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Thu, 14 May 2026 08:15:48 +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 +oCGHbSEBWoGHgAAD6G6ig (envelope-from ); Thu, 14 May 2026 08:15:48 +0000 Date: Thu, 14 May 2026 10:15:47 +0200 From: Oscar Salvador To: Muchun Song Cc: Andrew Morton , David Hildenbrand , Muchun Song , Michael Ellerman , Madhavan Srinivasan , Lorenzo Stoakes , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Nicholas Piggin , Christophe Leroy , Ackerley Tng , Frank van der Linden , aneesh.kumar@linux.ibm.com, joao.m.martins@oracle.com, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 06/69] mm/sparse: Panic on memmap and usemap allocation failure Message-ID: References: <20260513130542.35604-1-songmuchun@bytedance.com> <20260513130542.35604-7-songmuchun@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260513130542.35604-7-songmuchun@bytedance.com> X-Stat-Signature: qp5caw3aczko5y6ajm8qihxartd7z5hp X-Rspamd-Queue-Id: F33DCA000E X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1778746550-220697 X-HE-Meta: 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 y05DNVJt HxKabd8x6n2UO/jZEGZeE7rHmemnDBML9tY2UIHONcnNuCu3H3w7IenMKsPuswuLFXaVSgwz3BGTUg8qyfn/e7D7OQ3HznlA0lCOvT7qs9EAO0QR/AWTnEnc/y2IFRe4iI4Jxyax2TFXjz/DQBC1GblDsdsnYyi81VFFxeYDvH3leh3lkDKFaUPeI8nJ+Jv8K9myqSclOsEUstQIRlrcHS5vl+d0nfu60W3mSyy2WFOrwKk+JK58X0y/c2Ra/8imrm/iTVXoTEoyc9VGi/PAfGtoQwXpFvkz8V0CRL5pQV/kNIjd0/5zACp2UHw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, May 13, 2026 at 09:04:34PM +0800, Muchun Song wrote: > When vmemmap or usemap allocation fails, sparse_init_nid() currently > marks the section non-present and continues. Later boot-time code can > still walk PFNs in that section without checking for this partial setup, > which leads to invalid accesses. subsection_map_init() can also touch an > unallocated usemap. > > Auditing and fixing all early PFN walkers for this case is not worth the > complexity. These allocation failures are expected to be fatal anyway, > and other memory models already treat them that way. > > Make memmap and usemap allocation failures panic immediately instead of > trying to recover and crashing later in less obvious ways. This is also > consistent with how other memory model configurations handle memmap > allocation failures. > > Signed-off-by: Muchun Song > Acked-by: Mike Rapoport (Microsoft) Yes, one could argue that if we fail to allocate memory at that early stage we are already screwed. Acked-by: Oscar Salvador -- Oscar Salvador SUSE Labs