f2fs: add sysfs nodes to get GC info for each GC mode

Added gc_reclaimed_segments and gc_segment_mode sysfs nodes.
1) "gc_reclaimed_segments" shows how many segments have been
reclaimed by GC during a specific GC mode.
2) "gc_segment_mode" is used to control for which gc mode
the "gc_reclaimed_segments" node shows.

Signed-off-by: Daeho Jeong <daehojeong@google.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

Documentation/ABI/testing/sysfs-fs-f2fs

@@ -493,3 +493,17 @@ Contact:	"Chao Yu" <yuchao0@huawei.com>
 Description:	When ATGC is on, it controls age threshold to bypass GCing young
 		candidates whose age is not beyond the threshold, by default it was
 		initialized as 604800 seconds (equals to 7 days).
+
+What:		/sys/fs/f2fs/<disk>/gc_reclaimed_segments
+Date:		July 2021
+Contact:	"Daeho Jeong" <daehojeong@google.com>
+Description:	Show how many segments have been reclaimed by GC during a specific
+		GC mode (0: GC normal, 1: GC idle CB, 2: GC idle greedy,
+		3: GC idle AT, 4: GC urgent high, 5: GC urgent low)
+		You can re-initialize this value to "0".
+
+What:		/sys/fs/f2fs/<disk>/gc_segment_mode
+Date:		July 2021
+Contact:	"Daeho Jeong" <daehojeong@google.com>
+Description:	You can control for which gc mode the "gc_reclaimed_segments" node shows.
+		Refer to the description of the modes in "gc_reclaimed_segments".

fs/f2fs/debug.c

@@ -450,6 +450,15 @@ static int stat_show(struct seq_file *s, void *v)
 				si->data_segs, si->bg_data_segs);
 		seq_printf(s, "  - node segments : %d (%d)\n",
 				si->node_segs, si->bg_node_segs);
+		seq_printf(s, "  - Reclaimed segs : Normal (%d), Idle CB (%d), "
+				"Idle Greedy (%d), Idle AT (%d), "
+				"Urgent High (%d), Urgent Low (%d)\n",
+				si->sbi->gc_reclaimed_segs[GC_NORMAL],
+				si->sbi->gc_reclaimed_segs[GC_IDLE_CB],
+				si->sbi->gc_reclaimed_segs[GC_IDLE_GREEDY],
+				si->sbi->gc_reclaimed_segs[GC_IDLE_AT],
+				si->sbi->gc_reclaimed_segs[GC_URGENT_HIGH],
+				si->sbi->gc_reclaimed_segs[GC_URGENT_LOW]);
 		seq_printf(s, "Try to move %d blocks (BG: %d)\n", si->tot_blks,
 				si->bg_data_blks + si->bg_node_blks);
 		seq_printf(s, "  - data blocks : %d (%d)\n", si->data_blks,

fs/f2fs/f2fs.h

@@ -1253,6 +1253,7 @@ enum {
 	GC_IDLE_AT,
 	GC_URGENT_HIGH,
 	GC_URGENT_LOW,
+	MAX_GC_MODE,
 };
 
 enum {
@@ -1733,6 +1734,10 @@ struct f2fs_sb_info {
 	struct kmem_cache *inline_xattr_slab;	/* inline xattr entry */
 	unsigned int inline_xattr_slab_size;	/* default inline xattr slab size */
 
+	/* For reclaimed segs statistics per each GC mode */
+	unsigned int gc_segment_mode;		/* GC state for reclaimed segments */
+	unsigned int gc_reclaimed_segs[MAX_GC_MODE];	/* Reclaimed segs for each mode */
+
 #ifdef CONFIG_F2FS_FS_COMPRESSION
 	struct kmem_cache *page_array_slab;	/* page array entry */
 	unsigned int page_array_slab_size;	/* default page array slab size */

fs/f2fs/gc.c

@@ -1646,6 +1646,7 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
 							force_migrate);
 
 		stat_inc_seg_count(sbi, type, gc_type);
+		sbi->gc_reclaimed_segs[sbi->gc_mode]++;
 		migrated++;
 
 freed:

fs/f2fs/sysfs.c

@@ -307,6 +307,14 @@ static ssize_t f2fs_sbi_show(struct f2fs_attr *a,
 		return sysfs_emit(buf, "%u\n", sbi->compr_new_inode);
 #endif
 
+	if (!strcmp(a->attr.name, "gc_segment_mode"))
+		return sysfs_emit(buf, "%u\n", sbi->gc_segment_mode);
+
+	if (!strcmp(a->attr.name, "gc_reclaimed_segments")) {
+		return sysfs_emit(buf, "%u\n",
+			sbi->gc_reclaimed_segs[sbi->gc_segment_mode]);
+	}
+
 	ui = (unsigned int *)(ptr + a->offset);
 
 	return sprintf(buf, "%u\n", *ui);
@@ -515,6 +523,21 @@ out:
 		return count;
 	}
 
+	if (!strcmp(a->attr.name, "gc_segment_mode")) {
+		if (t < MAX_GC_MODE)
+			sbi->gc_segment_mode = t;
+		else
+			return -EINVAL;
+		return count;
+	}
+
+	if (!strcmp(a->attr.name, "gc_reclaimed_segments")) {
+		if (t != 0)
+			return -EINVAL;
+		sbi->gc_reclaimed_segs[sbi->gc_segment_mode] = 0;
+		return count;
+	}
+
 	*ui = (unsigned int)t;
 
 	return count;
@@ -740,6 +763,9 @@ F2FS_RW_ATTR(ATGC_INFO, atgc_management, atgc_candidate_count, max_candidate_cou
 F2FS_RW_ATTR(ATGC_INFO, atgc_management, atgc_age_weight, age_weight);
 F2FS_RW_ATTR(ATGC_INFO, atgc_management, atgc_age_threshold, age_threshold);
 
+F2FS_RW_ATTR(F2FS_SBI, f2fs_sb_info, gc_segment_mode, gc_segment_mode);
+F2FS_RW_ATTR(F2FS_SBI, f2fs_sb_info, gc_reclaimed_segments, gc_reclaimed_segs);
+
 #define ATTR_LIST(name) (&f2fs_attr_##name.attr)
 static struct attribute *f2fs_attrs[] = {
 	ATTR_LIST(gc_urgent_sleep_time),
@@ -812,6 +838,8 @@ static struct attribute *f2fs_attrs[] = {
 	ATTR_LIST(atgc_candidate_count),
 	ATTR_LIST(atgc_age_weight),
 	ATTR_LIST(atgc_age_threshold),
+	ATTR_LIST(gc_segment_mode),
+	ATTR_LIST(gc_reclaimed_segments),
 	NULL,
 };
 ATTRIBUTE_GROUPS(f2fs);