diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 43ab2a0831a3..7914007cdb8a 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -1675,6 +1675,7 @@ struct f2fs_sb_info {
 	unsigned int meta_ino_num;		/* meta inode number*/
 	unsigned int log_blocks_per_seg;	/* log2 blocks per segment */
 	unsigned int blocks_per_seg;		/* blocks per segment */
+	unsigned int unusable_blocks_per_sec;	/* unusable blocks per section */
 	unsigned int segs_per_sec;		/* segments per section */
 	unsigned int secs_per_zone;		/* sections per zone */
 	unsigned int total_sections;		/* total section count */
diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
index 00d6bc556a6b..6c3f82d519ea 100644
--- a/fs/f2fs/segment.h
+++ b/fs/f2fs/segment.h
@@ -101,6 +101,9 @@ static inline void sanity_check_seg_type(struct f2fs_sb_info *sbi,
 		GET_SEGNO_FROM_SEG0(sbi, blk_addr)))
 #define BLKS_PER_SEC(sbi)					\
 	((sbi)->segs_per_sec * (sbi)->blocks_per_seg)
+#define CAP_BLKS_PER_SEC(sbi)					\
+	((sbi)->segs_per_sec * (sbi)->blocks_per_seg -		\
+	 (sbi)->unusable_blocks_per_sec)
 #define GET_SEC_FROM_SEG(sbi, segno)				\
 	(((segno) == -1) ? -1: (segno) / (sbi)->segs_per_sec)
 #define GET_SEG_FROM_SEC(sbi, secno)				\