SMA->trim() did not return the trimmed space to the pool causing

the SMA to run out of space eventually.

bin/varnishd/storage_malloc.c

@@ -153,6 +153,7 @@ sma_trim(struct storage *s, size_t size)
 	struct sma_sc *sma_sc;
 	struct sma *sma;
 	void *p;
+	size_t delta;
 
 	CHECK_OBJ_NOTNULL(s, STORAGE_MAGIC);
 	CAST_OBJ_NOTNULL(sma, s->priv, SMA_MAGIC);
@@ -160,12 +161,16 @@ sma_trim(struct storage *s, size_t size)
 
 	assert(sma->sz == sma->s.space);
 	assert(size < sma->sz);
+	delta = sma->sz - size;
+	if (delta < 256)
+		return;
 	if ((p = realloc(sma->s.ptr, size)) != NULL) {
 		Lck_Lock(&sma_sc->sma_mtx);
-		sma_sc->stats->g_bytes -= (sma->sz - size);
-		sma_sc->stats->c_freed += sma->sz - size;
+		sma_sc->sma_alloc -= delta;
+		sma_sc->stats->g_bytes -= delta;
+		sma_sc->stats->c_freed += delta;
 		if (sma_sc->sma_max != SIZE_MAX)
-			sma_sc->stats->g_space += sma->sz - size;
+			sma_sc->stats->g_space += delta;
 		sma->sz = size;
 		Lck_Unlock(&sma_sc->sma_mtx);
 		sma->s.ptr = p;