Re: [PATCH v2 4/8] mm/memory_hotplug: Create memory block devices after arch_add_memory()

David Hildenbrand
2019-05-08T08:35:26Z

On 07.05.19 20:38, David Hildenbrand wrote:
> Only memory to be added to the buddy and to be onlined/offlined by
> user space using memory block devices needs (and should have!) memory
> block devices.
>
> Factor out creation of memory block devices Create all devices after
> arch_add_memory() succeeded. We can later drop the want_memblock parameter,
> because it is now effectively stale.
>
> Only after memory block devices have been added, memory can be onlined
> by user space. This implies, that memory is not visible to user space at
> all before arch_add_memory() succeeded.
>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: "Rafael J. Wysocki" <rafael@kernel.org>
> Cc: David Hildenbrand <david@redhat.com>
> Cc: "mike.travis@hpe.com" <mike.travis@hpe.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Ingo Molnar <mingo@kernel.org>
> Cc: Andrew Banman <andrew.banman@hpe.com>
> Cc: Oscar Salvador <osalvador@suse.de>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
> Cc: Qian Cai <cai@lca.pw>
> Cc: Wei Yang <richard.weiyang@gmail.com>
> Cc: Arun KS <arunks@codeaurora.org>
> Cc: Mathieu Malaterre <malat@debian.org>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
> drivers/base/memory.c | 70 ++++++++++++++++++++++++++----------------
> include/linux/memory.h | 2 +-
> mm/memory_hotplug.c | 15 ++++-----
> 3 files changed, 53 insertions(+), 34 deletions(-)
>
> diff --git a/drivers/base/memory.c b/drivers/base/memory.c
> index 6e0cb4fda179..862c202a18ca 100644
> --- a/drivers/base/memory.c
> +++ b/drivers/base/memory.c
> @@ -701,44 +701,62 @@ static int add_memory_block(int base_section_nr)
> return 0;
> }
>
> +static void unregister_memory(struct memory_block *memory)
> +{
> + BUG_ON(memory->dev.bus != &memory_subsys);
> +
> + /* drop the ref. we got via find_memory_block() */
> + put_device(&memory->dev);
> + device_unregister(&memory->dev);
> +}
> +
> /*
> - * need an interface for the VM to add new memory regions,
> - * but without onlining it.
> + * Create memory block devices for the given memory area. Start and size
> + * have to be aligned to memory block granularity. Memory block devices
> + * will be initialized as offline.
> */
> -int hotplug_memory_register(int nid, struct mem_section *section)
> +int hotplug_memory_register(unsigned long start, unsigned long size)
> {
> - int ret = 0;
> + unsigned long block_nr_pages = memory_block_size_bytes() >> PAGE_SHIFT;
> + unsigned long start_pfn = PFN_DOWN(start);
> + unsigned long end_pfn = start_pfn + (size >> PAGE_SHIFT);
> + unsigned long pfn;
> struct memory_block *mem;
> + int ret = 0;
>
> - mutex_lock(&mem_sysfs_mutex);
> + BUG_ON(!IS_ALIGNED(start, memory_block_size_bytes()));
> + BUG_ON(!IS_ALIGNED(size, memory_block_size_bytes()));
>
> - mem = find_memory_block(section);
> - if (mem) {
> - mem->section_count++;
> - put_device(&mem->dev);
> - } else {
> - ret = init_memory_block(&mem, section, MEM_OFFLINE);
> + mutex_lock(&mem_sysfs_mutex);
> + for (pfn = start_pfn; pfn != end_pfn; pfn += block_nr_pages) {
> + mem = find_memory_block(__pfn_to_section(pfn));
> + if (mem) {
> + WARN_ON_ONCE(false);
> + put_device(&mem->dev);
> + continue;
> + }
> + ret = init_memory_block(&mem, __pfn_to_section(pfn),
> + MEM_OFFLINE);
> if (ret)
> - goto out;
> - mem->section_count++;
> + break;
> + mem->section_count = memory_block_size_bytes() /
> + MIN_MEMORY_BLOCK_SIZE;
> + }
> + if (ret) {
> + end_pfn = pfn;
> + for (pfn = start_pfn; pfn != end_pfn; pfn += block_nr_pages) {
> + mem = find_memory_block(__pfn_to_section(pfn));
> + if (!mem)
> + continue;
> + mem->section_count = 0;
> + unregister_memory(mem);
> + }
> }
> -
> -out:
> mutex_unlock(&mem_sysfs_mutex);
> return ret;
> }
>
> -static void
> -unregister_memory(struct memory_block *memory)
> -{
> - BUG_ON(memory->dev.bus != &memory_subsys);
> -
> - /* drop the ref. we got via find_memory_block() */
> - put_device(&memory->dev);
> - device_unregister(&memory->dev);
> -}
> -
> -void unregister_memory_section(struct mem_section *section)
> +static int remove_memory_section(struct mem_section *section)
> {

The function change is misplaces in this patch will drop it so this
patch compiles without the other patches.

--

Thanks,

David / dhildenb