From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 F14D334D3B5; Tue, 9 Jun 2026 14:41:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781016071; cv=none; b=j1CPubpXXu4oxqgC2vXKqEBaX50cc+xcT8tv1vAeoZosCICBzEFEteHdE9rlSWZZE0N7sEwH/0unZHyqn+gvFug8gYrzccYKdMcxlVsaqT7twtACMWT0HgbFSds9ej6blFtVf61GcmcwYr/zEz3Gb+UQxvkUjC2rFRgdCQD6qZ4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781016071; c=relaxed/simple; bh=/u81EElxj1ij8xTBPIpvX9Ln3B+z5bXSRr+bxSSwy78=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=jhmp2kHJYYx9PTDaq6u/S9ejHP0i48FhTpK1/zpLA0zIPR5ntEy61LI4pkDwwD7F8GF+wrzKI/gJvZ5rE///5KmMEnqke0ePU7zofe60iLJEotGZKd2079J/D4xvCH63tKmjS+t62IqSB1Zqy9ahzfH01/kaZv2AzqHuVY2CYko= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=MooxQ3yX; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="MooxQ3yX" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7892E1F00893; Tue, 9 Jun 2026 14:41:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1781016069; bh=njEURiQmXFZM6WEGnC38JEeiBkoFTQqy3aaC8k9YWik=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=MooxQ3yXGNmCMYmAPyS4YaT8WUSTSGiIaRoRUrQlfEEfZaPRJGr8nQsjCwZjSEYvW +VA8sZQvyoU3Gf9pqv7RAk0VGxiNzXbLySE+VosNUgKSApgJo0GMEy6xxKdAeaCzfY MgXL+725kEpcMEFLegVCB/FbW/IjOL3awFxiXIwi4g5kkaj/smuNvNe0nMg35Vi/Gn uvlnuUidgLUMTg5zoyiegeYecMwZr/wKe/+PsawghTVFtmMV5hWirungglBGyBa6Zy 9C1ym/GFh0SPxD68AHX6upnJiFfuOlXDd9nhoIG87kQ90npFnHjPWSD3O9MvVIEBH0 0Gg6RJVuddH1A== Message-ID: <174b8d76-5514-4942-af5d-c975ff95ee03@kernel.org> Date: Tue, 9 Jun 2026 16:41:01 +0200 Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v9 2/6] mm/memory-failure: surface unhandlable kernel pages as -ENOTRECOVERABLE To: Breno Leitao , Miaohe Lin , Andrew Morton , Lorenzo Stoakes , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Shuah Khan , Naoya Horiguchi , Jonathan Corbet , Shuah Khan , "Liam R. Howlett" , lance.yang@linux.dev, Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers 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 References: <20260609-ecc_panic-v9-0-432a74002e74@debian.org> <20260609-ecc_panic-v9-2-432a74002e74@debian.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <20260609-ecc_panic-v9-2-432a74002e74@debian.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 6/9/26 12:56, 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 HWPoisonKernelOwned(), a small predicate that positively > identifies pages the hwpoison handler cannot recover from: > > HWPoisonKernelOwned(p, flags) := > !(MF_SOFT_OFFLINE && page_has_movable_ops(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. > > The MF_SOFT_OFFLINE / page_has_movable_ops() opt-out mirrors the > same exception in HWPoisonHandlable(): soft-offline is allowed to > migrate movable_ops pages even though they are not on the LRU, and > we must not pre-empt that with an unrecoverable verdict. > > 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 | 60 +++++++++++++++++++++++++++++++++++++++++++++++++++-- > 1 file changed, 58 insertions(+), 2 deletions(-) > > diff --git a/mm/memory-failure.c b/mm/memory-failure.c > index f4d3e6e20e13..eed9de387694 100644 > --- a/mm/memory-failure.c > +++ b/mm/memory-failure.c > @@ -1325,6 +1325,46 @@ 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. > + * These page types are owned by kernel internals (no userspace mapping > + * to unmap, no file mapping to invalidate, no migration target), so the > + * shake_page() / retry loop in get_any_page() can never turn them into > + * something HWPoisonHandlable() will accept. Short-circuit them to > + * -ENOTRECOVERABLE so callers can panic on operator request instead of > + * spinning through retries that exit as a transient-looking -EIO. > + * > + * The MF_SOFT_OFFLINE / page_has_movable_ops() opt-out mirrors > + * HWPoisonHandlable(): soft-offline is allowed to migrate movable_ops > + * pages even though they are not on the LRU. > + */ > +static inline bool HWPoisonKernelOwned(struct page *page, unsigned long flags) > +{ > + struct page *head; > + > + if ((flags & MF_SOFT_OFFLINE) && page_has_movable_ops(page)) > + return false; > + On a second look: Do we really need that? The page types below never support migration. So I guess that check is not required? Apart from that, looks good with two comments: a) HWPoisonKernelOwned: this is not the common style for us to name functions. is_kernel_owned_page() or sth like that would do. b) The function doc can likely be simplified a bit. No need to mention the short-circuit stuff, for example, IMHO. -- Cheers, David