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Patch series "dax/kmem: atomic whole-device hotplug via sysfs", v7. The dax kmem driver onlines memory during probe using the system default policy, with no atomic control for the state of an entire region at runtime - only by toggling individual memory blocks. Offlining and removing a whole region therefore races with other userland controllers that interfere between the two steps. This series adds a sysfs "state" attribute for atomic whole-device hotplug control, plus the mm and dax plumbing to support it. Transitions are atomic across every range of the device. The state names mirror the per-block memoryX/state ABI with one modification: - "unplugged": memory blocks are not present - "online": online as system RAM, zone chosen by the kernel - "online_kernel": online in ZONE_NORMAL - "online_movable": online in ZONE_MOVABLE "offline" (blocks present but offline) is reportable for backward compatibility but is not writable because it entices the race condition we are trying to solve (separate atomic steps for offline and unplug). 'unplugged' (atomic offline+remove of the whole device) is the new capability provided by the new kmem sysfs attribute. dax/kmem probe still creates the memory blocks by default when the default policy is "offline", to preserve backwards compatibility. This patch (of 10): Memory hotplug operations require ranges aligned to memory block boundaries. This is a generic operation for hotplug. Add memory_block_aligned_range() as a common helper in <linux/memory.h> that aligns the start address up and end address down to memory block boundaries. Guard against end underflow when the range falls below the first memory block boundary, returning an empty range instead. Update dax/kmem to use this helper. Link: https://lore.kernel.org/20260712154505.3564379-1-gourry@gourry.net Link: https://lore.kernel.org/20260712154505.3564379-2-gourry@gourry.net Signed-off-by: Gregory Price <gourry@gourry.net> Reviewed-by: Dave Jiang <dave.jiang@intel.com> Reviewed-by: Dan Williams <djbw@kernel.org> Acked-by: David Hildenbrand (Arm) <david@kernel.org> Cc: Alison Schofield <alison.schofield@intel.com> Cc: Danilo Krummrich <dakr@kernel.org> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Liam R. Howlett <liam@infradead.org> Cc: Lorenzo Stoakes <ljs@kernel.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Oscar Salvador <osalvador@suse.de> Cc: "Rafael J. Wysocki" <rafael@kernel.org> Cc: Shuah Khan <shuah@kernel.org> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Vishal Verma <vishal.l.verma@intel.com> Cc: Vlastimil Babka <vbabka@kernel.org> Cc: Hannes Reinecke <hare@suse.de> Cc: Pankaj Gupta <pankaj.gupta@amd.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Linux kernel ============ The Linux kernel is the core of any Linux operating system. It manages hardware, system resources, and provides the fundamental services for all other software. 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