On 03/04/2015 12:52 PM, Kirill A. Shutemov wrote:
On Mon, Feb 23, 2015 at 05:21:31PM +0100, Vlastimil Babka wrote:
On 02/12/2015 05:18 PM, Kirill A. Shutemov wrote:
@@ -1052,21 +1052,24 @@ void page_add_anon_rmap(struct page *page,
* Everybody else should continue to use page_add_anon_rmap above.
*/
void do_page_add_anon_rmap(struct page *page,
- struct vm_area_struct *vma, unsigned long address, int exclusive)
+ struct vm_area_struct *vma, unsigned long address, int flags)
{
int first = atomic_inc_and_test(&page->_mapcount);
if (first) {
+ bool compound = flags & RMAP_COMPOUND;
+ int nr = compound ? hpage_nr_pages(page) : 1;
hpage_nr_pages(page) is:
static inline int hpage_nr_pages(struct page *page)
{
if (unlikely(PageTransHuge(page)))
return HPAGE_PMD_NR;
return 1;
}
and later...
/*
* We use the irq-unsafe __{inc|mod}_zone_page_stat because
* these counters are not modified in interrupt context, and
* pte lock(a spinlock) is held, which implies preemption
* disabled.
*/
- if (PageTransHuge(page))
+ if (compound) {
+ VM_BUG_ON_PAGE(!PageTransHuge(page), page);
this means that we could assume that
(compound == true) => (PageTransHuge(page) == true)
and simplify above to:
int nr = compound ? HPAGE_PMD_NR : 1;
Right?
No. HPAGE_PMD_NR is defined based on HPAGE_PMD_SHIFT which is BUILD_BUG()
without CONFIG_TRANSPARENT_HUGEPAGE. We will get compiler error without
the helper.
Oh, OK. But that doesn't mean there couldn't be another helper that
would work in this case, or even open-coded #ifdefs in these functions.
Apparently "compound" has to be always false for
!CONFIG_TRANSPARENT_HUGEPAGE, as in that case PageTransHuge is defined
as 0 and the VM_BUG_ON would trigger if compound was true. So without
such ifdefs or wrappers, you are also adding dead code and pointless
tests for !CONFIG_TRANSPARENT_HUGEPAGE?
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