linux-kernel - Re: [PATCH v4 4/6] io_uring: rsrc: avoid use of vmas parameter in pin_user

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Date:   Tue, 18 Apr 2023 17:55:48 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Lorenzo Stoakes <lstoakes@...il.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Matthew Wilcox <willy@...radead.org>, Jens Axboe <axboe@...nel.dk>,
        Pavel Begunkov <asml.silence@...il.com>,
        io-uring@...r.kernel.org
Subject: Re: [PATCH v4 4/6] io_uring: rsrc: avoid use of vmas parameter in
 pin_user_pages()

On 18.04.23 17:49, Lorenzo Stoakes wrote:
> We are shortly to remove pin_user_pages(), and instead perform the required
> VMA checks ourselves. In most cases there will be a single VMA so this
> should caues no undue impact on an already slow path.
> 
> Doing this eliminates the one instance of vmas being used by
> pin_user_pages().
> 
> Suggested-by: Matthew Wilcox (Oracle) <willy@...radead.org>
> Signed-off-by: Lorenzo Stoakes <lstoakes@...il.com>
> ---
>   io_uring/rsrc.c | 55 ++++++++++++++++++++++++++++---------------------
>   1 file changed, 31 insertions(+), 24 deletions(-)
> 
> diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c
> index 7a43aed8e395..3a927df9d913 100644
> --- a/io_uring/rsrc.c
> +++ b/io_uring/rsrc.c
> @@ -1138,12 +1138,37 @@ static int io_buffer_account_pin(struct io_ring_ctx *ctx, struct page **pages,
>   	return ret;
>   }
>   
> +static int check_vmas_locked(unsigned long addr, unsigned long len)

TBH, the whole "_locked" suffix is a bit confusing.

I was wondering why you'd want to check whether the VMAs are locked ...

> +{
> +	struct file *file;
> +	VMA_ITERATOR(vmi, current->mm, addr);
> +	struct vm_area_struct *vma = vma_next(&vmi);
> +	unsigned long end = addr + len;
> +
> +	if (WARN_ON_ONCE(!vma))
> +		return -EINVAL;
> +
> +	file = vma->vm_file;
> +	if (file && !is_file_hugepages(file))
> +		return -EOPNOTSUPP;

You'd now be rejecting vma_is_shmem() here, no?


-- 
Thanks,

David / dhildenb