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Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1qJyyL-000HxX-Pp; Thu, 13 Jul 2023 16:15:17 +0000 Date: Thu, 13 Jul 2023 17:15:17 +0100 From: Matthew Wilcox To: Kefeng Wang Cc: linux-mm@kvack.org, Andrew Morton , surenb@google.com, 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 Subject: Re: [PATCH rfc -next 01/10] mm: add a generic VMA lock-based page fault handler Message-ID: References: <20230713095339.189715-1-wangkefeng.wang@huawei.com> <20230713095339.189715-2-wangkefeng.wang@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230713095339.189715-2-wangkefeng.wang@huawei.com> X-Stat-Signature: 1udswynwsqr7pnasfs7sy83hzhbxx55n X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: A5467C0022 X-Rspam-User: X-HE-Tag: 1689264931-485186 X-HE-Meta: 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 kuJJndLg q7lOdyvkPllMoVkaqJ8ExrNwQv3iy3VOqiUno7hhsIo5HRVLZXtjQO8OdMmwWmvtoDNWML0x/+V0O7EsNF5/F8HnHxIstOzBaevjzt9wlowIhWslMCsD4SeNERscOQajizvV5kVZIWNMoyjQ= 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: > +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_flags, _regs, _fault_code) \ > + _name.mm = _mm; \ > + _name.address = _address; \ > + _name.fault_flags = _fault_flags; \ > + _name.vm_flags = _vm_flags; \ > + _name.regs = _regs; \ > + _name.fault_code = _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) == 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. 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 = 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 = handle_mm_fault(vma, vmlf->address, > + vmlf->fault_flags | FAULT_FLAG_VMA_LOCK, > + vmlf->regs); > + *ret = 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 > >