diff mbox series

[v2,4/8] mm: Optimise find_subpage for !THP

Message ID 20200318140253.6141-5-willy@infradead.org (mailing list archive)
State New, archived
Headers show
Series Misc MM patches | expand

Commit Message

Matthew Wilcox March 18, 2020, 2:02 p.m. UTC 
From: "Matthew Wilcox (Oracle)" <willy@infradead.org>

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.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 include/linux/pagemap.h | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

Comments

Christoph Hellwig March 19, 2020, 10:18 a.m. UTC | #1 
On Wed, Mar 18, 2020 at 07:02:49AM -0700, Matthew Wilcox wrote:
> From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
> 
> 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.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>
diff mbox series

Patch

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 68db0ed8535d..fcb4887e65e8 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -343,9 +343,7 @@  static inline struct page *find_subpage(struct page *head, pgoff_t index)
 	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);