[PATCH 2/4] rangeset: add rangeset_reset helper function

[Oleksandr Andrushchenko <andr2000@gmail.com>]

From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>

This helper destroys all the ranges of the rangeset given.
Please note, that it uses rangeset_remove_range which returns an error
code on failure. This error code can be ignored as while destroying all
the ranges no memory allocation is expected, so in this case it must not
fail.

To make sure this remains valid use BUG_ON if that changes in the future.

Suggested-by: Roger Pau Monné <roger.pau@citrix.com>
Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
---
 xen/common/rangeset.c      | 6 ++++++
 xen/include/xen/rangeset.h | 3 +++
 2 files changed, 9 insertions(+)

diff --git a/xen/common/rangeset.c b/xen/common/rangeset.c
index ea27d651723b..9ca2b06cff22 100644
--- a/xen/common/rangeset.c
+++ b/xen/common/rangeset.c
@@ -525,6 +525,12 @@ void rangeset_swap(struct rangeset *a, struct rangeset *b)
     write_unlock(&b->lock);
 }
 
+void rangeset_reset(struct rangeset *r)
+{
+    /* This doesn't allocate anything and must not fail. */
+    BUG_ON(rangeset_remove_range(r, 0, ~0ULL));
+}
+
 /*****************************
  * Pretty-printing functions
  */
diff --git a/xen/include/xen/rangeset.h b/xen/include/xen/rangeset.h
index f7c69394d66a..e0d70d88bdd7 100644
--- a/xen/include/xen/rangeset.h
+++ b/xen/include/xen/rangeset.h
@@ -95,6 +95,9 @@ bool_t __must_check rangeset_contains_singleton(
 /* swap contents */
 void rangeset_swap(struct rangeset *a, struct rangeset *b);
 
+/* Destroy all ranges. */
+void rangeset_reset(struct rangeset *r);
+
 /* Rangeset pretty printing. */
 void rangeset_domain_printk(
     struct domain *d);
-- 
2.25.1