, 
unsigned int order,
                for (i = 0; i < XA_CHUNK_SIZE; i++) {
                        if ((i & mask) == 0) {
                                RCU_INIT_POINTER(node->slots[i], entry);
-                               sibling = xa_mk_sibling(0);
+                               sibling = xa_mk_sibling(i);
                        } else {
                                RCU_INIT_POINTER(node->slots[i], sibling);
                        }
-- 
2.30.2