Messages in this thread | | | Date | Fri, 07 Jun 2013 08:56:10 -0700 | From | Dave Hansen <> | Subject | Re: [PATCHv4 14/39] thp, mm: rewrite delete_from_page_cache() to support huge pages |
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On 06/07/2013 08:10 AM, Kirill A. Shutemov wrote: > + /* > + * When we add a huge page to page cache we take only reference to head > + * page, but on split we need to take addition reference to all tail > + * pages since they are still in page cache after splitting. > + */ > + init_tail_refcount = PageAnon(page) ? 0 : 1;
What's the "init" for in the name?
In add_to_page_cache_locked() in patch 12/39, you do > + spin_lock_irq(&mapping->tree_lock); > + for (i = 0; i < nr; i++) { > + page_cache_get(page + i);
That looks to me to be taking references to the tail pages. What gives? :)
> for (i = HPAGE_PMD_NR - 1; i >= 1; i--) { > struct page *page_tail = page + i; > > @@ -1587,8 +1595,9 @@ static void __split_huge_page_refcount(struct page *page, > * atomic_set() here would be safe on all archs (and > * not only on x86), it's safer to use atomic_add(). > */ > - atomic_add(page_mapcount(page) + page_mapcount(page_tail) + 1, > - &page_tail->_count); > + atomic_add(init_tail_refcount + page_mapcount(page) + > + page_mapcount(page_tail) + 1, > + &page_tail->_count); > > /* after clearing PageTail the gup refcount can be released */ > smp_mb();
This does look much better in general, though.
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