Date:   Sat, 18 Dec 2021 17:31:34 +0300
From:   "Kirill A. Shutemov" <kirill@shutemov.name>
To:     David Hildenbrand <david@redhat.com>
Cc:     linux-kernel@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>,
        Hugh Dickins <hughd@google.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        David Rientjes <rientjes@google.com>,
        Shakeel Butt <shakeelb@google.com>,
        John Hubbard <jhubbard@nvidia.com>,
        Jason Gunthorpe <jgg@nvidia.com>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Mike Rapoport <rppt@linux.ibm.com>,
        Yang Shi <shy828301@gmail.com>,
        "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
        Matthew Wilcox <willy@infradead.org>,
        Vlastimil Babka <vbabka@suse.cz>, Jann Horn <jannh@google.com>,
        Michal Hocko <mhocko@kernel.org>,
        Nadav Amit <namit@vmware.com>, Rik van Riel <riel@surriel.com>,
        Roman Gushchin <guro@fb.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Peter Xu <peterx@redhat.com>,
        Donald Dutile <ddutile@redhat.com>,
        Christoph Hellwig <hch@lst.de>,
        Oleg Nesterov <oleg@redhat.com>, Jan Kara <jack@suse.cz>,
        linux-mm@kvack.org, linux-kselftest@vger.kernel.org,
        linux-doc@vger.kernel.org
Subject: Re: [PATCH v1 03/11] mm: simplify hugetlb and file-THP handling in
 __page_mapcount()
Message-ID: <20211218143134.rdnyw6zarkysckrw@box.shutemov.name>
References: <20211217113049.23850-1-david@redhat.com>
 <20211217113049.23850-4-david@redhat.com>
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On Fri, Dec 17, 2021 at 12:30:41PM +0100, David Hildenbrand wrote:
> Let's return early for hugetlb, which really only relies on the compound
> mapcount so far and does not support PageDoubleMap() yet. Use the chance
> to cleanup the file-THP case to make it easier to grasp. While at it, use
> head_compound_mapcount().
> 
> This is a preparation for further changes.
> 
> Reviewed-by: Peter Xu <peterx@redhat.com>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
>  mm/util.c | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/mm/util.c b/mm/util.c
> index 741ba32a43ac..3239e75c148d 100644
> --- a/mm/util.c
> +++ b/mm/util.c
> @@ -732,15 +732,18 @@ int __page_mapcount(struct page *page)
>  {
>  	int ret;
>  
> -	ret = atomic_read(&page->_mapcount) + 1;
> +	if (PageHuge(page))
> +		return compound_mapcount(page);

It would be nice to make PageHuge() inlinable first. It's a shame the we
need to have to do a function call for PageHuge() check.

Otherwise, looks good:

Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>

-- 
 Kirill A. Shutemov