[PATCH 3/3] fs: Add {init, exit}_sequence_fs() helper functions

[Youling Tang]

From: Youling Tang <tangyouling@xxxxxxxxxx>

In theory init_sequence_fs() and exit_sequence_fs() should match their
sequence, thus normally they should look like this:
    init_sequence_fs()   |   exit_sequence_fs()
-------------------------+------------------------
    init_A();            |
    init_B();            |
    init_C();            |
                         |   exit_C();
                         |   exit_B();
                         |   exit_A();

Providing {init, exit}_sequence_fs() helps functions ensure that modules
init/exit match their order, while also simplifying the code.

For more details see commit 5565b8e0adcd ("btrfs: make module init/exit
match their sequence").

Signed-off-by: Youling Tang <tangyouling@xxxxxxxxxx>
---
 fs/btrfs/super.c   | 36 ++----------------------------------
 fs/ext4/super.c    | 41 ++---------------------------------------
 fs/f2fs/super.c    | 36 ++----------------------------------
 include/linux/fs.h | 38 ++++++++++++++++++++++++++++++++++++++
 4 files changed, 44 insertions(+), 107 deletions(-)

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index f05cce7c8b8d..1101991a9a63 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -2478,13 +2478,6 @@ static void unregister_btrfs(void)
 	unregister_filesystem(&btrfs_fs_type);
 }
 
-/* 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);
-};
-
 static const struct init_sequence mod_init_seq[] = {
 	{
 		.init_func = btrfs_props_init,
@@ -2551,40 +2544,15 @@ static const struct init_sequence mod_init_seq[] = {
 
 static bool mod_init_result[ARRAY_SIZE(mod_init_seq)];
 
-static __always_inline void btrfs_exit_btrfs_fs(void)
-{
-	int i;
-
-	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;
-	}
-}
-
 static void __exit exit_btrfs_fs(void)
 {
-	btrfs_exit_btrfs_fs();
+	exit_sequence_fs(mod_init_seq, mod_init_result, ARRAY_SIZE(mod_init_seq));
 	btrfs_cleanup_fs_uuids();
 }
 
 static int __init init_btrfs_fs(void)
 {
-	int ret;
-	int i;
-
-	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) {
-			btrfs_exit_btrfs_fs();
-			return ret;
-		}
-		mod_init_result[i] = true;
-	}
-	return 0;
+	return init_sequence_fs(mod_init_seq, mod_init_result, ARRAY_SIZE(mod_init_seq));
 }
 
 late_initcall(init_btrfs_fs);
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index ec1e63facb10..cb5b7449c80b 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -7328,13 +7328,6 @@ static void unregister_ext(void)
 	unregister_filesystem(&ext4_fs_type);
 }
 
-/* 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);
-};
-
 static const struct init_sequence mod_init_seq[] = {
 	{
 		.init_func = ext4_init_es,
@@ -7371,40 +7364,10 @@ static const struct init_sequence mod_init_seq[] = {
 
 static bool mod_init_result[ARRAY_SIZE(mod_init_seq)];
 
-static __always_inline void ext4_exit_ext4_fs(void)
-{
-	int i;
-
-	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;
-	}
-}
-
 static void __exit ext4_exit_fs(void)
 {
 	ext4_destroy_lazyinit_thread();
-	ext4_exit_ext4_fs();
-}
-
-static __always_inline int ext4_init_ext4_fs(void)
-{
-	int ret;
-	int i;
-
-	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;
+	exit_sequence_fs(mod_init_seq, mod_init_result, ARRAY_SIZE(mod_init_seq));
 }
 
 /* Shared across all ext4 file systems */
@@ -7421,7 +7384,7 @@ static int __init ext4_init_fs(void)
 	for (int i = 0; i < EXT4_WQ_HASH_SZ; i++)
 		init_waitqueue_head(&ext4__ioend_wq[i]);
 
-	return ext4_init_ext4_fs();
+	return init_sequence_fs(mod_init_seq, mod_init_result, ARRAY_SIZE(mod_init_seq));
 }
 
 MODULE_AUTHOR("Remy Card, Stephen Tweedie, Andrew Morton, Andreas Dilger, Theodore Ts'o and others");
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 19509942b837..b4be24865ab3 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -4950,13 +4950,6 @@ static void unregister_f2fs(void)
 	unregister_filesystem(&f2fs_fs_type);
 }
 
-/* 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);
-};
-
 static const struct init_sequence mod_init_seq[] = {
 	{
 		.init_func = init_inodecache,
@@ -5017,39 +5010,14 @@ static const struct init_sequence mod_init_seq[] = {
 
 static bool mod_init_result[ARRAY_SIZE(mod_init_seq)];
 
-static __always_inline void f2fs_exit_f2fs_fs(void)
-{
-	int i;
-
-	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;
-	}
-}
-
 static void __exit exit_f2fs_fs(void)
 {
-	f2fs_exit_f2fs_fs();
+	exit_sequence_fs(mod_init_seq, mod_init_result, ARRAY_SIZE(mod_init_seq));
 }
 
 static int __init init_f2fs_fs(void)
 {
-	int ret;
-	int i;
-
-	for (i = 0; i < ARRAY_SIZE(mod_init_seq); i++) {
-		BUG_ON(mod_init_result[i]);
-		ret = mod_init_seq[i].init_func();
-		if (ret < 0) {
-			f2fs_exit_f2fs_fs();
-			return ret;
-		}
-		mod_init_result[i] = true;
-	}
-	return 0;
+	return init_sequence_fs(mod_init_seq, mod_init_result, ARRAY_SIZE(mod_init_seq));
 }
 
 module_init(init_f2fs_fs)
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 0283cf366c2a..b173194b7f14 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2598,6 +2598,44 @@ extern void iput(struct inode *);
 int inode_update_timestamps(struct inode *inode, int flags);
 int generic_update_time(struct inode *, int);
 
+/* 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);
+};
+
+static __always_inline void exit_sequence_fs(const struct init_sequence *mod_init_seq,
+					     bool *mod_init_result, int num)
+{
+	int i;
+
+	for (i = num - 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;
+	}
+}
+
+static __always_inline int init_sequence_fs(const struct init_sequence *mod_init_seq,
+					    bool *mod_init_result, int num)
+{
+	int ret, i;
+
+	for (i = 0; i < num; i++) {
+		BUG_ON(mod_init_result[i]);
+		ret = mod_init_seq[i].init_func();
+		if (ret < 0) {
+			exit_sequence_fs(mod_init_seq, mod_init_result, num);
+			return ret;
+		}
+		mod_init_result[i] = true;
+	}
+	return 0;
+}
+
 /* /sys/fs */
 extern struct kobject *fs_kobj;
 
-- 
2.34.1