Date:   Tue, 14 Feb 2023 19:19:16 -0800 (PST)
Subject:     Re: [PATCH] mm: remove zap_page_range and create zap_vma_pages
In-Reply-To: <20230104002732.232573-1-mike.kravetz@oracle.com>
CC:     linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org,
        linux-s390@vger.kernel.org, netdev@vger.kernel.org,
        Christoph Hellwig <hch@infradead.org>, david@redhat.com,
        mhocko@suse.com, peterx@redhat.com, nadav.amit@gmail.com,
        willy@infradead.org, vbabka@suse.cz, riel@surriel.com,
        Will Deacon <will@kernel.org>, mpe@ellerman.id.au,
        borntraeger@linux.ibm.com, dave.hansen@linux.intel.com,
        brauner@kernel.org, edumazet@google.com, akpm@linux-foundation.org,
        mike.kravetz@oracle.com
From:   Palmer Dabbelt <palmer@dabbelt.com>
To:     mike.kravetz@oracle.com
Message-ID: <mhng-6dc92fd9-0fe6-4a0d-974f-4f4468f143e4@palmer-ri-x1c9>
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On Tue, 03 Jan 2023 16:27:32 PST (-0800), mike.kravetz@oracle.com wrote:
> zap_page_range was originally designed to unmap pages within an address
> range that could span multiple vmas.  While working on [1], it was
> discovered that all callers of zap_page_range pass a range entirely within
> a single vma.  In addition, the mmu notification call within zap_page
> range does not correctly handle ranges that span multiple vmas.  When
> crossing a vma boundary, a new mmu_notifier_range_init/end call pair
> with the new vma should be made.
>
> Instead of fixing zap_page_range, do the following:
> - Create a new routine zap_vma_pages() that will remove all pages within
>   the passed vma.  Most users of zap_page_range pass the entire vma and
>   can use this new routine.
> - For callers of zap_page_range not passing the entire vma, instead call
>   zap_page_range_single().
> - Remove zap_page_range.
>
> [1] https://lore.kernel.org/linux-mm/20221114235507.294320-2-mike.kravetz@oracle.com/
> Suggested-by: Peter Xu <peterx@redhat.com>
> Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>

[...]

> diff --git a/arch/riscv/kernel/vdso.c b/arch/riscv/kernel/vdso.c
> index e410275918ac..5c30212d8d1c 100644
> --- a/arch/riscv/kernel/vdso.c
> +++ b/arch/riscv/kernel/vdso.c
> @@ -124,13 +124,11 @@ int vdso_join_timens(struct task_struct *task, struct time_namespace *ns)
>  	mmap_read_lock(mm);
>
>  	for_each_vma(vmi, vma) {
> -		unsigned long size = vma->vm_end - vma->vm_start;
> -
>  		if (vma_is_special_mapping(vma, vdso_info.dm))
> -			zap_page_range(vma, vma->vm_start, size);
> +			zap_vma_pages(vma);
>  #ifdef CONFIG_COMPAT
>  		if (vma_is_special_mapping(vma, compat_vdso_info.dm))
> -			zap_page_range(vma, vma->vm_start, size);
> +			zap_vma_pages(vma);
>  #endif
>  	}

Acked-by: Palmer Dabbelt <palmer@rivosinc.com> # RISC-V

Thanks!