Typo fixed.

src/event/ngx_event_pipe.c

diff --git a/src/event/ngx_event_pipe.c b/src/event/ngx_event_pipe.c
index 4dfb88f..4ef9b71 100644
--- a/src/event/ngx_event_pipe.c
+++ b/src/event/ngx_event_pipe.c
@@ -220,8 +220,8 @@
             {
 
                 /*
-                 * if it is allowed, then save some bufs from r->in
-                 * to a temporary file, and add them to a r->out chain
+                 * if it is allowed, then save some bufs from p->in
+                 * to a temporary file, and add them to a p->out chain
                  */
 
                 rc = ngx_event_pipe_write_chain_to_temp_file(p);