nginx/SOURCES/0010-Optimized-chain-link-usage.patch

From f3bcc0bcfb6eda3f4874fe2531d546ba724c518c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Lubo=C5=A1=20Uhliarik?= <luhliari@redhat.com>
Date: Wed, 12 Jun 2024 12:49:28 +0200
Subject: [PATCH] Optimized chain link usage

Previously chain links could sometimes be dropped instead of being reused,
which could result in increased memory consumption during long requests.
---
 src/core/ngx_output_chain.c                    | 10 ++++++++--
 src/http/modules/ngx_http_grpc_module.c        |  5 ++++-
 .../modules/ngx_http_gunzip_filter_module.c    | 18 ++++++++++++++----
 src/http/modules/ngx_http_gzip_filter_module.c | 10 +++++++---
 src/http/modules/ngx_http_ssi_filter_module.c  |  8 ++++++--
 src/http/modules/ngx_http_sub_filter_module.c  |  8 ++++++--
 6 files changed, 45 insertions(+), 14 deletions(-)

diff --git a/src/core/ngx_output_chain.c b/src/core/ngx_output_chain.c
index 5c3dbe8..4aa1b02 100644
--- a/src/core/ngx_output_chain.c
+++ b/src/core/ngx_output_chain.c
@@ -121,7 +121,10 @@ ngx_output_chain(ngx_output_chain_ctx_t *ctx, ngx_chain_t *in)
 
                 ngx_debug_point();
 
-                ctx->in = ctx->in->next;
+                cl = ctx->in;
+                ctx->in = cl->next;
+
+                ngx_free_chain(ctx->pool, cl);
 
                 continue;
             }
@@ -207,7 +210,10 @@ ngx_output_chain(ngx_output_chain_ctx_t *ctx, ngx_chain_t *in)
             /* delete the completed buf from the ctx->in chain */
 
             if (ngx_buf_size(ctx->in->buf) == 0) {
-                ctx->in = ctx->in->next;
+                cl = ctx->in;
+                ctx->in = cl->next;
+
+                ngx_free_chain(ctx->pool, cl);
             }
 
             cl = ngx_alloc_chain_link(ctx->pool);
diff --git a/src/http/modules/ngx_http_grpc_module.c b/src/http/modules/ngx_http_grpc_module.c
index 53bc547..9f13089 100644
--- a/src/http/modules/ngx_http_grpc_module.c
+++ b/src/http/modules/ngx_http_grpc_module.c
@@ -1230,7 +1230,7 @@ ngx_http_grpc_body_output_filter(void *data, ngx_chain_t *in)
     ngx_buf_t              *b;
     ngx_int_t               rc;
     ngx_uint_t              next, last;
-    ngx_chain_t            *cl, *out, **ll;
+    ngx_chain_t            *cl, *out, *ln, **ll;
     ngx_http_upstream_t    *u;
     ngx_http_grpc_ctx_t    *ctx;
     ngx_http_grpc_frame_t  *f;
@@ -1458,7 +1458,10 @@ ngx_http_grpc_body_output_filter(void *data, ngx_chain_t *in)
             last = 1;
         }
 
+        ln = in;
         in = in->next;
+
+        ngx_free_chain(r->pool, ln);
     }
 
     ctx->in = in;
diff --git a/src/http/modules/ngx_http_gunzip_filter_module.c b/src/http/modules/ngx_http_gunzip_filter_module.c
index c1341f5..5d170a1 100644
--- a/src/http/modules/ngx_http_gunzip_filter_module.c
+++ b/src/http/modules/ngx_http_gunzip_filter_module.c
@@ -333,6 +333,8 @@ static ngx_int_t
 ngx_http_gunzip_filter_add_data(ngx_http_request_t *r,
     ngx_http_gunzip_ctx_t *ctx)
 {
+    ngx_chain_t  *cl;
+
     if (ctx->zstream.avail_in || ctx->flush != Z_NO_FLUSH || ctx->redo) {
         return NGX_OK;
     }
@@ -344,8 +346,11 @@ ngx_http_gunzip_filter_add_data(ngx_http_request_t *r,
         return NGX_DECLINED;
     }
 
-    ctx->in_buf = ctx->in->buf;
-    ctx->in = ctx->in->next;
+    cl = ctx->in;
+    ctx->in_buf = cl->buf;
+    ctx->in = cl->next;
+
+    ngx_free_chain(r->pool, cl);
 
     ctx->zstream.next_in = ctx->in_buf->pos;
     ctx->zstream.avail_in = ctx->in_buf->last - ctx->in_buf->pos;
@@ -374,6 +379,7 @@ static ngx_int_t
 ngx_http_gunzip_filter_get_buf(ngx_http_request_t *r,
     ngx_http_gunzip_ctx_t *ctx)
 {
+    ngx_chain_t             *cl;
     ngx_http_gunzip_conf_t  *conf;
 
     if (ctx->zstream.avail_out) {
@@ -383,8 +389,12 @@ ngx_http_gunzip_filter_get_buf(ngx_http_request_t *r,
     conf = ngx_http_get_module_loc_conf(r, ngx_http_gunzip_filter_module);
 
     if (ctx->free) {
-        ctx->out_buf = ctx->free->buf;
-        ctx->free = ctx->free->next;
+
+        cl = ctx->free;
+        ctx->out_buf = cl->buf;
+        ctx->free = cl->next;
+
+        ngx_free_chain(r->pool, cl);
 
         ctx->out_buf->flush = 0;
 
diff --git a/src/http/modules/ngx_http_gzip_filter_module.c b/src/http/modules/ngx_http_gzip_filter_module.c
index b8c5ccc..1d17a6d 100644
--- a/src/http/modules/ngx_http_gzip_filter_module.c
+++ b/src/http/modules/ngx_http_gzip_filter_module.c
@@ -978,10 +978,14 @@ static void
 ngx_http_gzip_filter_free_copy_buf(ngx_http_request_t *r,
     ngx_http_gzip_ctx_t *ctx)
 {
-    ngx_chain_t  *cl;
+    ngx_chain_t  *cl, *ln;
+
+    for (cl = ctx->copied; cl; /* void */) {
+        ln = cl;
+        cl = cl->next;
 
-    for (cl = ctx->copied; cl; cl = cl->next) {
-        ngx_pfree(r->pool, cl->buf->start);
+        ngx_pfree(r->pool, ln->buf->start);
+        ngx_free_chain(r->pool, ln);
     }
 
     ctx->copied = NULL;
diff --git a/src/http/modules/ngx_http_ssi_filter_module.c b/src/http/modules/ngx_http_ssi_filter_module.c
index 6737965..a55f6e5 100644
--- a/src/http/modules/ngx_http_ssi_filter_module.c
+++ b/src/http/modules/ngx_http_ssi_filter_module.c
@@ -455,9 +455,13 @@ ngx_http_ssi_body_filter(ngx_http_request_t *r, ngx_chain_t *in)
     while (ctx->in || ctx->buf) {
 
         if (ctx->buf == NULL) {
-            ctx->buf = ctx->in->buf;
-            ctx->in = ctx->in->next;
+
+            cl = ctx->in;
+            ctx->buf = cl->buf;
+            ctx->in = cl->next;
             ctx->pos = ctx->buf->pos;
+
+            ngx_free_chain(r->pool, cl);
         }
 
         if (ctx->state == ssi_start_state) {
diff --git a/src/http/modules/ngx_http_sub_filter_module.c b/src/http/modules/ngx_http_sub_filter_module.c
index 6d3de59..456bb27 100644
--- a/src/http/modules/ngx_http_sub_filter_module.c
+++ b/src/http/modules/ngx_http_sub_filter_module.c
@@ -335,9 +335,13 @@ ngx_http_sub_body_filter(ngx_http_request_t *r, ngx_chain_t *in)
     while (ctx->in || ctx->buf) {
 
         if (ctx->buf == NULL) {
-            ctx->buf = ctx->in->buf;
-            ctx->in = ctx->in->next;
+
+            cl = ctx->in;
+            ctx->buf = cl->buf;
+            ctx->in = cl->next;
             ctx->pos = ctx->buf->pos;
+
+            ngx_free_chain(r->pool, cl);
         }
 
         if (ctx->buf->flush || ctx->buf->recycled) {
-- 
2.44.0