f2fs: prevent an f2fs_gc loop during disable_checkpoint

Don't get stuck in the f2fs_gc loop while disabling checkpoint. Instead, we have
a time-based management.
Reviewed-by: Chao Yu <chao@kernel.org>
Reviewed-by: Daeho Jeong <daehojeong@google.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/super.c

@@ -2191,6 +2191,7 @@ static int f2fs_disable_checkpoint(struct f2fs_sb_info *sbi)
 			.init_gc_type = FG_GC,
 			.should_migrate_blocks = false,
 			.err_gc_skipped = true,
+			.no_bg_gc = true,
 			.nr_free_secs = 1 };
 
 		f2fs_down_write(&sbi->gc_lock);