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

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Message-ID: <21bc9c1e-9941-9f51-0a38-85ae406ff2cd@redhat.com>
Date:   Tue, 18 Apr 2023 17:56:40 +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 17:55, David Hildenbrand wrote:
> 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 ...

FWIW, "check_vmas_compatible_locked" might be better. But the "_locked" 
is still annoying.

-- 
Thanks,

David / dhildenb