f2fs: fix to avoid call kvfree under spinlock

vfree() don't wish to be called from interrupt context, move it
out of spin_lock_irqsave() coverage.
Signed-off-by: NChao Yu <yuchao0@huawei.com>
Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/f2fs.h

@@ -1640,6 +1640,7 @@ static inline void clear_ckpt_flags(struct f2fs_sb_info *sbi, unsigned int f)
 static inline void disable_nat_bits(struct f2fs_sb_info *sbi, bool lock)
 {
 	unsigned long flags;
+	unsigned char *nat_bits;
 
 	/*
 	 * In order to re-enable nat_bits we need to call fsck.f2fs by
@@ -1650,10 +1651,12 @@ static inline void disable_nat_bits(struct f2fs_sb_info *sbi, bool lock)
 	if (lock)
 		spin_lock_irqsave(&sbi->cp_lock, flags);
 	__clear_ckpt_flags(F2FS_CKPT(sbi), CP_NAT_BITS_FLAG);
-	kvfree(NM_I(sbi)->nat_bits);
+	nat_bits = NM_I(sbi)->nat_bits;
 	NM_I(sbi)->nat_bits = NULL;
 	if (lock)
 		spin_unlock_irqrestore(&sbi->cp_lock, flags);
+
+	kvfree(nat_bits);
 }
 
 static inline bool enabled_nat_bits(struct f2fs_sb_info *sbi,