[PATCH v2 2/2] f2fs: introduce get_section_mtime

[liuderong]

From: liuderong <liuderong@xxxxxxxx>

When segs_per_sec is larger than 1, section may contain free segments,
mtime should be the mean value of each valid segments,
so introduce get_section_mtime to exclude free segments in a section.

Signed-off-by: liuderong <liuderong@xxxxxxxx>
---
 fs/f2fs/f2fs.h    |  2 ++
 fs/f2fs/gc.c      | 15 ++-------------
 fs/f2fs/segment.c | 41 ++++++++++++++++++++++++++++++++++++-----
 3 files changed, 40 insertions(+), 18 deletions(-)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 4dcdcdd..d6adf0f 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -3762,6 +3762,8 @@ enum rw_hint f2fs_io_type_to_rw_hint(struct f2fs_sb_info *sbi,
 unsigned int f2fs_usable_segs_in_sec(struct f2fs_sb_info *sbi);
 unsigned int f2fs_usable_blks_in_seg(struct f2fs_sb_info *sbi,
 			unsigned int segno);
+unsigned long long get_section_mtime(struct f2fs_sb_info *sbi,
+			unsigned int segno);
 
 #define DEF_FRAGMENT_SIZE	4
 #define MIN_FRAGMENT_SIZE	1
diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index 6299639..03c6117 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -332,20 +332,14 @@ static unsigned int check_bg_victims(struct f2fs_sb_info *sbi)
 static unsigned int get_cb_cost(struct f2fs_sb_info *sbi, unsigned int segno)
 {
 	struct sit_info *sit_i = SIT_I(sbi);
-	unsigned int secno = GET_SEC_FROM_SEG(sbi, segno);
-	unsigned int start = GET_SEG_FROM_SEC(sbi, secno);
 	unsigned long long mtime = 0;
 	unsigned int vblocks;
 	unsigned char age = 0;
 	unsigned char u;
-	unsigned int i;
 	unsigned int usable_segs_per_sec = f2fs_usable_segs_in_sec(sbi);
 
-	for (i = 0; i < usable_segs_per_sec; i++)
-		mtime += get_seg_entry(sbi, start + i)->mtime;
+	mtime = get_section_mtime(sbi, segno);
 	vblocks = get_valid_blocks(sbi, segno, true);
-
-	mtime = div_u64(mtime, usable_segs_per_sec);
 	vblocks = div_u64(vblocks, usable_segs_per_sec);
 
 	u = BLKS_TO_SEGS(sbi, vblocks * 100);
@@ -485,10 +479,7 @@ static void add_victim_entry(struct f2fs_sb_info *sbi,
 				struct victim_sel_policy *p, unsigned int segno)
 {
 	struct sit_info *sit_i = SIT_I(sbi);
-	unsigned int secno = GET_SEC_FROM_SEG(sbi, segno);
-	unsigned int start = GET_SEG_FROM_SEC(sbi, secno);
 	unsigned long long mtime = 0;
-	unsigned int i;
 
 	if (unlikely(is_sbi_flag_set(sbi, SBI_CP_DISABLED))) {
 		if (p->gc_mode == GC_AT &&
@@ -496,9 +487,7 @@ static void add_victim_entry(struct f2fs_sb_info *sbi,
 			return;
 	}
 
-	for (i = 0; i < SEGS_PER_SEC(sbi); i++)
-		mtime += get_seg_entry(sbi, start + i)->mtime;
-	mtime = div_u64(mtime, SEGS_PER_SEC(sbi));
+	mtime = get_section_mtime(sbi, segno);
 
 	/* Handle if the system time has changed by the user */
 	if (mtime < sit_i->min_mtime)
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 6627394..e62e722 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -5389,6 +5389,41 @@ unsigned int f2fs_usable_segs_in_sec(struct f2fs_sb_info *sbi)
 	return SEGS_PER_SEC(sbi);
 }
 
+unsigned long long get_section_mtime(struct f2fs_sb_info *sbi,
+	unsigned int segno)
+{
+	unsigned int usable_segs_per_sec = f2fs_usable_segs_in_sec(sbi);
+	unsigned int secno = 0, start = 0;
+	struct free_segmap_info *free_i = FREE_I(sbi);
+	unsigned int valid_seg_count = 0;
+	unsigned long long mtime = 0;
+	unsigned int i = 0;
+
+	if (segno == NULL_SEGNO)
+		return 0;
+
+	secno = GET_SEC_FROM_SEG(sbi, segno);
+	start = GET_SEG_FROM_SEC(sbi, secno);
+
+	if (!__is_large_section(sbi))
+		return get_seg_entry(sbi, start + i)->mtime;
+
+	for (i = 0; i < usable_segs_per_sec; i++) {
+		/* for large section, only check the mtime of valid segments */
+		spin_lock(&free_i->segmap_lock);
+		if (test_bit(start + i, free_i->free_segmap)) {
+			mtime += get_seg_entry(sbi, start + i)->mtime;
+			valid_seg_count++;
+		}
+		spin_unlock(&free_i->segmap_lock);
+	}
+
+	if (valid_seg_count == 0)
+		return 0;
+
+	return div_u64(mtime, valid_seg_count);
+}
+
 /*
  * Update min, max modified time for cost-benefit GC algorithm
  */
@@ -5402,13 +5437,9 @@ static void init_min_max_mtime(struct f2fs_sb_info *sbi)
 	sit_i->min_mtime = ULLONG_MAX;
 
 	for (segno = 0; segno < MAIN_SEGS(sbi); segno += SEGS_PER_SEC(sbi)) {
-		unsigned int i;
 		unsigned long long mtime = 0;
 
-		for (i = 0; i < SEGS_PER_SEC(sbi); i++)
-			mtime += get_seg_entry(sbi, segno + i)->mtime;
-
-		mtime = div_u64(mtime, SEGS_PER_SEC(sbi));
+		mtime = get_section_mtime(sbi, segno);
 
 		if (sit_i->min_mtime > mtime)
 			sit_i->min_mtime = mtime;
-- 
2.7.4