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

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Message-ID: <20210210231519.GR4718@ziepe.ca>
Date:   Wed, 10 Feb 2021 19:15:19 -0400
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Joao Martins <joao.m.martins@...cle.com>
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 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>

> +/**
> + * 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

Jason