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From:   Matthew Wilcox <willy@infradead.org>
To:     linux-fsdevel@vger.kernel.org
Cc:     "Matthew Wilcox (Oracle)" <willy@infradead.org>,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: [PATCH v6 11/51] mm: Add thp_head
Date:   Wed, 10 Jun 2020 13:13:05 -0700
Message-Id: <20200610201345.13273-12-willy@infradead.org>
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From: "Matthew Wilcox (Oracle)" <willy@infradead.org>

This is like compound_head() but compiles away when
CONFIG_TRANSPARENT_HUGEPAGE is not enabled.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 include/linux/huge_mm.h | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index dcdfd21763a3..bd13e9ac3437 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -266,6 +266,15 @@ static inline spinlock_t *pud_trans_huge_lock(pud_t *pud,
 		return NULL;
 }
 
+/**
+ * thp_head - Head page of a transparent huge page.
+ * @page: Any page (tail, head or regular) found in the page cache.
+ */
+static inline struct page *thp_head(struct page *page)
+{
+	return compound_head(page);
+}
+
 /**
  * thp_order - Order of a transparent huge page.
  * @page: Head page of a transparent huge page.
@@ -342,6 +351,12 @@ static inline struct list_head *page_deferred_list(struct page *page)
 #define HPAGE_PUD_MASK ({ BUILD_BUG(); 0; })
 #define HPAGE_PUD_SIZE ({ BUILD_BUG(); 0; })
 
+static inline struct page *thp_head(struct page *page)
+{
+	VM_BUG_ON_PGFLAGS(PageTail(page), page);
+	return page;
+}
+
 static inline unsigned int thp_order(struct page *page)
 {
 	VM_BUG_ON_PGFLAGS(PageTail(page), page);
-- 
2.26.2