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[96.255.20.138]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-5070d53f0fcsm38640631cf.9.2026.02.22.00.49.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 22 Feb 2026 00:49:33 -0800 (PST) From: Gregory Price To: lsf-pc@lists.linux-foundation.org Cc: linux-kernel@vger.kernel.org, linux-cxl@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, damon@lists.linux.dev, kernel-team@meta.com, gregkh@linuxfoundation.org, rafael@kernel.org, dakr@kernel.org, dave@stgolabs.net, jonathan.cameron@huawei.com, dave.jiang@intel.com, alison.schofield@intel.com, vishal.l.verma@intel.com, ira.weiny@intel.com, dan.j.williams@intel.com, longman@redhat.com, akpm@linux-foundation.org, david@kernel.org, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, osalvador@suse.de, ziy@nvidia.com, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, gourry@gourry.net, ying.huang@linux.alibaba.com, apopple@nvidia.com, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, yury.norov@gmail.com, linux@rasmusvillemoes.dk, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, tj@kernel.org, hannes@cmpxchg.org, mkoutny@suse.com, jackmanb@google.com, sj@kernel.org, baolin.wang@linux.alibaba.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, muchun.song@linux.dev, xu.xin16@zte.com.cn, chengming.zhou@linux.dev, jannh@google.com, linmiaohe@huawei.com, nao.horiguchi@gmail.com, pfalcato@suse.de, rientjes@google.com, shakeel.butt@linux.dev, riel@surriel.com, harry.yoo@oracle.com, cl@gentwo.org, roman.gushchin@linux.dev, chrisl@kernel.org, kasong@tencent.com, shikemeng@huaweicloud.com, nphamcs@gmail.com, bhe@redhat.com, zhengqi.arch@bytedance.com, terry.bowman@amd.com Subject: [RFC PATCH v4 10/27] mm/swap: add free_folio callback for folio release cleanup Date: Sun, 22 Feb 2026 03:48:25 -0500 Message-ID: <20260222084842.1824063-11-gourry@gourry.net> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260222084842.1824063-1-gourry@gourry.net> References: <20260222084842.1824063-1-gourry@gourry.net> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit When a folio's refcount drops to zero, the service may need to perform cleanup before the page returns to the buddy allocator (e.g. zeroing pages to scrub stale compressed data / release compression ratio). Add folio_managed_on_free() to wrap both zone_device and private node semantics for this operation since they are the same. One difference between zone_device and private node folios: - private nodes may choose to either take a reference and return true ("handled"), or return false to return it back to the buddy. - zone_device returns the page to the buddy (always returns true) Signed-off-by: Gregory Price --- include/linux/node_private.h | 6 ++++++ mm/internal.h | 30 ++++++++++++++++++++++++++++++ mm/swap.c | 21 ++++++++++----------- 3 files changed, 46 insertions(+), 11 deletions(-) diff --git a/include/linux/node_private.h b/include/linux/node_private.h index 7687a4cf990c..09ea7c4cb13c 100644 --- a/include/linux/node_private.h +++ b/include/linux/node_private.h @@ -39,10 +39,16 @@ struct vm_fault; * callback to prevent node_private from being freed. * These callbacks MUST NOT sleep. * + * @free_folio: Called when a folio refcount drops to 0 + * [folio-referenced callback] + * Returns: true if handled (skip return to buddy) + * false if no op (return to buddy) + * * @flags: Operation exclusion flags (NP_OPS_* constants). * */ struct node_private_ops { + bool (*free_folio)(struct folio *folio); unsigned long flags; }; diff --git a/mm/internal.h b/mm/internal.h index 97023748e6a9..658da41cdb8e 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -1412,6 +1412,36 @@ int numa_migrate_check(struct folio *folio, struct vm_fault *vmf, void free_zone_device_folio(struct folio *folio); int migrate_device_coherent_folio(struct folio *folio); +/** + * folio_managed_on_free - Notify managed-memory service that folio + * refcount reached zero. + * @folio: the folio being freed + * + * Returns true if the folio is fully handled (zone_device -- caller + * must return immediately). Returns false if the callback ran but + * the folio should continue through the normal free path + * (private_node -- pages go back to buddy). + * + * Returns false for normal folios (no-op). + */ +static inline bool folio_managed_on_free(struct folio *folio) +{ + if (folio_is_zone_device(folio)) { + free_zone_device_folio(folio); + return true; + } + if (folio_is_private_node(folio)) { + const struct node_private_ops *ops = + folio_node_private_ops(folio); + + if (ops && ops->free_folio) { + if (ops->free_folio(folio)) + return true; + } + } + return false; +} + struct vm_struct *__get_vm_area_node(unsigned long size, unsigned long align, unsigned long shift, unsigned long vm_flags, unsigned long start, diff --git a/mm/swap.c b/mm/swap.c index 2260dcd2775e..dca306e1ae6d 100644 --- a/mm/swap.c +++ b/mm/swap.c @@ -37,6 +37,7 @@ #include #include #include +#include #include "internal.h" @@ -96,10 +97,9 @@ static void page_cache_release(struct folio *folio) void __folio_put(struct folio *folio) { - if (unlikely(folio_is_zone_device(folio))) { - free_zone_device_folio(folio); - return; - } + if (unlikely(folio_is_private_managed(folio))) + if (folio_managed_on_free(folio)) + return; if (folio_test_hugetlb(folio)) { free_huge_folio(folio); @@ -961,19 +961,18 @@ void folios_put_refs(struct folio_batch *folios, unsigned int *refs) if (is_huge_zero_folio(folio)) continue; - if (folio_is_zone_device(folio)) { + if (!folio_ref_sub_and_test(folio, nr_refs)) + continue; + + if (unlikely(folio_is_private_managed(folio))) { if (lruvec) { unlock_page_lruvec_irqrestore(lruvec, flags); lruvec = NULL; } - if (folio_ref_sub_and_test(folio, nr_refs)) - free_zone_device_folio(folio); - continue; + if (folio_managed_on_free(folio)) + continue; } - if (!folio_ref_sub_and_test(folio, nr_refs)) - continue; - /* hugetlb has its own memcg */ if (folio_test_hugetlb(folio)) { if (lruvec) { -- 2.53.0