linux-kernel - [PATCH v2 14/28] mm: Convert page_maybe_dma

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Date:   Mon, 10 Jan 2022 04:23:52 +0000
From:   "Matthew Wilcox (Oracle)" <willy@...radead.org>
To:     linux-mm@...ck.org
Cc:     "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        John Hubbard <jhubbard@...dia.com>,
        Christoph Hellwig <hch@...radead.org>,
        William Kucharski <william.kucharski@...cle.com>,
        linux-kernel@...r.kernel.org, Jason Gunthorpe <jgg@...pe.ca>
Subject: [PATCH v2 14/28] mm: Convert page_maybe_dma_pinned() to use a folio

Replace three calls to compound_head() with one.  This removes the last
user of compound_pincount(), so remove that helper too.

Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
---
 include/linux/mm.h | 21 ++++++++-------------
 1 file changed, 8 insertions(+), 13 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index bf9624ca61c3..d3769897c8ac 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -934,13 +934,6 @@ static inline int head_compound_pincount(struct page *head)
 	return atomic_read(compound_pincount_ptr(head));
 }
 
-static inline int compound_pincount(struct page *page)
-{
-	VM_BUG_ON_PAGE(!PageCompound(page), page);
-	page = compound_head(page);
-	return head_compound_pincount(page);
-}
-
 static inline void set_compound_order(struct page *page, unsigned int order)
 {
 	page[1].compound_order = order;
@@ -1340,18 +1333,20 @@ void unpin_user_pages(struct page **pages, unsigned long npages);
  */
 static inline bool page_maybe_dma_pinned(struct page *page)
 {
-	if (PageCompound(page))
-		return compound_pincount(page) > 0;
+	struct folio *folio = page_folio(page);
+
+	if (folio_test_large(folio))
+		return atomic_read(folio_pincount_ptr(folio)) > 0;
 
 	/*
-	 * page_ref_count() is signed. If that refcount overflows, then
-	 * page_ref_count() returns a negative value, and callers will avoid
+	 * folio_ref_count() is signed. If that refcount overflows, then
+	 * folio_ref_count() returns a negative value, and callers will avoid
 	 * further incrementing the refcount.
 	 *
-	 * Here, for that overflow case, use the signed bit to count a little
+	 * Here, for that overflow case, use the sign bit to count a little
 	 * bit higher via unsigned math, and thus still get an accurate result.
 	 */
-	return ((unsigned int)page_ref_count(compound_head(page))) >=
+	return ((unsigned int)folio_ref_count(folio)) >=
 		GUP_PIN_COUNTING_BIAS;
 }
 
-- 
2.33.0