linux-kernel - [PATCH v1] f2fs: Fix over-estimating free section during FG GC

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Date:   Fri, 12 May 2023 13:16:10 +0900
From:   Yonggil Song <yonggil.song@...sung.com>
To:     "jaegeuk@...nel.org" <jaegeuk@...nel.org>,
        "chao@...nel.org" <chao@...nel.org>,
        "linux-f2fs-devel@...ts.sourceforge.net" 
        <linux-f2fs-devel@...ts.sourceforge.net>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     Seokhwan Kim <sukka.kim@...sung.com>,
        Daejun Park <daejun7.park@...sung.com>,
        beomsu kim <beomsu7.kim@...sung.com>
Subject: [PATCH v1] f2fs: Fix over-estimating free section during FG GC

There was a bug that finishing FG GC unconditionally because free sections
are over-estimated after checkpoint in FG GC.
This patch initializes sec_freed by every checkpoint in FG GC.

Signed-off-by: Yonggil Song <yonggil.song@...sung.com>
---
 fs/f2fs/gc.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index d455140322a8..51d7e8d29bf1 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -1797,7 +1797,7 @@ int f2fs_gc(struct f2fs_sb_info *sbi, struct f2fs_gc_control *gc_control)
 {
 	int gc_type = gc_control->init_gc_type;
 	unsigned int segno = gc_control->victim_segno;
-	int sec_freed = 0, seg_freed = 0, total_freed = 0;
+	int sec_freed = 0, seg_freed = 0, total_freed = 0, total_sec_freed = 0;
 	int ret = 0;
 	struct cp_control cpc;
 	struct gc_inode_list gc_list = {
@@ -1842,6 +1842,8 @@ int f2fs_gc(struct f2fs_sb_info *sbi, struct f2fs_gc_control *gc_control)
 			ret = f2fs_write_checkpoint(sbi, &cpc);
 			if (ret)
 				goto stop;
+			/* Reset due to checkpoint */
+			sec_freed = 0;
 		}
 	}
 
@@ -1866,15 +1868,17 @@ int f2fs_gc(struct f2fs_sb_info *sbi, struct f2fs_gc_control *gc_control)
 				gc_control->should_migrate_blocks);
 	total_freed += seg_freed;
 
-	if (seg_freed == f2fs_usable_segs_in_sec(sbi, segno))
+	if (seg_freed == f2fs_usable_segs_in_sec(sbi, segno)) {
 		sec_freed++;
+		total_sec_freed++;
+	}
 
 	if (gc_type == FG_GC) {
 		sbi->cur_victim_sec = NULL_SEGNO;
 
 		if (has_enough_free_secs(sbi, sec_freed, 0)) {
 			if (!gc_control->no_bg_gc &&
-			    sec_freed < gc_control->nr_free_secs)
+			    total_sec_freed < gc_control->nr_free_secs)
 				goto go_gc_more;
 			goto stop;
 		}
@@ -1901,6 +1905,8 @@ int f2fs_gc(struct f2fs_sb_info *sbi, struct f2fs_gc_control *gc_control)
 		ret = f2fs_write_checkpoint(sbi, &cpc);
 		if (ret)
 			goto stop;
+		/* Reset due to checkpoint */
+		sec_freed = 0;
 	}
 go_gc_more:
 	segno = NULL_SEGNO;
@@ -1913,7 +1919,7 @@ int f2fs_gc(struct f2fs_sb_info *sbi, struct f2fs_gc_control *gc_control)
 	if (gc_type == FG_GC)
 		f2fs_unpin_all_sections(sbi, true);
 
-	trace_f2fs_gc_end(sbi->sb, ret, total_freed, sec_freed,
+	trace_f2fs_gc_end(sbi->sb, ret, total_freed, total_sec_freed,
 				get_pages(sbi, F2FS_DIRTY_NODES),
 				get_pages(sbi, F2FS_DIRTY_DENTS),
 				get_pages(sbi, F2FS_DIRTY_IMETA),
@@ -1927,7 +1933,7 @@ int f2fs_gc(struct f2fs_sb_info *sbi, struct f2fs_gc_control *gc_control)
 	put_gc_inode(&gc_list);
 
 	if (gc_control->err_gc_skipped && !ret)
-		ret = sec_freed ? 0 : -EAGAIN;
+		ret = total_sec_freed ? 0 : -EAGAIN;
 	return ret;
 }
 
-- 
2.34.1