opcache: file_cache_read_only code review update 5 (#16484)

Author: iamacarpet

UPGRADING

@@ -105,9 +105,14 @@ PHP 8.5 UPGRADE NOTES
     readline_callback_handler_install() have been changed to true, rather
     than bool.
 
-- opcache:
+- Opcache:
   . Introduce opcache.file_cache_read_only to support a read-only
     opcache.file_cache directory, for use with read-only Docker containers.
+    Best used with `opcache.validate_timestamps=0`, `opcache.revalidate_freq=0`
+    and `opcache.enable_file_override=1`.
+    Note: this cache isn't portable between PHP builds, enforced by the
+    inclusion of the `zend_system_id` both in the directory path, and
+    each cache file.
 
 ========================================
 10. New Global Constants

ext/opcache/ZendAccelerator.c

@@ -1411,10 +1411,9 @@ zend_result zend_accel_invalidate(zend_string *filename, bool force)
 	}
 
 	if (ZCG(accel_directives).file_cache) {
-		if (ZCG(accel_directives).file_cache_read_only) {
-			return FAILURE;
+		if (!ZCG(accel_directives).file_cache_read_only) {
+			zend_file_cache_invalidate(realpath);
 		}
-		zend_file_cache_invalidate(realpath);
 	}
 
 	persistent_script = zend_accel_hash_find(&ZCSG(hash), realpath);

ext/opcache/zend_file_cache.c

@@ -1847,7 +1847,9 @@ zend_persistent_script *zend_file_cache_script_load(zend_file_handle *file_handl
 		zend_accel_error(ACCEL_LOG_WARNING, "opcache cannot read from file '%s' (info)\n", filename);
 		zend_file_cache_flock(fd, LOCK_UN);
 		close(fd);
-		zend_file_cache_unlink(filename);
+		if (!ZCG(accel_directives).file_cache_read_only) {
+			zend_file_cache_unlink(filename);
+		}
 		efree(filename);
 		return NULL;
 	}
@@ -1857,15 +1859,19 @@ zend_persistent_script *zend_file_cache_script_load(zend_file_handle *file_handl
 		zend_accel_error(ACCEL_LOG_WARNING, "opcache cannot read from file '%s' (wrong header)\n", filename);
 		zend_file_cache_flock(fd, LOCK_UN);
 		close(fd);
-		zend_file_cache_unlink(filename);
+		if (!ZCG(accel_directives).file_cache_read_only) {
+			zend_file_cache_unlink(filename);
+		}
 		efree(filename);
 		return NULL;
 	}
 	if (memcmp(info.system_id, zend_system_id, 32) != 0) {
 		zend_accel_error(ACCEL_LOG_WARNING, "opcache cannot read from file '%s' (wrong \"system_id\")\n", filename);
 		zend_file_cache_flock(fd, LOCK_UN);
 		close(fd);
-		zend_file_cache_unlink(filename);
+		if (!ZCG(accel_directives).file_cache_read_only) {
+			zend_file_cache_unlink(filename);
+		}
 		efree(filename);
 		return NULL;
 	}
@@ -1877,7 +1883,9 @@ zend_persistent_script *zend_file_cache_script_load(zend_file_handle *file_handl
 			zend_accel_error(ACCEL_LOG_WARNING, "opcache cannot unlock file '%s'\n", filename);
 		}
 		close(fd);
-		zend_file_cache_unlink(filename);
+		if (!ZCG(accel_directives).file_cache_read_only) {
+			zend_file_cache_unlink(filename);
+		}
 		efree(filename);
 		return NULL;
 	}
@@ -1895,7 +1903,9 @@ zend_persistent_script *zend_file_cache_script_load(zend_file_handle *file_handl
 		zend_accel_error(ACCEL_LOG_WARNING, "opcache cannot read from file '%s' (mem)\n", filename);
 		zend_file_cache_flock(fd, LOCK_UN);
 		close(fd);
-		zend_file_cache_unlink(filename);
+		if (!ZCG(accel_directives).file_cache_read_only) {
+			zend_file_cache_unlink(filename);
+		}
 		zend_arena_release(&CG(arena), checkpoint);
 		efree(filename);
 		return NULL;
@@ -1909,7 +1919,9 @@ zend_persistent_script *zend_file_cache_script_load(zend_file_handle *file_handl
 	if (ZCG(accel_directives).file_cache_consistency_checks &&
 	    (actual_checksum = zend_adler32(ADLER32_INIT, mem, info.mem_size + info.str_size)) != info.checksum) {
 		zend_accel_error(ACCEL_LOG_WARNING, "corrupted file '%s' excepted checksum: 0x%08x actual checksum: 0x%08x\n", filename, info.checksum, actual_checksum);
-		zend_file_cache_unlink(filename);
+		if (!ZCG(accel_directives).file_cache_read_only) {
+			zend_file_cache_unlink(filename);
+		}
 		zend_arena_release(&CG(arena), checkpoint);
 		efree(filename);
 		return NULL;