From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from canpmsgout01.his.huawei.com (canpmsgout01.his.huawei.com [113.46.200.216]) (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 A866929AB05; Mon, 6 Jul 2026 12:22:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=113.46.200.216 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783340542; cv=none; b=tmoYMW9+C4GWzRhwBGsP2cazGYYLQNJK5NHaS+LPv94+qnW03iyVpdqZQnln9j3E2LKvi/9C9QT+MQ7iVPGnzR/lkA82+JOtpH/s118/GbkNwaM3qEFooaHS09m3MECOMW6J1rkKogtsoFejDcfcYLnSdcCupr0QzTxtnfYqQHI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783340542; c=relaxed/simple; bh=LCvKrUyihnFS4hob/L7N3B0mtCrPOVsnb9cK/e8JCi8=; h=Subject:To:CC:References:From:Message-ID:Date:MIME-Version: In-Reply-To:Content-Type; b=l4HSjnaXU2lR4ReZNMEQtgvdbo9e8+TwgPMKcy+kaRZpSkKnG2UZZm9aXa5JeezIvdaXJL22ypMt9cC2S9scMOgghJm50APTEgLdRU3RbiPLy09nqW/oaOlgOOcW3olS07tIubpX+wtQgGHPRvGvtquPplgh+3v53iGMfzUNu40= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; dkim=pass (1024-bit key) header.d=huawei.com header.i=@huawei.com header.b=ao6wcOs8; arc=none smtp.client-ip=113.46.200.216 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=huawei.com header.i=@huawei.com header.b="ao6wcOs8" dkim-signature: v=1; a=rsa-sha256; d=huawei.com; s=dkim; c=relaxed/relaxed; q=dns/txt; h=From; bh=FqwiknrRupuJ+YbQZhTDPFtrox28ElGL/EoIq2WfmbY=; b=ao6wcOs8Q5O0NVhjycbAW1PzuYgJP4S9ueRwTqolkKu7NjzVYtgU476ZL2YoTz0GZ5CYUG9hW q3AhbPYdUrsp0tNVvxM+DIUtCw7piYh62hyoJk4gJwHwEkAjpB4nlSbIveM55jgeWUnNVqe9Xdg 1IY7cu9UXDg/xwQ3nqpH2MA= Received: from mail.maildlp.com (unknown [172.19.162.223]) by canpmsgout01.his.huawei.com (SkyGuard) with ESMTPS id 4gv3Cw5ZCKz1T4Fk; Mon, 6 Jul 2026 20:13:16 +0800 (CST) Received: from dggemv712-chm.china.huawei.com (unknown [10.1.198.32]) by mail.maildlp.com (Postfix) with ESMTPS id C382A40561; Mon, 6 Jul 2026 20:22:14 +0800 (CST) Received: from kwepemq500010.china.huawei.com (7.202.194.235) by dggemv712-chm.china.huawei.com (10.1.198.32) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Mon, 6 Jul 2026 20:22:14 +0800 Received: from [10.173.124.160] (10.173.124.160) by kwepemq500010.china.huawei.com (7.202.194.235) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Mon, 6 Jul 2026 20:22:13 +0800 Subject: Re: [PATCH v10 2/6] mm/memory-failure: surface unhandlable kernel pages as -ENOTRECOVERABLE To: Breno Leitao CC: , , , , , , Andrew Morton , David Hildenbrand , "Lorenzo Stoakes" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Shuah Khan , Naoya Horiguchi , Jonathan Corbet , Shuah Khan , "Liam R. Howlett" , , Steven Rostedt , "Masami Hiramatsu" , Mathieu Desnoyers References: <20260630-ecc_panic-v10-0-c6ed5b62eea2@debian.org> <20260630-ecc_panic-v10-2-c6ed5b62eea2@debian.org> From: Miaohe Lin Message-ID: <157b0e23-9f1e-1af2-bb44-44f1f2cab8a5@huawei.com> Date: Mon, 6 Jul 2026 20:22:12 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: <20260630-ecc_panic-v10-2-c6ed5b62eea2@debian.org> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-ClientProxiedBy: kwepems500001.china.huawei.com (7.221.188.70) To kwepemq500010.china.huawei.com (7.202.194.235) On 2026/6/30 20:46, Breno Leitao wrote: > get_any_page() collapses every HWPoisonHandlable() rejection into a > single -EIO via the __get_hwpoison_page() -> -EBUSY -> shake_page() > -> retry path. That is correct for the transient case (a userspace > folio briefly off LRU during migration or compaction, which a later > shake can drag back), but wrong for stable kernel-owned pages: slab, > page-table, large-kmalloc and PG_reserved pages will never become > HWPoisonHandlable(), so the retry loop is wasted work and the final > -EIO loses the "this is structurally unrecoverable" information. > memory_failure() then maps -EIO into MF_MSG_GET_HWPOISON, which the > panic-on-unrecoverable sysctl deliberately does not act on. > > Introduce is_kernel_owned_page(), a small predicate that positively > identifies pages the hwpoison handler cannot recover from: > > is_kernel_owned_page(p) := > PageReserved(p) || > PageSlab(head) || PageTable(head) || PageLargeKmalloc(head) > > where head = compound_head(p). > > PG_reserved is a per-page flag (PF_NO_COMPOUND) and is tested on the > page directly. The slab, page-table and large-kmalloc page-type bits > are only stored on the head page, so those tests resolve the compound > head first, then re-read compound_head(page) afterwards: a concurrent > split or compound free that moves head invalidates the just-read flags > and the loop retries. The lookup still takes no refcount, mirroring > the rest of get_any_page(); the recheck closes the common split race, > and a residual free->alloc->free in the same window can only mis-tag > a genuinely poisoned page, never reclassify a handlable one. > > No MF_SOFT_OFFLINE / page_has_movable_ops() opt-out is needed: a > movable_ops page is always PageOffline or PageZsmalloc, whose > page_type is mutually exclusive with slab, page-table and > large-kmalloc, and it never carries PG_reserved, so it can never > match any of the checks above. > > The list is intentionally not exhaustive. vmalloc and kernel-stack > pages, for example, do not carry a page_type bit and would need a > different oracle; they keep going through the existing retry path > unchanged. This is the smallest set we can identify with certainty > by page type. > > Wire the helper into the top of get_any_page() to short-circuit > those pages before the retry loop runs. On a hit, drop the caller's > MF_COUNT_INCREASED reference (if any) and return -ENOTRECOVERABLE > straight away. Pages outside the helper's positive list still take > the existing retry path and return -EIO, leaving operator-visible > behaviour for those cases unchanged. > > Extend the unhandlable-page pr_err() to fire for either errno and > update the get_hwpoison_page() kerneldoc to document the new return. > > memory_failure() still folds every negative return into > MF_MSG_GET_HWPOISON via its existing "else if (res < 0)" branch, so > this patch on its own only changes the errno that soft_offline_page() > can propagate to its callers. A follow-up wires -ENOTRECOVERABLE > through memory_failure() and reports MF_MSG_KERNEL for the > unrecoverable cases, which is what the > panic_on_unrecoverable_memory_failure sysctl observes. > > Suggested-by: David Hildenbrand > Suggested-by: Lance Yang > Signed-off-by: Breno Leitao > --- > mm/memory-failure.c | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++-- > 1 file changed, 50 insertions(+), 2 deletions(-) > > diff --git a/mm/memory-failure.c b/mm/memory-failure.c > index f4d3e6e20e13f..087658484e242 100644 > --- a/mm/memory-failure.c > +++ b/mm/memory-failure.c > @@ -1325,6 +1325,38 @@ static inline bool HWPoisonHandlable(struct page *page, unsigned long flags) > return PageLRU(page) || is_free_buddy_page(page); > } > > +/* > + * Positive identification of pages the hwpoison handler cannot recover: > + * pages owned by kernel internals with no userspace mapping to unmap, no > + * file mapping to invalidate, and no migration target. > + */ > +static inline bool is_kernel_owned_page(struct page *page) > +{ > + struct page *head; > + bool kernel_owned; > + > + /* PG_reserved is a per-page flag, never set on a compound page. */ > + if (PageReserved(page)) > + return true; > + > + /* > + * Page-type bits live only on the head page, so resolve any tail > + * first. The check takes no refcount; recheck the head afterwards > + * so a concurrent split or compound free cannot leave us trusting > + * a stale view. A residual free->alloc->free cannot be closed here > + * (frozen slab and large-kmalloc pages cannot be pinned), but is > + * harmless: where a wrong verdict could panic, memory_failure() has > + * already set PageHWPoison, which bars the page from the allocator. > + */ > +retry: > + head = compound_head(page); It's irrelevant to this issue but should we use folio? Anyway, this patch looks good to me. Acked-by: Miaohe Lin Thanks. .