Cache: prefix-based temporary files. On Linux, the rename syscall can be slow due to a global file system lock, acquired for the entire rename operation, unless both old and new files are in the same directory. To address this temporary files are now created in the same directory as the expected resulting cache file when using the "use_temp_path=off" parameter. This change mostly reverts 99639bfdfa2a and 3281de8142f5, restoring the behaviour as of a9138c35120d (with minor changes).

diff --git a/src/core/ngx_file.c b/src/core/ngx_file.c
index 8359c0f..b7dd4bc 100644
--- a/src/core/ngx_file.c
+++ b/src/core/ngx_file.c

@@ -141,12 +141,27 @@
 ngx_create_temp_file(ngx_file_t *file, ngx_path_t *path, ngx_pool_t *pool,
     ngx_uint_t persistent, ngx_uint_t clean, ngx_uint_t access)
 {
+    size_t                    levels;
+    u_char                   *p;
     uint32_t                  n;
     ngx_err_t                 err;
+    ngx_str_t                 name;
+    ngx_uint_t                prefix;
     ngx_pool_cleanup_t       *cln;
     ngx_pool_cleanup_file_t  *clnf;
 
-    file->name.len = path->name.len + 1 + path->len + 10;
+    if (file->name.len) {
+        name = file->name;
+        levels = 0;
+        prefix = 1;
+
+    } else {
+        name = path->name;
+        levels = path->len;
+        prefix = 0;
+    }
+
+    file->name.len = name.len + 1 + levels + 10;
 
     file->name.data = ngx_pnalloc(pool, file->name.len + 1);
     if (file->name.data == NULL) {
@@ -159,7 +174,13 @@
     }
 #endif
 
-    ngx_memcpy(file->name.data, path->name.data, path->name.len);
+    p = ngx_cpymem(file->name.data, name.data, name.len);
+
+    if (prefix) {
+        *p = '.';
+    }
+
+    p += 1 + levels;
 
     n = (uint32_t) ngx_next_temp_number(0);
 
@@ -169,10 +190,11 @@
     }
 
     for ( ;; ) {
-        (void) ngx_sprintf(file->name.data + path->name.len + 1 + path->len,
-                           "%010uD%Z", n);
+        (void) ngx_sprintf(p, "%010uD%Z", n);
 
-        ngx_create_hashed_filename(path, file->name.data, file->name.len);
+        if (!prefix) {
+            ngx_create_hashed_filename(path, file->name.data, file->name.len);
+        }
 
         ngx_log_debug1(NGX_LOG_DEBUG_CORE, file->log, 0,
                        "hashed path: %s", file->name.data);

diff --git a/src/http/ngx_http_cache.h b/src/http/ngx_http_cache.h
index 70342d0..4075f3d 100644
--- a/src/http/ngx_http_cache.h
+++ b/src/http/ngx_http_cache.h

@@ -151,7 +151,6 @@
     ngx_slab_pool_t                 *shpool;
 
     ngx_path_t                      *path;
-    ngx_path_t                      *temp_path;
 
     off_t                            max_size;
     size_t                           bsize;
@@ -171,6 +170,9 @@
     ngx_msec_t                       manager_threshold;
 
     ngx_shm_zone_t                  *shm_zone;
+
+    ngx_uint_t                       use_temp_path;
+                                     /* unsigned use_temp_path:1 */
 };
 
 

diff --git a/src/http/ngx_http_file_cache.c b/src/http/ngx_http_file_cache.c
index ac5c103..3c8ad7d 100644
--- a/src/http/ngx_http_file_cache.c
+++ b/src/http/ngx_http_file_cache.c

@@ -2112,6 +2112,17 @@
         return NGX_ERROR;
     }
 
+    /*
+     * Temporary files in cache have a suffix consisting of a dot
+     * followed by 10 digits.
+     */
+
+    if (name->len >= 2 * NGX_HTTP_CACHE_KEY_LEN + 1 + 10
+        && name->data[name->len - 10 - 1] == '.')
+    {
+        return NGX_OK;
+    }
+
     if (ctx->size < (off_t) sizeof(ngx_http_file_cache_header_t)) {
         ngx_log_error(NGX_LOG_CRIT, ctx->log, 0,
                       "cache file \"%s\" is too small", name->data);
@@ -2256,7 +2267,6 @@
     off_t                   max_size;
     u_char                 *last, *p;
     time_t                  inactive;
-    size_t                  len;
     ssize_t                 size;
     ngx_str_t               s, name, *value;
     ngx_int_t               loader_files, manager_files;
@@ -2529,37 +2539,6 @@
         return NGX_CONF_ERROR;
     }
 
-    if (!use_temp_path) {
-        cache->temp_path = ngx_pcalloc(cf->pool, sizeof(ngx_path_t));
-        if (cache->temp_path == NULL) {
-            return NGX_CONF_ERROR;
-        }
-
-        len = cache->path->name.len + sizeof("/temp") - 1;
-
-        p = ngx_pnalloc(cf->pool, len + 1);
-        if (p == NULL) {
-            return NGX_CONF_ERROR;
-        }
-
-        cache->temp_path->name.len = len;
-        cache->temp_path->name.data = p;
-
-        p = ngx_cpymem(p, cache->path->name.data, cache->path->name.len);
-        ngx_memcpy(p, "/temp", sizeof("/temp"));
-
-        ngx_memcpy(&cache->temp_path->level, &cache->path->level,
-                   NGX_MAX_PATH_LEVEL * sizeof(size_t));
-
-        cache->temp_path->len = cache->path->len;
-        cache->temp_path->conf_file = cf->conf_file->file.name.data;
-        cache->temp_path->line = cf->conf_file->line;
-
-        if (ngx_add_path(cf, &cache->temp_path) != NGX_OK) {
-            return NGX_CONF_ERROR;
-        }
-    }
-
     cache->shm_zone = ngx_shared_memory_add(cf, &name, size, cmd->post);
     if (cache->shm_zone == NULL) {
         return NGX_CONF_ERROR;
@@ -2575,6 +2554,8 @@
     cache->shm_zone->init = ngx_http_file_cache_init;
     cache->shm_zone->data = cache;
 
+    cache->use_temp_path = use_temp_path;
+
     cache->inactive = inactive;
     cache->max_size = max_size;
 

diff --git a/src/http/ngx_http_upstream.c b/src/http/ngx_http_upstream.c
index fbd94d1..a6dd55e 100644
--- a/src/http/ngx_http_upstream.c
+++ b/src/http/ngx_http_upstream.c

@@ -2997,8 +2997,9 @@
         p->temp_file->persistent = 1;
 
 #if (NGX_HTTP_CACHE)
-        if (r->cache && r->cache->file_cache->temp_path) {
-            p->temp_file->path = r->cache->file_cache->temp_path;
+        if (r->cache && !r->cache->file_cache->use_temp_path) {
+            p->temp_file->path = r->cache->file_cache->path;
+            p->temp_file->file.name = r->cache->file.name;
         }
 #endif