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Wed, 07 Oct 2026 05:10:41 +0000 X-Mizu-Trace-ID: af8f4c7b60dce85b X-Migadu-Flow: FLOW_OUT Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable From: Muchun Song Mime-Version: 1.0 (1.0) Subject: Re: [PATCH v2] mm/hugetlb: use kvmalloc_objs for hugetlb_fault_mutex_table Date: Wed, 7 Oct 2026 07:10:08 +0200 Message-Id: <5714BF9B-9FE3-41DC-A215-EEAAEBD7F9D3@linux.dev> References: <20261006160128.31447-1-dheerajkumar.srivastava@amd.com> Cc: osalvador@suse.de, david@kernel.org, akpm@linux-foundation.org, davidlohr@hp.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Vasant.Hegde@amd.com, bharata@amd.com, dheerajkumar.srivastava@amd.com In-Reply-To: <20261006160128.31447-1-dheerajkumar.srivastava@amd.com> To: Dheeraj Kumar Srivastava X-Mailer: iPhone Mail (24A446) X-Stat-Signature: p1nfr88pdaada5fkf88x4ao8gqxkakae X-Rspamd-Queue-Id: 7F1C0140006 X-Rspam-User: X-Rspamd-Server: rspam02 X-HE-Tag: 1791356142-941043 X-HE-Meta: U2FsdGVkX18z2ffPNlPakNNxlL+WQj5mYzYMcLOm+FwhyWCrqu5zHQDWpD6v9xnHnAmkrG05flR1NkYkYMiC/IPefa7LOnl+lf+YHNAsgRWuMdPIWaqV3edm+kpISqDGHX/V1qPWfDLbhKv5iNZTvNLj9go0hWOYpO3tdOhvqQbCvPmkdc4/PBdr0dxEWad4yoV1WaEhpiuHp1bElSMrMb04WjgPiE2QF6iEM58AYzgVf0G8oZY6ahfw8+BCylAQy6ph/CW0LfDQ6eDXG0WVR2Ev17sFmEPUmADDnrFYnziPySfwYMtKw3j06ESAuThkmk+fXrHvpKSNepRovx/YZEAVK8ZmIB+UXZGnxvsHEpEmEY1ZSSLDAN4pHhFOWZJKjANDZ9FntQGynUQT3FOPdaAol1rASKYOY/H4PVUs/B4SRSOmpLhc2o1Eb2mo33lt9egLsYTiQlpV1PeEyQmU9G6LCn2Fou2aDjPDBlWjU1cA/ZBAq1jTgdS4TKQ198RqWtZtMX2JPopuOn7Vw/INlJufYnQayPG/iCo2/EGr9rXEg1ELRqrYJJjw8f1PLZnf7EPzMz26OaxJXMnu7KtKRvbZ4dYFF+Yz50XXmaviSLPBfY5LJrYH+eDtCZMijwC7l2epmsL0wnfa5vdsRfLSSCX81/8ih6lzjFf39FatVoc3leJ0ryDa/EAx6P2t1Dzyp5J2OPeWvpf9X4G3cgMN0weui0WynoLnVJFpJPjxmFDX4IKXsMnuBZjI+sDJhFz+vaeNII7K567w3tDyiuumwDNpeTAeUTSEQQ0ErfV1jDZfsqGhjBNhbl1g8FwasUzI5YJ4IK8Pob+A967FIkJSVtSFT5TA3wDF7lX6X18XxWV4yx0+fU6/NcLtnPjZG2HlX7MGphWzPhp9I0F+DS53r3bNOFMcLZ6A0PyAg4KIi68ZT8zIKNgX8PcTHC9XFHHPLkqiJQDzgzrQRsIp268 BYgU/5TJ SVzgLcfaar7QbSKsu2UAMNukvAWtST59Oa2eO4AFk/IwafnZiPW+eJyHItyY5C+A4+PA52xauMFDE7noqoVuwq2TNBD7ymN7gT0HOCAVyUrZG8jrERQVBhsWel6lIDhQSVO+bbbp4lBertcb/KnQemXz0HAeDde5wQJ3qcuEbpLsLIIdPW9gxND09u4agFcydOfKZQ0ePkHYoIgNXrw0ppas2tVoG4ClwHhMWc1E1qdiNfN1pB6uHmSjENPAh3WFzf8fYnzkj529Bn9nBK107d/ypBKcRO6z3p9d7OwhQ6rN/nhS6c5uLFrDY6vDwEdTRHjD7Oje6mD2D/qLBNahMY/9ZY5Bp6kDny9cc2xn+C7FwjluH86QZVX1KZWdoFR3hOTF5rayKJDWdl6RpB0juSYtRKnd642TwAFtoomp+xdvxB5ctxfwliUu90rAHWWpiuGawJxX9ROkoYbnbyT4m2RJ4HA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: > On Oct 6, 2026, at 18:02, Dheeraj Kumar Srivastava wrote: >=20 > =EF=BB=BFOn systems/VMs with a large number of CPUs (e.g. 4096), hugetlb_i= nit() > computes num_fault_mutexes =3D roundup_pow_of_two(8 * num_possible_cpus())= > =3D 32768. The subsequent kmalloc for the mutex table can exceed > MAX_PAGE_ORDER when struct mutex is enlarged by debug options like > CONFIG_DEBUG_MUTEXES and CONFIG_DEBUG_LOCK_ALLOC, resulting in: >=20 > WARNING: at __alloc_frozen_pages_noprof (order > MAX_PAGE_ORDER) > kernel BUG at mm/hugetlb.c (BUG_ON(!hugetlb_fault_mutex_table)) > Kernel panic - not syncing: Fatal exception >=20 > Switch to kvmalloc_objs() so the allocation falls back to vmalloc when > the contiguous physical allocation is too large. The table is only > accessed by index, so virtual contiguity is sufficient. >=20 > Fixes: 8382d914ebf7 ("mm, hugetlb: improve page-fault scalability") > Signed-off-by: Dheeraj Kumar Srivastava Thanks for your fix. Acked-by: Muchun Song Thanks=20=