XArray: add cmpxchg order test

XArray multi-index entries do not keep track of the order stored once the
entry is being marked as used with cmpxchg (conditionally replaced with
NULL).  Add a test to check the order is actually lost.  The test also
verifies the order and entries for all the tied indexes before and after
the NULL replacement with xa_cmpxchg.

Add another entry at 1 << order that keeps the node around and the order
information for the NULL-entry after xa_cmpxchg.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Daniel Gomez <[email protected]>
Signed-off-by: Luis Chamberlain <[email protected]>
Cc: Darrick J. Wong <[email protected]>
Cc: Dave Chinner <[email protected]>
Cc: Hannes Reinecke <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Pankaj Raghav <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: dkruces

lib/test_xarray.c

@@ -423,6 +423,59 @@ static noinline void check_cmpxchg(struct xarray *xa)
 	XA_BUG_ON(xa, !xa_empty(xa));
 }
 
+static noinline void check_cmpxchg_order(struct xarray *xa)
+{
+#ifdef CONFIG_XARRAY_MULTI
+	void *FIVE = xa_mk_value(5);
+	unsigned int i, order = 3;
+
+	XA_BUG_ON(xa, xa_store_order(xa, 0, order, FIVE, GFP_KERNEL));
+
+	/* Check entry FIVE has the order saved */
+	XA_BUG_ON(xa, xa_get_order(xa, xa_to_value(FIVE)) != order);
+
+	/* Check all the tied indexes have the same entry and order */
+	for (i = 0; i < (1 << order); i++) {
+		XA_BUG_ON(xa, xa_load(xa, i) != FIVE);
+		XA_BUG_ON(xa, xa_get_order(xa, i) != order);
+	}
+
+	/* Ensure that nothing is stored at index '1 << order' */
+	XA_BUG_ON(xa, xa_load(xa, 1 << order) != NULL);
+
+	/*
+	 * Additionally, keep the node information and the order at
+	 * '1 << order'
+	 */
+	XA_BUG_ON(xa, xa_store_order(xa, 1 << order, order, FIVE, GFP_KERNEL));
+	for (i = (1 << order); i < (1 << order) + (1 << order) - 1; i++) {
+		XA_BUG_ON(xa, xa_load(xa, i) != FIVE);
+		XA_BUG_ON(xa, xa_get_order(xa, i) != order);
+	}
+
+	/* Conditionally replace FIVE entry at index '0' with NULL */
+	XA_BUG_ON(xa, xa_cmpxchg(xa, 0, FIVE, NULL, GFP_KERNEL) != FIVE);
+
+	/* Verify the order is lost at FIVE (and old) entries */
+	XA_BUG_ON(xa, xa_get_order(xa, xa_to_value(FIVE)) != 0);
+
+	/* Verify the order and entries are lost in all the tied indexes */
+	for (i = 0; i < (1 << order); i++) {
+		XA_BUG_ON(xa, xa_load(xa, i) != NULL);
+		XA_BUG_ON(xa, xa_get_order(xa, i) != 0);
+	}
+
+	/* Verify node and order are kept at '1 << order' */
+	for (i = (1 << order); i < (1 << order) + (1 << order) - 1; i++) {
+		XA_BUG_ON(xa, xa_load(xa, i) != FIVE);
+		XA_BUG_ON(xa, xa_get_order(xa, i) != order);
+	}
+
+	xa_store_order(xa, 0, BITS_PER_LONG - 1, NULL, GFP_KERNEL);
+	XA_BUG_ON(xa, !xa_empty(xa));
+#endif
+}
+
 static noinline void check_reserve(struct xarray *xa)
 {
 	void *entry;
@@ -1976,6 +2029,7 @@ static int xarray_checks(void)
 	check_xas_erase(&array);
 	check_insert(&array);
 	check_cmpxchg(&array);
+	check_cmpxchg_order(&array);
 	check_reserve(&array);
 	check_reserve(&xa0);
 	check_multi_store(&array);