Upstream: keep request body file from removal if requested. The new request flag "preserve_body" indicates that the request body file should not be removed by the upstream module because it may be used later by a subrequest. The flag is set by the SSI (ticket #585), addition and slice modules. Additionally, it is also set by the upstream module when a background cache update subrequest is started to prevent the request body file removal after an internal redirect. Only the main request is now allowed to remove the file.

--- a/src/http/modules/ngx_http_addition_filter_module.c
+++ b/src/http/modules/ngx_http_addition_filter_module.c
@@ -123,6 +123,8 @@ ngx_http_addition_header_filter(ngx_http
     ngx_http_clear_accept_ranges(r);
     ngx_http_weak_etag(r);
 
+    r->preserve_body = 1;
+
     return ngx_http_next_header_filter(r);
 }