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Date:   Wed, 23 Oct 2019 10:24:20 -0700
From:   Matthew Wilcox <willy@infradead.org>
To:     Yang Shi <yang.shi@linux.alibaba.com>
Cc:     hughd@google.com, aarcange@redhat.com,
        kirill.shutemov@linux.intel.com, gavin.dg@linux.alibaba.com,
        akpm@linux-foundation.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [v2 PATCH] mm: thp: handle page cache THP correctly in
 PageTransCompoundMap
Message-ID: <20191023172420.GB2963@bombadil.infradead.org>
References: <1571850304-82802-1-git-send-email-yang.shi@linux.alibaba.com>
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On Thu, Oct 24, 2019 at 01:05:04AM +0800, Yang Shi wrote:
> +	return map_count >= 0 &&
> +	       map_count == atomic_read(&head[1].compound_mapcount);
>  }

I didn't like Hugh's duplicate definition either.  May I suggest:

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 2f2199a51941..3d0efd937d2b 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -695,11 +695,6 @@ static inline void *kvcalloc(size_t n, size_t size, gfp_t flags)
 
 extern void kvfree(const void *addr);
 
-static inline atomic_t *compound_mapcount_ptr(struct page *page)
-{
-	return &page[1].compound_mapcount;
-}
-
 static inline int compound_mapcount(struct page *page)
 {
 	VM_BUG_ON_PAGE(!PageCompound(page), page);
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 2222fa795284..270aa8fd2800 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -221,6 +221,11 @@ struct page {
 #endif
 } _struct_page_alignment;
 
+static inline atomic_t *compound_mapcount_ptr(struct page *page)
+{
+	return &page[1].compound_mapcount;
+}
+
 /*
  * Used for sizing the vmemmap region on some architectures
  */