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 6D139E8305F for ; Tue, 3 Feb 2026 07:59:44 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id B856A6B0005; Tue, 3 Feb 2026 02:59:43 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id B33856B0088; Tue, 3 Feb 2026 02:59:43 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A69A36B0089; Tue, 3 Feb 2026 02:59:43 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 950106B0005 for ; Tue, 3 Feb 2026 02:59:43 -0500 (EST) Received: from smtpin05.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 4E7F1C1A8D for ; Tue, 3 Feb 2026 07:59:42 +0000 (UTC) X-FDA: 84402396204.05.5970595 Received: from out-182.mta1.migadu.com (out-182.mta1.migadu.com [95.215.58.182]) by imf24.hostedemail.com (Postfix) with ESMTP id 370BE180004 for ; Tue, 3 Feb 2026 07:59:39 +0000 (UTC) Authentication-Results: imf24.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=hvEDj+0r; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf24.hostedemail.com: domain of hao.ge@linux.dev designates 95.215.58.182 as permitted sender) smtp.mailfrom=hao.ge@linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1770105580; 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-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=RPwfNBBHlYJbOgr7k75lbMbddBPH7V51tCqCs1C01RU=; b=sUVwjTBvreIc+vsT/xs58/Flm+DpIl6I5TOpiSBUvKUiVtgr882vqf9z3sU1Vvw5Y/4lD9 3++WY9791So3XJH3xSfwuyIzAPnsD0aqNHMxOyeeb0cjC3RzLVEgtbumylI/rubbCaAr+h Sd8YD/CujDsoSIeq1vpNxIcCllwvDiw= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1770105580; a=rsa-sha256; cv=none; b=j6ETooOtgcWVdY+dj8QQgLlLIjIG48jWe7JRf/qfMzFsbQX2Mg8waUInATUpfgnSlzW648 WHrntOuuLFBeu8sSDOtbyUcWc5mmjOuh/5bzl/cn+l9JQBM2+G0VPjgWOL1UpYgX2y1u5f r+j3/cWvo7HNjqP6eIQ+adjcncHnSmo= ARC-Authentication-Results: i=1; imf24.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=hvEDj+0r; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf24.hostedemail.com: domain of hao.ge@linux.dev designates 95.215.58.182 as permitted sender) smtp.mailfrom=hao.ge@linux.dev Message-ID: <3b6ffbe3-61ef-42d5-b7e9-5ad54188949b@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1770105578; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=RPwfNBBHlYJbOgr7k75lbMbddBPH7V51tCqCs1C01RU=; b=hvEDj+0rr79NrWLV3MPrSPMFtQ3kstfqPrKtSSCxcbrEifDvU0RtbCSe7B6JjA6sbAj+Hw iJLVCMYREh0bkw6put6C6aBT1WKGhzO4EAlmN4h+ZJgHsfcnIuniPqesFEoHuZRye7HlRA 3NjoeQOFbxjgiXH0EMmhAXrGDZVYMKI= Date: Tue, 3 Feb 2026 15:58:44 +0800 MIME-Version: 1.0 Subject: Re: [PATCH] codetag: Avoid codetag race between same slab object alloc and free To: Vlastimil Babka , Suren Baghdasaryan , Andrew Morton , Christoph Lameter , David Rientjes , Roman Gushchin , Harry Yoo Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260203073006.151710-1-hao.ge@linux.dev> Content-Language: en-US X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Hao Ge In-Reply-To: <20260203073006.151710-1-hao.ge@linux.dev> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Queue-Id: 370BE180004 X-Stat-Signature: qkyz69ea5fkb78ystbuihgugkxkfyjfn X-Rspam-User: X-Rspamd-Server: rspam02 X-HE-Tag: 1770105579-758304 X-HE-Meta: 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 ZS7NLHsO VhXIj1+dw9zCgmXsTJzp9brblP+wBvPC8eDNSl8rf1Aj3qI8sl29GsiZpurBJJ5+QJtl8+dSEKWszfXIRMSEge8WdkJWFgsP9M6c3e6om7+JX2WSNOzDmnM9IiqJkeH3B98BPD2O5gpd3Dor/JKLr8Gq92EiQE6Jp0q/bPkuXdFRq8rke9d744fmRfWIB3ojNKBDSNEHX4zWRa1oJ8riZIY3EeLkDR1py4qiD7QXwDo0ACCY= 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: On 2026/2/3 15:30, Hao Ge wrote: > When CONFIG_MEM_ALLOC_PROFILING_DEBUG is enabled, the following warning > may be noticed: > > [ 3959.023862] ------------[ cut here ]------------ > [ 3959.023891] alloc_tag was not cleared (got tag for lib/xarray.c:378) > [ 3959.023947] WARNING: ./include/linux/alloc_tag.h:155 at alloc_tag_add+0x128/0x178, CPU#6: mkfs.ntfs/113998 > [ 3959.023978] Modules linked in: dns_resolver tun brd overlay exfat btrfs blake2b libblake2b xor xor_neon raid6_pq loop sctp ip6_udp_tunnel udp_tunnel ext4 crc16 mbcache jbd2 rfkill sunrpc vfat fat sg fuse nfnetlink sr_mod virtio_gpu cdrom drm_client_lib virtio_dma_buf drm_shmem_helper drm_kms_helper ghash_ce drm sm4 backlight virtio_net net_failover virtio_scsi failover virtio_console virtio_blk virtio_mmio dm_mirror dm_region_hash dm_log dm_multipath dm_mod i2c_dev aes_neon_bs aes_ce_blk [last unloaded: hwpoison_inject] > [ 3959.024170] CPU: 6 UID: 0 PID: 113998 Comm: mkfs.ntfs Kdump: loaded Tainted: G W 6.19.0-rc7+ #7 PREEMPT(voluntary) > [ 3959.024182] Tainted: [W]=WARN > [ 3959.024186] Hardware name: QEMU KVM Virtual Machine, BIOS unknown 2/2/2022 > [ 3959.024192] pstate: 604000c5 (nZCv daIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--) > [ 3959.024199] pc : alloc_tag_add+0x128/0x178 > [ 3959.024207] lr : alloc_tag_add+0x128/0x178 > [ 3959.024214] sp : ffff80008b696d60 > [ 3959.024219] x29: ffff80008b696d60 x28: 0000000000000000 x27: 0000000000000240 > [ 3959.024232] x26: 0000000000000000 x25: 0000000000000240 x24: ffff800085d17860 > [ 3959.024245] x23: 0000000000402800 x22: ffff0000c0012dc0 x21: 00000000000002d0 > [ 3959.024257] x20: ffff0000e6ef3318 x19: ffff800085ae0410 x18: 0000000000000000 > [ 3959.024269] x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000 > [ 3959.024281] x14: 0000000000000000 x13: 0000000000000001 x12: ffff600064101293 > [ 3959.024292] x11: 1fffe00064101292 x10: ffff600064101292 x9 : dfff800000000000 > [ 3959.024305] x8 : 00009fff9befed6e x7 : ffff000320809493 x6 : 0000000000000001 > [ 3959.024316] x5 : ffff000320809490 x4 : ffff600064101293 x3 : ffff800080691838 > [ 3959.024328] x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffff0000d5bcd640 > [ 3959.024340] Call trace: > [ 3959.024346] alloc_tag_add+0x128/0x178 (P) > [ 3959.024355] __alloc_tagging_slab_alloc_hook+0x11c/0x1a8 > [ 3959.024362] kmem_cache_alloc_lru_noprof+0x1b8/0x5e8 > [ 3959.024369] xas_alloc+0x304/0x4f0 > [ 3959.024381] xas_create+0x1e0/0x4a0 > [ 3959.024388] xas_store+0x68/0xda8 > [ 3959.024395] __filemap_add_folio+0x5b0/0xbd8 > [ 3959.024409] filemap_add_folio+0x16c/0x7e0 > [ 3959.024416] __filemap_get_folio_mpol+0x2dc/0x9e8 > [ 3959.024424] iomap_get_folio+0xfc/0x180 > [ 3959.024435] __iomap_get_folio+0x2f8/0x4b8 > [ 3959.024441] iomap_write_begin+0x198/0xc18 > [ 3959.024448] iomap_write_iter+0x2ec/0x8f8 > [ 3959.024454] iomap_file_buffered_write+0x19c/0x290 > [ 3959.024461] blkdev_write_iter+0x38c/0x978 > [ 3959.024470] vfs_write+0x4d4/0x928 > [ 3959.024482] ksys_write+0xfc/0x1f8 > [ 3959.024489] __arm64_sys_write+0x74/0xb0 > [ 3959.024496] invoke_syscall+0xd4/0x258 > [ 3959.024507] el0_svc_common.constprop.0+0xb4/0x240 > [ 3959.024514] do_el0_svc+0x48/0x68 > [ 3959.024520] el0_svc+0x40/0xf8 > [ 3959.024526] el0t_64_sync_handler+0xa0/0xe8 > [ 3959.024533] el0t_64_sync+0x1ac/0x1b0 > [ 3959.024540] ---[ end trace 0000000000000000 ]--- > > This is due to a race condition that occurs when two threads concurrently > perform allocation and freeing operations on the same slab object. > > When a process is preparing to allocate a slab object, another process > successfully preempts the CPU, and then proceeds to free a slab object. > However, before the freeing process can invoke `alloc_tag_sub()`, it is > preempted again by the original allocating process. At this point, the > allocating process acquires the same slab object, and subsequently triggers > a warning when it invokes `alloc_tag_add()`. > > Signed-off-by: Hao Ge > --- > Hi Suren > > I'm not sure if my solution still has any issues, so I'd like to > get your suggestions on it. At the very least, my understanding is > that READ_ONCE and WRITE_ONCE should be used in pairs. > > I look forward to your suggestions. > > Thanks > --- > mm/slub.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/mm/slub.c b/mm/slub.c > index f77b7407c51b..0d84fc917a89 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -2261,8 +2261,13 @@ __alloc_tagging_slab_alloc_hook(struct kmem_cache *s, void *object, gfp_t flags) > * If other users appear then mem_alloc_profiling_enabled() > * check should be added before alloc_tag_add(). > */ > - if (likely(obj_exts)) > + if (likely(obj_exts)) { > + > + while (!READ_ONCE(obj_exts->ref.ct)) > + cpu_relax(); > + My apologies for forgetting to update this part when submitting the patch — I've already made the change in my local environment: while (READ_ONCE(obj_exts->ref.ct)) cpu_relax(); I'd also welcome any thoughts or feedback from others in the community. > alloc_tag_add(&obj_exts->ref, current->alloc_tag, s->size); > + } > else > alloc_tag_set_inaccurate(current->alloc_tag); > }