Disk cache should consistently create parent directories when needed

In !25925 I attempted to fix an error spam caused by the disk cache not
creating parent directories of the cache directory when needed,
resulting in failure to create the disk cache. Presumably that is bad
for performance.

Unfortunately I did a really bad job and only fixed the edge case where
the cache dir is given by $MESA_SHADER_CACHE_DIR rather than the general
case. Here I attempt to be more comprehensive.

Fixes #8294

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/30160>

src/util/disk_cache_os.c

@@ -105,6 +105,7 @@ disk_cache_get_function_identifier(void *ptr, struct mesa_sha1 *ctx)
 #include "util/rand_xor.h"
 
 /* Create a directory named 'path' if it does not already exist.
+ * This is for use by mkdir_with_parents_if_needed(). Use that instead.
  *
  * Returns: 0 if path already exists as a directory or if created.
  *         -1 in all other cases.
@@ -182,7 +183,6 @@ mkdir_with_parents_if_needed(const char *path)
  *
  * Returns NULL on any error, such as:
  *
- *      <path> does not exist or is not a directory
  *      <path>/<name> exists but is not a directory
  *      <path>/<name> cannot be created as a directory
  */
@@ -190,17 +190,13 @@ static char *
 concatenate_and_mkdir(void *ctx, const char *path, const char *name)
 {
    char *new_path;
-   struct stat sb;
-
-   if (stat(path, &sb) != 0 || ! S_ISDIR(sb.st_mode))
-      return NULL;
 
    new_path = ralloc_asprintf(ctx, "%s/%s", path, name);
 
-   if (mkdir_if_needed(new_path) == 0)
+   if (mkdir_with_parents_if_needed(new_path) == 0)
       return new_path;
-   else
-      return NULL;
+
+   return NULL;
 }
 
 struct lru_file {
@@ -444,7 +440,7 @@ make_cache_file_directory(struct disk_cache *cache, const cache_key key)
    if (asprintf(&dir, "%s/%c%c", cache->path, buf[0], buf[1]) == -1)
       return;
 
-   mkdir_if_needed(dir);
+   mkdir_with_parents_if_needed(dir);
    free(dir);
 }
 
@@ -904,9 +900,6 @@ disk_cache_generate_cache_dir(void *mem_ctx, const char *gpu_name,
    }
 
    if (path) {
-      if (mkdir_with_parents_if_needed(path) == -1)
-         return NULL;
-
       path = concatenate_and_mkdir(mem_ctx, path, cache_dir_name);
       if (!path)
          return NULL;
@@ -916,9 +909,6 @@ disk_cache_generate_cache_dir(void *mem_ctx, const char *gpu_name,
       char *xdg_cache_home = secure_getenv("XDG_CACHE_HOME");
 
       if (xdg_cache_home) {
-         if (mkdir_if_needed(xdg_cache_home) == -1)
-            return NULL;
-
          path = concatenate_and_mkdir(mem_ctx, xdg_cache_home, cache_dir_name);
          if (!path)
             return NULL;

src/util/tests/cache_test.cpp

@@ -201,20 +201,9 @@ test_disk_cache_create(void *mem_ctx, const char *cache_dir_name,
 
    /* Test with XDG_CACHE_HOME set */
    setenv("XDG_CACHE_HOME", CACHE_TEST_TMP "/xdg-cache-home", 1);
-   cache = disk_cache_create("test", driver_id, 0);
-   EXPECT_FALSE(cache_exists(cache))
-      << "disk_cache_create with XDG_CACHE_HOME set with a non-existing parent directory";
-
-   err = mkdir(CACHE_TEST_TMP, 0755);
-   if (err != 0) {
-      fprintf(stderr, "Error creating %s: %s\n", CACHE_TEST_TMP, strerror(errno));
-      GTEST_FAIL();
-   }
-   disk_cache_destroy(cache);
-
    cache = disk_cache_create("test", driver_id, 0);
    EXPECT_TRUE(cache_exists(cache))
-      << "disk_cache_create with XDG_CACHE_HOME set";
+      << "disk_cache_create with XDG_CACHE_HOME set with a non-existing parent directory";
 
    char *path = ralloc_asprintf(
       mem_ctx, "%s%s", CACHE_TEST_TMP "/xdg-cache-home/", cache_dir_name);
@@ -1456,4 +1445,4 @@ TEST_F(Cache, DeleteOldCache)
    rmdir(cache_dir_name);
    rmdir(dir_name);
 #endif
-}
+}