[PATCH 2/3] ext4: make ext4 init/exit match their sequence

[Youling Tang <youling.tang@linux.dev>]

From: Youling Tang <tangyouling@kylinos.cn>

Use init_sequence to ensure that modules init and exit are in sequence
and to simplify the code.

Signed-off-by: Youling Tang <tangyouling@kylinos.cn>
---
 fs/ext4/super.c | 175 +++++++++++++++++++++++++-----------------------
 1 file changed, 93 insertions(+), 82 deletions(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index c682fb927b64..ec1e63facb10 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -7314,103 +7314,114 @@ static struct file_system_type ext4_fs_type = {
 };
 MODULE_ALIAS_FS("ext4");
 
-/* Shared across all ext4 file systems */
-wait_queue_head_t ext4__ioend_wq[EXT4_WQ_HASH_SZ];
-
-static int __init ext4_init_fs(void)
+static int register_ext(void)
 {
-	int i, err;
-
-	ratelimit_state_init(&ext4_mount_msg_ratelimit, 30 * HZ, 64);
-	ext4_li_info = NULL;
+	register_as_ext3();
+	register_as_ext2();
+	return register_filesystem(&ext4_fs_type);
+}
 
-	/* Build-time check for flags consistency */
-	ext4_check_flag_values();
+static void unregister_ext(void)
+{
+	unregister_as_ext2();
+	unregister_as_ext3();
+	unregister_filesystem(&ext4_fs_type);
+}
 
-	for (i = 0; i < EXT4_WQ_HASH_SZ; i++)
-		init_waitqueue_head(&ext4__ioend_wq[i]);
+/* Helper structure for long init/exit functions. */
+struct init_sequence {
+	int (*init_func)(void);
+	/* Can be NULL if the init_func doesn't need cleanup. */
+	void (*exit_func)(void);
+};
 
-	err = ext4_init_es();
-	if (err)
-		return err;
+static const struct init_sequence mod_init_seq[] = {
+	{
+		.init_func = ext4_init_es,
+		.exit_func = ext4_exit_es,
+	}, {
+		.init_func = ext4_init_pending,
+		.exit_func = ext4_exit_pending,
+	}, {
+		.init_func = ext4_init_post_read_processing,
+		.exit_func = ext4_exit_post_read_processing,
+	}, {
+		.init_func = ext4_init_pageio,
+		.exit_func = ext4_exit_pageio,
+	}, {
+		.init_func = ext4_init_system_zone,
+		.exit_func = ext4_exit_system_zone,
+	}, {
+		.init_func = ext4_init_sysfs,
+		.exit_func = ext4_exit_sysfs,
+	}, {
+		.init_func = ext4_init_mballoc,
+		.exit_func = ext4_exit_mballoc,
+	}, {
+		.init_func = init_inodecache,
+		.exit_func = destroy_inodecache,
+	}, {
+		.init_func = ext4_fc_init_dentry_cache,
+		.exit_func = ext4_fc_destroy_dentry_cache,
+	}, {
+		.init_func = register_ext,
+		.exit_func = unregister_ext,
+	}
+};
 
-	err = ext4_init_pending();
-	if (err)
-		goto out7;
+static bool mod_init_result[ARRAY_SIZE(mod_init_seq)];
 
-	err = ext4_init_post_read_processing();
-	if (err)
-		goto out6;
+static __always_inline void ext4_exit_ext4_fs(void)
+{
+	int i;
 
-	err = ext4_init_pageio();
-	if (err)
-		goto out5;
+	for (i = ARRAY_SIZE(mod_init_seq) - 1; i >= 0; i--) {
+		if (!mod_init_result[i])
+			continue;
+		if (mod_init_seq[i].exit_func)
+			mod_init_seq[i].exit_func();
+		mod_init_result[i] = false;
+	}
+}
 
-	err = ext4_init_system_zone();
-	if (err)
-		goto out4;
+static void __exit ext4_exit_fs(void)
+{
+	ext4_destroy_lazyinit_thread();
+	ext4_exit_ext4_fs();
+}
 
-	err = ext4_init_sysfs();
-	if (err)
-		goto out3;
+static __always_inline int ext4_init_ext4_fs(void)
+{
+	int ret;
+	int i;
 
-	err = ext4_init_mballoc();
-	if (err)
-		goto out2;
-	err = init_inodecache();
-	if (err)
-		goto out1;
+	for (i = 0; i < ARRAY_SIZE(mod_init_seq); i++) {
+		ASSERT(!mod_init_result[i]);
+		ret = mod_init_seq[i].init_func();
+		if (ret < 0) {
+			ext4_exit_ext4_fs();
+			return ret;
+		}
+		mod_init_result[i] = true;
+	}
+	return 0;
+}
 
-	err = ext4_fc_init_dentry_cache();
-	if (err)
-		goto out05;
+/* Shared across all ext4 file systems */
+wait_queue_head_t ext4__ioend_wq[EXT4_WQ_HASH_SZ];
 
-	register_as_ext3();
-	register_as_ext2();
-	err = register_filesystem(&ext4_fs_type);
-	if (err)
-		goto out;
+static int __init ext4_init_fs(void)
+{
+	ratelimit_state_init(&ext4_mount_msg_ratelimit, 30 * HZ, 64);
+	ext4_li_info = NULL;
 
-	return 0;
-out:
-	unregister_as_ext2();
-	unregister_as_ext3();
-	ext4_fc_destroy_dentry_cache();
-out05:
-	destroy_inodecache();
-out1:
-	ext4_exit_mballoc();
-out2:
-	ext4_exit_sysfs();
-out3:
-	ext4_exit_system_zone();
-out4:
-	ext4_exit_pageio();
-out5:
-	ext4_exit_post_read_processing();
-out6:
-	ext4_exit_pending();
-out7:
-	ext4_exit_es();
+	/* Build-time check for flags consistency */
+	ext4_check_flag_values();
 
-	return err;
-}
+	for (int i = 0; i < EXT4_WQ_HASH_SZ; i++)
+		init_waitqueue_head(&ext4__ioend_wq[i]);
 
-static void __exit ext4_exit_fs(void)
-{
-	ext4_destroy_lazyinit_thread();
-	unregister_as_ext2();
-	unregister_as_ext3();
-	unregister_filesystem(&ext4_fs_type);
-	ext4_fc_destroy_dentry_cache();
-	destroy_inodecache();
-	ext4_exit_mballoc();
-	ext4_exit_sysfs();
-	ext4_exit_system_zone();
-	ext4_exit_pageio();
-	ext4_exit_post_read_processing();
-	ext4_exit_es();
-	ext4_exit_pending();
+	return ext4_init_ext4_fs();
 }
 
 MODULE_AUTHOR("Remy Card, Stephen Tweedie, Andrew Morton, Andreas Dilger, Theodore Ts'o and others");
-- 
2.34.1