f2fs: use aggressive GC policy during f2fs_disable_checkpoint()

Let's enable GC_URGENT_HIGH mode during f2fs_disable_checkpoint(),
so that we can use SSR allocator for GCed data/node persistence,
it can improve the performance due to it avoiding migration of
data/node locates in selected target segment of SSR allocator.

Signed-off-by: Chao Yu <chao.yu@oppo.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/super.c

@@ -2080,6 +2080,7 @@ static int f2fs_disable_checkpoint(struct f2fs_sb_info *sbi)
 {
 	unsigned int s_flags = sbi->sb->s_flags;
 	struct cp_control cpc;
+	unsigned int gc_mode;
 	int err = 0;
 	int ret;
 	block_t unusable;
@@ -2092,6 +2093,9 @@ static int f2fs_disable_checkpoint(struct f2fs_sb_info *sbi)
 
 	f2fs_update_time(sbi, DISABLE_TIME);
 
+	gc_mode = sbi->gc_mode;
+	sbi->gc_mode = GC_URGENT_HIGH;
+
 	while (!f2fs_time_over(sbi, DISABLE_TIME)) {
 		f2fs_down_write(&sbi->gc_lock);
 		err = f2fs_gc(sbi, true, false, false, NULL_SEGNO);
@@ -2129,6 +2133,7 @@ static int f2fs_disable_checkpoint(struct f2fs_sb_info *sbi)
 out_unlock:
 	f2fs_up_write(&sbi->gc_lock);
 restore_flag:
+	sbi->gc_mode = gc_mode;
 	sbi->sb->s_flags = s_flags;	/* Restore SB_RDONLY status */
 	return err;
 }