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Mon, 09 Feb 2026 22:31:49 -0800 (PST) Received: from localhost ([196.207.164.177]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-48320961505sm215017735e9.4.2026.02.09.22.31.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 09 Feb 2026 22:31:49 -0800 (PST) Date: Tue, 10 Feb 2026 09:31:46 +0300 From: Dan Carpenter To: oe-kbuild@lists.linux.dev, Nhat Pham , linux-mm@kvack.org Cc: lkp@intel.com, oe-kbuild-all@lists.linux.dev, akpm@linux-foundation.org, hannes@cmpxchg.org, hughd@google.com, yosry.ahmed@linux.dev, mhocko@kernel.org, roman.gushchin@linux.dev, shakeel.butt@linux.dev, muchun.song@linux.dev, len.brown@intel.com, chengming.zhou@linux.dev, kasong@tencent.com, chrisl@kernel.org, huang.ying.caritas@gmail.com, ryan.roberts@arm.com, shikemeng@huaweicloud.com, viro@zeniv.linux.org.uk, baohua@kernel.org, bhe@redhat.com, osalvador@suse.de, lorenzo.stoakes@oracle.com, christophe.leroy@csgroup.eu, pavel@kernel.org, kernel-team@meta.com, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-pm@vger.kernel.org, peterx@redhat.com, riel@surriel.com, joshua.hahnjy@gmail.com Subject: Re: [PATCH v3 14/20] mm: swap: decouple virtual swap slot from backing store Message-ID: <202602092300.lZO4Ee4N-lkp@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260208215839.87595-15-nphamcs@gmail.com> X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 941771C000A X-Stat-Signature: beujyomj6pg4xoxoautsmrnrengimwwn X-Rspam-User: X-HE-Tag: 1770705111-858303 X-HE-Meta: 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 lfZowjOv 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Nhat, kernel test robot noticed the following build warnings: url: https://github.com/intel-lab-lkp/linux/commits/Nhat-Pham/mm-swap-decouple-swap-cache-from-physical-swap-infrastructure/20260209-120606 base: 05f7e89ab9731565d8a62e3b5d1ec206485eeb0b patch link: https://lore.kernel.org/r/20260208215839.87595-15-nphamcs%40gmail.com patch subject: [PATCH v3 14/20] mm: swap: decouple virtual swap slot from backing store config: powerpc-randconfig-r073-20260209 (https://download.01.org/0day-ci/archive/20260209/202602092300.lZO4Ee4N-lkp@intel.com/config) compiler: powerpc-linux-gcc (GCC) 15.2.0 smatch version: v0.5.0-8994-gd50c5a4c 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 | Reported-by: Dan Carpenter | Closes: https://lore.kernel.org/r/202602092300.lZO4Ee4N-lkp@intel.com/ smatch warnings: mm/vswap.c:733 vswap_alloc_swap_slot() warn: variable dereferenced before check 'folio' (see line 701) vim +/folio +733 mm/vswap.c 19a5fe94e9aae4 Nhat Pham 2026-02-08 694 bool vswap_alloc_swap_slot(struct folio *folio) 19a5fe94e9aae4 Nhat Pham 2026-02-08 695 { 19a5fe94e9aae4 Nhat Pham 2026-02-08 696 int i, nr = folio_nr_pages(folio); 19a5fe94e9aae4 Nhat Pham 2026-02-08 697 struct vswap_cluster *cluster = NULL; 19a5fe94e9aae4 Nhat Pham 2026-02-08 698 struct swap_info_struct *si; 19a5fe94e9aae4 Nhat Pham 2026-02-08 699 struct swap_cluster_info *ci; 19a5fe94e9aae4 Nhat Pham 2026-02-08 700 swp_slot_t slot = { .val = 0 }; 19a5fe94e9aae4 Nhat Pham 2026-02-08 @701 swp_entry_t entry = folio->swap; folio dereference here 19a5fe94e9aae4 Nhat Pham 2026-02-08 702 struct swp_desc *desc; 19a5fe94e9aae4 Nhat Pham 2026-02-08 703 bool fallback = false; 19a5fe94e9aae4 Nhat Pham 2026-02-08 704 19a5fe94e9aae4 Nhat Pham 2026-02-08 705 /* 19a5fe94e9aae4 Nhat Pham 2026-02-08 706 * We might have already allocated a backing physical swap slot in past 19a5fe94e9aae4 Nhat Pham 2026-02-08 707 * attempts (for instance, when we disable zswap). If the entire range is 19a5fe94e9aae4 Nhat Pham 2026-02-08 708 * already swapfile-backed we can skip swapfile case. 19a5fe94e9aae4 Nhat Pham 2026-02-08 709 */ 19a5fe94e9aae4 Nhat Pham 2026-02-08 710 if (vswap_swapfile_backed(entry, nr)) 19a5fe94e9aae4 Nhat Pham 2026-02-08 711 return true; 19a5fe94e9aae4 Nhat Pham 2026-02-08 712 19a5fe94e9aae4 Nhat Pham 2026-02-08 713 if (swap_slot_alloc(&slot, folio_order(folio))) and here 19a5fe94e9aae4 Nhat Pham 2026-02-08 714 return false; 19a5fe94e9aae4 Nhat Pham 2026-02-08 715 19a5fe94e9aae4 Nhat Pham 2026-02-08 716 if (!slot.val) 19a5fe94e9aae4 Nhat Pham 2026-02-08 717 return false; 19a5fe94e9aae4 Nhat Pham 2026-02-08 718 7f88e3ea20f231 Nhat Pham 2026-02-08 719 /* establish the vrtual <-> physical swap slots linkages. */ 7f88e3ea20f231 Nhat Pham 2026-02-08 720 si = __swap_slot_to_info(slot); 7f88e3ea20f231 Nhat Pham 2026-02-08 721 ci = swap_cluster_lock(si, swp_slot_offset(slot)); 7f88e3ea20f231 Nhat Pham 2026-02-08 722 vswap_rmap_set(ci, slot, entry.val, nr); 7f88e3ea20f231 Nhat Pham 2026-02-08 723 swap_cluster_unlock(ci); 7f88e3ea20f231 Nhat Pham 2026-02-08 724 7f88e3ea20f231 Nhat Pham 2026-02-08 725 rcu_read_lock(); 7f88e3ea20f231 Nhat Pham 2026-02-08 726 for (i = 0; i < nr; i++) { 7f88e3ea20f231 Nhat Pham 2026-02-08 727 desc = vswap_iter(&cluster, entry.val + i); 7f88e3ea20f231 Nhat Pham 2026-02-08 728 VM_WARN_ON(!desc); 7f88e3ea20f231 Nhat Pham 2026-02-08 729 19a5fe94e9aae4 Nhat Pham 2026-02-08 730 if (desc->type == VSWAP_FOLIO) { 19a5fe94e9aae4 Nhat Pham 2026-02-08 731 /* case 1: fallback from zswap store failure */ 19a5fe94e9aae4 Nhat Pham 2026-02-08 732 fallback = true; 19a5fe94e9aae4 Nhat Pham 2026-02-08 @733 if (!folio) So it can't be NULL here. 19a5fe94e9aae4 Nhat Pham 2026-02-08 734 folio = desc->swap_cache; So we'll never do this assignment and it will never become NULL. 19a5fe94e9aae4 Nhat Pham 2026-02-08 735 else 19a5fe94e9aae4 Nhat Pham 2026-02-08 736 VM_WARN_ON(folio != desc->swap_cache); 19a5fe94e9aae4 Nhat Pham 2026-02-08 737 } else { 19a5fe94e9aae4 Nhat Pham 2026-02-08 738 /* 19a5fe94e9aae4 Nhat Pham 2026-02-08 739 * Case 2: zswap writeback. 19a5fe94e9aae4 Nhat Pham 2026-02-08 740 * 19a5fe94e9aae4 Nhat Pham 2026-02-08 741 * No need to free zswap entry here - it will be freed once zswap 19a5fe94e9aae4 Nhat Pham 2026-02-08 742 * writeback suceeds. 19a5fe94e9aae4 Nhat Pham 2026-02-08 743 */ 19a5fe94e9aae4 Nhat Pham 2026-02-08 744 VM_WARN_ON(desc->type != VSWAP_ZSWAP); 19a5fe94e9aae4 Nhat Pham 2026-02-08 745 VM_WARN_ON(fallback); 19a5fe94e9aae4 Nhat Pham 2026-02-08 746 } 19a5fe94e9aae4 Nhat Pham 2026-02-08 747 desc->type = VSWAP_SWAPFILE; 7f88e3ea20f231 Nhat Pham 2026-02-08 748 desc->slot.val = slot.val + i; 7f88e3ea20f231 Nhat Pham 2026-02-08 749 } 7f88e3ea20f231 Nhat Pham 2026-02-08 750 spin_unlock(&cluster->lock); 7f88e3ea20f231 Nhat Pham 2026-02-08 751 rcu_read_unlock(); 19a5fe94e9aae4 Nhat Pham 2026-02-08 752 return true; 7f88e3ea20f231 Nhat Pham 2026-02-08 753 } -- 0-DAY CI Kernel Test Service https://github.com/intel/lkp-tests/wiki