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Fri, 20 Jun 2025 12:50:20 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id wMA/BAxZVWiqLgAAD6G6ig (envelope-from ); Fri, 20 Jun 2025 12:50:20 +0000 Date: Fri, 20 Jun 2025 14:50:18 +0200 From: Oscar Salvador To: David Hildenbrand Cc: 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 Subject: Re: [PATCH RFC 01/14] mm/memory: drop highest_memmap_pfn sanity check in vm_normal_page() Message-ID: References: <20250617154345.2494405-1-david@redhat.com> <20250617154345.2494405-2-david@redhat.com> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250617154345.2494405-2-david@redhat.com> X-Spamd-Result: default: False [-4.30 / 50.00]; BAYES_HAM(-3.00)[99.99%]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-0.998]; MIME_GOOD(-0.10)[text/plain]; MISSING_XM_UA(0.00)[]; MIME_TRACE(0.00)[0:+]; RCPT_COUNT_TWELVE(0.00)[29]; ARC_NA(0.00)[]; TO_DN_SOME(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; RCVD_TLS_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; R_RATELIMIT(0.00)[to_ip_from(RLhwqoz3wsm4df3nfubx4grhps)]; RCVD_COUNT_TWO(0.00)[2]; FUZZY_BLOCKED(0.00)[rspamd.com]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo] X-Spam-Level: X-Spam-Flag: NO X-Spam-Score: -4.30 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 I'm confused, I'm missing something here. Before this change we would return NULL if e.g: pfn > highest_memmap_pfn, but now we just print the warning and call pfn_to_page() anyway. AFAIK, pfn_to_page() doesn't return NULL? -- Oscar Salvador SUSE Labs