XArray: Fix xa_for_each with a single element at 0

The following sequence of calls would result in an infinite loop in
xa_find_after():

	xa_store(xa, 0, x, GFP_KERNEL);
	index = 0;
	xa_for_each(xa, entry, index, ULONG_MAX, XA_PRESENT) { }

xa_find_after() was confusing the situation where we found no entry in
the tree with finding a multiorder entry, so it would look for the
successor entry forever.  Just check for this case explicitly.  Includes
a few new checks in the test suite to be sure this doesn't reappear.

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

diff --git a/lib/test_xarray.c b/lib/test_xarray.c
index aa47754150cee9a0374ca16195f17c061225a538..126127658b4943ee764ce2d754c9f4c7933fef5d 100644 (file)
--- a/lib/test_xarray.c
+++ b/lib/test_xarray.c
@@ -702,7 +702,7 @@ static noinline void check_multi_find_2(struct xarray *xa)
        }
 }
 
-static noinline void check_find(struct xarray *xa)
+static noinline void check_find_1(struct xarray *xa)
 {
        unsigned long i, j, k;
 
@@ -748,6 +748,34 @@ static noinline void check_find(struct xarray *xa)
                XA_BUG_ON(xa, xa_get_mark(xa, i, XA_MARK_0));
        }
        XA_BUG_ON(xa, !xa_empty(xa));
+}
+
+static noinline void check_find_2(struct xarray *xa)
+{
+       void *entry;
+       unsigned long i, j, index = 0;
+
+       xa_for_each(xa, entry, index, ULONG_MAX, XA_PRESENT) {
+               XA_BUG_ON(xa, true);
+       }
+
+       for (i = 0; i < 1024; i++) {
+               xa_store_index(xa, index, GFP_KERNEL);
+               j = 0;
+               index = 0;
+               xa_for_each(xa, entry, index, ULONG_MAX, XA_PRESENT) {
+                       XA_BUG_ON(xa, xa_mk_value(index) != entry);
+                       XA_BUG_ON(xa, index != j++);
+               }
+       }
+
+       xa_destroy(xa);
+}
+
+static noinline void check_find(struct xarray *xa)
+{
+       check_find_1(xa);
+       check_find_2(xa);
        check_multi_find(xa);
        check_multi_find_2(xa);
 }

diff --git a/lib/xarray.c b/lib/xarray.c
index 8b176f009c0877853087772b18cd53ef15b2c099..c991ff4523ef19ed88937aa905de49b06e1a8c54 100644 (file)
--- a/lib/xarray.c
+++ b/lib/xarray.c
@@ -1829,6 +1829,8 @@ void *xa_find_after(struct xarray *xa, unsigned long *indexp,
                        entry = xas_find_marked(&xas, max, filter);
                else
                        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;