test_xarray: fix failure in check_pause when CONFIG_XARRAY_MULTI is not defined

In case CONFIG_XARRAY_MULTI is not defined, xa_store_order can store a
multi-index entry but xas_for_each can't tell sbiling entry from valid
entry.  So the check_pause failed when we store a multi-index entry and
wish xas_for_each can handle it normally.  Avoid to store multi-index
entry when CONFIG_XARRAY_MULTI is disabled to fix the failure.

Link: https://lkml.kernel.org/r/20250213163659.414309-1-shikemeng@huaweicloud.com
Fixes: c9ba524 ("Xarray: move forward index correctly in xas_pause()")
Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Closes: https://lore.kernel.org/r/CAMuHMdU_bfadUO=0OZ=AoQ9EAmQPA4wsLCBqohXR+QCeCKRn4A@mail.gmail.com
Tested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: Kemeng Shi

lib/test_xarray.c

@@ -1418,7 +1418,7 @@ static noinline void check_pause(struct xarray *xa)
 {
 	XA_STATE(xas, xa, 0);
 	void *entry;
-	unsigned int order;
+	int order;
 	unsigned long index = 1;
 	unsigned int count = 0;
 
@@ -1450,7 +1450,7 @@ static noinline void check_pause(struct xarray *xa)
 	xa_destroy(xa);
 
 	index = 0;
-	for (order = XA_CHUNK_SHIFT; order > 0; order--) {
+	for (order = order_limit - 1; order >= 0; order--) {
 		XA_BUG_ON(xa, xa_store_order(xa, index, order,
 					xa_mk_index(index), GFP_KERNEL));
 		index += 1UL << order;
@@ -1462,24 +1462,25 @@ static noinline void check_pause(struct xarray *xa)
 	rcu_read_lock();
 	xas_for_each(&xas, entry, ULONG_MAX) {
 		XA_BUG_ON(xa, entry != xa_mk_index(index));
-		index += 1UL << (XA_CHUNK_SHIFT - count);
+		index += 1UL << (order_limit - count - 1);
 		count++;
 	}
 	rcu_read_unlock();
-	XA_BUG_ON(xa, count != XA_CHUNK_SHIFT);
+	XA_BUG_ON(xa, count != order_limit);
 
 	index = 0;
 	count = 0;
-	xas_set(&xas, XA_CHUNK_SIZE / 2 + 1);
+	/* test unaligned index */
+	xas_set(&xas, 1 % (1UL << (order_limit - 1)));
 	rcu_read_lock();
 	xas_for_each(&xas, entry, ULONG_MAX) {
 		XA_BUG_ON(xa, entry != xa_mk_index(index));
-		index += 1UL << (XA_CHUNK_SHIFT - count);
+		index += 1UL << (order_limit - count - 1);
 		count++;
 		xas_pause(&xas);
 	}
 	rcu_read_unlock();
-	XA_BUG_ON(xa, count != XA_CHUNK_SHIFT);
+	XA_BUG_ON(xa, count != order_limit);
 
 	xa_destroy(xa);