f2fs: retry gc if one section is not successfully reclaimed

If FG_GC failed to reclaim one section, let's retry with another section
from the start, since we can get anoterh good candidate.
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/gc.c

@@ -391,7 +391,7 @@ static int check_valid_map(struct f2fs_sb_info *sbi,
  * On validity, copy that node with cold status, otherwise (invalid node)
  * ignore that.
  */
-static void gc_node_segment(struct f2fs_sb_info *sbi,
+static int gc_node_segment(struct f2fs_sb_info *sbi,
 		struct f2fs_summary *sum, unsigned int segno, int gc_type)
 {
 	bool initial = true;
@@ -411,7 +411,7 @@ static void gc_node_segment(struct f2fs_sb_info *sbi,
 
 		/* stop BG_GC if there is not enough free sections. */
 		if (gc_type == BG_GC && has_not_enough_free_secs(sbi, 0))
-			return;
+			return 0;
 
 		if (check_valid_map(sbi, segno, off) == 0)
 			continue;
@@ -461,13 +461,11 @@ static void gc_node_segment(struct f2fs_sb_info *sbi,
 		};
 		sync_node_pages(sbi, 0, &wbc);
 
-		/*
-		 * In the case of FG_GC, it'd be better to reclaim this victim
-		 * completely.
-		 */
-		if (get_valid_blocks(sbi, segno, 1) != 0)
-			goto next_step;
+		/* return 1 only if FG_GC succefully reclaimed one */
+		if (get_valid_blocks(sbi, segno, 1) == 0)
+			return 1;
 	}
+	return 0;
 }
 
 /*
@@ -649,7 +647,7 @@ static void move_data_page(struct inode *inode, block_t bidx, int gc_type)
  * If the parent node is not valid or the data block address is different,
  * the victim data block is ignored.
  */
-static void gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
+static int gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
 		struct gc_inode_list *gc_list, unsigned int segno, int gc_type)
 {
 	struct super_block *sb = sbi->sb;
@@ -672,7 +670,7 @@ static void gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
 
 		/* stop BG_GC if there is not enough free sections. */
 		if (gc_type == BG_GC && has_not_enough_free_secs(sbi, 0))
-			return;
+			return 0;
 
 		if (check_valid_map(sbi, segno, off) == 0)
 			continue;
@@ -737,15 +735,11 @@ static void gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
 	if (gc_type == FG_GC) {
 		f2fs_submit_merged_bio(sbi, DATA, WRITE);
 
-		/*
-		 * In the case of FG_GC, it'd be better to reclaim this victim
-		 * completely.
-		 */
-		if (get_valid_blocks(sbi, segno, 1) != 0) {
-			phase = 2;
-			goto next_step;
-		}
+		/* return 1 only if FG_GC succefully reclaimed one */
+		if (get_valid_blocks(sbi, segno, 1) == 0)
+			return 1;
 	}
+	return 0;
 }
 
 static int __get_victim(struct f2fs_sb_info *sbi, unsigned int *victim,
@@ -761,12 +755,13 @@ static int __get_victim(struct f2fs_sb_info *sbi, unsigned int *victim,
 	return ret;
 }
 
-static void do_garbage_collect(struct f2fs_sb_info *sbi, unsigned int segno,
+static int do_garbage_collect(struct f2fs_sb_info *sbi, unsigned int segno,
 				struct gc_inode_list *gc_list, int gc_type)
 {
 	struct page *sum_page;
 	struct f2fs_summary_block *sum;
 	struct blk_plug plug;
+	int nfree = 0;
 
 	/* read segment summary of victim */
 	sum_page = get_sum_page(sbi, segno);
@@ -786,10 +781,11 @@ static void do_garbage_collect(struct f2fs_sb_info *sbi, unsigned int segno,
 
 	switch (GET_SUM_TYPE((&sum->footer))) {
 	case SUM_TYPE_NODE:
-		gc_node_segment(sbi, sum->entries, segno, gc_type);
+		nfree = gc_node_segment(sbi, sum->entries, segno, gc_type);
 		break;
 	case SUM_TYPE_DATA:
-		gc_data_segment(sbi, sum->entries, gc_list, segno, gc_type);
+		nfree = gc_data_segment(sbi, sum->entries, gc_list,
+							segno, gc_type);
 		break;
 	}
 	blk_finish_plug(&plug);
@@ -798,6 +794,7 @@ static void do_garbage_collect(struct f2fs_sb_info *sbi, unsigned int segno,
 	stat_inc_call_count(sbi->stat_info);
 
 	f2fs_put_page(sum_page, 0);
+	return nfree;
 }
 
 int f2fs_gc(struct f2fs_sb_info *sbi)
@@ -836,13 +833,10 @@ int f2fs_gc(struct f2fs_sb_info *sbi)
 								META_SSA);
 
 	for (i = 0; i < sbi->segs_per_sec; i++)
-		do_garbage_collect(sbi, segno + i, &gc_list, gc_type);
+		nfree += do_garbage_collect(sbi, segno + i, &gc_list, gc_type);
 
-	if (gc_type == FG_GC) {
+	if (gc_type == FG_GC)
 		sbi->cur_victim_sec = NULL_SEGNO;
-		nfree++;
-		WARN_ON(get_valid_blocks(sbi, segno, sbi->segs_per_sec));
-	}
 
 	if (has_not_enough_free_secs(sbi, nfree))
 		goto gc_more;