kernel/linux.git/include/linux/memory_hotplug.h, branch v7.3-rc1

mm/memory_hotplug: add offline_and_remove_memory_ranges()

2026-08-07T01:56:59+00:00

offline_and_remove_memory() handles a single contiguous range. Callers that manage a device composed of several ranges (dax/kmem) currently have to call it in a loop, which gives up atomicity. In addition to pushing rollback logic into the driver, the lack of atomicity creates a race condition between system daemons trying to manage the same resource: - Manager 1: Offlines memory blocks. Removes device. ^^^^ - Manager 2: Detects offline memory blocks, re-onlines them. Add offline_and_remove_memory_ranges(), which takes an array of ranges and processes them as one operation under a single lock_device_hotplug(): - Phase 1 offlines every block of every range. - Phase 2 removes the ranges only if all ranges are offline. - If any offline fails, the whole operation is reverted. This gives callers all-or-nothing semantics for the offline step, so a failed or interrupted unplug leaves the device in a consistent state. This also resolves the battling managers race - the second manager's operation simply fails when the block is destroyed / cannot be onlined. offline_and_remove_memory() becomes a thin wrapper that passes its single range to the new helper, so the offline/rollback logic lives in one place. Link: https://lore.kernel.org/20260712154505.3564379-7-gourry@gourry.net Signed-off-by: Gregory Price Suggested-by: David Hildenbrand (Arm) Reviewed-by: Dave Jiang Acked-by: David Hildenbrand (Arm) Reviewed-by: Dan Williams Cc: Alison Schofield Cc: Danilo Krummrich Cc: Greg Kroah-Hartman Cc: Hannes Reinecke Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Michal Hocko Cc: Mike Rapoport Cc: Oscar Salvador Cc: Pankaj Gupta Cc: "Rafael J. Wysocki" Cc: Shuah Khan Cc: Suren Baghdasaryan Cc: Vishal Verma Cc: Vlastimil Babka Signed-off-by: Andrew Morton

mm/memory_hotplug: add __add_memory_driver_managed() with online_type arg

2026-08-07T01:56:59+00:00

Existing callers of add_memory_driver_managed cannot select the preferred online type (ZONE_NORMAL vs ZONE_MOVABLE), requiring it to hot-add memory as offline blocks, and then follow up by onlining each memory block individually. Most drivers prefer the system default, but the CXL driver wants to plumb a preferred policy through the dax kmem driver. Refactor APIs to add a new interface which allows the dax kmem module to select a preferred policy. Overriding the configured auto-online policy is only safe for known in-tree modules, where we know the override reflects a different, user-requested policy. We do not want arbitrary out-of-tree drivers silently overriding the system-wide onlining policy, so restrict the new interface to the kmem module using EXPORT_SYMBOL_FOR_MODULES() rather than a plain EXPORT_SYMBOL_GPL(). Other in-tree modules (e.g. cxl_core) can be added to the allowed list as the need arises. Refactor add_memory_driver_managed, extract __add_memory_driver_managed - Add proper kernel-doc for add_memory_driver_managed while refactoring - New helper accepts an explicit online_type. - New helper validates online_type is between OFFLINE and ONLINE_MOVABLE Refactor: add_memory_resource, extract __add_memory_resource - new helper accepts an explicit online_type Original APIs now explicitly pass the system-default to new helpers. No functional change for existing users. Link: https://lore.kernel.org/20260712154505.3564379-6-gourry@gourry.net Signed-off-by: Gregory Price Acked-by: David Hildenbrand (Arm) Reviewed-by: Pankaj Gupta Reviewed-by: Dave Jiang Reviewed-by: Dan Williams Cc: Alison Schofield Cc: Danilo Krummrich Cc: Greg Kroah-Hartman Cc: Hannes Reinecke Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Michal Hocko Cc: Mike Rapoport Cc: Oscar Salvador Cc: "Rafael J. Wysocki" Cc: Shuah Khan Cc: Suren Baghdasaryan Cc: Vishal Verma Cc: Vlastimil Babka Signed-off-by: Andrew Morton

mm/memory_hotplug: export mhp_get_default_online_type

2026-08-07T01:56:59+00:00

Drivers which may pass hotplug policy down to DAX need MMOP_ symbols and the mhp_get_default_online_type function for hotplug use cases. Some drivers (cxl) co-mingle their hotplug and devdax use-cases into the same driver code, and chose the dax_kmem path as the default driver path - making it difficult to require hotplug as a predicate to building the overall driver (it may break other non-hotplug use-cases). Export mhp_get_default_online_type function to allow these drivers to build when hotplug is disabled and still use the DAX use case. In the built-out case we simply return MMOP_OFFLINE as it's non-destructive. The internal function can never return -1 either, so we choose this to allow for defining the function with 'enum mmop'. Link: https://lore.kernel.org/20260712154505.3564379-5-gourry@gourry.net Signed-off-by: Gregory Price Reviewed-by: Dave Jiang Reviewed-by: Dan Williams Acked-by: David Hildenbrand (Arm) Cc: Alison Schofield Cc: Danilo Krummrich Cc: Greg Kroah-Hartman Cc: Hannes Reinecke Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Michal Hocko Cc: Mike Rapoport Cc: Oscar Salvador Cc: Pankaj Gupta Cc: "Rafael J. Wysocki" Cc: Shuah Khan Cc: Suren Baghdasaryan Cc: Vishal Verma Cc: Vlastimil Babka Signed-off-by: Andrew Morton

mm/memory_hotplug: add mhp_online_type_to_str() and export string helpers

2026-08-07T01:56:58+00:00

Add mhp_online_type_to_str() as the inverse of mhp_online_type_from_str(), and export both so a driver can render and parse the memory online type through its own sysfs interface. Link: https://lore.kernel.org/20260712154505.3564379-3-gourry@gourry.net Signed-off-by: Gregory Price Reviewed-by: Dave Jiang Acked-by: David Hildenbrand (Arm) Reviewed-by: Dan Williams Cc: Alison Schofield Cc: Danilo Krummrich Cc: Greg Kroah-Hartman Cc: Hannes Reinecke Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Michal Hocko Cc: Mike Rapoport Cc: Oscar Salvador Cc: Pankaj Gupta Cc: "Rafael J. Wysocki" Cc: Shuah Khan Cc: Suren Baghdasaryan Cc: Vishal Verma Cc: Vlastimil Babka Signed-off-by: Andrew Morton

mm/mm_init: handle alloc_percpu failure in free_area_init_core_hotplug

2026-07-31T02:40:31+00:00

We miss a failed allocation check for pgdat->per_cpu_nodestats, which results in a NULL deref when we offset into the per-cpu area. Propagate -ENOMEM up the stack and leave per_cpu_nodestats pointing at boot_nodestats so a later online can retry the allocation. hotadd_init_pgdat() returns NULL on failure, which __try_online_node() already maps to -ENOMEM. On failure nothing needs to be unwound: - the node is never marked online - per_cpu_nodestats is left pointing at boot_nodestats - __add_memory_resource() cleans up pending memblock resources - later online attempts retry the per_cpu_nodestats allocation Link: https://lore.kernel.org/20260701221613.2818148-1-gourry@gourry.net Fixes: 75ef71840539 ("mm, vmstat: add infrastructure for per-node vmstats") Signed-off-by: Gregory Price Reported-by: Sashiko Link: https://sashiko.dev/#/patchset/20260627202243.758289-1-gourry%40gourry.net Acked-by: David Hildenbrand (Arm) Cc: Johannes Weiner Cc: Mel Gorman Cc: Mike Rapoport Cc: Oscar Salvador Cc: Vlastimil Babka Signed-off-by: Andrew Morton

mm/sparse-vmemmap: pass @pgmap argument to memory deactivation paths

2026-05-29T04:04:54+00:00

Currently, the memory hot-remove call chain -- arch_remove_memory(), __remove_pages(), sparse_remove_section() and section_deactivate() -- does not carry the struct dev_pagemap pointer. This prevents the lower levels from knowing whether the section was originally populated with vmemmap optimizations (e.g., DAX with vmemmap optimization enabled). Without this information, we cannot call vmemmap_can_optimize() to determine if the vmemmap pages were optimized. As a result, the vmemmap page accounting during teardown will mistakenly assume a non-optimized allocation, leading to incorrect memmap statistics. To lay the groundwork for fixing the vmemmap page accounting, we need to pass the @pgmap pointer down to the deactivation location. Plumb the @pgmap argument through the APIs of arch_remove_memory(), __remove_pages() and sparse_remove_section(), mirroring the corresponding *_activate() paths. Link: https://lore.kernel.org/20260428081855.1249045-4-songmuchun@bytedance.com Signed-off-by: Muchun Song Acked-by: Mike Rapoport (Microsoft) Reviewed-by: Oscar Salvador Acked-by: David Hildenbrand (Arm) Acked-by: Liam R. Howlett Cc: "Aneesh Kumar K.V" Cc: Joao Martins Cc: Lorenzo Stoakes Cc: Madhavan Srinivasan Cc: Michael Ellerman Cc: Michal Hocko Cc: Nicholas Piggin Cc: Suren Baghdasaryan Cc: Vlastimil Babka Signed-off-by: Andrew Morton

mm/sparse: remove sparse_decode_mem_map()

2026-04-05T20:53:32+00:00

section_deactivate() applies to CONFIG_SPARSEMEM_VMEMMAP only. So we can just use pfn_to_page() (after making sure we have the start PFN of the section), and remove sparse_decode_mem_map(). Link: https://lkml.kernel.org/r/20260320-sparsemem_cleanups-v2-9-096addc8800d@kernel.org Signed-off-by: David Hildenbrand (Arm) Reviewed-by: Lorenzo Stoakes (Oracle) Reviewed-by: Mike Rapoport (Microsoft) Cc: Axel Rasmussen Cc: Liam Howlett Cc: Michal Hocko Cc: Oscar Salvador Cc: Sidhartha Kumar Cc: Suren Baghdasaryan Cc: Vlastimil Babka Cc: Wei Xu Cc: Yuanchu Xie Signed-off-by: Andrew Morton

mm: name the anonymous MMOP enum as enum mmop

2026-04-05T20:53:01+00:00

Give the MMOP enum (MMOP_OFFLINE, MMOP_ONLINE, etc) a proper type name so the compiler can help catch invalid values being assigned to variables of this type. Leave the existing functions returning int alone to allow for value-or-error pattern to remain unchanged without churn. mmop_default_online_type is left as int because it uses the -1 sentinal value to signal it hasn't been initialized yet. Keep the uint8_t buffer in offline_and_remove_memory() as-is for space efficiency, with an explicit cast when we consume the value. Move the enum definition before the CONFIG_MEMORY_HOTPLUG guard so it is unconditionally available for struct memory_block in memory.h. No functional change. Link: https://lore.kernel.org/linux-mm/3424eba7-523b-4351-abd0-3a888a3e5e61@kernel.org/ Link: https://lkml.kernel.org/r/20260211215447.2194189-1-gourry@gourry.net Signed-off-by: Gregory Price Suggested-by: Jonathan Cameron Suggested-by: "David Hildenbrand (arm)" Reviewed-by: Ben Cheatham Acked-by: David Hildenbrand (Arm) Reviewed-by: Dave Jiang Reviewed-by: Davidlohr Bueso Reviewed-by: Jonathan Cameron Cc: Danilo Krummrich Cc: Greg Kroah-Hartman Cc: Liam Howlett Cc: Lorenzo Stoakes Cc: Michal Hocko Cc: Mike Rapoport Cc: Oscar Salvador Cc: Suren Baghdasaryan Cc: Vlastimil Babka Signed-off-by: Andrew Morton

mm/memory_hotplug: Remove MEM_PREPARE_ONLINE/MEM_FINISH_OFFLINE notifiers

2025-10-14T12:24:53+00:00

MEM_PREPARE_ONLINE/MEM_FINISH_OFFLINE memory notifiers were introduced to prepare the transition of memory to and from a physically accessible state. This enhancement was crucial for implementing the "memmap on memory" feature for s390. With introduction of dynamic (de)configuration of hotpluggable memory, memory can be brought to accessible state before add_memory(). Memory can be brought to inaccessible state before remove_memory(). Hence, there is no need of MEM_PREPARE_ONLINE/MEM_FINISH_OFFLINE memory notifiers anymore. This basically reverts commit c5f1e2d18909 ("mm/memory_hotplug: introduce MEM_PREPARE_ONLINE/MEM_FINISH_OFFLINE notifiers") Additionally, apply minor adjustments to the function parameters of move_pfn_range_to_zone() and mhp_supports_memmap_on_memory() to ensure compatibility with the latest branch. Acked-by: David Hildenbrand Signed-off-by: Sumanth Korikkar Signed-off-by: Heiko Carstens

mm/page_alloc: add support for initializing pageblock as isolated

2025-07-13T23:38:17+00:00

MIGRATE_ISOLATE is a standalone bit, so a pageblock cannot be initialized to just MIGRATE_ISOLATE. Add init_pageblock_migratetype() to enable initialize a pageblock with a migratetype and isolated. Link: https://lkml.kernel.org/r/20250617021115.2331563-4-ziy@nvidia.com Signed-off-by: Zi Yan Reviewed-by: Vlastimil Babka Acked-by: David Hildenbrand Cc: Baolin Wang Cc: Brendan Jackman Cc: Johannes Weiner Cc: Kirill A. Shuemov Cc: Mel Gorman Cc: Michal Hocko Cc: Oscar Salvador Cc: Richard Chang Cc: Suren Baghdasaryan Signed-off-by: Andrew Morton