linux-kernel - [PATCH] f2fs: remain last victim segment number ascending order

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Date:	Mon, 22 Feb 2016 09:44:38 -0800
From:	Jaegeuk Kim <jaegeuk@...nel.org>
To:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	linux-f2fs-devel@...ts.sourceforge.net
Cc:	Jaegeuk Kim <jaegeuk@...nel.org>
Subject: [PATCH] f2fs: remain last victim segment number ascending order

This patch avoids to remain inefficient victim segment number selected by
a victim.

For example, if all the dirty segments has same valid blocks, we can get
the victim segments descending order due to keeping wrong last segment number.

Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
---
 fs/f2fs/gc.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index 47ade35..c013534 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -270,7 +270,7 @@ static int get_victim_by_default(struct f2fs_sb_info *sbi,
 {
 	struct dirty_seglist_info *dirty_i = DIRTY_I(sbi);
 	struct victim_sel_policy p;
-	unsigned int secno, max_cost;
+	unsigned int secno, max_cost, last_victim;
 	unsigned int last_segment = MAIN_SEGS(sbi);
 	unsigned int nsearched = 0;
 
@@ -285,6 +285,7 @@ static int get_victim_by_default(struct f2fs_sb_info *sbi,
 	if (p.max_search == 0)
 		goto out;
 
+	last_victim = sbi->last_victim[p.gc_mode];
 	if (p.alloc_mode == LFS && gc_type == FG_GC) {
 		p.min_segno = check_bg_victims(sbi);
 		if (p.min_segno != NULL_SEGNO)
@@ -332,7 +333,10 @@ static int get_victim_by_default(struct f2fs_sb_info *sbi,
 		}
 next:
 		if (nsearched >= p.max_search) {
-			sbi->last_victim[p.gc_mode] = segno;
+			if (!sbi->last_victim[p.gc_mode] && segno <= last_victim)
+				sbi->last_victim[p.gc_mode] = last_victim + 1;
+			else
+				sbi->last_victim[p.gc_mode] = segno + 1;
 			break;
 		}
 	}
-- 
2.6.3