[ Upstream commit e7547daccd6a37522f0af74ec4b5a3036f3dd328 ] This patch prepares extent_cache to be ready for addition. Reviewed-by: Chao Yu <chao@kernel.org> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org> Stable-dep-of: 043d2d00b443 ("f2fs: factor out victim_entry usage from general rb_tree use") Signed-off-by: Sasha Levin <sashal@kernel.org>