| Date | Wed, 09 Nov 2011 13:28:29 -0800 | From | Greg KH <> | Subject | [187/262] powerpc: gup_hugepte() support THP based tail recounting |
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3.0-stable review patch. If anyone has any objections, please let me know.
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From: Andrea Arcangeli <aarcange@redhat.com>
commit 3526741f0964c88bc2ce511e1078359052bf225b upstream.
Up to this point the code assumed old refcounting for hugepages (pre-thp). This updates the code directly to the thp mapcount tail page refcounting.
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <jweiner@redhat.com> Cc: Rik van Riel <riel@redhat.com> Cc: Mel Gorman <mgorman@suse.de> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- arch/powerpc/mm/hugetlbpage.c | 24 +++++++++++++++++++++++- 1 file changed, 23 insertions(+), 1 deletion(-)
--- a/arch/powerpc/mm/hugetlbpage.c +++ b/arch/powerpc/mm/hugetlbpage.c @@ -385,12 +385,23 @@ follow_huge_pmd(struct mm_struct *mm, un return NULL; } +static inline void get_huge_page_tail(struct page *page) +{ + /* + * __split_huge_page_refcount() cannot run + * from under us. + */ + VM_BUG_ON(page_mapcount(page) < 0); + VM_BUG_ON(atomic_read(&page->_count) != 0); + atomic_inc(&page->_mapcount); +} + static noinline int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long addr, unsigned long end, int write, struct page **pages, int *nr) { unsigned long mask; unsigned long pte_end; - struct page *head, *page; + struct page *head, *page, *tail; pte_t pte; int refs; @@ -413,6 +424,7 @@ static noinline int gup_hugepte(pte_t *p head = pte_page(pte); page = head + ((addr & (sz-1)) >> PAGE_SHIFT); + tail = page; do { VM_BUG_ON(compound_head(page) != head); pages[*nr] = page; @@ -431,6 +443,16 @@ static noinline int gup_hugepte(pte_t *p *nr -= refs; while (refs--) put_page(head); + } else { + /* + * Any tail page need their mapcount reference taken + * before we return. + */ + while (refs--) { + if (PageTail(tail)) + get_huge_page_tail(tail); + tail++; + } } return 1;
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