From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-133.freemail.mail.aliyun.com (out30-133.freemail.mail.aliyun.com [115.124.30.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6F91C3B8D7B for ; Mon, 28 Sep 2026 10:58:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.133 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790593108; cv=none; b=ETjqCOa6WtZeJ3MlcHvUvbVeONRyHNhbgRZsS5QXOK8Ym7wxhtAQkOR74UiNygP2Hp3jaQkrOXffu/dwD/IidlTJsSlo0wvUzWb0BonWLCVoxj8Q6F4hM0rKqp2qpy9JpzTEtM8mZw7TWtfNoerAKAL/YmVCLieQ9YGBwcirgGI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790593108; c=relaxed/simple; bh=i8HBRtQ9DEuQuqAnjXpDtMoZjN5eg2xj6iX54OzYeF0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=nxvVe8Tn+P8+3zJbcW2+KiEMwUucdp9LzuIQaLVa79e3GMq/vyOx3F6Vgwg+GCXdIy9ZkEc9vw3zvdVYi1I6FIHYGUfuNLtJ25WiNsuy+eFKWmfCd2fPnbFnPlHM+Rjb/H1RtejoxqjIio6cMlW4aNwDIb1oXwI+biAL3ysaeU0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=KPkv/fqc; arc=none smtp.client-ip=115.124.30.133 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="KPkv/fqc" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1790593103; h=From:To:Subject:Date:Message-ID:MIME-Version; bh=EW80Ao4GSnyo3++EWYs+N/9yYhqs951UWTJTytHYXHI=; b=KPkv/fqclzYLSyxP3CTYUHMtTi6NIfZcA+e9Qu+jkr4L/pgwcOXjRxm1AXOOF9ianwynNTN6Y/XBAcqiZvyTdy47S8WmmrytDaSWN3SkH1mXQ3dH3lGrwzcLEFm9vs5MSUsIQfwdZz3ZJD3dB+x6FIIynBEs0h7JrhSg289rc8Q= X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R101e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=maildocker-contentspam033032089153;MF=xiangzao@linux.alibaba.com;NM=1;PH=DS;RN=16;SR=0;TI=SMTPD_---0XBma20y_1790593101; Received: from banye.tbsite.net(mailfrom:xiangzao@linux.alibaba.com fp:SMTPD_---0XBma20y_1790593101 cluster:ay36) by smtp.aliyun-inc.com; Mon, 28 Sep 2026 18:58:21 +0800 From: Yuanhe Shu To: akpm@linux-foundation.org Cc: xiangzao@linux.alibaba.com, david@kernel.org, vbabka@kernel.org, linmiaohe@huawei.com, nao.horiguchi@gmail.com, ziy@nvidia.com, ying.huang@linux.alibaba.com, wangkefeng.wang@huawei.com, tujinjiang@huawei.com, mgorman@techsingularity.net, kaitao.cheng@linux.dev, chengkaitao@kylinos.cn, muchun.song@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH 1/2] mm/compaction: skip folios containing hwpoisoned pages Date: Mon, 28 Sep 2026 18:58:04 +0800 Message-ID: <20260928105805.1215770-2-xiangzao@linux.alibaba.com> X-Mailer: git-send-email 2.43.7 In-Reply-To: <20260928105805.1215770-1-xiangzao@linux.alibaba.com> References: <20260928105805.1215770-1-xiangzao@linux.alibaba.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit memory_failure() sets PG_hwpoison on the error page before it manages to pin the folio via get_hwpoison_page(). Compaction running on another CPU can isolate that same folio in the meantime, so HWPoisonHandlable() then fails on !PageLRU(), the retry loop in get_any_page() exhausts itself and memory_failure() gives up with MF_IGNORED - while compaction still has the folio on its migratepages list, flagged PG_hwpoison. Nothing stops compaction from migrating such a folio afterwards. The corrupted data is copied into a fresh folio that carries no poison marker, and no hwpoison PTE entry is installed on the way back: the userspace mapping is silently redirected to the corrupted copy and no SIGBUS is ever delivered. Note that a large folio with a PG_hwpoisoned subpage can also sit on the LRU without any race at all, via the THP-split-failure path of memory_failure() (kill_procs_now() + MF_MSG_UNSPLIT_THP). Guarding compaction is therefore needed regardless of how the race in memory_failure() itself might be addressed. folio_mc_copy() does not close this hole: it only detects corruption at copy time and only where ARCH_HAS_COPY_MC is implemented (x86_64 and PPC64; elsewhere copy_mc_highpage() degrades to a plain copy). Software-injected poison - what MADV_HWPOISON and the hwpoison-inject interface produce, and what tests and fuzzers exercise - never traps during the copy on any architecture. An isolation-time check avoids the migration entirely, on all architectures and for both real and simulated poison. The check itself is two flag tests on the head page (PG_hwpoison and the folio-level has_hwpoisoned marker), not a walk over subpages. Neither page reclaim nor memory hotplug lets such a folio be copied into a fresh one: reclaim unmaps the poisoned order-0 page, and skips the hwpoisoned large folios it cannot safely unmap, in shrink_folio_list() commit 1b0449544c64 ("mm/vmscan: don't try to reclaim hwpoison folio") commit 9f1e8cd0b7c4 ("mm/vmscan: fix hwpoisoned large folio handling in shrink_folio_list") while memory hotplug refuses to migrate them in do_migrate_range() commit 5f5ee52d4f58 ("mm/hwpoison: introduce folio_contain_hwpoisoned_page() helper"). Skip them in compaction as well, for the same reason reclaim settled on skipping: the UCE is rare and a race with compaction is rarer still, so skipping is enough, and a later memory_failure() will handle the folio if the UCE is triggered again - while a migrated folio would silently propagate the corruption instead. Deterministic validation on v7.3-rc4-75-g62f4c998b297: order-4 mTHP folios were brought into the stable "large, on LRU, PG_hwpoisoned subpage" state by pinning a sibling subpage with vmsplice and injecting MADV_HWPOISON on another subpage, which makes memory_failure() take the THP-split-failure path; after triggering compaction, /proc/kpageflags shows which poisoned folios moved. The unpatched kernel migrated 16/16 poisoned folios and 16/16 clean controls in the same pageblocks; with this patch, 0/16 poisoned folios were migrated while their controls still migrated 16/16. Soft offline is not affected: it only sets the poison marker after its own migration has succeeded. Signed-off-by: Yuanhe Shu --- mm/compaction.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/mm/compaction.c b/mm/compaction.c index a049415512c6..491adcbc5313 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -1093,6 +1093,14 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, if (unlikely(!folio)) goto isolate_fail; + /* + * Migrating would copy the corrupted data into a fresh + * folio with no poison marker; skip, as memory hotplug + * refuses to migrate such folios for the same reason. + */ + if (folio_contain_hwpoisoned_page(folio)) + goto isolate_fail_put; + /* * Migration will fail if an anonymous page is pinned in memory, * so avoid taking lru_lock and isolating it unnecessarily in an -- 2.43.7