* mm/list_lru.c:514:3-8: WARNING: NULL check before some freeing functions is not needed.
@ 2024-12-29 1:59 kernel test robot
2024-12-29 9:39 ` Kairui Song
0 siblings, 1 reply; 2+ messages in thread
From: kernel test robot @ 2024-12-29 1:59 UTC (permalink / raw)
To: Kairui Song
Cc: oe-kbuild-all, linux-kernel, Andrew Morton, Linux Memory Management List
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@intel.com/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@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202412290924.UTP7GH2Z-lkp@intel.com/
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);
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
^ permalink raw reply [flat|nested] 2+ messages in thread* Re: mm/list_lru.c:514:3-8: WARNING: NULL check before some freeing functions is not needed.
2024-12-29 1:59 mm/list_lru.c:514:3-8: WARNING: NULL check before some freeing functions is not needed kernel test robot
@ 2024-12-29 9:39 ` Kairui Song
0 siblings, 0 replies; 2+ messages in thread
From: Kairui Song @ 2024-12-29 9:39 UTC (permalink / raw)
To: kernel test robot
Cc: oe-kbuild-all, linux-kernel, Andrew Morton, Linux Memory Management List
On Sun, Dec 29, 2024 at 10:00 AM kernel test robot <lkp@intel.com> 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@intel.com/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@intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202412290924.UTP7GH2Z-lkp@intel.com/
>
> 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
>
^ permalink raw reply [flat|nested] 2+ messages in thread
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