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Subject: Re: [PATCH v2 5/5] f2fs: support age threshold based garbage
 collection
To:     Jaegeuk Kim <jaegeuk@kernel.org>
CC:     <linux-f2fs-devel@lists.sourceforge.net>,
        <linux-kernel@vger.kernel.org>, <chao@kernel.org>
References: <20200804131449.50517-1-yuchao0@huawei.com>
 <20200804131449.50517-6-yuchao0@huawei.com>
 <20200825193404.GA2614120@google.com>
From:   Chao Yu <yuchao0@huawei.com>
Message-ID: <7986af8c-1fe9-7140-f1c0-d8b4a58f702c@huawei.com>
Date:   Mon, 31 Aug 2020 14:59:27 +0800
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Hi Jaegeuk,

I've changed code a bit to fix some bugs, including:
- gc_idle = 3 (GC_IDLE_AT) description
- disallow set gc_idle to 3 if atgc is off
- keep compatibility with checkpoint disabling

Could you please check and merge below diff?

From: Chao Yu <yuchao0@huawei.com>

Signed-off-by: Chao Yu <yuchao0@huawei.com>
---
  Documentation/ABI/testing/sysfs-fs-f2fs |  3 ++-
  fs/f2fs/gc.c                            | 12 +++++++++++-
  fs/f2fs/sysfs.c                         | 11 ++++++++---
  3 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-fs-f2fs b/Documentation/ABI/testing/sysfs-fs-f2fs
index 7f730c4c8df2..834d0becae6d 100644
--- a/Documentation/ABI/testing/sysfs-fs-f2fs
+++ b/Documentation/ABI/testing/sysfs-fs-f2fs
@@ -22,7 +22,8 @@ Contact:	"Namjae Jeon" <namjae.jeon@samsung.com>
  Description:	Controls the victim selection policy for garbage collection.
  		Setting gc_idle = 0(default) will disable this option. Setting
  		gc_idle = 1 will select the Cost Benefit approach & setting
-		gc_idle = 2 will select the greedy approach.
+		gc_idle = 2 will select the greedy approach & setting
+		gc_idle = 3 will select the age-threshold based approach.

  What:		/sys/fs/f2fs/<disk>/reclaim_segments
  Date:		October 2013
diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index 6413886e52d4..3c0edb8b4cc5 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -388,6 +388,16 @@ static void add_victim_entry(struct f2fs_sb_info *sbi,
  	unsigned long long mtime = 0;
  	unsigned int i;

+	if (unlikely(is_sbi_flag_set(sbi, SBI_CP_DISABLED)) {
+		if (p->gc_mode == GC_AT &&
+			get_valid_blocks(sbi, segno, true) == 0)
+			return;
+
+		if (p->alloc_mode == AT_SSR &&
+			get_seg_entry(sbi, segno)->ckpt_valid_blocks == 0)
+			return;
+	}
+
  	for (i = 0; i < sbi->segs_per_sec; i++)
  		mtime += get_seg_entry(sbi, start + i)->mtime;
  	mtime = div_u64(mtime, sbi->segs_per_sec);
@@ -721,7 +731,7 @@ static int get_victim_by_default(struct f2fs_sb_info *sbi,
  		/* Don't touch checkpointed data */
  		if (unlikely(is_sbi_flag_set(sbi, SBI_CP_DISABLED) &&
  					get_ckpt_valid_blocks(sbi, segno) &&
-					p.alloc_mode != SSR))
+					p.alloc_mode == LFS))
  			goto next;
  		if (gc_type == BG_GC && test_bit(secno, dirty_i->victim_secmap))
  			goto next;
diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
index 88ed9969cc86..bacfa9c35e6b 100644
--- a/fs/f2fs/sysfs.c
+++ b/fs/f2fs/sysfs.c
@@ -375,12 +375,17 @@ static ssize_t __sbi_store(struct f2fs_attr *a,
  		return count;
  	}
  	if (!strcmp(a->attr.name, "gc_idle")) {
-		if (t == GC_IDLE_CB)
+		if (t == GC_IDLE_CB) {
  			sbi->gc_mode = GC_IDLE_CB;
-		else if (t == GC_IDLE_GREEDY)
+		} else if (t == GC_IDLE_GREEDY) {
  			sbi->gc_mode = GC_IDLE_GREEDY;
-		else
+		} else if (t == GC_IDLE_AT) {
+			if (!sbi->am.atgc_enabled)
+				return -EINVAL;
+			sbi->gc_mode = GC_AT;
+		} else {
  			sbi->gc_mode = GC_NORMAL;
+		}
  		return count;
  	}

-- 
2.26.2