[PATCH] migration: Simplify get_qlist

[Eric Auger <eric.auger@redhat.com>]

Instead of inserting read elements at the head and
then reversing the list, it is simpler to add
each element after the previous one. Introduce
QLIST_RAW_INSERT_AFTER helper and use it in
get_qlist().

Signed-off-by: Eric Auger <eric.auger@redhat.com>
Suggested-by: Juan Quintela <quintela@redhat.com>

---
---
 include/qemu/queue.h      | 19 ++++++-------------
 migration/vmstate-types.c | 10 +++++++---
 2 files changed, 13 insertions(+), 16 deletions(-)

diff --git a/include/qemu/queue.h b/include/qemu/queue.h
index 4d4554a7ce..19425f973f 100644
--- a/include/qemu/queue.h
+++ b/include/qemu/queue.h
@@ -515,6 +515,12 @@ union {                                                                 \
              (elm);                                                            \
              (elm) = *QLIST_RAW_NEXT(elm, entry))
 
+#define QLIST_RAW_INSERT_AFTER(head, prev, elem, entry) do {                   \
+        *QLIST_RAW_NEXT(prev, entry) = elem;                                   \
+        *QLIST_RAW_PREVIOUS(elem, entry) = QLIST_RAW_NEXT(prev, entry);        \
+        *QLIST_RAW_NEXT(elem, entry) = NULL;                                   \
+} while (0)
+
 #define QLIST_RAW_INSERT_HEAD(head, elm, entry) do {                           \
         void *first = *QLIST_RAW_FIRST(head);                                  \
         *QLIST_RAW_FIRST(head) = elm;                                          \
@@ -527,17 +533,4 @@ union {                                                                 \
         }                                                                      \
 } while (0)
 
-#define QLIST_RAW_REVERSE(head, elm, entry) do {                               \
-        void *iter = *QLIST_RAW_FIRST(head), *prev = NULL, *next;              \
-        while (iter) {                                                         \
-            next = *QLIST_RAW_NEXT(iter, entry);                               \
-            *QLIST_RAW_PREVIOUS(iter, entry) = QLIST_RAW_NEXT(next, entry);    \
-            *QLIST_RAW_NEXT(iter, entry) = prev;                               \
-            prev = iter;                                                       \
-            iter = next;                                                       \
-        }                                                                      \
-        *QLIST_RAW_FIRST(head) = prev;                                         \
-        *QLIST_RAW_PREVIOUS(prev, entry) = QLIST_RAW_FIRST(head);              \
-} while (0)
-
 #endif /* QEMU_SYS_QUEUE_H */
diff --git a/migration/vmstate-types.c b/migration/vmstate-types.c
index 1eee36773a..35e784c9d9 100644
--- a/migration/vmstate-types.c
+++ b/migration/vmstate-types.c
@@ -879,7 +879,7 @@ static int get_qlist(QEMUFile *f, void *pv, size_t unused_size,
     /* offset of the QLIST entry in a QLIST element */
     size_t entry_offset = field->start;
     int version_id = field->version_id;
-    void *elm;
+    void *elm, *prev = NULL;
 
     trace_get_qlist(field->name, vmsd->name, vmsd->version_id);
     if (version_id > vmsd->version_id) {
@@ -900,9 +900,13 @@ static int get_qlist(QEMUFile *f, void *pv, size_t unused_size,
             g_free(elm);
             return ret;
         }
-        QLIST_RAW_INSERT_HEAD(pv, elm, entry_offset);
+        if (!prev) {
+            QLIST_RAW_INSERT_HEAD(pv, elm, entry_offset);
+        } else {
+            QLIST_RAW_INSERT_AFTER(pv, prev, elm, entry_offset);
+        }
+        prev = elm;
     }
-    QLIST_RAW_REVERSE(pv, elm, entry_offset);
     trace_get_qlist_end(field->name, vmsd->name);
 
     return ret;
-- 
2.20.1