linux-kernel - Re: [PATCH v3 1/4] mm/gup: add compound page list iterator

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Date:   Wed, 10 Feb 2021 19:20:10 -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 1/4] mm/gup: add compound page list iterator

On Fri, Feb 05, 2021 at 08:41:24PM +0000, Joao Martins wrote:
> Add an helper that iterates over head pages in a list of pages. It
> essentially counts the tails until the next page to process has a
> different head that the current. This is going to be used by
> unpin_user_pages() family of functions, to batch the head page refcount
> updates once for all passed consecutive tail pages.
> 
> Suggested-by: Jason Gunthorpe <jgg@...dia.com>
> Signed-off-by: Joao Martins <joao.m.martins@...cle.com>
> Reviewed-by: John Hubbard <jhubbard@...dia.com>
> ---
>  mm/gup.c | 26 ++++++++++++++++++++++++++
>  1 file changed, 26 insertions(+)

Reviewed-by: Jason Gunthorpe <jgg@...dia.com>

This can be used for check_and_migrate_cma_pages() too (there is a
series around to change this logic though, not sure if it is landed
yet)

Jason