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[2003:d8:2f25:900:2e1e:d717:2543:c4d6]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3b8fc28a830sm6142600f8f.16.2025.08.08.07.23.52 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 08 Aug 2025 07:23:53 -0700 (PDT) Message-ID: <687b556e-0196-4a38-986a-2e7b0308e03d@redhat.com> Date: Fri, 8 Aug 2025 16:23:52 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4] mm: fix accounting of memmap pages To: Sumanth Korikkar , Andrew Morton , linux-mm , LKML , richard.weiyang@gmail.com Cc: Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , linux-s390 References: <20250807183545.1424509-1-sumanthk@linux.ibm.com> From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAmgsLPQFCRvGjuMACgkQTd4Q 9wD/g1o0bxAAqYC7gTyGj5rZwvy1VesF6YoQncH0yI79lvXUYOX+Nngko4v4dTlOQvrd/vhb 02e9FtpA1CxgwdgIPFKIuXvdSyXAp0xXuIuRPQYbgNriQFkaBlHe9mSf8O09J3SCVa/5ezKM OLW/OONSV/Fr2VI1wxAYj3/Rb+U6rpzqIQ3Uh/5Rjmla6pTl7Z9/o1zKlVOX1SxVGSrlXhqt kwdbjdj/csSzoAbUF/duDuhyEl11/xStm/lBMzVuf3ZhV5SSgLAflLBo4l6mR5RolpPv5wad GpYS/hm7HsmEA0PBAPNb5DvZQ7vNaX23FlgylSXyv72UVsObHsu6pT4sfoxvJ5nJxvzGi69U s1uryvlAfS6E+D5ULrV35taTwSpcBAh0/RqRbV0mTc57vvAoXofBDcs3Z30IReFS34QSpjvl Hxbe7itHGuuhEVM1qmq2U72ezOQ7MzADbwCtn+yGeISQqeFn9QMAZVAkXsc9Wp0SW/WQKb76 FkSRalBZcc2vXM0VqhFVzTb6iNqYXqVKyuPKwhBunhTt6XnIfhpRgqveCPNIasSX05VQR6/a OBHZX3seTikp7A1z9iZIsdtJxB88dGkpeMj6qJ5RLzUsPUVPodEcz1B5aTEbYK6428H8MeLq NFPwmknOlDzQNC6RND8Ez7YEhzqvw7263MojcmmPcLelYbfOwU0EVcufkQEQAOfX3n0g0fZz 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+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCaCwtJQUJG8aPFAAKCRBN3hD3AP+DWlDnD/4k2TW+HyOOOePVm23F5HOhNNd7nNv3 Vq2cLcW1DteHUdxMO0X+zqrKDHI5hgnE/E2QH9jyV8mB8l/ndElobciaJcbl1cM43vVzPIWn 01vW62oxUNtEvzLLxGLPTrnMxWdZgxr7ACCWKUnMGE2E8eca0cT2pnIJoQRz242xqe/nYxBB /BAK+dsxHIfcQzl88G83oaO7vb7s/cWMYRKOg+WIgp0MJ8DO2IU5JmUtyJB+V3YzzM4cMic3 bNn8nHjTWw/9+QQ5vg3TXHZ5XMu9mtfw2La3bHJ6AybL0DvEkdGxk6YHqJVEukciLMWDWqQQ RtbBhqcprgUxipNvdn9KwNpGciM+hNtM9kf9gt0fjv79l/FiSw6KbCPX9b636GzgNy0Ev2UV m00EtcpRXXMlEpbP4V947ufWVK2Mz7RFUfU4+ETDd1scMQDHzrXItryHLZWhopPI4Z+ps0rB CQHfSpl+wG4XbJJu1D8/Ww3FsO42TMFrNr2/cmqwuUZ0a0uxrpkNYrsGjkEu7a+9MheyTzcm vyU2knz5/stkTN2LKz5REqOe24oRnypjpAfaoxRYXs+F8wml519InWlwCra49IUSxD1hXPxO WBe5lqcozu9LpNDH/brVSzHCSb7vjNGvvSVESDuoiHK8gNlf0v+epy5WYd7CGAgODPvDShGN g3eXuA== Organization: Red Hat In-Reply-To: <20250807183545.1424509-1-sumanthk@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 07.08.25 20:35, Sumanth Korikkar wrote: > For !CONFIG_SPARSEMEM_VMEMMAP, memmap page accounting is currently done > upfront in sparse_buffer_init(). However, sparse_buffer_alloc() may > return NULL in failure scenario. > > Also, memmap pages may be allocated either from the memblock allocator > during early boot or from the buddy allocator. When removed via > arch_remove_memory(), accounting of memmap pages must reflect the > original allocation source. > > To ensure correctness: > * Account memmap pages after successful allocation in sparse_init_nid() > and section_activate(). > * Account memmap pages in section_deactivate() based on allocation > source. > > Cc: stable@vger.kernel.org > Fixes: 15995a352474 ("mm: report per-page metadata information") > Suggested-by: David Hildenbrand > Signed-off-by: Sumanth Korikkar > --- > v4: > * Add fixes and suggested-by. > > v3: > * Account memmap pages for !CONFIG_SPARSEMEM_VMEMMAP and only when memmap > allocation succeeds. Thanks Wei Yang. > > v2: > * Account memmap pages for !CONFIG_SPARSEMEM_VMEMMAP in > section_deactivate(). Thanks David. > * https://lore.kernel.org/all/20250804151328.2326642-1-sumanthk@linux.ibm.com/ > > v1: > * Account memmap pages for early sections. > * https://lore.kernel.org/all/20250804084015.270570-1-sumanthk@linux.ibm.com/ > > mm/sparse-vmemmap.c | 5 ----- > mm/sparse.c | 15 +++++++++------ > 2 files changed, 9 insertions(+), 11 deletions(-) > > diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c > index fd2ab5118e13..41aa0493eb03 100644 > --- a/mm/sparse-vmemmap.c > +++ b/mm/sparse-vmemmap.c > @@ -578,11 +578,6 @@ struct page * __meminit __populate_section_memmap(unsigned long pfn, > if (r < 0) > return NULL; > > - if (system_state == SYSTEM_BOOTING) > - memmap_boot_pages_add(DIV_ROUND_UP(end - start, PAGE_SIZE)); > - else > - memmap_pages_add(DIV_ROUND_UP(end - start, PAGE_SIZE)); > - > return pfn_to_page(pfn); > } > > diff --git a/mm/sparse.c b/mm/sparse.c > index 066cbf82acb8..24323122f6cb 100644 > --- a/mm/sparse.c > +++ b/mm/sparse.c > @@ -454,9 +454,6 @@ static void __init sparse_buffer_init(unsigned long size, int nid) > */ > sparsemap_buf = memmap_alloc(size, section_map_size(), addr, nid, true); > sparsemap_buf_end = sparsemap_buf + size; > -#ifndef CONFIG_SPARSEMEM_VMEMMAP > - memmap_boot_pages_add(DIV_ROUND_UP(size, PAGE_SIZE)); > -#endif > } > > static void __init sparse_buffer_fini(void) > @@ -567,6 +564,8 @@ static void __init sparse_init_nid(int nid, unsigned long pnum_begin, > sparse_buffer_fini(); > goto failed; > } > + memmap_boot_pages_add(DIV_ROUND_UP(PAGES_PER_SECTION * sizeof(struct page), > + PAGE_SIZE)); IIRC, we can have partially populated boot sections, where only some subsections actually have a memmap ... so this calculation is possibly wrong in some cases. -- Cheers, David / dhildenb