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[2003:cb:c711:c600:c1d6:7158:f946:f083]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-42bacaac810sm44098825e9.33.2024.08.29.12.44.01 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 29 Aug 2024 12:44:02 -0700 (PDT) Message-ID: <32a451ee-6836-4d4d-814c-752c15415aae@redhat.com> Date: Thu, 29 Aug 2024 21:44:01 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 07/19] mm/fork: Accept huge pfnmap entries To: Peter Xu Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Gavin Shan , Catalin Marinas , x86@kernel.org, Ingo Molnar , Andrew Morton , Paolo Bonzini , Dave Hansen , Thomas Gleixner , Alistair Popple , kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Sean Christopherson , Oscar Salvador , Jason Gunthorpe , Borislav Petkov , Zi Yan , Axel Rasmussen , Yan Zhao , Will Deacon , Kefeng Wang , Alex Williamson References: <20240826204353.2228736-1-peterx@redhat.com> <20240826204353.2228736-8-peterx@redhat.com> <78d77162-11df-4437-b70b-fa04f868a494@redhat.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 7C000120004 X-Stat-Signature: 6rqytoffwc4o7n14sieo1pbddzzfqa1g X-Rspamd-Server: rspam09 X-Rspam-User: X-HE-Tag: 1724960648-425427 X-HE-Meta: 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 rO7vnN/c W4qDpDDBx0e/bLfD7TnluGkaN2MB3qNqFRdmvvOCzxduDgyAwCnKhQvYPiGL6w8dEi14hHMhT+WOI6toKe4S0RMKGvMcA2zK7xr5IL8r9OfhSZg3kCGYs2XOrBmWU38e+Z9BOzebGmk37Ey1Ima3qjS8pHQ6Zcr817FB8U7aNacJnTERlAYptErkRjVflDkE8uvShoewZ1/55yH+dZz1nScc7WrovQpY6zA7GFpX1AWQnwta2pUqU1D7wrxRYbqfN2s8ISg4+GAeVZy9g/pCTN5yq/LNfnNbSO9X3nrHXOdKqNN0VqGie4QUCgBvoJ5KP6RTkeFtnptqlK79QT/svKCtIS9ZPYDBCm2YVQjU+vmzStUzyw1KtPIsbTdhNpj3shlApijrlTkAbfbYAUdzRpoMYCFcKXRbssrtICblwFAgYXso= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 29.08.24 20:26, Peter Xu wrote: > On Thu, Aug 29, 2024 at 05:10:42PM +0200, David Hildenbrand wrote: >> On 26.08.24 22:43, Peter Xu wrote: >>> Teach the fork code to properly copy pfnmaps for pmd/pud levels. Pud is >>> much easier, the write bit needs to be persisted though for writable and >>> shared pud mappings like PFNMAP ones, otherwise a follow up write in either >>> parent or child process will trigger a write fault. >>> >>> Do the same for pmd level. >>> >>> Signed-off-by: Peter Xu >>> --- >>> mm/huge_memory.c | 29 ++++++++++++++++++++++++++--- >>> 1 file changed, 26 insertions(+), 3 deletions(-) >>> >>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >>> index e2c314f631f3..15418ffdd377 100644 >>> --- a/mm/huge_memory.c >>> +++ b/mm/huge_memory.c >>> @@ -1559,6 +1559,24 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, >>> pgtable_t pgtable = NULL; >>> int ret = -ENOMEM; >>> + pmd = pmdp_get_lockless(src_pmd); >>> + if (unlikely(pmd_special(pmd))) { >> >> I assume I have to clean up your mess here as well? > > Can you leave meaningful and explicit comment? I'll try to address. Sorry Peter, but I raised all that as reply to v1. For example, I stated that vm_normal_page_pmd() already *exist* and why these pmd_special() checks should be kept there. I hear you, you're not interested in cleaning that up. So at this point it's easier for me to clean it up myself. -- Cheers, David / dhildenb