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Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Jonathan Corbet , Shuah Khan , Randy Dunlap , Peter Xu , Breno Leitao , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Peter Zijlstra , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , Arnd Bergmann , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Gerd Hoffmann , linux-doc@vger.kernel.org, linux-arch@vger.kernel.org, linux-s390@vger.kernel.org, Josef Bacik , stable@kernel.org Content-Transfer-Encoding: quoted-printable Message-Id: <8DF234F5-8EAF-427C-928C-8DD6E53FC501@linux.dev> References: <20261028-fixes_hugetlb-v1-0-a0a033db180f@kernel.org> <20261028-fixes_hugetlb-v1-5-a0a033db180f@kernel.org> To: "David Hildenbrand (Arm)" X-Mailer: Apple Mail (2.3901.100.1.1.12) X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 670F920003 X-Stat-Signature: ypann9kpy46dewuo4p9bahndgrryy1am X-Spam-Status: No, score=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS autolearn=ham autolearn_force=no version=4.0.1 X-Rspam-User: X-HE-Tag: 1793245905-102017 X-HE-Meta: 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 JhaKScAc n/8Y3nTz9qAkVSPE8gtQbdNt/39mhHwzJEJauc+kNqbGMC7D+GzHguDFfUB6bFlLV1DyXzY8QIY40nCvSOdvea91F485JurpaoWxLMv1RB5yUidEbLVouTE+PXKK6rGAsNzqor54m6LHoW1dPi9yzW8NR7jJZIeUZXmhP04KKjWm45Yo/8Y49/W6yhNcj2qA0jtInPVChvVSgIcFVSTjstpWKgMiqpykRZQyjTjJLwUrk+sWtYkc+vi1+62fNTVVJruBE4osTv4hqS/3EZKg3/1swSytEegKsxgCppoBqgL3/3DB7GTUArHhqJ9wzZnb57RhqbrNxSEeTz+Ug9okXbP/arqr22VCe7n1T7KkJJZdEiYdjvIAayEIZjIjtZh0Yb7wivtmHlwARZG4nXaYcwb+nd4iJBcYOf4XFZY7SYZ+NSyQ= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 > On Oct 29, 2026, at 04:13, David Hildenbrand (Arm) = wrote: >=20 > From: Josef Bacik >=20 > Surplus folios are accounted per node. When shrinking the pool, > set_max_huge_pages() removes free folios through > remove_pool_hugetlb_folio() and accounts them as persistent folios. >=20 > It can select a node whose folios are all surplus and leave its = surplus > count larger than its total count. Free surplus folios can back > reservations created by gather_surplus_pages(). >=20 > For example, with nr_overcommit_hugepages =3D 8 on two nodes: >=20 > (node columns show total/free/surplus) >=20 > total free surp node0 node1 > mmap() of one page, bound to node 0 1 1 1 1 1 1 0 0 0 > node1/nr_hugepages =3D 7 8 8 1 1 1 1 7 7 0 > nr_hugepages =3D 6 7 7 1 0 0 1 7 7 0 > munmap() 7 7 1 0 0 1 7 7 0 > nr_hugepages =3D 0 1 1 1 0 0 1 1 1 0 >=20 > After shrinking to six persistent folios, node 0 has no folios but its > surplus count is still one. Releasing the reservation cannot clear = that > count, and shrinking the pool to zero leaves one free page on node 1. >=20 > A later write to node0/nr_hugepages underflows the unsigned per-node > persistent count: 0 - 1, resulting in allocation of many folios. >=20 > Use persistent_huge_pages_node() to skip nodes with no persistent = folios, > as adjust_pool_surplus() does. This also excludes temporary folios. >=20 > Fixes: e4e574b767ba ("hugetlb: Try to grow hugetlb pool for MAP_SHARED = mappings") > Cc: stable@kernel.org > Signed-off-by: Josef Bacik > [ david: cleanup code and description ] > Signed-off-by: David Hildenbrand (Arm) Acked-by: Muchun Song Thanks.