From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx> Subject: include/linux/pagemap.h: optimise find_subpage for !THP If THP is disabled, find_subpage() can become a no-op by using hpage_nr_pages() instead of compound_nr(). hpage_nr_pages() embeds a check for PageTail, so we can drop the check here. Link: http://lkml.kernel.org/r/20200318140253.6141-5-willy@xxxxxxxxxxxxx Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> Reviewed-by: Christoph Hellwig <hch@xxxxxx> Cc: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx> Cc: Pankaj Gupta <pankaj.gupta.linux@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/pagemap.h | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) --- a/include/linux/pagemap.h~mm-optimise-find_subpage-for-thp +++ a/include/linux/pagemap.h @@ -341,9 +341,7 @@ static inline struct page *find_subpage( if (PageHuge(head)) return head; - VM_BUG_ON_PAGE(PageTail(head), head); - - return head + (index & (compound_nr(head) - 1)); + return head + (index & (hpage_nr_pages(head) - 1)); } struct page *find_get_entry(struct address_space *mapping, pgoff_t offset); _
