1 files changed, 80 insertions, 0 deletions

diff --git a/lib/xarray.c b/lib/xarray.c
index 24494f42daa6..70e04810c8c2 100644
--- a/lib/xarray.c
+++ b/lib/xarray.c
@@ -1444,6 +1444,86 @@ void *xa_find_after(struct xarray *xa, unsigned long *indexp,
 }
 EXPORT_SYMBOL(xa_find_after);
 
+static unsigned int xas_extract_present(struct xa_state *xas, void **dst,
+                        unsigned long max, unsigned int n)
+{
+        void *entry;
+        unsigned int i = 0;
+
+        rcu_read_lock();
+        xas_for_each(xas, entry, max) {
+                if (xas_retry(xas, entry))
+                        continue;
+                dst[i++] = entry;
+                if (i == n)
+                        break;
+        }
+        rcu_read_unlock();
+
+        return i;
+}
+
+static unsigned int xas_extract_marked(struct xa_state *xas, void **dst,
+                        unsigned long max, unsigned int n, xa_mark_t mark)
+{
+        void *entry;
+        unsigned int i = 0;
+
+        rcu_read_lock();
+        xas_for_each_marked(xas, entry, max, mark) {
+                if (xas_retry(xas, entry))
+                        continue;
+                dst[i++] = entry;
+                if (i == n)
+                        break;
+        }
+        rcu_read_unlock();
+
+        return i;
+}
+
+/**
+ * xa_extract() - Copy selected entries from the XArray into a normal array.
+ * @xa: The source XArray to copy from.
+ * @dst: The buffer to copy entries into.
+ * @start: The first index in the XArray eligible to be selected.
+ * @max: The last index in the XArray eligible to be selected.
+ * @n: The maximum number of entries to copy.
+ * @filter: Selection criterion.
+ *
+ * Copies up to @n entries that match @filter from the XArray.  The
+ * copied entries will have indices between @start and @max, inclusive.
+ *
+ * The @filter may be an XArray mark value, in which case entries which are
+ * marked with that mark will be copied.  It may also be %XA_PRESENT, in
+ * which case all entries which are not NULL will be copied.
+ *
+ * The entries returned may not represent a snapshot of the XArray at a
+ * moment in time.  For example, if another thread stores to index 5, then
+ * index 10, calling xa_extract() may return the old contents of index 5
+ * and the new contents of index 10.  Indices not modified while this
+ * function is running will not be skipped.
+ *
+ * If you need stronger guarantees, holding the xa_lock across calls to this
+ * function will prevent concurrent modification.
+ *
+ * Context: Any context.  Takes and releases the RCU lock.
+ * Return: The number of entries copied.
+ */
+unsigned int xa_extract(struct xarray *xa, void **dst, unsigned long start,
+                        unsigned long max, unsigned int n, xa_mark_t filter)
+{
+        XA_STATE(xas, xa, start);
+
+        if (!n)
+                return 0;
+
+        if ((__force unsigned int)filter < XA_MAX_MARKS)
+                return xas_extract_marked(&xas, dst, max, n, filter);
+        return xas_extract_present(&xas, dst, max, n);
+}
+EXPORT_SYMBOL(xa_extract);
+
 #ifdef XA_DEBUG
 void xa_dump_node(const struct xa_node *node)
 {