virtio-mem wants to offline and remove a memory block once it unplugged all subblocks (e.g., using alloc_contig_range()). Let's provide an interface to do that from a driver. virtio-mem already supports to offline partially unplugged memory blocks. Offlining a fully unplugged memory block will not require to migrate any pages. All unplugged subblocks are PageOffline() and have a reference count of 0 - so offlining code will simply skip them. All we need an interface to trigger the "offlining" and the removing in a single operation - to make sure the memory block cannot get onlined by user space again before it gets removed. To keep things simple, allow to only work on a single memory block. Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: David Hildenbrand <david@xxxxxxxxxx> Cc: Oscar Salvador <osalvador@xxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxx> Cc: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx> Cc: Wei Yang <richard.weiyang@xxxxxxxxx> Cc: Dan Williams <dan.j.williams@xxxxxxxxx> Cc: Qian Cai <cai@xxxxxx> Signed-off-by: David Hildenbrand <david@xxxxxxxxxx> --- include/linux/memory_hotplug.h | 1 + mm/memory_hotplug.c | 35 ++++++++++++++++++++++++++++++++++ 2 files changed, 36 insertions(+) diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h index ba0dca6aac6e..586f5c59c291 100644 --- a/include/linux/memory_hotplug.h +++ b/include/linux/memory_hotplug.h @@ -310,6 +310,7 @@ extern void try_offline_node(int nid); extern int offline_pages(unsigned long start_pfn, unsigned long nr_pages); extern int remove_memory(int nid, u64 start, u64 size); extern void __remove_memory(int nid, u64 start, u64 size); +extern int offline_and_remove_memory(int nid, u64 start, u64 size); #else static inline bool is_mem_section_removable(unsigned long pfn, diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index da01453a04e6..d04369e6d3cc 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -1825,4 +1825,39 @@ int remove_memory(int nid, u64 start, u64 size) return rc; } EXPORT_SYMBOL_GPL(remove_memory); + +/* + * Try to offline and remove a memory block. Might take a long time to + * finish in case memory is still in use. Primarily useful for memory devices + * that logically unplugged all memory (so it's no longer in use) and want to + * offline + remove the memory block. + */ +int offline_and_remove_memory(int nid, u64 start, u64 size) +{ + struct memory_block *mem; + int rc = -EINVAL; + + if (!IS_ALIGNED(start, memory_block_size_bytes()) || + size != memory_block_size_bytes()) + return rc; + + lock_device_hotplug(); + mem = find_memory_block(__pfn_to_section(PFN_DOWN(start))); + if (mem) + rc = device_offline(&mem->dev); + /* Ignore if the device is already offline. */ + if (rc > 0) + rc = 0; + + /* + * In case we succeeded to offline the memory block, remove it. + * This cannot fail as it cannot get onlined in the meantime. + */ + if (!rc && try_remove_memory(nid, start, size)) + BUG(); + unlock_device_hotplug(); + + return rc; +} +EXPORT_SYMBOL_GPL(offline_and_remove_memory); #endif /* CONFIG_MEMORY_HOTREMOVE */ -- 2.23.0