mm/hugetlb: remove unnecessary memory fetch in PageHeadHuge()

Commit f1e61557f023 ("mm: pack compound_dtor and compound_order into one
word in struct page") changed compound_dtor from a pointer to an array
index in order to pack it.  To check if page has the hugeltbfs
compound_dtor, we can just compare the index directly without fetching the
function pointer.  Said commit did that with PageHuge() and we can do the
same with PageHeadHuge() to make the code a bit smaller and faster.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Acked-by: David Rientjes <rientjes@google.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Neha Agarwal <nehaagarwal@google.com>
Link: http://lkml.kernel.org/r/20200311172440.6988-1-vbabka@suse.cz
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 4b84640..f9ea1e5 100644 (file)
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1528,7 +1528,7 @@ int PageHeadHuge(struct page *page_head)
        if (!PageHead(page_head))
                return 0;
 
-       return get_compound_page_dtor(page_head) == free_huge_page;
+       return page_head[1].compound_dtor == HUGETLB_PAGE_DTOR;
 }
 
 /*