f2fs: avoid frequent costly fsck triggers

If we want to re-enable nat_bits, we rely on fsck which requires full scan
of directory tree. Let's do that by regular fsck or unclean shutdown.
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/f2fs.h

@@ -1621,7 +1621,11 @@ static inline void disable_nat_bits(struct f2fs_sb_info *sbi, bool lock)
 {
 	unsigned long flags;
 
-	set_sbi_flag(sbi, SBI_NEED_FSCK);
+	/*
+	 * In order to re-enable nat_bits we need to call fsck.f2fs by
+	 * set_sbi_flag(sbi, SBI_NEED_FSCK). But it may give huge cost,
+	 * so let's rely on regular fsck or unclean shutdown.
+	 */
 
 	if (lock)
 		spin_lock_irqsave(&sbi->cp_lock, flags);