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 C7DEACD8CA4 for ; Tue, 9 Jun 2026 09:08:39 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 379EA6B008A; Tue, 9 Jun 2026 05:08:39 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 32AC56B008C; Tue, 9 Jun 2026 05:08:39 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 240C46B0092; Tue, 9 Jun 2026 05:08:39 -0400 (EDT) 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 1728E6B008A for ; Tue, 9 Jun 2026 05:08:39 -0400 (EDT) Received: from smtpin06.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay03.hostedemail.com (Postfix) with ESMTP id B5284A0413 for ; Tue, 9 Jun 2026 09:08:38 +0000 (UTC) X-FDA: 84859798716.06.5ECA0A2 Received: from out-177.mta1.migadu.com (out-177.mta1.migadu.com [95.215.58.177]) by imf28.hostedemail.com (Postfix) with ESMTP id 8A991C0009 for ; Tue, 9 Jun 2026 09:08:36 +0000 (UTC) Authentication-Results: imf28.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=hfr7GTaI; spf=pass (imf28.hostedemail.com: domain of lance.yang@linux.dev designates 95.215.58.177 as permitted sender) smtp.mailfrom=lance.yang@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=1780996117; 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=Bk+cuqVkiscfXQOg4Fx57mt0jx9ijz84xEuHbEOrHnY=; b=NLgTCfbd9RwKbl2GiqT60u75GnUtum23W7+11Z4s58SV1bb2vnzE9xiqLE6V+pCur4ZaCz q6O4z3wONu3uslxH/bFVdpdjCaKWIvZGYfLa2OjgOEzCVszCUzVDLF1CIdJE3kAy1KQycD yxIaPcEKE+Dv768daEc0k59tTDCu/xA= ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1780996117; b=s8z1p6Hqc54shPiG2EL2HDHnpDVGvMHNDO9HXatlRlz2gooZ8cGcsdwjHG8HeMODDQTC/p pCi2DKB4pLSBr833Y3GkjFWN501d4VaXHLMzdYcPuezZg9E/5rS+vC4lkWvLT6KwnhMneN ZENKaeSoheKU4UssZ6rbXNfDkGXVwOY= ARC-Authentication-Results: i=1; imf28.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=hfr7GTaI; spf=pass (imf28.hostedemail.com: domain of lance.yang@linux.dev designates 95.215.58.177 as permitted sender) smtp.mailfrom=lance.yang@linux.dev; dmarc=pass (policy=none) header.from=linux.dev Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1780996114; 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=Bk+cuqVkiscfXQOg4Fx57mt0jx9ijz84xEuHbEOrHnY=; b=hfr7GTaIOxEAe5xwodnf8gchpVC+CiIkwRdFShplJcUJFtzPmOK1trlHgkVaZMgy9vt+zM +j/MS1T1gPELGLosMYUNtpIGnqJcb/YWUD5btv+XufH/GnFFMvuwx5Sdpu1v0Rfj92qnKZ GJ7UF+QuxRptHJRUZ9++OfMXio3i5ic= Date: Tue, 9 Jun 2026 17:08:14 +0800 MIME-Version: 1.0 Subject: Re: [PATCH v8 2/6] mm/memory-failure: surface unhandlable kernel pages as -ENOTRECOVERABLE To: "David Hildenbrand (Arm)" , Miaohe Lin , Breno Leitao Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-trace-kernel@vger.kernel.org, kernel-team@meta.com, Andrew Morton , Lorenzo Stoakes , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Shuah Khan , Naoya Horiguchi , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Jonathan Corbet , Shuah Khan , "Liam R. Howlett" References: <20260527-ecc_panic-v8-0-9ea0cfa16bb0@debian.org> <20260527-ecc_panic-v8-2-9ea0cfa16bb0@debian.org> <19f968f5-1289-f573-4406-e5c91dcd8923@huawei.com> <33ef8821-c809-b7d1-ea77-6e8a07a6e784@huawei.com> <21732071-14a1-486a-951c-34de97b7c757@kernel.org> <4b27467e-935f-5587-2f48-5a794c30a592@huawei.com> <4953bcee-5a0f-2bc5-7295-63e5e7513e8b@huawei.com> Content-Language: en-US X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Lance Yang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Queue-Id: 8A991C0009 X-Rspam-User: X-Stat-Signature: 6jwfjcgwp4bxauy5xd3mkwumr9hnygxq X-Rspamd-Server: rspam08 X-HE-Tag: 1780996116-538354 X-HE-Meta: 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 TZlevW+9 GjgLhjMe/l7vlt2bwcheaKZQkYLK6HqzSPzK+Lji+ot6EfyXh2aehVzpVIylqKMT8Y/hMH6QghT634MPEByV96LjWL5a3nv45RCj+CLpxCrwfaNGIkHtKJZVJWDWtoMxnJXVu9DrOmIyfLLGNnyRN5atsn6BFHgfQ09EY4IiWRqzpP6vPtiqbBjFan3Sz90V5lluRC/93O/+WKh5QGMGqZKdehOOcWu/F+pXwBOiIi/cgIISOuLKAZEctUqvTfyqAJHCbzxqk1+vJcle9OZqyYT7sd57z07Sj/0Kz Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2026/6/9 15:09, David Hildenbrand (Arm) wrote: > On 6/9/26 04:39, Miaohe Lin wrote: >> On 2026/6/8 22:15, Breno Leitao wrote: >>> On Fri, Jun 05, 2026 at 11:42:53AM +0200, David Hildenbrand (Arm) wrote: >>>> >>>> I mean, any such races can currently already happen one way or the other? >>>> >>>> Really, the only way to not get races is to tryget the (compound)page, >>>> revalidate that the page is still part of the compound page. >>>> >>>> I'm not sure if that's really a good idea. >>>> >>>> But my memory is a bit vague in which scenarios we already hold a page reference >>>> here to prevent any concurrent freeing? >>> >>> No, we don't hold one here in the case that matters. >>> >>> HWPoisonKernelOwned() runs at the very top of get_any_page(), before >>> try_again: and before __get_hwpoison_page(). The first refcount taken in >>> the whole path is the folio_try_get() inside __get_hwpoison_page(), which >>> runs *after* the short-circuit. >>> >>> So get_any_page() itself never holds a reference at the check -- the only way >>> one exists is if the caller passed MF_COUNT_INCREASED (count_increased == >>> true). >>> >>> So on the MCE/GHES path -- the one this panic option exists for -- no >>> reference is held when HWPoisonKernelOwned() does its compound_head() + >>> PageSlab()/PageTable()/PageLargeKmalloc() checks. >>> >>> Given that, I'd rather keep it racy and take no refcount than add a >>> tryget + revalidate purely for this check. As I've said earleir, an operator >> >> Would it be acceptable to add a simple recheck? Something like below: >> >> retry: >> head = compound_head(page); >> PageSlab()/PageTable()/PageLargeKmalloc() checks >> if (head != compound_head(page)) >> goto retry > > Sure. I guess it could still be racy in some weird scenarios where we > free+allocate+free in-between. +1, sounds reasonable to me. Still racy, but acceptable here I guess :D