f2fs: replace __get_victim by dirty_segments in FG_GC

In FG_GC process, it will search victim section twice. This will
cause some dirty section with less valid blocks skip garbage
collection.

section # 26425 : valid blocks # 3
142.037567: get_victim_by_default: victim 26425 : valid blocks # 3
142.037585: f2fs_get_victim: dev = (259,30), type = No TYPE, policy = (Foreground GC, LFS-mode, Greedy), victim = 26425 ofs_unit = 1, pre_victim_secno = 26425, prefree = 0, free = 244
142.039494: f2fs_get_victim: dev = (259,30), type = Hot DATA, policy = (Background GC, SSR-mode, Greedy), victim = 19022 ofs_unit = 1, pre_victim_secno = 26425, prefree = 0, free = 24
142.070247: new_curseg: Debug: alloc new segment 26746
142.244341: f2fs_get_victim: dev = (259,30), type = No TYPE, policy = (Foreground GC, LFS-mode, Greedy), victim = 26054 ofs_unit = 1, pre_victim_secno = 26054, prefree = 0, free = 243
142.254475: do_garbage_collect: Debug: FG_GC, seg_freed = 1
142.293131: f2fs_get_victim: dev = (259,30), type = Warm DATA, policy = (Background GC, SSR-mode, Greedy), victim = 23466 ofs_unit = 1, pre_victim_secno = -1, prefree = 0, free = 244
142.319001: f2fs_get_victim: dev = (259,30), type = Warm DATA, policy = (Background GC, SSR-mode, Greedy), victim = 23467 ofs_unit = 1, pre_victim_secno = -1, prefree = 0, free = 244
142.368879: get_victim_by_default: victim 26425 : valid blocks # 3
142.368894: f2fs_get_victim: dev = (259,30), type = No TYPE, policy = (Foreground GC, LFS-mode, Greedy), victim = 26425 ofs_unit = 1, pre_victim_secno = 26425, prefree = 0, free = 244
142.378127: f2fs_get_victim: dev = (259,30), type = Hot DATA, policy = (Background GC, SSR-mode, Greedy), victim = 19612 ofs_unit = 1, pre_victim_secno = 26425, prefree = 0, free = 24
142.416917: new_curseg: Debug: alloc new segment 26054
142.656794: f2fs_get_victim: dev = (259,30), type = No TYPE, policy = (Foreground GC, LFS-mode, Greedy), victim = 25404 ofs_unit = 1, pre_victim_secno = 25404, prefree = 0, free = 243
142.662139: do_garbage_collect: Debug: FG_GC, seg_freed = 1
142.684159: new_curseg: Debug: alloc new segment 25197
142.685059: get_victim_by_default: victim 26425 : valid blocks # 3
142.685079: f2fs_get_victim: dev = (259,30), type = No TYPE, policy = (Foreground GC, LFS-mode, Greedy), victim = 26425 ofs_unit = 1, pre_victim_secno = 26425, prefree = 0, free = 243
142.701427: f2fs_get_victim: dev = (259,30), type = No TYPE, policy = (Foreground GC, LFS-mode, Greedy), victim = 26238 ofs_unit = 1, pre_victim_secno = 26238, prefree = 0, free = 243
142.707105: do_garbage_collect: Debug: FG_GC, seg_freed = 1
142.802444: f2fs_get_victim: dev = (259,30), type = Warm DATA, policy = (Background GC, SSR-mode, Greedy), victim = 23473 ofs_unit = 1, pre_victim_secno = -1, prefree = 0, free = 244
142.804422: get_victim_by_default: victim 26425 : valid blocks # 3
142.804443: f2fs_get_victim: dev = (259,30), type = No TYPE, policy = (Foreground GC, LFS-mode, Greedy), victim = 26425 ofs_unit = 1, pre_victim_secno = 26425, prefree = 0, free = 244
142.851567: f2fs_get_victim: dev = (259,30), type = Hot DATA, policy = (Background GC, SSR-mode, Greedy), victim = 19092 ofs_unit = 1, pre_victim_secno = 26425, prefree = 0, free = 24
142.865014: new_curseg: Debug: alloc new segment 26238
143.082245: f2fs_get_victim: dev = (259,30), type = No TYPE, policy = (Foreground GC, LFS-mode, Greedy), victim = 26307 ofs_unit = 1, pre_victim_secno = 26307, prefree = 0, free = 244
143.088252: do_garbage_collect: Debug: FG_GC, seg_freed = 1
143.128307: new_curseg: Debug: alloc new segment 25404
143.181846: get_victim_by_default: victim 26425 : valid blocks # 3
143.181872: f2fs_get_victim: dev = (259,30), type = No TYPE, policy = (Foreground GC, LFS-mode, Greedy), victim = 26425 ofs_unit = 1, pre_victim_secno = 26425, prefree = 0, free = 244

Signed-off-by: Yunlei He <heyunlei@huawei.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/gc.c

@@ -927,8 +927,6 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync, bool background)
 
 	cpc.reason = __get_cp_reason(sbi);
 gc_more:
-	segno = NULL_SEGNO;
-
 	if (unlikely(!(sbi->sb->s_flags & MS_ACTIVE)))
 		goto stop;
 	if (unlikely(f2fs_cp_error(sbi))) {
@@ -943,12 +941,10 @@ gc_more:
 		 * enough free sections, we should flush dent/node blocks and do
 		 * garbage collections.
 		 */
-		if (__get_victim(sbi, &segno, gc_type) ||
-						prefree_segments(sbi)) {
+		if (dirty_segments(sbi) || prefree_segments(sbi)) {
 			ret = write_checkpoint(sbi, &cpc);
 			if (ret)
 				goto stop;
-			segno = NULL_SEGNO;
 		} else if (has_not_enough_free_secs(sbi, 0, 0)) {
 			ret = write_checkpoint(sbi, &cpc);
 			if (ret)
@@ -959,7 +955,7 @@ gc_more:
 		goto stop;
 	}
 
-	if (segno == NULL_SEGNO && !__get_victim(sbi, &segno, gc_type))
+	if (!__get_victim(sbi, &segno, gc_type))
 		goto stop;
 	ret = 0;