Re: [PATCH v3 09/11] mm/memory_hotplug: Remove memory block devices before arch_remove_memory()

David Hildenbrand
2019-06-05T09:00:28Z

On 05.06.19 00:07, Wei Yang wrote:
> On Mon, May 27, 2019 at 01:11:50PM +0200, David Hildenbrand wrote:
>> Let's factor out removing of memory block devices, which is only
>> necessary for memory added via add_memory() and friends that created
>> memory block devices. Remove the devices before calling
>> arch_remove_memory().
>>
>> This finishes factoring out memory block device handling from
>> arch_add_memory() and arch_remove_memory().
>>
>> 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: Andrew Banman <andrew.banman@hpe.com>
>> Cc: Ingo Molnar <mingo@kernel.org>
>> Cc: Alex Deucher <alexander.deucher@amd.com>
>> Cc: "David S. Miller" <davem@davemloft.net>
>> Cc: Mark Brown <broonie@kernel.org>
>> Cc: Chris Wilson <chris@chris-wilson.co.uk>
>> Cc: Oscar Salvador <osalvador@suse.de>
>> Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
>> Cc: Michal Hocko <mhocko@suse.com>
>> Cc: Pavel Tatashin <pavel.tatashin@microsoft.com>
>> Cc: Arun KS <arunks@codeaurora.org>
>> Cc: Mathieu Malaterre <malat@debian.org>
>> Reviewed-by: Dan Williams <dan.j.williams@intel.com>
>> Signed-off-by: David Hildenbrand <david@redhat.com>
>> ---
>> drivers/base/memory.c | 37 ++++++++++++++++++-------------------
>> drivers/base/node.c | 11 ++++++-----
>> include/linux/memory.h | 2 +-
>> include/linux/node.h | 6 ++----
>> mm/memory_hotplug.c | 5 +++--
>> 5 files changed, 30 insertions(+), 31 deletions(-)
>>
>> diff --git a/drivers/base/memory.c b/drivers/base/memory.c
>> index 5a0370f0c506..f28efb0bf5c7 100644
>> --- a/drivers/base/memory.c
>> +++ b/drivers/base/memory.c
>> @@ -763,32 +763,31 @@ int create_memory_block_devices(unsigned long start, unsigned long size)
>> return ret;
>> }
>>
>> -void unregister_memory_section(struct mem_section *section)
>> +/*
>> + * Remove memory block devices for the given memory area. Start and size
>> + * have to be aligned to memory block granularity. Memory block devices
>> + * have to be offline.
>> + */
>> +void remove_memory_block_devices(unsigned long start, unsigned long size)
>> {
>> + const int start_block_id = pfn_to_block_id(PFN_DOWN(start));
>> + const int end_block_id = pfn_to_block_id(PFN_DOWN(start + size));
>> struct memory_block *mem;
>> + int block_id;
>>
>> - if (WARN_ON_ONCE(!present_section(section)))
>> + if (WARN_ON_ONCE(!IS_ALIGNED(start, memory_block_size_bytes()) ||
>> + !IS_ALIGNED(size, memory_block_size_bytes())))
>> return;
>>
>> mutex_lock(&mem_sysfs_mutex);
>> -
>> - /*
>> - * Some users of the memory hotplug do not want/need memblock to
>> - * track all sections. Skip over those.
>> - */
>> - mem = find_memory_block(section);
>> - if (!mem)
>> - goto out_unlock;
>> -
>> - unregister_mem_sect_under_nodes(mem, __section_nr(section));
>> -
>> - mem->section_count--;
>> - if (mem->section_count = 0)
>> + for (block_id = start_block_id; block_id != end_block_id; block_id++) {
>> + mem = find_memory_block_by_id(block_id, NULL);
>> + if (WARN_ON_ONCE(!mem))
>> + continue;
>> + mem->section_count = 0;
>
> Is this step necessary?

It's what the previous code does, it might not be - I'll leave it like
that for now. As mentioned in another reply, I might remove the
section_count completely, eventually.

--

Thanks,

David / dhildenb