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Message-ID: <ZLAjFQGgcjt4ykS7@casper.infradead.org>
Date: Thu, 13 Jul 2023 17:15:17 +0100
From: Matthew Wilcox <willy@...radead.org>
To: Kefeng Wang <wangkefeng.wang@...wei.com>
Cc: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
surenb@...gle.com, Russell King <linux@...linux.org.uk>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will@...nel.org>,
Huacai Chen <chenhuacai@...nel.org>,
WANG Xuerui <kernel@...0n.name>,
Michael Ellerman <mpe@...erman.id.au>,
Nicholas Piggin <npiggin@...il.com>,
Christophe Leroy <christophe.leroy@...roup.eu>,
Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>,
Albert Ou <aou@...s.berkeley.edu>,
Alexander Gordeev <agordeev@...ux.ibm.com>,
Gerald Schaefer <gerald.schaefer@...ux.ibm.com>,
Heiko Carstens <hca@...ux.ibm.com>,
Vasily Gorbik <gor@...ux.ibm.com>,
Christian Borntraeger <borntraeger@...ux.ibm.com>,
Sven Schnelle <svens@...ux.ibm.com>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Andy Lutomirski <luto@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
x86@...nel.org, linux-arm-kernel@...ts.infradead.org,
linux-kernel@...r.kernel.org, loongarch@...ts.linux.dev,
linuxppc-dev@...ts.ozlabs.org, linux-riscv@...ts.infradead.org,
linux-s390@...r.kernel.org
Subject: Re: [PATCH rfc -next 01/10] mm: add a generic VMA lock-based page
fault handler
> +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
>
>
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