fellow_cache: only run the estimate update after the current fcs is full

src/fellow_cache.c

@@ -5258,6 +5258,23 @@ fellow_busy_obj_getspace(struct fellow_busy *fbo, size_t *sz, uint8_t **ptr)
 	if (*sz + fbo->sz_returned > fbo->fc->tune->objsize_max)
 		*sz = fbo->fc->tune->objsize_max - fbo->sz_returned;
 
+	fcs = fbo->body_seg;
+	if (fcs != NULL && fcs->state == FCS_BUSY) {
+		AN(fcs->alloc.size);
+		if (fcs->u.fcs.len < fcs->alloc.size) {
+			spc = fcs->alloc.size - fcs->u.fcs.len;
+			assert(spc > 0);
+			if (spc < *sz)
+				*sz = spc;
+			*ptr = (uint8_t *)fcs->alloc.ptr + fcs->u.fcs.len;
+			return (FCR_OK(fbo));
+		}
+
+		assert(fcs->u.fcs.len == fcs->alloc.size);
+		unbusy = fcs;
+		fcs = NULL;
+	}
+
 	/*
 	 * for content-length, varnish-cache will ask for less and less.
 	 *
@@ -5285,23 +5302,6 @@ fellow_busy_obj_getspace(struct fellow_busy *fbo, size_t *sz, uint8_t **ptr)
 			fbo->sz_increment <<= 1;
 		}
 	}
-
-	fcs = fbo->body_seg;
-	if (fcs != NULL && fcs->state == FCS_BUSY) {
-		AN(fcs->alloc.size);
-		if (fcs->u.fcs.len < fcs->alloc.size) {
-			spc = fcs->alloc.size - fcs->u.fcs.len;
-			assert(spc > 0);
-			if (spc < *sz)
-				*sz = spc;
-			*ptr = (uint8_t *)fcs->alloc.ptr + fcs->u.fcs.len;
-			return (FCR_OK(fbo));
-		}
-
-		assert(fcs->u.fcs.len == fcs->alloc.size);
-		unbusy = fcs;
-		fcs = NULL;
-	}
 	if (fcs == NULL) {
 		fcr = fellow_busy_body_seg_next(fbo);
 		if (fcr.status != fcr_ok)