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[99.254.121.117]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-45682c82a52sm7101381cf.16.2024.08.29.11.26.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 29 Aug 2024 11:26:24 -0700 (PDT) Date: Thu, 29 Aug 2024 14:26:22 -0400 From: Peter Xu To: David Hildenbrand 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 Subject: Re: [PATCH v2 07/19] mm/fork: Accept huge pfnmap entries Message-ID: References: <20240826204353.2228736-1-peterx@redhat.com> <20240826204353.2228736-8-peterx@redhat.com> <78d77162-11df-4437-b70b-fa04f868a494@redhat.com> MIME-Version: 1.0 In-Reply-To: <78d77162-11df-4437-b70b-fa04f868a494@redhat.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline X-Stat-Signature: e5k5ngrnrwxjhqz468gjjee5r76pgydg X-Rspamd-Queue-Id: 3272F80020 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1724955987-983241 X-HE-Meta: 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 ecdsgPCd GDQciMiuaqTesS+19gT/LN3ggbxiMxSP0RM0vIqWgKc19eonMzewF4XEjjhv6aV1c/1bpeQwPJk+r/rhHtKgaaDHVNbHW51FRQz91Za5cDZHkjmu03tCNGctRu8kEaZ8jNgBG2+I988ei2mTr3dMj3F2ZfQ06DKs4NyFLbJ1smshaR671XhDY77QaIU2l9RZXIFAS/YzrXkKP1+S2ao9WBhChIAaUVABz7DP/CXcYsNQ/9dkg2MhrMdmy6/8LpG/3R1dUQu0aproGd/AMHiLNEROoxBOSp9AbXdEUzwyjWDsD4ueLDoWMO6WZh5N/4Na3xisCvedV3P2ObRhYmLZoIqSfUYobLpgWtgCd3GkkU5BaiaBQ2FGE3sWVGVV7+TTrO1CeNEZaU/AuDEs2Zv0VQVTcsZZ77Eg1oR7tc89qO7a2YMXkybOPlY9gjdsBpGs/AfaLSmSX6f0fV2HoDsyD5ImKUZzlTZ8pUzPKThC8Ql/3YWc= 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 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. -- Peter Xu