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Message-ID: <202502250720.9ueIb7Xh-lkp@intel.com>
Date: Tue, 25 Feb 2025 07:13:35 +0800
From: kernel test robot <lkp@...el.com>
To: Kairui Song <kasong@...cent.com>
Cc: oe-kbuild-all@...ts.linux.dev, linux-kernel@...r.kernel.org,
Andrew Morton <akpm@...ux-foundation.org>,
Linux Memory Management List <linux-mm@...ck.org>
Subject: mm/list_lru.c:552:3-8: WARNING: NULL check before some freeing
functions is not needed.
Hi Kairui,
First bad commit (maybe != root cause):
tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head: d082ecbc71e9e0bf49883ee4afd435a77a5101b6
commit: fb56fdf8b9a2f7397f8a83dce50189f3f0cf71af mm/list_lru: split the lock to per-cgroup scope
date: 4 months ago
config: mips-randconfig-r052-20250224 (https://download.01.org/0day-ci/archive/20250225/202502250720.9ueIb7Xh-lkp@intel.com/config)
compiler: clang version 19.1.3 (https://github.com/llvm/llvm-project ab51eccf88f5321e7c60591c5546b254b6afab99)
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@...el.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202502250720.9ueIb7Xh-lkp@intel.com/
cocci warnings: (new ones prefixed by >>)
>> mm/list_lru.c:552:3-8: WARNING: NULL check before some freeing functions is not needed.
vim +552 mm/list_lru.c
88f2ef73fd6649 Muchun Song 2022-03-22 508
88f2ef73fd6649 Muchun Song 2022-03-22 509 int memcg_list_lru_alloc(struct mem_cgroup *memcg, struct list_lru *lru,
88f2ef73fd6649 Muchun Song 2022-03-22 510 gfp_t gfp)
88f2ef73fd6649 Muchun Song 2022-03-22 511 {
88f2ef73fd6649 Muchun Song 2022-03-22 512 unsigned long flags;
d70110704d2d52 Muchun Song 2022-03-22 513 struct list_lru_memcg *mlru;
28e98022b31efd Kairui Song 2024-11-05 514 struct mem_cgroup *pos, *parent;
bbca91cca9a902 Muchun Song 2022-03-22 515 XA_STATE(xas, &lru->xa, 0);
88f2ef73fd6649 Muchun Song 2022-03-22 516
88f2ef73fd6649 Muchun Song 2022-03-22 517 if (!list_lru_memcg_aware(lru) || memcg_list_lru_allocated(memcg, lru))
88f2ef73fd6649 Muchun Song 2022-03-22 518 return 0;
88f2ef73fd6649 Muchun Song 2022-03-22 519
88f2ef73fd6649 Muchun Song 2022-03-22 520 gfp &= GFP_RECLAIM_MASK;
88f2ef73fd6649 Muchun Song 2022-03-22 521 /*
88f2ef73fd6649 Muchun Song 2022-03-22 522 * Because the list_lru can be reparented to the parent cgroup's
88f2ef73fd6649 Muchun Song 2022-03-22 523 * list_lru, we should make sure that this cgroup and all its
d70110704d2d52 Muchun Song 2022-03-22 524 * ancestors have allocated list_lru_memcg.
88f2ef73fd6649 Muchun Song 2022-03-22 525 */
28e98022b31efd Kairui Song 2024-11-05 526 do {
28e98022b31efd Kairui Song 2024-11-05 527 /*
28e98022b31efd Kairui Song 2024-11-05 528 * Keep finding the farest parent that wasn't populated
28e98022b31efd Kairui Song 2024-11-05 529 * until found memcg itself.
28e98022b31efd Kairui Song 2024-11-05 530 */
28e98022b31efd Kairui Song 2024-11-05 531 pos = memcg;
28e98022b31efd Kairui Song 2024-11-05 532 parent = parent_mem_cgroup(pos);
28e98022b31efd Kairui Song 2024-11-05 533 while (!memcg_list_lru_allocated(parent, lru)) {
28e98022b31efd Kairui Song 2024-11-05 534 pos = parent;
28e98022b31efd Kairui Song 2024-11-05 535 parent = parent_mem_cgroup(pos);
88f2ef73fd6649 Muchun Song 2022-03-22 536 }
88f2ef73fd6649 Muchun Song 2022-03-22 537
fb56fdf8b9a2f7 Kairui Song 2024-11-05 538 mlru = memcg_init_list_lru_one(lru, gfp);
28e98022b31efd Kairui Song 2024-11-05 539 if (!mlru)
28e98022b31efd Kairui Song 2024-11-05 540 return -ENOMEM;
28e98022b31efd Kairui Song 2024-11-05 541 xas_set(&xas, pos->kmemcg_id);
28e98022b31efd Kairui Song 2024-11-05 542 do {
bbca91cca9a902 Muchun Song 2022-03-22 543 xas_lock_irqsave(&xas, flags);
28e98022b31efd Kairui Song 2024-11-05 544 if (!xas_load(&xas) && !css_is_dying(&pos->css)) {
bbca91cca9a902 Muchun Song 2022-03-22 545 xas_store(&xas, mlru);
28e98022b31efd Kairui Song 2024-11-05 546 if (!xas_error(&xas))
28e98022b31efd Kairui Song 2024-11-05 547 mlru = NULL;
bbca91cca9a902 Muchun Song 2022-03-22 548 }
bbca91cca9a902 Muchun Song 2022-03-22 549 xas_unlock_irqrestore(&xas, flags);
28e98022b31efd Kairui Song 2024-11-05 550 } while (xas_nomem(&xas, gfp));
28e98022b31efd Kairui Song 2024-11-05 551 if (mlru)
28e98022b31efd Kairui Song 2024-11-05 @552 kfree(mlru);
28e98022b31efd Kairui Song 2024-11-05 553 } while (pos != memcg && !css_is_dying(&pos->css));
88f2ef73fd6649 Muchun Song 2022-03-22 554
bbca91cca9a902 Muchun Song 2022-03-22 555 return xas_error(&xas);
88f2ef73fd6649 Muchun Song 2022-03-22 556 }
60d3fd32a7a9da Vladimir Davydov 2015-02-12 557 #else
bbca91cca9a902 Muchun Song 2022-03-22 558 static inline void memcg_init_list_lru(struct list_lru *lru, bool memcg_aware)
60d3fd32a7a9da Vladimir Davydov 2015-02-12 559 {
60d3fd32a7a9da Vladimir Davydov 2015-02-12 560 }
60d3fd32a7a9da Vladimir Davydov 2015-02-12 561
:::::: The code at line 552 was first introduced by commit
:::::: 28e98022b31efdb8f1ba310d938cd9b97ededfe4 mm/list_lru: simplify reparenting and initial allocation
:::::: TO: Kairui Song <kasong@...cent.com>
:::::: CC: Andrew Morton <akpm@...ux-foundation.org>
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
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