linux-kernel - Re: [PATCH 1/7] mm/gup: remove unused vmas parameter from get_user

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Message-ID: <ZD1DQrSLlMn4CUZX@nvidia.com>
Date:   Mon, 17 Apr 2023 10:01:54 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Lorenzo Stoakes <lstoakes@...il.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Matthew Wilcox <willy@...radead.org>,
        David Hildenbrand <david@...hat.com>, x86@...nel.org,
        linux-sgx@...r.kernel.org, amd-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, kvm@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        "H . Peter Anvin" <hpa@...or.com>, Xinhui Pan <Xinhui.Pan@....com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Dimitri Sivanich <dimitri.sivanich@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [PATCH 1/7] mm/gup: remove unused vmas parameter from
 get_user_pages()

On Sat, Apr 15, 2023 at 12:27:13AM +0100, Lorenzo Stoakes wrote:
> No invocation of get_user_pages() uses the vmas parameter, so remove
> it.
> 
> The GUP API is confusing and caveated. Recent changes have done much to
> improve that, however there is more we can do. Exporting vmas is a prime
> target as the caller has to be extremely careful to preclude their use
> after the mmap_lock has expired or otherwise be left with dangling
> pointers.
> 
> Removing the vmas parameter focuses the GUP functions upon their primary
> purpose - pinning (and outputting) pages as well as performing the actions
> implied by the input flags.
> 
> This is part of a patch series aiming to remove the vmas parameter
> altogether.
> 
> Signed-off-by: Lorenzo Stoakes <lstoakes@...il.com>
> Suggested-by: Matthew Wilcox (Oracle) <willy@...radead.org>
> ---
>  arch/x86/kernel/cpu/sgx/ioctl.c     | 2 +-
>  drivers/gpu/drm/radeon/radeon_ttm.c | 2 +-
>  drivers/misc/sgi-gru/grufault.c     | 2 +-
>  include/linux/mm.h                  | 3 +--
>  mm/gup.c                            | 9 +++------
>  mm/gup_test.c                       | 5 ++---
>  virt/kvm/kvm_main.c                 | 4 ++--
>  7 files changed, 11 insertions(+), 16 deletions(-)

Reviewed-by: Jason Gunthorpe <jgg@...dia.com>

Jason