linux-kernel - Re: [PATCH v4 03/23] mm/gup: move try_get_compound

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Message-ID: <20191113105023.GG6367@quack2.suse.cz>
Date:   Wed, 13 Nov 2019 11:50:23 +0100
From:   Jan Kara <jack@...e.cz>
To:     John Hubbard <jhubbard@...dia.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Alex Williamson <alex.williamson@...hat.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Björn Töpel <bjorn.topel@...el.com>,
        Christoph Hellwig <hch@...radead.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Dave Chinner <david@...morbit.com>,
        David Airlie <airlied@...ux.ie>,
        "David S . Miller" <davem@...emloft.net>,
        Ira Weiny <ira.weiny@...el.com>, Jan Kara <jack@...e.cz>,
        Jason Gunthorpe <jgg@...pe.ca>, Jens Axboe <axboe@...nel.dk>,
        Jonathan Corbet <corbet@....net>,
        Jérôme Glisse <jglisse@...hat.com>,
        Magnus Karlsson <magnus.karlsson@...el.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Michal Hocko <mhocko@...e.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Paul Mackerras <paulus@...ba.org>,
        Shuah Khan <shuah@...nel.org>,
        Vlastimil Babka <vbabka@...e.cz>, bpf@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, kvm@...r.kernel.org,
        linux-block@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-media@...r.kernel.org, linux-rdma@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, netdev@...r.kernel.org,
        linux-mm@...ck.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 03/23] mm/gup: move try_get_compound_head() to top,
 fix minor issues

On Tue 12-11-19 20:26:50, John Hubbard wrote:
> An upcoming patch uses try_get_compound_head() more widely,
> so move it to the top of gup.c.
> 
> Also fix a tiny spelling error and a checkpatch.pl warning.
> 
> Signed-off-by: John Hubbard <jhubbard@...dia.com>

Looks good. You can add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza

> ---
>  mm/gup.c | 29 +++++++++++++++--------------
>  1 file changed, 15 insertions(+), 14 deletions(-)
> 
> diff --git a/mm/gup.c b/mm/gup.c
> index 199da99e8ffc..933524de6249 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -29,6 +29,21 @@ struct follow_page_context {
>  	unsigned int page_mask;
>  };
>  
> +/*
> + * Return the compound head page with ref appropriately incremented,
> + * or NULL if that failed.
> + */
> +static inline struct page *try_get_compound_head(struct page *page, int refs)
> +{
> +	struct page *head = compound_head(page);
> +
> +	if (WARN_ON_ONCE(page_ref_count(head) < 0))
> +		return NULL;
> +	if (unlikely(!page_cache_add_speculative(head, refs)))
> +		return NULL;
> +	return head;
> +}
> +
>  /**
>   * put_user_pages_dirty_lock() - release and optionally dirty gup-pinned pages
>   * @pages:  array of pages to be maybe marked dirty, and definitely released.
> @@ -1793,20 +1808,6 @@ static void __maybe_unused undo_dev_pagemap(int *nr, int nr_start,
>  	}
>  }
>  
> -/*
> - * Return the compund head page with ref appropriately incremented,
> - * or NULL if that failed.
> - */
> -static inline struct page *try_get_compound_head(struct page *page, int refs)
> -{
> -	struct page *head = compound_head(page);
> -	if (WARN_ON_ONCE(page_ref_count(head) < 0))
> -		return NULL;
> -	if (unlikely(!page_cache_add_speculative(head, refs)))
> -		return NULL;
> -	return head;
> -}
> -
>  #ifdef CONFIG_ARCH_HAS_PTE_SPECIAL
>  static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
>  			 unsigned int flags, struct page **pages, int *nr)
> -- 
> 2.24.0
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR