linux-kernel - Re: [RFC PATCH] mm: remove zap_page_range and change callers to use zap_vma_page

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Message-ID: <mhng-3136c2a0-6953-4794-856c-46cacdc2c30a@palmer-ri-x1c9>
Date:   Thu, 29 Dec 2022 08:22:23 -0800 (PST)
From:   Palmer Dabbelt <palmer@...belt.com>
To:     mike.kravetz@...cle.com
CC:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-riscv@...ts.infradead.org,
        linux-s390@...r.kernel.org, netdev@...r.kernel.org,
        david@...hat.com, mhocko@...e.com, peterx@...hat.com,
        nadav.amit@...il.com, willy@...radead.org, vbabka@...e.cz,
        riel@...riel.com, Will Deacon <will@...nel.org>,
        mpe@...erman.id.au, borntraeger@...ux.ibm.com,
        dave.hansen@...ux.intel.com, brauner@...nel.org,
        edumazet@...gle.com, akpm@...ux-foundation.org,
        mike.kravetz@...cle.com
Subject:     Re: [RFC PATCH] mm: remove zap_page_range and change callers to use zap_vma_page_range

On Fri, 16 Dec 2022 11:20:12 PST (-0800), mike.kravetz@...cle.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 as calls
> should be vma specific.
>
> Instead of fixing zap_page_range, change all callers to use the new
> routine zap_vma_page_range.  zap_vma_page_range is just a wrapper around
> zap_page_range_single passing in NULL zap details.  The name is also
> more in line with other exported routines that operate within a vma.
> We can then remove zap_page_range.
>
> Also, change madvise_dontneed_single_vma to use this new routine.
>
> [1] https://lore.kernel.org/linux-mm/20221114235507.294320-2-mike.kravetz@oracle.com/
> Suggested-by: Peter Xu <peterx@...hat.com>
> Signed-off-by: Mike Kravetz <mike.kravetz@...cle.com>
> ---
>  arch/arm64/kernel/vdso.c                |  4 ++--
>  arch/powerpc/kernel/vdso.c              |  2 +-
>  arch/powerpc/platforms/book3s/vas-api.c |  2 +-
>  arch/powerpc/platforms/pseries/vas.c    |  2 +-
>  arch/riscv/kernel/vdso.c                |  4 ++--
>  arch/s390/kernel/vdso.c                 |  2 +-
>  arch/s390/mm/gmap.c                     |  2 +-
>  arch/x86/entry/vdso/vma.c               |  2 +-
>  drivers/android/binder_alloc.c          |  2 +-
>  include/linux/mm.h                      |  7 ++++--
>  mm/madvise.c                            |  4 ++--
>  mm/memory.c                             | 30 -------------------------
>  mm/page-writeback.c                     |  2 +-
>  net/ipv4/tcp.c                          |  6 ++---
>  14 files changed, 22 insertions(+), 49 deletions(-)

[snip]

> diff --git a/arch/riscv/kernel/vdso.c b/arch/riscv/kernel/vdso.c
> index e410275918ac..a405119da2c0 100644
> --- a/arch/riscv/kernel/vdso.c
> +++ b/arch/riscv/kernel/vdso.c
> @@ -127,10 +127,10 @@ int vdso_join_timens(struct task_struct *task, struct time_namespace *ns)
>  		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_page_range(vma, vma->vm_start, size);
>  #ifdef CONFIG_COMPAT
>  		if (vma_is_special_mapping(vma, compat_vdso_info.dm))
> -			zap_page_range(vma, vma->vm_start, size);
> +			zap_vma_page_range(vma, vma->vm_start, size);
>  #endif
>  	}

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

Thanks!