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b=MMSb57VeWOdXEwlbRHF4H1wJyw7LzX8e2zt39PI2tcH5khVQ/JKO0bzfWh+hgHTy/ /f2AnrsyQvgXBfNReRpAvGpe7P6Iba3WDMzdxgabnfwgwWqOfYq+QeuCIKIfw82yOZ SbpoH+qAjPOALH5Pu5Begy9Whtf2B9RzbCSoXxxHUdwiAt1hZ8nNx8SZvbZDGghdqJ 9uEGk97TUCdjSh/lbRaAMjoMNm36B01uDz7I8kCrAdiclBC0uoNDwJM9+YvC76Z/p/ 6Zt4xHhoLHShLkd9bbEK0Un+0sxAF9MWduSGYLr2P7a9Eqen3WyM5qcjEXaL0L/eu+ OyDj4h0l+avrg== Message-ID: Date: Wed, 13 May 2026 09:54:19 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 1/4] mm/memory-failure: report MF_MSG_KERNEL for reserved pages To: Lance Yang Cc: leitao@debian.org, linmiaohe@huawei.com, nao.horiguchi@gmail.com, akpm@linux-foundation.org, corbet@lwn.net, skhan@linuxfoundation.org, ljs@kernel.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, shuah@kernel.org, rostedt@goodmis.org, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, liam@infradead.org, 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: <9504c193-8c01-4d03-8f62-c50fd7fbdbc0@kernel.org> <20260512124837.38883-1-lance.yang@linux.dev> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 291F3140005 X-Stat-Signature: t93crtj7akd6u3o183s47oj81ogzn985 X-Rspam-User: X-HE-Tag: 1778658868-789197 X-HE-Meta: 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 XGDdNLZ8 cxnhwtfk3VeMsqcsRtgj7XedSuOPZvlX+c4jqPNQhCkm8F179lFmTRcqwDxkyLuSUKie0Yywaq7eacdOCZY2hzADbSSfejG7d9Rgc2fOM+3B1xDzPzW+NGY3pjNPiIDfc4YKRSHqoBAranJ3d3UYKATIYLasj+qcAQjkMOttx/QNjfrWIgZ1afcKxBrkuhMVVlFUzFwK38ilaVOzO22L/dYQjs9J9lw7S49E+OuTCIieWda2knEuZ+/HGbxyCMORs2Jc6eHlwzlch5gCpEZuKc7/EaMHQuAbCpYTZgIwQFy732hsoZFlgyYLjyuykcoqW3Nq9AspOeciY31X/DWF7gahmtQDathJAwOXFPWa8roicXVraHFdOvpGca9AhmmHvYzepcp9NTiNVhxi+lXTbbdItdH20rFiB5v99oOuPLKMCu90vM2EKwTPczdlqU9Tz3ABPRvQf6XkD7maYYSFwJf8922FmIL0TvUoq Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 5/12/26 14:48, Lance Yang wrote: > > On Tue, May 12, 2026 at 10:17:00AM +0200, David Hildenbrand (Arm) wrote: >> On 5/11/26 17:38, Breno Leitao wrote: >>> When get_hwpoison_page() returns a negative value, distinguish >>> reserved pages from other failure cases by reporting MF_MSG_KERNEL >>> instead of MF_MSG_GET_HWPOISON. Reserved pages belong to the kernel >>> and should be classified accordingly for proper handling. >>> >>> Sample PG_reserved before the get_hwpoison_page() call. In the >>> MF_COUNT_INCREASED path get_any_page() can drop the caller's >>> reference before returning -EIO, after which the underlying page may >>> have been freed and reallocated with page->flags reset; reading >>> PageReserved(p) at that point would observe stale or unrelated state. >>> The pre-call snapshot reflects what the page actually was at the >>> time of the failure event. >>> >>> Acked-by: Miaohe Lin >>> Reviewed-by: Lance Yang >>> Signed-off-by: Breno Leitao >>> --- >>> mm/memory-failure.c | 19 ++++++++++++++++++- >>> 1 file changed, 18 insertions(+), 1 deletion(-) >>> >>> diff --git a/mm/memory-failure.c b/mm/memory-failure.c >>> index 866c4428ac7ef..f112fb27a8ff6 100644 >>> --- a/mm/memory-failure.c >>> +++ b/mm/memory-failure.c >>> @@ -2348,6 +2348,7 @@ int memory_failure(unsigned long pfn, int flags) >>> unsigned long page_flags; >>> bool retry = true; >>> int hugetlb = 0; >>> + bool is_reserved; >>> >>> if (!sysctl_memory_failure_recovery) >>> panic("Memory failure on page %lx", pfn); >>> @@ -2411,6 +2412,18 @@ int memory_failure(unsigned long pfn, int flags) >>> * In fact it's dangerous to directly bump up page count from 0, >>> * that may make page_ref_freeze()/page_ref_unfreeze() mismatch. >>> */ >>> + /* >>> + * Pages with PG_reserved set are not currently managed by the >>> + * page allocator (memblock-reserved memory, driver reservations, >>> + * etc.), so classify them as kernel-owned for reporting. >>> + * >>> + * Sample the flag before get_hwpoison_page(): in the >>> + * MF_COUNT_INCREASED path, get_any_page() can drop the caller's >>> + * reference before returning -EIO, after which page->flags may >>> + * have been reset by the allocator. >>> + */ >>> + is_reserved = PageReserved(p); >>> + >>> res = get_hwpoison_page(p, flags); >>> if (!res) { >>> if (is_free_buddy_page(p)) { >>> @@ -2432,7 +2445,11 @@ int memory_failure(unsigned long pfn, int flags) >>> } >>> goto unlock_mutex; >>> } else if (res < 0) { >>> - res = action_result(pfn, MF_MSG_GET_HWPOISON, MF_IGNORED); >>> + if (is_reserved) >>> + res = action_result(pfn, MF_MSG_KERNEL, MF_IGNORED); >>> + else >>> + res = action_result(pfn, MF_MSG_GET_HWPOISON, >>> + MF_IGNORED); >>> goto unlock_mutex; >>> } >>> >>> >> >> It's a bit odd that we need this handling when we already have handling for >> reserved pages in error_states[]. >> >> HWPoisonHandlable() would always essentially reject PG_reserved pages. So >> __get_hwpoison_page() ... would always fail? Making >> get_hwpoison_page()->get_any_page() always fail? >> >> But then, we never call identify_page_state()? And never call me_kernel()? > > Looks like we never get that far ... Right, likely that should be removed+cleaned up then. -- Cheers, David