From: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>
Since we're checking that PageTail isn't true when we're writing to the
bits, we don't need to call compound_head() either. This saves us four
instructions per invocation of SetPageFoo / ClearPageFoo for those bits
with a TailRead policy.
---
include/linux/page-flags.h | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 1960b5e4b9ab..38ed6f4365d2 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -174,8 +174,10 @@ static __always_inline
struct page *PagePolicyTailRead(struct page *page, bool modify)
{
CheckPageInit(page);
- VM_BUG_ON_PGFLAGS(modify && PageTail(page), page);
- return compound_head(page);
+ if (!modify)
+ return compound_head(page);
+ VM_BUG_ON_PGFLAGS(PageTail(page), page);
+ return page;
}
static __always_inline struct page *PagePolicyNoCompound(struct page *page)
--
2.16.3
