f2fs: introduce gc_urgent_mid mode

We need a mid level of gc urgent mode to do GC forcibly in a period
of given gc_urgent_sleep_time, but not like using greedy GC approach
and switching to SSR mode such as gc urgent high mode. This can be
used for more aggressive periodic storage clean up.

Signed-off-by: Daeho Jeong <[email protected]>
Signed-off-by: Jaegeuk Kim <[email protected]>
Change-Id: If8b5292fe850300eee400323d9ca2291a3496832

Documentation/ABI/testing/sysfs-fs-f2fs

@@ -228,9 +228,13 @@ Description:	Shows current reserved blocks in system, it may be temporarily
 What:		/sys/fs/f2fs/<disk>/gc_urgent
 Date:		August 2017
 Contact:	"Jaegeuk Kim" <[email protected]>
-Description:	Do background GC agressively when set. When gc_urgent = 1,
-		background thread starts to do GC by given gc_urgent_sleep_time
-		interval. It is set to 0 by default.
+Description:	Do background GC aggressively when set. Set to 0 by default.
+		gc urgent(1): does GC forcibly in a period of given
+		gc_urgent_sleep_time and ignores I/O idling check. uses greedy
+		GC approach and turns SSR mode on.
+		gc urgent mid(3): does GC forcibly in a period of given
+		gc_urgent_sleep_time and executes a mid level of I/O idling check.
+		uses cost benefit GC approach.
 
 What:		/sys/fs/f2fs/<disk>/gc_urgent_sleep_time
 Date:		August 2017
@@ -356,7 +360,7 @@ Date:		July 2021
 Contact:	"Daeho Jeong" <[email protected]>
 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), You can re-initialize this value to "0".
+		4: GC urgent, 5: GC urgent mid), You can re-initialize this value to "0".
 
 What:		/sys/fs/f2fs/<disk>/gc_segment_mode
 Date:		July 2021

fs/f2fs/debug.c

@@ -412,7 +412,8 @@ static int stat_show(struct seq_file *s, void *v)
 		seq_printf(s, "    - Idle CB : %d\n", si->sbi->gc_reclaimed_segs[GC_IDLE_CB]);
 		seq_printf(s, "    - Idle Greedy : %d\n", si->sbi->gc_reclaimed_segs[GC_IDLE_GREEDY]);
 		seq_printf(s, "    - Idle AT : %d\n", si->sbi->gc_reclaimed_segs[GC_IDLE_AT]);
-		seq_printf(s, "    - Urgent : %d\n", si->sbi->gc_reclaimed_segs[GC_URGENT]);
+		seq_printf(s, "    - Urgent High : %d\n", si->sbi->gc_reclaimed_segs[GC_URGENT]);
+		seq_printf(s, "    - Urgent Mid : %d\n", si->sbi->gc_reclaimed_segs[GC_URGENT_MID]);
 		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

@@ -1308,6 +1308,7 @@ enum {
 	GC_IDLE_GREEDY,
 	GC_IDLE_AT,
 	GC_URGENT,
+	GC_URGENT_MID,
 	MAX_GC_MODE,
 };
 
@@ -2421,6 +2422,9 @@ static inline bool is_idle(struct f2fs_sb_info *sbi, int type)
 	if (is_inflight_io(sbi, type))
 		return false;
 
+	if (sbi->gc_mode == GC_URGENT_MID)
+		return true;
+
 	return f2fs_time_over(sbi, type);
 }
 

fs/f2fs/gc.c

@@ -100,7 +100,8 @@ static int gc_thread_func(void *data)
 		 * invalidated soon after by user update or deletion.
 		 * So, I'd like to wait some time to collect dirty segments.
 		 */
-		if (sbi->gc_mode == GC_URGENT) {
+		if (sbi->gc_mode == GC_URGENT ||
+				sbi->gc_mode == GC_URGENT_MID) {
 			wait_ms = gc_th->urgent_sleep_time;
 			down_write(&sbi->gc_lock);
 			goto do_gc;

fs/f2fs/sysfs.c

@@ -406,14 +406,21 @@ static ssize_t __sbi_store(struct f2fs_attr *a,
 		return -EINVAL;
 
 	if (!strcmp(a->attr.name, "gc_urgent")) {
-		if (t >= 1) {
+		if (t == 1) {
 			sbi->gc_mode = GC_URGENT;
 			if (sbi->gc_thread) {
 				sbi->gc_thread->gc_wake = 1;
 				wake_up_interruptible_all(
 					&sbi->gc_thread->gc_wait_queue_head);
 				wake_up_discard_thread(sbi, true);
 			}
+		} else if (t == 3) {
+			sbi->gc_mode = GC_URGENT_MID;
+			if (sbi->gc_thread) {
+				sbi->gc_thread->gc_wake = 1;
+				wake_up_interruptible_all(
+					&sbi->gc_thread->gc_wait_queue_head);
+			}
 		} else {
 			sbi->gc_mode = GC_NORMAL;
 		}