[PATCH v2 6/6] super: add filesystem freezing helpers for suspend and hibernate

[Christian Brauner <brauner@xxxxxxxxxx>]

Allow the power subsystem to support filesystem freeze for
suspend and hibernate.

Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>
---
 fs/super.c         | 55 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/fs.h |  2 ++
 2 files changed, 57 insertions(+)

diff --git a/fs/super.c b/fs/super.c
index 666a2a16df87..4364b763e91f 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -1176,6 +1176,61 @@ void emergency_thaw_all(void)
 	}
 }
 
+static inline bool get_active_super(struct super_block *sb)
+{
+	bool active;
+
+	if (super_lock_excl(sb)) {
+		active = atomic_inc_not_zero(&sb->s_active);
+		super_unlock_excl(sb);
+	}
+	return active;
+}
+
+static void filesystems_freeze_callback(struct super_block *sb, void *unused)
+{
+	if (!sb->s_op->freeze_fs && !sb->s_op->freeze_super)
+		return;
+
+	if (!get_active_super(sb))
+		return;
+
+	if (sb->s_op->freeze_super)
+		sb->s_op->freeze_super(sb, FREEZE_MAY_NEST | FREEZE_HOLDER_KERNEL);
+	else
+		freeze_super(sb, FREEZE_MAY_NEST | FREEZE_HOLDER_KERNEL);
+
+	deactivate_super(sb);
+}
+
+void filesystems_freeze(bool hibernate)
+{
+	__iterate_supers(filesystems_freeze_callback, NULL,
+			 SUPER_ITER_UNLOCKED | SUPER_ITER_REVERSE);
+}
+
+static void filesystems_thaw_callback(struct super_block *sb, void *unused)
+{
+	if (!sb->s_op->freeze_fs && !sb->s_op->freeze_super)
+		return;
+
+	if (!get_active_super(sb))
+		return;
+
+	if (sb->s_op->thaw_super)
+		sb->s_op->thaw_super(sb, FREEZE_MAY_NEST | FREEZE_HOLDER_KERNEL);
+	else
+		thaw_super(sb, FREEZE_MAY_NEST | FREEZE_HOLDER_KERNEL);
+
+	deactivate_super(sb);
+}
+
+void filesystems_thaw(bool hibernate)
+{
+	__iterate_supers(filesystems_thaw_callback, NULL,
+			 SUPER_ITER_UNLOCKED | SUPER_ITER_REVERSE);
+}
+
 static DEFINE_IDA(unnamed_dev_ida);
 
 /**
diff --git a/include/linux/fs.h b/include/linux/fs.h
index c475fa874055..29bd28491eff 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3518,6 +3518,8 @@ extern void drop_super_exclusive(struct super_block *sb);
 extern void iterate_supers(void (*f)(struct super_block *, void *), void *arg);
 extern void iterate_supers_type(struct file_system_type *,
 			        void (*)(struct super_block *, void *), void *);
+void filesystems_freeze(bool hibernate);
+void filesystems_thaw(bool hibernate);
 
 extern int dcache_dir_open(struct inode *, struct file *);
 extern int dcache_dir_close(struct inode *, struct file *);

-- 
2.47.2