xarray: Add XArray conditional store operations

Like cmpxchg(), xa_cmpxchg will only store to the index if the current
entry matches the old entry.  It returns the current entry, which is
usually more useful than the errno returned by radix_tree_insert().
For the users who really only want the errno, the xa_insert() wrapper
provides a more convenient calling convention.

Signed-off-by: Matthew Wilcox <willy@infradead.org>

1 files changed, 20 insertions, 0 deletions

diff --git a/lib/test_xarray.c b/lib/test_xarray.c
index b711030fbc32..fb472258b639 100644
--- a/lib/test_xarray.c
+++ b/lib/test_xarray.c
@@ -198,6 +198,25 @@ static noinline void check_xa_shrink(struct xarray *xa)
         XA_BUG_ON(xa, !xa_empty(xa));
 }
 
+static noinline void check_cmpxchg(struct xarray *xa)
+{
+        void *FIVE = xa_mk_value(5);
+        void *SIX = xa_mk_value(6);
+        void *LOTS = xa_mk_value(12345678);
+
+        XA_BUG_ON(xa, !xa_empty(xa));
+        XA_BUG_ON(xa, xa_store_index(xa, 12345678, GFP_KERNEL) != NULL);
+        XA_BUG_ON(xa, xa_insert(xa, 12345678, xa, GFP_KERNEL) != -EEXIST);
+        XA_BUG_ON(xa, xa_cmpxchg(xa, 12345678, SIX, FIVE, GFP_KERNEL) != LOTS);
+        XA_BUG_ON(xa, xa_cmpxchg(xa, 12345678, LOTS, FIVE, GFP_KERNEL) != LOTS);
+        XA_BUG_ON(xa, xa_cmpxchg(xa, 12345678, FIVE, LOTS, GFP_KERNEL) != FIVE);
+        XA_BUG_ON(xa, xa_cmpxchg(xa, 5, FIVE, NULL, GFP_KERNEL) != NULL);
+        XA_BUG_ON(xa, xa_cmpxchg(xa, 5, NULL, FIVE, GFP_KERNEL) != NULL);
+        xa_erase_index(xa, 12345678);
+        xa_erase_index(xa, 5);
+        XA_BUG_ON(xa, !xa_empty(xa));
+}
+
 static noinline void check_multi_store(struct xarray *xa)
 {
 #ifdef CONFIG_XARRAY_MULTI
@@ -274,6 +293,7 @@ static int xarray_checks(void)
         check_xa_load(&array);
         check_xa_mark(&array);
         check_xa_shrink(&array);
+        check_cmpxchg(&array);
         check_multi_store(&array);
 
         printk("XArray: %u of %u tests passed\n", tests_passed, tests_run);