f2fs: ignore valid ratio when free section count is low

Otherwise F2FS will not do GC in background in low free section.

Signed-off-by: Daeho Jeong <daehojeong@google.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

Author: Daeho Jeong

fs/f2fs/gc.c

@@ -384,14 +384,15 @@ static unsigned int get_cb_cost(struct f2fs_sb_info *sbi, unsigned int segno)
 }
 
 static inline unsigned int get_gc_cost(struct f2fs_sb_info *sbi,
-			unsigned int segno, struct victim_sel_policy *p)
+			unsigned int segno, struct victim_sel_policy *p,
+			unsigned int valid_thresh_ratio)
 {
 	if (p->alloc_mode == SSR)
 		return get_seg_entry(sbi, segno)->ckpt_valid_blocks;
 
-	if (p->one_time_gc && (get_valid_blocks(sbi, segno, true) >=
-		CAP_BLKS_PER_SEC(sbi) * sbi->gc_thread->valid_thresh_ratio /
-		100))
+	if (p->one_time_gc && (valid_thresh_ratio < 100) &&
+			(get_valid_blocks(sbi, segno, true) >=
+			CAP_BLKS_PER_SEC(sbi) * valid_thresh_ratio / 100))
 		return UINT_MAX;
 
 	/* alloc_mode == LFS */
@@ -772,6 +773,7 @@ int f2fs_get_victim(struct f2fs_sb_info *sbi, unsigned int *result,
 	unsigned int secno, last_victim;
 	unsigned int last_segment;
 	unsigned int nsearched;
+	unsigned int valid_thresh_ratio = 100;
 	bool is_atgc;
 	int ret = 0;
 
@@ -781,7 +783,11 @@ int f2fs_get_victim(struct f2fs_sb_info *sbi, unsigned int *result,
 	p.alloc_mode = alloc_mode;
 	p.age = age;
 	p.age_threshold = sbi->am.age_threshold;
-	p.one_time_gc = one_time;
+	if (one_time) {
+		p.one_time_gc = one_time;
+		if (has_enough_free_secs(sbi, 0, NR_PERSISTENT_LOG))
+			valid_thresh_ratio = sbi->gc_thread->valid_thresh_ratio;
+	}
 
 retry:
 	select_policy(sbi, gc_type, type, &p);
@@ -907,7 +913,7 @@ int f2fs_get_victim(struct f2fs_sb_info *sbi, unsigned int *result,
 			goto next;
 		}
 
-		cost = get_gc_cost(sbi, segno, &p);
+		cost = get_gc_cost(sbi, segno, &p, valid_thresh_ratio);
 
 		if (p.min_cost > cost) {
 			p.min_segno = segno;