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Shutemov" References: <1583F4CF-6CD8-4AB6-A2F6-60E6AEE5D5B2@redhat.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; prefer-encrypt=mutual; keydata= mQINBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABtCREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT6JAlgEEwEIAEICGwMFCQlmAYAGCwkIBwMCBhUI AgkKCwQWAgMBAh4BAheAFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl3pImkCGQEACgkQTd4Q 9wD/g1o+VA//SFvIHUAvul05u6wKv/pIR6aICPdpF9EIgEU448g+7FfDgQwcEny1pbEzAmiw zAXIQ9H0NZh96lcq+yDLtONnXk/bEYWHHUA014A1wqcYNRY8RvY1+eVHb0uu0KYQoXkzvu+s Dncuguk470XPnscL27hs8PgOP6QjG4jt75K2LfZ0eAqTOUCZTJxA8A7E9+XTYuU0hs7QVrWJ jQdFxQbRMrYz7uP8KmTK9/Cnvqehgl4EzyRaZppshruKMeyheBgvgJd5On1wWq4ZUV5PFM4x II3QbD3EJfWbaJMR55jI9dMFa+vK7MFz3rhWOkEx/QR959lfdRSTXdxs8V3zDvChcmRVGN8U Vo93d1YNtWnA9w6oCW1dnDZ4kgQZZSBIjp6iHcA08apzh7DPi08jL7M9UQByeYGr8KuR4i6e RZI6xhlZerUScVzn35ONwOC91VdYiQgjemiVLq1WDDZ3B7DIzUZ4RQTOaIWdtXBWb8zWakt/ ztGhsx0e39Gvt3391O1PgcA7ilhvqrBPemJrlb9xSPPRbaNAW39P8ws/UJnzSJqnHMVxbRZC Am4add/SM+OCP0w3xYss1jy9T+XdZa0lhUvJfLy7tNcjVG/sxkBXOaSC24MFPuwnoC9WvCVQ ZBxouph3kqc4Dt5X1EeXVLeba+466P1fe1rC8MbcwDkoUo65Ag0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAGJAiUEGAECAA8FAlXLn5ECGwwFCQlmAYAACgkQTd4Q 9wD/g1qA6w/+M+ggFv+JdVsz5+ZIc6MSyGUozASX+bmIuPeIecc9UsFRatc91LuJCKMkD9Uv GOcWSeFpLrSGRQ1Z7EMzFVU//qVs6uzhsNk0RYMyS0B6oloW3FpyQ+zOVylFWQCzoyyf227y GW8HnXunJSC+4PtlL2AY4yZjAVAPLK2l6mhgClVXTQ/S7cBoTQKP+jvVJOoYkpnFxWE9pn4t H5QIFk7Ip8TKr5k3fXVWk4lnUi9MTF/5L/mWqdyIO1s7cjharQCstfWCzWrVeVctpVoDfJWp 4LwTuQ5yEM2KcPeElLg5fR7WB2zH97oI6/Ko2DlovmfQqXh9xWozQt0iGy5tWzh6I0JrlcxJ ileZWLccC4XKD1037Hy2FLAjzfoWgwBLA6ULu0exOOdIa58H4PsXtkFPrUF980EEibUp0zFz GotRVekFAceUaRvAj7dh76cToeZkfsjAvBVb4COXuhgX6N4pofgNkW2AtgYu1nUsPAo+NftU CxrhjHtLn4QEBpkbErnXQyMjHpIatlYGutVMS91XTQXYydCh5crMPs7hYVsvnmGHIaB9ZMfB njnuI31KBiLUks+paRkHQlFcgS2N3gkRBzH7xSZ+t7Re3jvXdXEzKBbQ+dC3lpJB0wPnyMcX FOTT3aZT7IgePkt5iC/BKBk3hqKteTnJFeVIT7EC+a6YUFg= Organization: Red Hat GmbH Message-ID: <5186091f-4de5-d2cd-1e97-56b078d86886@redhat.com> Date: Tue, 4 Feb 2020 09:40:30 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Content-Transfer-Encoding: quoted-printable Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04.02.20 00:17, Alexander Duyck wrote: > On Mon, Feb 3, 2020 at 1:44 PM David Hildenbrand wro= te: >> >> >> >>> Am 03.02.2020 um 22:35 schrieb Alexander Duyck : >>> >>> =EF=BB=BFOn Mon, Jan 13, 2020 at 6:40 AM David Hildenbrand wrote: >>>> >>>> Let's update the pfn manually whenever we continue the loop. This ma= kes >>>> the code easier to read but also less error prone (and we can direct= ly >>>> fix one issue). >>>> >>>> When overlap_memmap_init() returns true, pfn is updated to >>>> "memblock_region_memory_end_pfn(r)". So it already points at the *ne= xt* >>>> pfn to process. Incrementing the pfn another time is wrong, we might >>>> leave one uninitialized. I spotted this by inspecting the code, so I= have >>>> no idea if this is relevant in practise (with kernelcore=3Dmirror). >>>> >>>> Fixes: a9a9e77fbf27 ("mm: move mirrored memory specific code outside= of memmap_init_zone") >>>> Cc: Pavel Tatashin >>>> Cc: Andrew Morton >>>> Cc: Michal Hocko >>>> Cc: Oscar Salvador >>>> Cc: Kirill A. Shutemov >>>> Signed-off-by: David Hildenbrand >>>> --- >>>> mm/page_alloc.c | 9 ++++++--- >>>> 1 file changed, 6 insertions(+), 3 deletions(-) >>>> >>>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >>>> index a41bd7341de1..a92791512077 100644 >>>> --- a/mm/page_alloc.c >>>> +++ b/mm/page_alloc.c >>>> @@ -5905,18 +5905,20 @@ void __meminit memmap_init_zone(unsigned lon= g size, int nid, unsigned long zone, >>>> } >>>> #endif >>>> >>>> - for (pfn =3D start_pfn; pfn < end_pfn; pfn++) { >>>> + for (pfn =3D start_pfn; pfn < end_pfn; ) { >>>> /* >>>> * There can be holes in boot-time mem_map[]s handed = to this >>>> * function. They do not exist on hotplugged memory. >>>> */ >>>> if (context =3D=3D MEMMAP_EARLY) { >>>> if (!early_pfn_valid(pfn)) { >>>> - pfn =3D next_pfn(pfn) - 1; >>>> + pfn =3D next_pfn(pfn); >>>> continue; >>>> } >>>> - if (!early_pfn_in_nid(pfn, nid)) >>>> + if (!early_pfn_in_nid(pfn, nid)) { >>>> + pfn++; >>>> continue; >>>> + } >>>> if (overlap_memmap_init(zone, &pfn)) >>>> continue; >>>> if (defer_init(nid, pfn, end_pfn)) >>> >>> I'm pretty sure this is a bit broken. The overlap_memmap_init is goin= g >>> to return memblock_region_memory_end_pfn instead of the start of the >>> next region. I think that is going to stick you in a mirrored region >>> without advancing in that case. You would also need to have that case >>> do a pfn++ before the continue; >> >> Thanks for having a look. >> >> Did you read the description regarding this change? >=20 > Actually I hadn't read it all that closely, so my bad on that. The > part that had caught my attention though was that > memblock_region_memory_end is using PFN_DOWN to identify the end of > the memory region, Given that we probably shouldn't be messing with > the PFNs that may contain any of this memory it might make more sense > to use memblock_region_reserved_end_pfn which uses PFN_UP so that we > exclude all memory that is in the mirrored region just in case > something doesn't end on a PFN aligned boundary. >=20 > If we know that the mirrored region is going to always be page size > aligned then I guess you are good to go. That was the only thing I > wasn't sure about. I think we can safely assume this for now. But I *think* we are fine either way: We are using memblock_region_memory_end() in all cases I spotted (especially consistently in overlap_memmap_init()) - so there is never a mis-match that could result in an endless loop. Anyhow, having mirrored sub-page regions would be weird either way :) (just like any zone that would end on sub-pages) >=20 > Reviewed-by: Alexander Duyck >=20 Thanks! --=20 Thanks, David / dhildenb