linux-kernel - [PATCH v1] f2fs: avoid victim selection from previous victim section

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Date:   Tue, 22 Nov 2022 11:36:56 +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>
Subject: [PATCH v1] f2fs: avoid victim selection from previous victim
 section

When f2fs chooses GC victim in large section & LFS mode,
next_victim_seg[gc_type] is referenced first. After segment is freed,
next_victim_seg[gc_type] has the next segment number.
However, next_victim_seg[gc_type] still has the last segment number
even after the last segment of section is freed. In this case, when f2fs
chooses a victim for the next GC round, the last segment of previous victim
section is chosen as a victim.

Initialize next_victim_seg[gc_type] to NULL_SEGNO for the last segment in
large section.

Fixes: e3080b0120a1 ("f2fs: support subsectional garbage collection")
Signed-off-by: Yonggil Song <yonggil.song@...sung.com>
---
 fs/f2fs/gc.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index 4546e01b2ee0..10677d53ef0e 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -1744,8 +1744,9 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
                                 get_valid_blocks(sbi, segno, false) == 0)
                         seg_freed++;
 
-                if (__is_large_section(sbi) && segno + 1 < end_segno)
-                        sbi->next_victim_seg[gc_type] = segno + 1;
+                if (__is_large_section(sbi))
+                        sbi->next_victim_seg[gc_type] =
+                                (segno + 1 < end_segno) ? segno + 1 : NULL_SEGNO;
 skip:
                 f2fs_put_page(sum_page, 0);
         }
-- 
2.34.1