[CRIU] [PATCH v1 12/17] rst: Implement rst_mem_free_last_bytes()

[Kirill Tkhai]

Function for freeing a part of lastly allocated memory hunk.
It will be used in next patches.

Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
---
 criu/include/rst-malloc.h |    1 +
 criu/rst-malloc.c         |   16 ++++++++++++----
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/criu/include/rst-malloc.h b/criu/include/rst-malloc.h
index 67391ba77..d885ff101 100644
--- a/criu/include/rst-malloc.h
+++ b/criu/include/rst-malloc.h
@@ -63,6 +63,7 @@ extern void *rst_mem_remap_ptr(unsigned long pos, int type);
  */
 extern void *rst_mem_alloc(unsigned long size, int type);
 extern void rst_mem_free_last(int type);
+extern void rst_mem_free_last_bytes(int type, unsigned long bytes);
 
 /* Word-align the current freelist pointer for the next allocation. If we don't
  * align pointers, some futex and atomic operations can fail.
diff --git a/criu/rst-malloc.c b/criu/rst-malloc.c
index 4f7357ca2..d72f2a095 100644
--- a/criu/rst-malloc.c
+++ b/criu/rst-malloc.c
@@ -184,15 +184,23 @@ void *rst_mem_alloc(unsigned long size, int type)
 	return ret;
 }
 
-void rst_mem_free_last(int type)
+void rst_mem_free_last_bytes(int type, unsigned long bytes)
 {
 	struct rst_mem_type_s *t = &rst_mems[type];
 
 	BUG_ON(!t->enabled);
+	BUG_ON(bytes > t->last);
+
+	t->free_mem -= bytes;
+	t->free_bytes += bytes;
+	t->last -= bytes;
+}
+
+void rst_mem_free_last(int type)
+{
+	struct rst_mem_type_s *t = &rst_mems[type];
 
-	t->free_mem -= t->last;
-	t->free_bytes += t->last;
-	t->last = 0; /* next free_last would be no-op */
+	return rst_mem_free_last_bytes(type, t->last);
 }
 
 unsigned long rst_mem_lock(void)