From 3df07b17ddc92863075b046c5f34d3ab540d1d50 Mon Sep 17 00:00:00 2001
From: Dominik Schilling <dominikschilling+git@gmail.com>
Date: Thu, 21 Apr 2016 19:58:27 +0000
Subject: [PATCH] Media: Don't cache the results of `wp_mkdir_p()` in a
 persistent cache.

To improve the performance of `wp_upload_dir()` the result of `wp_mkdir_p()` was stored in a persistent cache, introduced in [36565]. But this becomes an issue when WordPress is scaled horizontally. You may end up caching a value for a server where the directory doesn't exist which will prevent further uploads on other servers because of the persistent cache.
The fix is to use a non-persistent cache.

Props azaozz, ocean90.
See #34359.
Fixes #36621.
Built from https://develop.svn.wordpress.org/trunk@37285


git-svn-id: http://core.svn.wordpress.org/trunk@37251 1a063a9b-81f0-0310-95a4-ce76da25c4cd
---
 wp-includes/functions.php | 16 ++++++----------
 wp-includes/version.php   |  2 +-
 2 files changed, 7 insertions(+), 11 deletions(-)

diff --git a/wp-includes/functions.php b/wp-includes/functions.php
index ca1c4c91fc..1c4a445b74 100644
--- a/wp-includes/functions.php
+++ b/wp-includes/functions.php
@@ -1854,7 +1854,7 @@ function wp_get_upload_dir() {
  * @return array See above for description.
  */
 function wp_upload_dir( $time = null, $create_dir = true, $refresh_cache = false ) {
-	static $cache = array();
+	static $cache = array(), $tested_paths = array();
 
 	$key = sprintf( '%d-%s', get_current_blog_id(), (string) $time );
 
@@ -1874,13 +1874,10 @@ function wp_upload_dir( $time = null, $create_dir = true, $refresh_cache = false
 
 	if ( $create_dir ) {
 		$path = $uploads['path'];
-		$tested_paths = wp_cache_get( 'upload_dir_tested_paths' );
 
-		if ( ! is_array( $tested_paths ) ) {
-			$tested_paths = array();
-		}
-
-		if ( ! in_array( $path, $tested_paths, true ) ) {
+		if ( array_key_exists( $path, $tested_paths ) ) {
+			$uploads['error'] = $tested_paths[ $path ];
+		} else {
 			if ( ! wp_mkdir_p( $path ) ) {
 				if ( 0 === strpos( $uploads['basedir'], ABSPATH ) ) {
 					$error_path = str_replace( ABSPATH, '', $uploads['basedir'] ) . $uploads['subdir'];
@@ -1889,10 +1886,9 @@ function wp_upload_dir( $time = null, $create_dir = true, $refresh_cache = false
 				}
 
 				$uploads['error'] = sprintf( __( 'Unable to create directory %s. Is its parent directory writable by the server?' ), esc_html( $error_path ) );
-			} else {
-				$tested_paths[] = $path;
-				wp_cache_set( 'upload_dir_tested_paths', $tested_paths );
 			}
+
+			$tested_paths[ $path ] = $uploads['error'];
 		}
 	}
 
diff --git a/wp-includes/version.php b/wp-includes/version.php
index f41ccd05dd..4426069158 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.6-alpha-37283';
+$wp_version = '4.6-alpha-37285';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.