linux-kernel - [PATCH 05/75] mm/gup: Optimise compound_range

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Date:   Fri,  4 Feb 2022 19:57:42 +0000
From:   "Matthew Wilcox (Oracle)" <willy@...radead.org>
To:     linux-mm@...ck.org
Cc:     "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        linux-kernel@...r.kernel.org, Christoph Hellwig <hch@....de>,
        John Hubbard <jhubbard@...dia.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        William Kucharski <william.kucharski@...cle.com>
Subject: [PATCH 05/75] mm/gup: Optimise compound_range_next()

By definition, a compound page has an order >= 1, so the second half
of the test was redundant.  Also, this cannot be a tail page since
it's the result of calling compound_head(), so use PageHead() instead
of PageCompound().

Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
Reviewed-by: Christoph Hellwig <hch@....de>
Reviewed-by: John Hubbard <jhubbard@...dia.com>
Reviewed-by: Jason Gunthorpe <jgg@...dia.com>
Reviewed-by: William Kucharski <william.kucharski@...cle.com>
---
 mm/gup.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/gup.c b/mm/gup.c
index 26c73998c6df..75a0a1fd4c2a 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -262,7 +262,7 @@ static inline struct page *compound_range_next(struct page *start,
 
 	next = start + i;
 	page = compound_head(next);
-	if (PageCompound(page) && compound_order(page) >= 1)
+	if (PageHead(page))
 		nr = min_t(unsigned int,
 			   page + compound_nr(page) - next, npages - i);
 
-- 
2.34.1