linux-kernel - Re: [PATCH v3 3/4] mm/gup: add a range variant of unpin_user_pages_dirty

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Date:   Thu, 11 Feb 2021 10:52:03 +0000
From:   Joao Martins <joao.m.martins@...cle.com>
To:     John Hubbard <jhubbard@...dia.com>
Cc:     linux-kernel@...r.kernel.org, linux-rdma@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Doug Ledford <dledford@...hat.com>,
        Matthew Wilcox <willy@...radead.org>, linux-mm@...ck.org
Subject: Re: [PATCH v3 3/4] mm/gup: add a range variant of
 unpin_user_pages_dirty_lock()



On 2/10/21 11:19 PM, John Hubbard wrote:
> On 2/5/21 12:41 PM, Joao Martins wrote:
>> Add a unpin_user_page_range_dirty_lock() API which takes a starting page
>> and how many consecutive pages we want to unpin and optionally dirty.
>>
>> To that end, define another iterator for_each_compound_range()
>> that operates in page ranges as opposed to page array.
>>
>> For users (like RDMA mr_dereg) where each sg represents a
>> contiguous set of pages, we're able to more efficiently unpin
>> pages without having to supply an array of pages much of what
>> happens today with unpin_user_pages().
>>
>> Suggested-by: Jason Gunthorpe <jgg@...dia.com>
>> Signed-off-by: Joao Martins <joao.m.martins@...cle.com>
>> ---
>>   include/linux/mm.h |  2 ++
>>   mm/gup.c           | 62 ++++++++++++++++++++++++++++++++++++++++++++++
>>   2 files changed, 64 insertions(+)
>>
>> diff --git a/include/linux/mm.h b/include/linux/mm.h
>> index a608feb0d42e..b76063f7f18a 100644
>> --- a/include/linux/mm.h
>> +++ b/include/linux/mm.h
>> @@ -1265,6 +1265,8 @@ static inline void put_page(struct page *page)
>>   void unpin_user_page(struct page *page);
>>   void unpin_user_pages_dirty_lock(struct page **pages, unsigned long npages,
>>   				 bool make_dirty);
>> +void unpin_user_page_range_dirty_lock(struct page *page, unsigned long npages,
>> +				      bool make_dirty);
>>   void unpin_user_pages(struct page **pages, unsigned long npages);
>>   
>>   /**
>> diff --git a/mm/gup.c b/mm/gup.c
>> index 467a11df216d..938964d31494 100644
>> --- a/mm/gup.c
>> +++ b/mm/gup.c
>> @@ -215,6 +215,32 @@ void unpin_user_page(struct page *page)
>>   }
>>   EXPORT_SYMBOL(unpin_user_page);
>>   
>> +static inline void compound_range_next(unsigned long i, unsigned long npages,
>> +				       struct page **list, struct page **head,
>> +				       unsigned int *ntails)
> 
> Yes, the new names look good, and I have failed to find any logic errors, so:
> 
> Reviewed-by: John Hubbard <jhubbard@...dia.com>
> 

Thanks again for all the input!