f2fs: introduce cp_lock to protect updating of ckpt_flags

This patch introduces spinlock to protect updating process of ckpt_flags
field in struct f2fs_checkpoint, it avoids incorrectly updating in race
condition.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
[Jaegeuk Kim: add __is_set_ckpt_flags likewise __set_ckpt_flags]
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 04e9618..2fb8c35 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -797,6 +797,7 @@
 
 	/* for checkpoint */
 	struct f2fs_checkpoint *ckpt;		/* raw checkpoint pointer */
+	spinlock_t cp_lock;			/* for flag in ckpt */
 	struct inode *meta_inode;		/* cache meta blocks */
 	struct mutex cp_mutex;			/* checkpoint procedure lock */
 	struct rw_semaphore cp_rwsem;		/* blocking FS operations */
@@ -1064,26 +1065,50 @@
 	return le64_to_cpu(cp->checkpoint_ver);
 }
 
-static inline bool is_set_ckpt_flags(struct f2fs_checkpoint *cp, unsigned int f)
+static inline bool __is_set_ckpt_flags(struct f2fs_checkpoint *cp, unsigned int f)
 {
 	unsigned int ckpt_flags = le32_to_cpu(cp->ckpt_flags);
+
 	return ckpt_flags & f;
 }
 
-static inline void set_ckpt_flags(struct f2fs_checkpoint *cp, unsigned int f)
+static inline bool is_set_ckpt_flags(struct f2fs_sb_info *sbi, unsigned int f)
 {
-	unsigned int ckpt_flags = le32_to_cpu(cp->ckpt_flags);
+	return __is_set_ckpt_flags(F2FS_CKPT(sbi), f);
+}
+
+static inline void __set_ckpt_flags(struct f2fs_checkpoint *cp, unsigned int f)
+{
+	unsigned int ckpt_flags;
+
+	ckpt_flags = le32_to_cpu(cp->ckpt_flags);
 	ckpt_flags |= f;
 	cp->ckpt_flags = cpu_to_le32(ckpt_flags);
 }
 
-static inline void clear_ckpt_flags(struct f2fs_checkpoint *cp, unsigned int f)
+static inline void set_ckpt_flags(struct f2fs_sb_info *sbi, unsigned int f)
 {
-	unsigned int ckpt_flags = le32_to_cpu(cp->ckpt_flags);
+	spin_lock(&sbi->cp_lock);
+	__set_ckpt_flags(F2FS_CKPT(sbi), f);
+	spin_unlock(&sbi->cp_lock);
+}
+
+static inline void __clear_ckpt_flags(struct f2fs_checkpoint *cp, unsigned int f)
+{
+	unsigned int ckpt_flags;
+
+	ckpt_flags = le32_to_cpu(cp->ckpt_flags);
 	ckpt_flags &= (~f);
 	cp->ckpt_flags = cpu_to_le32(ckpt_flags);
 }
 
+static inline void clear_ckpt_flags(struct f2fs_sb_info *sbi, unsigned int f)
+{
+	spin_lock(&sbi->cp_lock);
+	__clear_ckpt_flags(F2FS_CKPT(sbi), f);
+	spin_unlock(&sbi->cp_lock);
+}
+
 static inline bool f2fs_discard_en(struct f2fs_sb_info *sbi)
 {
 	struct request_queue *q = bdev_get_queue(sbi->sb->s_bdev);
@@ -1129,8 +1154,8 @@
 
 static inline bool __exist_node_summaries(struct f2fs_sb_info *sbi)
 {
-	return (is_set_ckpt_flags(F2FS_CKPT(sbi), CP_UMOUNT_FLAG) ||
-			is_set_ckpt_flags(F2FS_CKPT(sbi), CP_FASTBOOT_FLAG));
+	return (is_set_ckpt_flags(sbi, CP_UMOUNT_FLAG) ||
+			is_set_ckpt_flags(sbi, CP_FASTBOOT_FLAG));
 }
 
 /*
@@ -1832,7 +1857,7 @@
 
 static inline bool f2fs_cp_error(struct f2fs_sb_info *sbi)
 {
-	return is_set_ckpt_flags(sbi->ckpt, CP_ERROR_FLAG);
+	return is_set_ckpt_flags(sbi, CP_ERROR_FLAG);
 }
 
 static inline bool is_dot_dotdot(const struct qstr *str)