From: David Hildenbrand <david@redhat.com>
To: Oscar Salvador <osalvador@suse.de>
Cc: akpm@linux-foundation.org, mhocko@suse.com,
dan.j.williams@intel.com, pasha.tatashin@soleen.com,
Jonathan.Cameron@huawei.com, anshuman.khandual@arm.com,
vbabka@suse.cz, linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 0/5] Allocate memmap from hotadded memory
Date: Wed, 26 Jun 2019 10:37:50 +0200 [thread overview]
Message-ID: <b2e25c78-03d3-8423-4bc7-1a5c4779d5ab@redhat.com> (raw)
In-Reply-To: <20190626082756.GD30863@linux>
On 26.06.19 10:27, Oscar Salvador wrote:
> On Wed, Jun 26, 2019 at 10:15:16AM +0200, Oscar Salvador wrote:
>> On Wed, Jun 26, 2019 at 10:11:06AM +0200, David Hildenbrand wrote:
>>> Back then, I already mentioned that we might have some users that
>>> remove_memory() they never added in a granularity it wasn't added. My
>>> concerns back then were never fully sorted out.
>>>
>>> arch/powerpc/platforms/powernv/memtrace.c
>>>
>>> - Will remove memory in memory block size chunks it never added
>>> - What if that memory resides on a DIMM added via MHP_MEMMAP_DEVICE?
>>>
>>> Will it at least bail out? Or simply break?
>>>
>>> IOW: I am not yet 100% convinced that MHP_MEMMAP_DEVICE is save to be
>>> introduced.
>>
>> Uhm, I will take a closer look and see if I can clear your concerns.
>> TBH, I did not try to use arch/powerpc/platforms/powernv/memtrace.c
>> yet.
>>
>> I will get back to you once I tried it out.
>
> On a second though, it would be quite trivial to implement a check in
> remove_memory() that does not allow to remove memory used with MHP_MEMMAP_DEVICE
> in a different granularity:
>
> +static bool check_vmemmap_granularity(u64 start, u64 size);
> +{
> + unsigned long pfn;
> + unsigned int nr_pages;
> + struct page *p;
> +
> + pfn = PHYS_PFN(start);
> + p = pfn_to_page(pfn);
> + nr_pages = size >> PAGE_SIZE;
> +
> + if (PageVmemmap(p)) {
> + struct page *h = vmemmap_get_head(p);
> + unsigned long sections = (unsigned long)h->private;
> +
> + if (sections * PAGES_PER_SECTION > nr_pages)
> + fail;
> + }
> + no_fail;
> +}
> +
> +
> static int __ref try_remove_memory(int nid, u64 start, u64 size)
> {
> int rc = 0;
>
> BUG_ON(check_hotplug_memory_range(start, size));
>
> mem_hotplug_begin();
>
> + rc = check_vmemmap_granularity(start, size);
> + if (rc)
> + goto done;
>
>
> The above is quite hacky, but it gives an idea.
> I will try the code from arch/powerpc/platforms/powernv/memtrace.c and see how
> can I implement a check.
>
Yeah, I would consider such a safety check mandatory for MHP_MEMMAP_DEVICE.
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2019-06-26 8:38 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-25 7:52 [PATCH v2 0/5] Allocate memmap from hotadded memory Oscar Salvador
2019-06-25 7:52 ` [PATCH v2 1/5] drivers/base/memory: Remove unneeded check in remove_memory_block_devices Oscar Salvador
2019-06-25 8:01 ` David Hildenbrand
2019-06-25 8:03 ` David Hildenbrand
2019-06-25 8:09 ` Oscar Salvador
2019-06-25 8:27 ` David Hildenbrand
2019-06-25 7:52 ` [PATCH v2 2/5] mm,memory_hotplug: Introduce MHP_VMEMMAP_FLAGS Oscar Salvador
2019-06-25 8:31 ` David Hildenbrand
2019-07-24 20:11 ` Dan Williams
2019-07-24 21:36 ` osalvador
2019-07-25 9:27 ` Oscar Salvador
2019-07-25 9:30 ` David Hildenbrand
2019-07-25 9:40 ` Oscar Salvador
2019-07-25 10:04 ` David Hildenbrand
2019-07-25 10:13 ` Oscar Salvador
2019-07-25 10:15 ` David Hildenbrand
2019-06-25 7:52 ` [PATCH v2 3/5] mm,memory_hotplug: Introduce Vmemmap page helpers Oscar Salvador
2019-06-25 10:28 ` David Hildenbrand
2019-06-26 9:48 ` Oscar Salvador
2019-06-25 7:52 ` [PATCH v2 4/5] mm,memory_hotplug: allocate memmap from the added memory range for sparse-vmemmap Oscar Salvador
2019-06-25 8:49 ` David Hildenbrand
2019-06-26 8:13 ` Oscar Salvador
2019-06-26 8:15 ` David Hildenbrand
2019-06-26 8:17 ` Anshuman Khandual
2019-06-26 8:28 ` Oscar Salvador
2019-07-24 21:49 ` Dan Williams
2019-06-25 7:52 ` [PATCH v2 5/5] mm,memory_hotplug: Allow userspace to enable/disable vmemmap Oscar Salvador
2019-06-25 8:25 ` [PATCH v2 0/5] Allocate memmap from hotadded memory David Hildenbrand
2019-06-25 8:33 ` David Hildenbrand
2019-06-26 8:03 ` Oscar Salvador
2019-06-26 8:11 ` David Hildenbrand
2019-06-26 8:15 ` Oscar Salvador
2019-06-26 8:27 ` Oscar Salvador
2019-06-26 8:37 ` David Hildenbrand [this message]
2019-06-26 8:28 ` David Hildenbrand
2019-07-02 6:42 ` Rashmica Gupta
2019-07-02 7:48 ` Oscar Salvador
2019-07-02 8:52 ` Rashmica Gupta
2019-07-10 1:14 ` Rashmica Gupta
2019-07-31 12:08 ` Michal Hocko
2019-07-31 23:06 ` Rashmica Gupta
2019-08-01 7:17 ` Michal Hocko
2019-08-01 7:18 ` David Hildenbrand
2019-08-01 7:24 ` Michal Hocko
2019-08-01 7:26 ` David Hildenbrand
2019-08-01 7:31 ` David Hildenbrand
2019-08-01 7:39 ` Michal Hocko
2019-08-01 7:48 ` Michal Hocko
2019-08-01 9:18 ` David Hildenbrand
2019-08-01 7:34 ` Michal Hocko
2019-08-01 7:50 ` David Hildenbrand
2019-08-01 8:04 ` Michal Hocko
2019-07-16 12:28 ` David Hildenbrand
2019-07-29 5:42 ` Rashmica Gupta
2019-07-29 8:06 ` David Hildenbrand
2019-07-30 7:08 ` Rashmica Gupta
2019-07-31 2:21 ` Rashmica Gupta
2019-07-31 9:39 ` David Hildenbrand
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