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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id 00721157ae682-716659a1440sm15515367b3.35.2025.07.06.23.31.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 06 Jul 2025 23:32:02 -0700 (PDT) Date: Sun, 6 Jul 2025 23:31:50 -0700 (PDT) From: Hugh Dickins To: David Hildenbrand cc: Lance Yang , Oscar Salvador , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, nvdimm@lists.linux.dev, Andrew Morton , Juergen Gross , Stefano Stabellini , Oleksandr Tyshchenko , Dan Williams , Alistair Popple , Matthew Wilcox , Jan Kara , Alexander Viro , Christian Brauner , Zi Yan , Baolin Wang , Lorenzo Stoakes , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jann Horn , Pedro Falcato , Lance Yang Subject: Re: [PATCH RFC 01/14] mm/memory: drop highest_memmap_pfn sanity check in vm_normal_page() In-Reply-To: Message-ID: References: <20250617154345.2494405-1-david@redhat.com> <20250617154345.2494405-2-david@redhat.com> <5e5e8d79-61b1-465d-ab5a-4fa82d401215@redhat.com> MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="-1463770367-1279896212-1751869921=:5466" X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 4C41E180003 X-Stat-Signature: qqgnnda7eupqsem9r1u7gg8jbsiba6hp X-HE-Tag: 1751869924-237306 X-HE-Meta: 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 4Skir6v+ 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. ---1463770367-1279896212-1751869921=:5466 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE On Fri, 4 Jul 2025, David Hildenbrand wrote: > On 03.07.25 16:44, Lance Yang wrote: > > On 2025/7/3 20:39, David Hildenbrand wrote: > >> On 03.07.25 14:34, Lance Yang wrote: > >>> On Mon, Jun 23, 2025 at 10:04=E2=80=AFPM David Hildenbrand > >>> wrote: > >>>> > >>>> On 20.06.25 14:50, Oscar Salvador wrote: > >>>>> On Tue, Jun 17, 2025 at 05:43:32PM +0200, David Hildenbrand wrote: > >>>>>> In 2009, we converted a VM_BUG_ON(!pfn_valid(pfn)) to the current > >>>>>> highest_memmap_pfn sanity check in commit 22b31eec63e5 ("badpage: > >>>>>> vm_normal_page use print_bad_pte"), because highest_memmap_pfn was > >>>>>> readily available. > >>>>>> > >>>>>> Nowadays, this is the last remaining highest_memmap_pfn user, and = this > >>>>>> sanity check is not really triggering ... frequently. > >>>>>> > >>>>>> Let's convert it to VM_WARN_ON_ONCE(!pfn_valid(pfn)), so we can > >>>>>> simplify and get rid of highest_memmap_pfn. Checking for > >>>>>> pfn_to_online_page() might be even better, but it would not handle > >>>>>> ZONE_DEVICE properly. > >>>>>> > >>>>>> Do the same in vm_normal_page_pmd(), where we don't even report a > >>>>>> problem at all ... > >>>>>> > >>>>>> What might be better in the future is having a runtime option like > >>>>>> page-table-check to enable such checks dynamically on-demand. > >>>>>> Something > >>>>>> for the future. > >>>>>> > >>>>>> Signed-off-by: David Hildenbrand The author of 22b31eec63e5 thinks this is not at all an improvement. Of course the condition is not triggering frequently, of course it should not happen: but it does happen, and it still seems worthwhile to catch it in production with a "Bad page map" than to let it run on to whatever kind of crash it hits instead. Hugh ---1463770367-1279896212-1751869921=:5466--