From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f65.google.com (mail-wm1-f65.google.com [209.85.128.65]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6E9B024E4C4 for ; Tue, 10 Feb 2026 06:31:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.65 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770705112; cv=none; b=JOTsnJDH+tNfcqNp22sWGlaRPJuavF1zg7MgFWvDnTiVq2arm7a5QR+ljWK06I/H0OfobEzeNaLAjhZb6gPZTjXCfiDLoiSXx0vPfeLbx9bir9ANNHlsTIitbDzN+PHQVN9EHXoxIopYk41TaeDvEQVJZCjwUf0PVkyilcM/2G0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770705112; c=relaxed/simple; bh=+dY5A7nwRVBRBd7BJ1hDL2J+oBIHOmLAIhWPxMtTN4o=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type: Content-Disposition:In-Reply-To; b=kpZZ6AnYfoI2oPftvffkj/nGULtgIXwW4IK5lmhqL8uzoxmr7wEU+b3V9zqHsOA7ka5q/BxAD32410q/KCn+Tbw3Nt1F0LaNjkc4M+uY60JzbWVAcpYBydU7G1VCQVJFoCmEuE/bnEpQVX6nOKSYcNEJsFLhLJvGTCVY+2bJKPw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linaro.org; spf=pass smtp.mailfrom=linaro.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b=U7N2G8Uw; arc=none smtp.client-ip=209.85.128.65 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linaro.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linaro.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="U7N2G8Uw" Received: by mail-wm1-f65.google.com with SMTP id 5b1f17b1804b1-47ee0291921so35829035e9.3 for ; Mon, 09 Feb 2026 22:31:51 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; t=1770705110; x=1771309910; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:message-id:subject:cc :to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=PuIvHjahYrqUwfgodntxdfFSIIlE9ggIgaeNW8+YxZc=; b=U7N2G8UwMwtnwPmbDdvrXVal6o2WZS+jJKtOpyf6nSz7PeirStusIC/NsW3quXzBoc vij7WcD9hovtkXX2KNlfJmPgdHRmpXQR/4nyu3+OuYaLulj1pWdvNLSgQCkqTUdxhUqx yrBDt93abC13ieuEMefe+LGue4Xw94xxdtyG8cCS3lZhMtxg3hOGFG4z+1W2JolhGdT/ F5w4aP5VbYQwhDEnXFUwLGYxCjqelQMMqp6+xBfdOaoeZfiu+r7++Q+GQxNoCrx1alzI UI7RYfl1nOWafRxgjidgCFF0FUfb2ng69fvy16uGN1QBEUlCHwL0cz06E9+t3yPGMUfu sM+w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1770705110; x=1771309910; h=in-reply-to:content-disposition:mime-version:message-id:subject:cc :to:from:date:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=PuIvHjahYrqUwfgodntxdfFSIIlE9ggIgaeNW8+YxZc=; b=SaFoxx3r9FG/N8nAMYL2XooQQTmcJbjIy/dyiUpcQrM0QKcDEENSS/9oLrdxt7RZWR 5tSKfNpEGhzbHWBixuGr3DldLZaC+r4ntsqSW1x2sDEPEUvYQox8yX+qABA1LV6znV3J ELVmeTlotSNfUwdP9X+8iv+GL6rQagWiSYLucUpUtVupADmNKGxwG9TiQ0FJDz0zL7Rs C4aWDHL1h3lbrXfSiFN8czNuNWstD8dTUiLRZY4IxaHbmz/pFlfy5F3JCox09MEfs7oJ NMvbkd7ixFXFYc/RtCwpSPCJMYj4PCveMPtZY+dWlzxiTOBCXt3pJYToROXAi/jpMmfM 5c1Q== X-Forwarded-Encrypted: i=1; AJvYcCWtCqsNVobmjmOuU3ZHt/CIq3YjoL9rrKKltqIB/5VTlyw3s/VY5Au5detLzdY6RoQ4N1mk+LKGvKQRKdQ=@vger.kernel.org X-Gm-Message-State: AOJu0YzTMPakop8Z3+8z5de5SADJu4T+RjE/CVc7hnJFAYkYm3+r9A3D bqFWvMv9jO4RddV2SJy1tYHzQB32zwviSycz8VVn62mrkkOVXScaLiaI5Thoh7bijj8= X-Gm-Gg: AZuq6aJ+onU8u+rzL3GYfU1P9cUk4kcwOu9IXYOmcJA0gL/sRg166RtmyZT/a0JGor/ HVuFMR+S328faENYtn2yMRguNsSJEP6N10AUoV1FKH8LDLZrxVBouoyjoaHB49M6m4bUgbMfBw4 T17d1KxLA4B0j6xbxBhKlBIhbr2Sjo0/Klz/KkoAAqkIZSJqDltylkznP1K1K9Tj1yjck5aMLZG dCcOyH5Va0eZvWhWdwc43xfMvhNVmlNESu+91xj8u+Hypwy0hQ5m09+HkXBzHLRlOZYyCoHA2ID UGnSUeRsmDgeWS35x6yjdOukPmH/xiNyTEZg8sJp+YaXRQK7AMkxUCO5OW+kCWibfmFIVZuLZXX CA1OcpqCi24co+Tk3if9EhK4fWZvGJS+Wiqe8/IScVSpoysWKt3j0wEb2BK2cFx8hXF1IT4aYL9 rIuxGHH5c1Z231x1GlTYK3whoW8GBh X-Received: by 2002:a05:600c:4f8a:b0:47a:8cce:2940 with SMTP id 5b1f17b1804b1-483201e3aaemr189459165e9.14.1770705109669; 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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260208215839.87595-15-nphamcs@gmail.com> 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