--- a/src/http/ngx_http_file_cache.c
+++ b/src/http/ngx_http_file_cache.c
@@ -10,6 +10,11 @@
 #include <ngx_md5.h>
 
 
+static ngx_int_t ngx_http_file_cache_read(ngx_http_request_t *r,
+    ngx_http_cache_t *c);
+#if (NGX_HAVE_FILE_AIO)
+static void ngx_http_cache_aio_event_handler(ngx_event_t *ev);
+#endif
 static ngx_int_t ngx_http_file_cache_exists(ngx_http_file_cache_t *cache,
     ngx_http_cache_t *c);
 static ngx_http_file_cache_node_t *
@@ -53,6 +58,7 @@ ngx_http_file_cache_init(ngx_shm_zone_t 
     ngx_http_file_cache_t  *ocache = data;
 
     size_t                  len;
+    ngx_uint_t              n;
     ngx_http_file_cache_t  *cache;
 
     cache = shm_zone->data;
@@ -68,6 +74,15 @@ ngx_http_file_cache_init(ngx_shm_zone_t 
             return NGX_ERROR;
         }
 
+        for (n = 0; n < 3; n++) {
+            if (cache->path->level[n] != ocache->path->level[n]) {
+                ngx_log_error(NGX_LOG_EMERG, shm_zone->shm.log, 0,
+                              "cache \"%V\" had previously different levels",
+                              &shm_zone->shm.name);
+                return NGX_ERROR;
+            }
+        }
+
         cache->sh = ocache->sh;
 
         cache->shpool = ocache->shpool;
@@ -75,6 +90,10 @@ ngx_http_file_cache_init(ngx_shm_zone_t 
 
         cache->max_size /= cache->bsize;
 
+        if (!cache->sh->cold || cache->sh->loading) {
+            cache->path->loader = NULL;
+        }
+
         return NGX_OK;
     }
 
@@ -100,6 +119,7 @@ ngx_http_file_cache_init(ngx_shm_zone_t 
     ngx_queue_init(&cache->sh->queue);
 
     cache->sh->cold = 1;
+    cache->sh->loading = 0;
     cache->sh->size = 0;
 
     cache->bsize = ngx_fs_bsize(cache->path->name.data);
@@ -158,20 +178,22 @@ ngx_http_file_cache_create_key(ngx_http_
 ngx_int_t
 ngx_http_file_cache_open(ngx_http_request_t *r)
 {
-    u_char                        *p;
-    time_t                         now;
-    ssize_t                        n;
-    ngx_int_t                      rc, rv;
-    ngx_uint_t                     cold, test;
-    ngx_path_t                    *path;
-    ngx_http_cache_t              *c;
-    ngx_pool_cleanup_t            *cln;
-    ngx_open_file_info_t           of;
-    ngx_http_file_cache_t         *cache;
-    ngx_http_core_loc_conf_t      *clcf;
-    ngx_http_file_cache_header_t  *h;
+    u_char                    *p;
+    ngx_int_t                  rc, rv;
+    ngx_uint_t                 cold, test;
+    ngx_path_t                *path;
+    ngx_http_cache_t          *c;
+    ngx_pool_cleanup_t        *cln;
+    ngx_open_file_info_t       of;
+    ngx_http_file_cache_t     *cache;
+    ngx_http_core_loc_conf_t  *clcf;
 
     c = r->cache;
+
+    if (c->buf) {
+        return ngx_http_file_cache_read(r, c);
+    }
+
     cache = c->file_cache;
 
     cln = ngx_pool_cleanup_add(r->pool, 0);
@@ -192,7 +214,7 @@ ngx_http_file_cache_open(ngx_http_reques
     cln->data = c;
 
     if (rc == NGX_AGAIN) {
-        return rc;
+        return NGX_HTTP_CACHE_SCARCE;
     }
 
     cold = cache->sh->cold;
@@ -212,11 +234,11 @@ ngx_http_file_cache_open(ngx_http_reques
         if (c->min_uses > 1) {
 
             if (!cold) {
-                return NGX_AGAIN;
+                return NGX_HTTP_CACHE_SCARCE;
             }
 
             test = 1;
-            rv = NGX_AGAIN;
+            rv = NGX_HTTP_CACHE_SCARCE;
 
         } else {
             c->temp_file = 1;
@@ -284,14 +306,58 @@ ngx_http_file_cache_open(ngx_http_reques
 
     c->file.fd = of.fd;
     c->file.log = r->connection->log;
+    c->uniq = of.uniq;
+    c->length = of.size;
 
     c->buf = ngx_create_temp_buf(r->pool, c->body_start);
     if (c->buf == NULL) {
         return NGX_ERROR;
     }
 
+    return ngx_http_file_cache_read(r, c);
+}
+
+
+static ngx_int_t
+ngx_http_file_cache_read(ngx_http_request_t *r, ngx_http_cache_t *c)
+{
+    time_t                         now;
+    ssize_t                        n;
+    ngx_int_t                      rc;
+    ngx_http_file_cache_t         *cache;
+    ngx_http_file_cache_header_t  *h;
+
+    c = r->cache;
+
+#if (NGX_HAVE_FILE_AIO)
+    {
+    ngx_http_core_loc_conf_t      *clcf;
+
+    clcf = ngx_http_get_module_loc_conf(r, ngx_http_core_module);
+
+    if (clcf->aio) {
+        n = ngx_file_aio_read(&c->file, c->buf->pos, c->body_start, 0, r->pool);
+
+        if (n == NGX_AGAIN) {
+            c->file.aio->data = r;
+            c->file.aio->handler = ngx_http_cache_aio_event_handler;
+
+            r->main->blocked++;
+            r->aio = 1;
+
+            return NGX_AGAIN;
+        }
+
+    } else {
+        n = ngx_read_file(&c->file, c->buf->pos, c->body_start, 0);
+    }
+    }
+#else
+
     n = ngx_read_file(&c->file, c->buf->pos, c->body_start, 0);
 
+#endif
+
     if (n == NGX_ERROR) {
         return n;
     }
@@ -316,12 +382,13 @@ ngx_http_file_cache_open(ngx_http_reques
     c->last_modified = h->last_modified;
     c->date = h->date;
     c->valid_msec = h->valid_msec;
-    c->length = of.size;
     c->body_start = h->body_start;
 
     r->cached = 1;
 
-    if (cold) {
+    cache = c->file_cache;
+
+    if (cache->sh->cold) {
 
         ngx_shmtx_lock(&cache->shpool->mutex);
 
@@ -329,7 +396,7 @@ ngx_http_file_cache_open(ngx_http_reques
             c->node->uses = 1;
             c->node->body_start = c->body_start;
             c->node->exists = 1;
-            c->node->uniq = of.uniq;
+            c->node->uniq = c->uniq;
 
             cache->sh->size += (c->length + cache->bsize - 1) / cache->bsize;
         }
@@ -364,6 +431,27 @@ ngx_http_file_cache_open(ngx_http_reques
 }
 
 
+#if (NGX_HAVE_FILE_AIO)
+
+
+static void
+ngx_http_cache_aio_event_handler(ngx_event_t *ev)
+{
+    ngx_event_aio_t     *aio;
+    ngx_http_request_t  *r;
+
+    aio = ev->data;
+    r = aio->data;
+
+    r->main->blocked--;
+    r->aio = 0;
+
+    r->connection->write->handler(r->connection->write);
+}
+
+#endif
+
+
 static ngx_int_t
 ngx_http_file_cache_exists(ngx_http_file_cache_t *cache, ngx_http_cache_t *c)
 {
@@ -635,7 +723,6 @@ ngx_http_file_cache_update(ngx_http_requ
     ext.time = -1;
     ext.create_path = 1;
     ext.delete_file = 1;
-    ext.log_rename_error = 1;
     ext.log = r->connection->log;
 
     rc = ngx_ext_rename_file(&tf->file.name, &c->file.name, &ext);
@@ -1026,39 +1113,8 @@ ngx_http_file_cache_manager(void *data)
 {
     ngx_http_file_cache_t  *cache = data;
 
-    off_t           size;
-    time_t          next;
-    ngx_tree_ctx_t  tree;
-
-    if (cache->sh->cold) {
-
-        ngx_log_debug0(NGX_LOG_DEBUG_HTTP, ngx_cycle->log, 0,
-                       "http file cache manager update");
-
-        tree.init_handler = NULL;
-        tree.file_handler = ngx_http_file_cache_manage_file;
-        tree.pre_tree_handler = ngx_http_file_cache_noop;
-        tree.post_tree_handler = ngx_http_file_cache_noop;
-        tree.spec_handler = ngx_http_file_cache_delete_file;
-        tree.data = cache;
-        tree.alloc = 0;
-        tree.log = ngx_cycle->log;
-
-        cache->last = ngx_current_msec;
-        cache->files = 0;
-
-        if (ngx_walk_tree(&tree, &cache->path->name) == NGX_ABORT) {
-            return 10;
-        }
-
-        cache->sh->cold = 0;
-
-        ngx_log_error(NGX_LOG_NOTICE, ngx_cycle->log, 0,
-                      "http file cache: %V %.3fM, bsize: %uz",
-                      &cache->path->name,
-                      ((double) cache->sh->size * cache->bsize) / (1024 * 1024),
-                      cache->bsize);
-    }
+    off_t   size;
+    time_t  next;
 
     next = ngx_http_file_cache_expire(cache);
 
@@ -1088,6 +1144,52 @@ ngx_http_file_cache_manager(void *data)
 }
 
 
+static void
+ngx_http_file_cache_loader(void *data)
+{
+    ngx_http_file_cache_t  *cache = data;
+
+    ngx_tree_ctx_t  tree;
+
+    if (!cache->sh->cold || cache->sh->loading) {
+        return;
+    }
+
+    if (!ngx_atomic_cmp_set(&cache->sh->loading, 0, ngx_pid)) {
+        return;
+    }
+
+    ngx_log_debug0(NGX_LOG_DEBUG_HTTP, ngx_cycle->log, 0,
+                   "http file cache loader");
+
+    tree.init_handler = NULL;
+    tree.file_handler = ngx_http_file_cache_manage_file;
+    tree.pre_tree_handler = ngx_http_file_cache_noop;
+    tree.post_tree_handler = ngx_http_file_cache_noop;
+    tree.spec_handler = ngx_http_file_cache_delete_file;
+    tree.data = cache;
+    tree.alloc = 0;
+    tree.log = ngx_cycle->log;
+
+    cache->last = ngx_current_msec;
+    cache->files = 0;
+
+    if (ngx_walk_tree(&tree, &cache->path->name) == NGX_ABORT) {
+        cache->sh->loading = 0;
+        return;
+    }
+
+    cache->sh->cold = 0;
+    cache->sh->loading = 0;
+
+    ngx_log_error(NGX_LOG_NOTICE, ngx_cycle->log, 0,
+                  "http file cache: %V %.3fM, bsize: %uz",
+                  &cache->path->name,
+                  ((double) cache->sh->size * cache->bsize) / (1024 * 1024),
+                  cache->bsize);
+}
+
+
 static ngx_int_t
 ngx_http_file_cache_manager_sleep(ngx_http_file_cache_t *cache)
 {
@@ -1468,6 +1570,7 @@ ngx_http_file_cache_set_slot(ngx_conf_t 
     }
 
     cache->path->manager = ngx_http_file_cache_manager;
+    cache->path->loader = ngx_http_file_cache_loader;
     cache->path->data = cache;
 
     if (ngx_add_path(cf, &cache->path) != NGX_OK) {