On Sun, Dec 29, 2024 at 10:00 AM kernel test robot <lkp@xxxxxxxxx> wrote: > > tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master > head: 059dd502b263d8a4e2a84809cf1068d6a3905e6f > commit: 28e98022b31efdb8f1ba310d938cd9b97ededfe4 mm/list_lru: simplify reparenting and initial allocation > date: 7 weeks ago > config: i386-randconfig-054-20241229 (https://download.01.org/0day-ci/archive/20241229/202412290924.UTP7GH2Z-lkp@xxxxxxxxx/config) > compiler: gcc-12 (Debian 12.2.0-14) 12.2.0 > > If you fix the issue in a separate patch/commit (i.e. not just a new version of > the same patch/commit), kindly add following tags > | Reported-by: kernel test robot <lkp@xxxxxxxxx> > | Closes: https://lore.kernel.org/oe-kbuild-all/202412290924.UTP7GH2Z-lkp@xxxxxxxxx/ > > cocci warnings: (new ones prefixed by >>) > >> mm/list_lru.c:514:3-8: WARNING: NULL check before some freeing functions is not needed. > > vim +514 mm/list_lru.c > > 470 > 471 int memcg_list_lru_alloc(struct mem_cgroup *memcg, struct list_lru *lru, > 472 gfp_t gfp) > 473 { > 474 unsigned long flags; > 475 struct list_lru_memcg *mlru; > 476 struct mem_cgroup *pos, *parent; > 477 XA_STATE(xas, &lru->xa, 0); > 478 > 479 if (!list_lru_memcg_aware(lru) || memcg_list_lru_allocated(memcg, lru)) > 480 return 0; > 481 > 482 gfp &= GFP_RECLAIM_MASK; > 483 /* > 484 * Because the list_lru can be reparented to the parent cgroup's > 485 * list_lru, we should make sure that this cgroup and all its > 486 * ancestors have allocated list_lru_memcg. > 487 */ > 488 do { > 489 /* > 490 * Keep finding the farest parent that wasn't populated > 491 * until found memcg itself. > 492 */ > 493 pos = memcg; > 494 parent = parent_mem_cgroup(pos); > 495 while (!memcg_list_lru_allocated(parent, lru)) { > 496 pos = parent; > 497 parent = parent_mem_cgroup(pos); > 498 } > 499 > 500 mlru = memcg_init_list_lru_one(gfp); > 501 if (!mlru) > 502 return -ENOMEM; > 503 xas_set(&xas, pos->kmemcg_id); > 504 do { > 505 xas_lock_irqsave(&xas, flags); > 506 if (!xas_load(&xas) && !css_is_dying(&pos->css)) { > 507 xas_store(&xas, mlru); > 508 if (!xas_error(&xas)) > 509 mlru = NULL; > 510 } > 511 xas_unlock_irqrestore(&xas, flags); > 512 } while (xas_nomem(&xas, gfp)); > 513 if (mlru) > > 514 kfree(mlru); Hmm, does it need a fix? mlru here is most likely always NULL, so in most cases this should save a function call, a really micro optimization. Perhaps a "if (unlikely(mlru))" is better, and silence the bot? > 515 } while (pos != memcg && !css_is_dying(&pos->css)); > 516 > 517 return xas_error(&xas); > 518 } > 519 #else > 520 static inline void memcg_init_list_lru(struct list_lru *lru, bool memcg_aware) > 521 { > 522 } > 523 > > -- > 0-DAY CI Kernel Test Service > https://github.com/intel/lkp-tests/wiki >
