mm/memory_hotplug: Introduce offline_and_remove_memory() (08b3acd7) · Commits · 戴 / test

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 is an interface to offline and remove the memory from kernel module context, where we don't have access to the memory block devices (esp. find_memory_block() and device_offline()) and the device hotplug lock. To keep things simple, allow to only work on a single memory block. Acked-by:

Michal Hocko <mhocko@suse.com> Tested-by:

Pankaj Gupta <pankaj.gupta.linux@gmail.com> Acked-by:

Andrew Morton <akpm@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: David Hildenbrand <david@redhat.com> Cc: Oscar Salvador <osalvador@suse.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Pavel Tatashin <pasha.tatashin@soleen.com> Cc: Wei Yang <richard.weiyang@gmail.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Qian Cai <cai@lca.pw> Signed-off-by:

David Hildenbrand <david@redhat.com> Link: https://lore.kernel.org/r/20200507140139.17083-9-david@redhat.com Signed-off-by:

Michael S. Tsirkin <mst@redhat.com>

include/linux/memory_hotplug.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -319,6 +319,7 @@ 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,

mm/memory_hotplug.c

+37 −0

Original line number	Diff line number	Diff line
		@@ -1821,4 +1821,41 @@ 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) {
		rc = try_remove_memory(nid, start, size);
		WARN_ON_ONCE(rc);
		}
		unlock_device_hotplug();

		return rc;
		}
		EXPORT_SYMBOL_GPL(offline_and_remove_memory);
		#endif /* CONFIG_MEMORY_HOTREMOVE */

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