linux-kernel - Re: [PATCH v2 bpf-next] mm: mmap: increase sockets maximum memory size pgoff for 32bits

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Message-ID: <CAJ8uoz0bBhdQSocQz8Y9tvrGCsCE9TDf3m1u6=sL4Eo5tZ17YQ@mail.gmail.com>
Date:   Tue, 13 Aug 2019 10:02:54 +0200
From:   Magnus Karlsson <magnus.karlsson@...il.com>
To:     Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>
Cc:     Björn Töpel <bjorn.topel@...el.com>,
        linux-mm@...ck.org, Xdp <xdp-newbies@...r.kernel.org>,
        Network Development <netdev@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>, linux-kernel@...r.kernel.org,
        akpm@...ux-foundation.org, Alexei Starovoitov <ast@...nel.org>,
        "Karlsson, Magnus" <magnus.karlsson@...el.com>
Subject: Re: [PATCH v2 bpf-next] mm: mmap: increase sockets maximum memory
 size pgoff for 32bits

On Mon, Aug 12, 2019 at 2:45 PM Ivan Khoronzhuk
<ivan.khoronzhuk@...aro.org> wrote:
>
> The AF_XDP sockets umem mapping interface uses XDP_UMEM_PGOFF_FILL_RING
> and XDP_UMEM_PGOFF_COMPLETION_RING offsets. The offsets seems like are
> established already and are part of configuration interface.
>
> But for 32-bit systems, while AF_XDP socket configuration, the values
> are to large to pass maximum allowed file size verification.
> The offsets can be tuned ofc, but instead of changing existent
> interface - extend max allowed file size for sockets.

Can you use mmap2() instead that takes a larger offset (2^44) even on
32-bit systems?

/Magnus

> Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>
> ---
>
> Based on bpf-next/master
>
> v2..v1:
>         removed not necessarily #ifdev as ULL and UL for 64 has same size
>
>  mm/mmap.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 7e8c3e8ae75f..578f52812361 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -1358,6 +1358,9 @@ static inline u64 file_mmap_size_max(struct file *file, struct inode *inode)
>         if (S_ISBLK(inode->i_mode))
>                 return MAX_LFS_FILESIZE;
>
> +       if (S_ISSOCK(inode->i_mode))
> +               return MAX_LFS_FILESIZE;
> +
>         /* Special "we do even unsigned file positions" case */
>         if (file->f_mode & FMODE_UNSIGNED_OFFSET)
>                 return 0;
> --
> 2.17.1
>