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Thu, 13 Jul 2023 13:12:30 -0700 (PDT) MIME-Version: 1.0 References: <20230713095339.189715-1-wangkefeng.wang@huawei.com> <20230713095339.189715-2-wangkefeng.wang@huawei.com> In-Reply-To: From: Suren Baghdasaryan Date: Thu, 13 Jul 2023 13:12:15 -0700 Message-ID: Subject: Re: [PATCH rfc -next 01/10] mm: add a generic VMA lock-based page fault handler To: Matthew Wilcox Cc: Kefeng Wang , linux-mm@kvack.org, Andrew Morton , Russell King , Catalin Marinas , Will Deacon , Huacai Chen , WANG Xuerui , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexander Gordeev , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Christian Borntraeger , Sven Schnelle , Dave Hansen , Andy Lutomirski , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, loongarch@lists.linux.dev, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 42CF2C0018 X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: ux547rfix7rm3ykfgn6h87dmgyko9mqg X-HE-Tag: 1689279151-690189 X-HE-Meta: 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 sspWq/TJ 9zkaCxrCcDokah7wOGlJsJMKjxcmTazNnE4W6+rJjw2/qJeoHDCEhQrR4eSxj7SpapkqGSLBVemab3s27CJSL1OxGTtyt8fyrTllccTp4Dh9ctbipKB0iotk8lOkebmoq81oglSHPvWIy30DG/15LZi3bmPpAsJPKOFpWkIBPqPmKDLjNn3RGd/b+DPZz8A8NQxRo42wlESKgzudUNoFxmJDydpS2nEGEiXFROny1upm+woyt0T9o4V/8ufkPWJNzn4C0lWr1vodvOIIS3kHxuEs3G1YerphGP3Ed 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: On Thu, Jul 13, 2023 at 9:15=E2=80=AFAM Matthew Wilcox wrote: > > > +int try_vma_locked_page_fault(struct vm_locked_fault *vmlf, vm_fault_t= *ret) > > +{ > > + struct vm_area_struct *vma; > > + vm_fault_t fault; > > > On Thu, Jul 13, 2023 at 05:53:29PM +0800, Kefeng Wang wrote: > > +#define VM_LOCKED_FAULT_INIT(_name, _mm, _address, _fault_flags, _vm_f= lags, _regs, _fault_code) \ > > + _name.mm =3D _mm; \ > > + _name.address =3D _address; \ > > + _name.fault_flags =3D _fault_flags; \ > > + _name.vm_flags =3D _vm_flags; \ > > + _name.regs =3D _regs; \ > > + _name.fault_code =3D _fault_code > > More consolidated code is a good idea; no question. But I don't think > this is the right way to do it. > > > +int __weak arch_vma_check_access(struct vm_area_struct *vma, > > + struct vm_locked_fault *vmlf); > > This should be: > > #ifndef vma_check_access > bool vma_check_access(struct vm_area_struct *vma, ) > { > return (vma->vm_flags & vm_flags) =3D=3D 0; > } > #endif > > and then arches which want to do something different can just define > vma_check_access. > > > +int try_vma_locked_page_fault(struct vm_locked_fault *vmlf, vm_fault_t= *ret) > > +{ > > + struct vm_area_struct *vma; > > + vm_fault_t fault; > > Declaring the vmf in this function and then copying it back is just wrong= . > We need to declare vm_fault_t earlier (in the arch fault handler) and > pass it in. Did you mean to say "we need to declare vmf (struct vm_fault) earlier (in the arch fault handler) and pass it in." ? > I don't think that creating struct vm_locked_fault is the > right idea either. > > > + if (!(vmlf->fault_flags & FAULT_FLAG_USER)) > > + return -EINVAL; > > + > > + vma =3D lock_vma_under_rcu(vmlf->mm, vmlf->address); > > + if (!vma) > > + return -EINVAL; > > + > > + if (arch_vma_check_access(vma, vmlf)) { > > + vma_end_read(vma); > > + return -EINVAL; > > + } > > + > > + fault =3D handle_mm_fault(vma, vmlf->address, > > + vmlf->fault_flags | FAULT_FLAG_VMA_LOCK, > > + vmlf->regs); > > + *ret =3D fault; > > + > > + if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED))) > > + vma_end_read(vma); > > + > > + if ((fault & VM_FAULT_RETRY)) > > + count_vm_vma_lock_event(VMA_LOCK_RETRY); > > + else > > + count_vm_vma_lock_event(VMA_LOCK_SUCCESS); > > + > > + return 0; > > +} > > + > > #endif /* CONFIG_PER_VMA_LOCK */ > > > > #ifndef __PAGETABLE_P4D_FOLDED > > -- > > 2.27.0 > > > >