Always use prev node if there's some room in it setDeferredReply (#8729)

this is a followup PR for #8699
instead of copying the deferred reply data to the previous node only if it has room for the entire thing,
we can now split the new payload, put part of it into the spare space in the prev node,
and the rest may fit into the next node.

1 files changed, 14 insertions, 5 deletions

diff --git a/src/networking.c b/src/networking.c
index 9bee8910f..850717b5a 100644
--- a/src/networking.c
+++ b/src/networking.c
@@ -582,13 +582,22 @@ void setDeferredReply(client *c, void *node, const char *s, size_t length) {
      * - It has enough room already allocated
      * - And not too large (avoid large memmove) */
     if (ln->prev != NULL && (prev = listNodeValue(ln->prev)) &&
-        prev->size - prev->used >= length)
+        prev->size - prev->used > 0)
     {
-        memcpy(prev->buf + prev->used, s, length);
-        prev->used += length;
-        listDelNode(c->reply, ln);
+        size_t len_to_copy = prev->size - prev->used;
+        if (len_to_copy > length)
+            len_to_copy = length;
+        memcpy(prev->buf + prev->used, s, len_to_copy);
+        prev->used += len_to_copy;
+        length -= len_to_copy;
+        if (length == 0) {
+            listDelNode(c->reply, ln);
+            return;
+        }
+        s += len_to_copy;
     }
-    else if (ln->next != NULL && (next = listNodeValue(ln->next)) &&
+
+    if (ln->next != NULL && (next = listNodeValue(ln->next)) &&
         next->size - next->used >= length &&
         next->used < PROTO_REPLY_CHUNK_BYTES * 4)
     {