f2fs: add GC_URGENT_LOW mode in gc_urgent

Added a new gc_urgent mode, GC_URGENT_LOW, in which mode
F2FS will lower the bar of checking idle in order to
process outstanding discard commands and GC a little bit
aggressively.
Signed-off-by: Daeho Jeong <daehojeong@google.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

Documentation/ABI/testing/sysfs-fs-f2fs

@@ -229,7 +229,9 @@ Date:		August 2017
 Contact:	"Jaegeuk Kim" <jaegeuk@kernel.org>
 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.
+		interval. When gc_urgent = 2, F2FS will lower the bar of
+		checking idle in order to process outstanding discard commands
+		and GC a little bit aggressively. It is set to 0 by default.
 
 What:		/sys/fs/f2fs/<disk>/gc_urgent_sleep_time
 Date:		August 2017

fs/f2fs/f2fs.h

@@ -1268,7 +1268,8 @@ enum {
 	GC_NORMAL,
 	GC_IDLE_CB,
 	GC_IDLE_GREEDY,
-	GC_URGENT,
+	GC_URGENT_HIGH,
+	GC_URGENT_LOW,
 };
 
 enum {
@@ -1525,6 +1526,7 @@ struct f2fs_sb_info {
 	unsigned int cur_victim_sec;		/* current victim section num */
 	unsigned int gc_mode;			/* current GC state */
 	unsigned int next_victim_seg[2];	/* next segment in victim section */
+
 	/* for skip statistic */
 	unsigned int atomic_files;              /* # of opened atomic file */
 	unsigned long long skipped_atomic_files[2];	/* FG_GC and BG_GC */
@@ -2465,7 +2467,7 @@ static inline void *f2fs_kmem_cache_alloc(struct kmem_cache *cachep,
 
 static inline bool is_idle(struct f2fs_sb_info *sbi, int type)
 {
-	if (sbi->gc_mode == GC_URGENT)
+	if (sbi->gc_mode == GC_URGENT_HIGH)
 		return true;
 
 	if (get_pages(sbi, F2FS_RD_DATA) || get_pages(sbi, F2FS_RD_NODE) ||
@@ -2483,6 +2485,10 @@ static inline bool is_idle(struct f2fs_sb_info *sbi, int type)
 			atomic_read(&SM_I(sbi)->fcc_info->queued_flush))
 		return false;
 
+	if (sbi->gc_mode == GC_URGENT_LOW &&
+			(type == DISCARD_TIME || type == GC_TIME))
+		return true;
+
 	return f2fs_time_over(sbi, type);
 }
 

fs/f2fs/gc.c

@@ -82,7 +82,7 @@ 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_HIGH) {
 			wait_ms = gc_th->urgent_sleep_time;
 			down_write(&sbi->gc_lock);
 			goto do_gc;
@@ -176,7 +176,7 @@ static int select_gc_type(struct f2fs_sb_info *sbi, int gc_type)
 		gc_mode = GC_CB;
 		break;
 	case GC_IDLE_GREEDY:
-	case GC_URGENT:
+	case GC_URGENT_HIGH:
 		gc_mode = GC_GREEDY;
 		break;
 	}
@@ -211,7 +211,7 @@ static void select_policy(struct f2fs_sb_info *sbi, int gc_type,
 	 * foreground GC and urgent GC cases.
 	 */
 	if (gc_type != FG_GC &&
-			(sbi->gc_mode != GC_URGENT) &&
+			(sbi->gc_mode != GC_URGENT_HIGH) &&
 			p->max_search > sbi->max_victim_search)
 		p->max_search = sbi->max_victim_search;
 

fs/f2fs/segment.c

@@ -174,7 +174,7 @@ bool f2fs_need_SSR(struct f2fs_sb_info *sbi)
 
 	if (f2fs_lfs_mode(sbi))
 		return false;
-	if (sbi->gc_mode == GC_URGENT)
+	if (sbi->gc_mode == GC_URGENT_HIGH)
 		return true;
 	if (unlikely(is_sbi_flag_set(sbi, SBI_CP_DISABLED)))
 		return true;
@@ -1759,7 +1759,7 @@ static int issue_discard_thread(void *data)
 			continue;
 		}
 
-		if (sbi->gc_mode == GC_URGENT)
+		if (sbi->gc_mode == GC_URGENT_HIGH)
 			__init_discard_policy(sbi, &dpolicy, DPOLICY_FORCE, 1);
 
 		sb_start_intwrite(sbi->sb);

fs/f2fs/sysfs.c

@@ -350,16 +350,20 @@ static ssize_t __sbi_store(struct f2fs_attr *a,
 		return -EINVAL;
 
 	if (!strcmp(a->attr.name, "gc_urgent")) {
-		if (t >= 1) {
-			sbi->gc_mode = GC_URGENT;
+		if (t == 0) {
+			sbi->gc_mode = GC_NORMAL;
+		} else if (t == 1) {
+			sbi->gc_mode = GC_URGENT_HIGH;
 			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 == 2) {
+			sbi->gc_mode = GC_URGENT_LOW;
 		} else {
-			sbi->gc_mode = GC_NORMAL;
+			return -EINVAL;
 		}
 		return count;
 	}