From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 30F89CCD18E for ; Tue, 14 Oct 2025 09:32:23 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 464A88E00AB; Tue, 14 Oct 2025 05:32:22 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 4158D8E0097; Tue, 14 Oct 2025 05:32:22 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 32B3F8E00AB; Tue, 14 Oct 2025 05:32:22 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 1B3348E0097 for ; Tue, 14 Oct 2025 05:32:22 -0400 (EDT) Received: from smtpin17.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id 7572013BB5B for ; Tue, 14 Oct 2025 09:32:21 +0000 (UTC) X-FDA: 83996204082.17.8717CEF Received: from out-189.mta0.migadu.com (out-189.mta0.migadu.com [91.218.175.189]) by imf03.hostedemail.com (Postfix) with ESMTP id 1EADC2000E for ; Tue, 14 Oct 2025 09:32:17 +0000 (UTC) Authentication-Results: imf03.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b="Lb/N2nbn"; spf=pass (imf03.hostedemail.com: domain of hao.ge@linux.dev designates 91.218.175.189 as permitted sender) smtp.mailfrom=hao.ge@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1760434340; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-transfer-encoding:content-transfer-encoding: in-reply-to:references:dkim-signature; bh=MaJVArJT5DSA2aQdi42cvv24ZzgEQA46Llp+u4DFk7o=; b=d3EKnMJS1/65rY4zIJ5xGWJP2FldqfmmSYynuekm+2sBO/CQXK5AVWBijav9AZqXh8fbdr XG4dYwWD6eLinhB/ulSt4KUn5Kymul0BlXYjbOTy2uJmAqZE6+voepBrGrSXqpGPWDeb4L pr9bJFe/q7phr77LJ2S7r9PwbNI0F9k= ARC-Authentication-Results: i=1; imf03.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b="Lb/N2nbn"; spf=pass (imf03.hostedemail.com: domain of hao.ge@linux.dev designates 91.218.175.189 as permitted sender) smtp.mailfrom=hao.ge@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1760434340; a=rsa-sha256; cv=none; b=7JgUmiPWglW+ytu6s+8dh5QjuH2JlDCuLz+R9xoMKxC5NbqAApafvkZBf2EtAT7Ay5C4Yk Qn9yvWWccCggiPQNVs1U8+Mm/ZdlyyE8x7lhJzeqT8X0Xdlm7YR6WplL1GrxhLnomRjxZn nO1MLiROudmhZFheetsetmRqHX+CirE= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1760434335; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=MaJVArJT5DSA2aQdi42cvv24ZzgEQA46Llp+u4DFk7o=; b=Lb/N2nbnUC+KtEZA5YdCQPpps9Cv3ryweXrraIB3a+qMPeI+DdRaj9d5dnTVQDFqYbd4/6 KO5FDqdZjAZeg+Yx8O+pttul2MOUXReq/nweJtW6skE52EkkWAoot8WsJkwQG95hqYkBap WDVhc31X/+SlJdB8eeDHTQJeLJ27Uxg= From: Hao Ge To: Vlastimil Babka , Alexei Starovoitov , Andrew Morton , Johannes Weiner , Shakeel Butt , Michal Hocko , Roman Gushchin , Muchun Song , Suren Baghdasaryan Cc: Harry Yoo , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Hao Ge Subject: [PATCH] slab: Introduce __SECOND_OBJEXT_FLAG for objext_flags Date: Tue, 14 Oct 2025 17:31:24 +0800 Message-Id: <20251014093124.300012-1-hao.ge@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Stat-Signature: nnk33aa3gfrpnqykdgmd7sg6aby9oy5x X-Rspamd-Queue-Id: 1EADC2000E X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1760434337-884266 X-HE-Meta: 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 UEcdVdGg RKsNWVSM1uMnSvssKQ7LqnsXXyzP+OlsCg6HEbPDytgUWeegqgBCMnfzRHNqZ/y73bV65E/EDEFY50rG7BqFIJ53HX3HRC11Qcld+sjN6neOK2rx1DdiMtba246HBCFI5V8cJcP0NzEWcSyBlRHgzkePcfiSX51s0Qu+Q7H3WkTsFvBTu14wgTg0cWEu+erqnvj4xogwx9lGWT3U4V63ku8TM8/c7iGJ9nzm0Z+JDUpntMO1GCAx4HDFOJw== 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: From: Hao Ge We should not reuse the first bit for OBJEXTS_ALLOC_FAIL. This is because the following scenarios may be encountered: Under heavy system load, certain sequences of events can trigger the VM_BUG_ON_FOLIO(folio->memcg_data & MEMCG_DATA_OBJEXTS, folio) check: 1. High system pressure may cause objext allocation failure for a slab. 2. When objext allocation fails, slab->obj_exts is set to OBJEXTS_ALLOC_FAIL (value 1). 3. Later, this slab may enter the release process. 4. During release of the associated folio, the existing VM_BUG_ON_FOLIO check validates folio->memcg_data. If the MEMCG_DATA_OBJEXTS bit is unexpectedly set here, the bug check gets triggered. We have obtained the following logs: [ 7108.343437] page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff0002deb97600 pfn:0x31eb96 [ 7108.343482] head: order:1 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0 [ 7108.343500] memcg:1 [ 7108.343507] flags: 0x17ffff800000040(head|node=0|zone=2|lastcpupid=0xfffff) [ 7108.343523] raw: 017ffff800000040 ffff0000c000cac0 dead000000000100 0000000000000000 [ 7108.343528] raw: ffff0002deb97600 0000000000240000 00000000ffffffff 0000000000000001 [ 7108.343534] head: 017ffff800000040 ffff0000c000cac0 dead000000000100 0000000000000000 [ 7108.343539] head: ffff0002deb97600 0000000000240000 00000000ffffffff 0000000000000001 [ 7108.343562] head: 017ffff800000001 fffffdffcb7ae581 00000000ffffffff 00000000ffffffff [ 7108.343569] head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000002 [ 7108.343574] page dumped because: VM_BUG_ON_FOLIO(folio->memcg_data & MEMCG_DATA_OBJEXTS) [ 7108.343601] ------------[ cut here ]------------ [ 7108.343607] kernel BUG at ./include/linux/memcontrol.h:537! [ 7108.343617] Internal error: Oops - BUG: 00000000f2000800 [#1] SMP [ 7108.345751] Modules linked in: squashfs isofs vhost_vsock vhost_net vmw_vsock_virtio_transport_common vfio_iommu_type1 vhost vfio vsock vhost_iotlb iommufd tap binfmt_misc nfsv3 nfs_acl nfs lockd grace netfs tls rds dns_resolver tun brd overlay ntfs3 exfat btrfs blake2b_generic xor xor_neon raid6_pq loop sctp ip6_udp_tunnel udp_tunnel nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib nft_reject_inet nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_ct nft_chain_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 nf_tables rfkill ip_set sunrpc vfat fat joydev sg sch_fq_codel nfnetlink virtio_gpu drm_client_lib virtio_dma_buf drm_shmem_helper sr_mod drm_kms_helper cdrom drm ghash_ce virtio_net virtio_scsi backlight virtio_console virtio_blk net_failover failover virtio_mmio dm_mirror dm_region_hash dm_log dm_multipath dm_mod fuse i2c_dev virtio_pci virtio_pci_legacy_dev virtio_pci_modern_dev virtio virtio_ring autofs4 aes_neon_bs aes_ce_blk [last unloaded: hwpoison_inject] [ 7108.355662] CPU: 7 UID: 0 PID: 4470 Comm: kylin-process-m Kdump: loaded Not tainted 6.18.0-rc1-dirty #54 PREEMPT(voluntary) [ 7108.356864] Hardware name: QEMU KVM Virtual Machine, BIOS unknown 2/2/2022 [ 7108.357621] pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) [ 7108.358981] pc : __free_frozen_pages+0xf18/0x18e8 [ 7108.359834] lr : __free_frozen_pages+0xf18/0x18e8 [ 7108.360379] sp : ffff8000a2bb7580 [ 7108.360786] x29: ffff8000a2bb7580 x28: fffffdffcb7ae580 x27: fffffdffcb7ae580 [ 7108.362013] x26: fffffdffcb7ae588 x25: 1fffffbff96f5cb1 x24: 1fffffbff96f5cb0 [ 7108.362804] x23: ffff8000839d6ba0 x22: ffff8000839d6000 x21: 0000000000000000 [ 7108.363596] x20: 0000000000000000 x19: 0000000000000001 x18: 0000000000000000 [ 7108.364393] x17: 445f47434d454d20 x16: 2620617461645f67 x15: 636d656d3e2d6f69 [ 7108.365498] x14: 6c6f66284f494c4f x13: 0000000000000001 x12: ffff600063fece93 [ 7108.366317] x11: 1fffe00063fece92 x10: ffff600063fece92 x9 : dfff800000000000 [ 7108.367610] x8 : 00009fff9c01316e x7 : ffff00031ff67493 x6 : 0000000000000001 [ 7108.368455] x5 : ffff00031ff67490 x4 : ffff600063fece93 x3 : 0000000000000000 [ 7108.369276] x2 : 0000000000000000 x1 : ffff000103fe5d40 x0 : 000000000000004c [ 7108.370140] Call trace: [ 7108.370463] __free_frozen_pages+0xf18/0x18e8 (P) [ 7108.371011] free_frozen_pages+0x1c/0x30 [ 7108.372040] __free_slab+0xd0/0x250 [ 7108.372471] free_slab+0x38/0x118 [ 7108.372882] free_to_partial_list+0x1d4/0x340 [ 7108.373813] __slab_free+0x24c/0x348 [ 7108.374253] ___cache_free+0xf0/0x110 [ 7108.374699] qlist_free_all+0x78/0x130 [ 7108.375156] kasan_quarantine_reduce+0x114/0x148 [ 7108.375695] __kasan_slab_alloc+0x7c/0xb0 [ 7108.376668] kmem_cache_alloc_noprof+0x164/0x5c8 [ 7108.377206] __alloc_object+0x44/0x1f8 [ 7108.377659] __create_object+0x34/0xc8 [ 7108.378196] kmemleak_alloc+0xb8/0xd8 [ 7108.378644] kmem_cache_alloc_noprof+0x368/0x5c8 [ 7108.379224] getname_flags.part.0+0xa4/0x610 [ 7108.379733] getname_flags+0x80/0xd8 [ 7108.380169] do_sys_openat2+0xb4/0x178 [ 7108.380921] __arm64_sys_openat+0x134/0x1d0 [ 7108.381952] invoke_syscall+0xd4/0x258 [ 7108.382408] el0_svc_common.constprop.0+0xb4/0x240 [ 7108.382965] do_el0_svc+0x48/0x68 [ 7108.383375] el0_svc+0x40/0xe0 [ 7108.383757] el0t_64_sync_handler+0xa0/0xe8 [ 7108.384465] el0t_64_sync+0x1ac/0x1b0 [ 7108.385284] Code: 91398021 aa1b03e0 91138021 97fd35e3 (d4210000) [ 7108.386553] SMP: stopping secondary CPUs [ 7108.389714] Starting crashdump kernel... [ 7108.390190] Bye! So, introduce __SECOND_OBJEXT_FLAG for objext_flags, adjust the corresponding order accordingly, and ensure that OBJEXTS_ALLOC_FAIL is no longer reused. Fixes: 7612833192d5 ("slab: Reuse first bit for OBJEXTS_ALLOC_FAIL") Signed-off-by: Hao Ge --- include/linux/memcontrol.h | 16 ++++++---------- 1 file changed, 6 insertions(+), 10 deletions(-) diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 873e510d6f8d..8ea023944fac 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -341,27 +341,23 @@ enum page_memcg_data_flags { __NR_MEMCG_DATA_FLAGS = (1UL << 2), }; -#define __OBJEXTS_ALLOC_FAIL MEMCG_DATA_OBJEXTS #define __FIRST_OBJEXT_FLAG __NR_MEMCG_DATA_FLAGS +#define __SECOND_OBJEXT_FLAG (__FIRST_OBJEXT_FLAG << 1) #else /* CONFIG_MEMCG */ -#define __OBJEXTS_ALLOC_FAIL (1UL << 0) #define __FIRST_OBJEXT_FLAG (1UL << 0) +#define __SECOND_OBJEXT_FLAG (1UL << 0) #endif /* CONFIG_MEMCG */ enum objext_flags { - /* - * Use bit 0 with zero other bits to signal that slabobj_ext vector - * failed to allocate. The same bit 0 with valid upper bits means - * MEMCG_DATA_OBJEXTS. - */ - OBJEXTS_ALLOC_FAIL = __OBJEXTS_ALLOC_FAIL, + /* slabobj_ext vector failed to allocate */ + OBJEXTS_ALLOC_FAIL = __FIRST_OBJEXT_FLAG, /* slabobj_ext vector allocated with kmalloc_nolock() */ - OBJEXTS_NOSPIN_ALLOC = __FIRST_OBJEXT_FLAG, + OBJEXTS_NOSPIN_ALLOC = __SECOND_OBJEXT_FLAG, /* the next bit after the last actual flag */ - __NR_OBJEXTS_FLAGS = (__FIRST_OBJEXT_FLAG << 1), + __NR_OBJEXTS_FLAGS = (__SECOND_OBJEXT_FLAG << 1), }; #define OBJEXTS_FLAGS_MASK (__NR_OBJEXTS_FLAGS - 1) -- 2.25.1