Message-ID: <658eda9c-d716-fcb7-ba0c-b36f646195f1@redhat.com>
Date:   Tue, 31 Jan 2023 15:00:08 +0100
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
 Thunderbird/102.6.0
Subject: Re: [RFC PATCH 01/19] mm: Introduce vm_account
Content-Language: en-US
To:     Alistair Popple <apopple@nvidia.com>, linux-mm@kvack.org,
        cgroups@vger.kernel.org
Cc:     linux-kernel@vger.kernel.org, jgg@nvidia.com, jhubbard@nvidia.com,
        tjmercier@google.com, hannes@cmpxchg.org, surenb@google.com,
        mkoutny@suse.com, daniel@ffwll.ch, linuxppc-dev@lists.ozlabs.org,
        linux-fpga@vger.kernel.org, linux-rdma@vger.kernel.org,
        virtualization@lists.linux-foundation.org, kvm@vger.kernel.org,
        netdev@vger.kernel.org, io-uring@vger.kernel.org,
        bpf@vger.kernel.org, rds-devel@oss.oracle.com,
        linux-kselftest@vger.kernel.org
References: <cover.f52b9eb2792bccb8a9ecd6bc95055705cfe2ae03.1674538665.git-series.apopple@nvidia.com>
 <748338ffe4c42d86669923159fe0426808ecb04d.1674538665.git-series.apopple@nvidia.com>
From:   David Hildenbrand <david@redhat.com>
Organization: Red Hat
In-Reply-To: <748338ffe4c42d86669923159fe0426808ecb04d.1674538665.git-series.apopple@nvidia.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 24.01.23 06:42, Alistair Popple wrote:
> Kernel drivers that pin pages should account these pages against
> either user->locked_vm or mm->pinned_vm and fail the pinning if
> RLIMIT_MEMLOCK is exceeded and CAP_IPC_LOCK isn't held.
> 
> Currently drivers open-code this accounting and use various methods to
> update the atomic variables and check against the limits leading to
> various bugs and inconsistencies. To fix this introduce a standard
> interface for charging pinned and locked memory. As this involves
> taking references on kernel objects such as mm_struct or user_struct
> we introduce a new vm_account struct to hold these references. Several
> helper functions are then introduced to grab references and check
> limits.
> 
> As the way these limits are charged and enforced is visible to
> userspace we need to be careful not to break existing applications by
> charging to different counters. As a result the vm_account functions
> support accounting to different counters as required.
> 
> A future change will extend this to also account against a cgroup for
> pinned pages.

The term "vm_account" is misleading, no? VM_ACCOUNT is for accounting 
towards the commit limit ....

-- 
Thanks,

David / dhildenb