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 10:24:59 +0000
From:   Joao Martins <joao.m.martins@...cle.com>
To:     Jason Gunthorpe <jgg@...pe.ca>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        linux-rdma@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Doug Ledford <dledford@...hat.com>,
        John Hubbard <jhubbard@...dia.com>,
        Matthew Wilcox <willy@...radead.org>
Subject: Re: [PATCH v3 3/4] mm/gup: add a range variant of
 unpin_user_pages_dirty_lock()



On 2/10/21 11:15 PM, Jason Gunthorpe wrote:
> On Fri, Feb 05, 2021 at 08:41:26PM +0000, 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(+)
> 
> Reviewed-by: Jason Gunthorpe <jgg@...dia.com>
> 
Thanks!

>> +/**
>> + * unpin_user_page_range_dirty_lock() - release and optionally dirty
>> + * gup-pinned page range
>> + *
>> + * @page:  the starting page of a range maybe marked dirty, and definitely released.
>> + * @npages: number of consecutive pages to release.
>> + * @make_dirty: whether to mark the pages dirty
>> + *
>> + * "gup-pinned page range" refers to a range of pages that has had one of the
>> + * get_user_pages() variants called on that page.
> 
> Tidy this language though, this only works with the pin_user_pages
> variants because it hardwires FOLL_PIN
> 
Yes, I can respin a v4 with that adjustment.