linux-kernel - Re: [PATCH v13 15/35] fs: Export anon_inode_getfile

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Message-ID: <20231102-freihalten-vorsah-fdd68051b005@brauner>
Date:   Thu, 2 Nov 2023 17:24:27 +0100
From:   Christian Brauner <brauner@...nel.org>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>, Marc Zyngier <maz@...nel.org>,
        Oliver Upton <oliver.upton@...ux.dev>,
        Huacai Chen <chenhuacai@...nel.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Anup Patel <anup@...infault.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>, kvm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
        linux-mips@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        kvm-riscv@...ts.infradead.org, linux-riscv@...ts.infradead.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Xiaoyao Li <xiaoyao.li@...el.com>,
        Xu Yilun <yilun.xu@...el.com>,
        Chao Peng <chao.p.peng@...ux.intel.com>,
        Fuad Tabba <tabba@...gle.com>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Anish Moorthy <amoorthy@...gle.com>,
        David Matlack <dmatlack@...gle.com>,
        Yu Zhang <yu.c.zhang@...ux.intel.com>,
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        Mickaël Salaün <mic@...ikod.net>,
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        Vishal Annapurve <vannapurve@...gle.com>,
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        Maciej Szmigiero <mail@...iej.szmigiero.name>,
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        Quentin Perret <qperret@...gle.com>,
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        Wang <wei.w.wang@...el.com>,
        Liam Merwick <liam.merwick@...cle.com>,
        Isaku Yamahata <isaku.yamahata@...il.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [PATCH v13 15/35] fs: Export anon_inode_getfile_secure() for use
 by KVM

On Fri, Oct 27, 2023 at 11:21:57AM -0700, Sean Christopherson wrote:
> Export anon_inode_getfile_secure() so that it can be used by KVM to create
> and manage file-based guest memory without need a fullblow filesystem.
> The "standard" anon_inode_getfd() doesn't work for KVM's use case as KVM
> needs a unique inode for each file, e.g. to be able to independently
> manage the size and lifecycle of a given file.
> 
> Note, KVM doesn't need a "secure" version, just unique inodes, i.e. ignore
> the name.
> 
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---

Before we enshrine this misleading name let's rename this to:

create_anon_inode_getfile()

I don't claim it's a great name but it's better than *_secure() which is
very confusing. So just:

struct file *create_anon_inode_getfile(const char *name,
                                       const struct file_operations *fops,
                                       void *priv, int flags)

May also just remove that context_inode argument from the exported
function. The only other caller is io_uring. And neither it nor this
patchset need the context_inode thing afaict. Merge conflict risk is
extremely low so carrying that as part of this patchset is fine and
shouldn't cause huge issues for you.