On Mon, May 18, 2015 at 01:49:39PM +0200, Vlastimil Babka wrote: > On 04/23/2015 11:03 PM, Kirill A. Shutemov wrote: > >With new THP refcounting, we don't need tricks to stabilize huge page. > >If we've got reference to tail page, it can't split under us. > > > >This patch effectively reverts a5b338f2b0b1. > > > >Signed-off-by: Kirill A. Shutemov <[email protected]> > >Tested-by: Sasha Levin <[email protected]> > >--- > > kernel/futex.c | 61 > > ++++++++++++---------------------------------------------- > > 1 file changed, 12 insertions(+), 49 deletions(-) > > > >diff --git a/kernel/futex.c b/kernel/futex.c > >index f4d8a85641ed..cf0192e60ef9 100644 > >--- a/kernel/futex.c > >+++ b/kernel/futex.c > >@@ -399,7 +399,7 @@ get_futex_key(u32 __user *uaddr, int fshared, union > >futex_key *key, int rw) > > { > > unsigned long address = (unsigned long)uaddr; > > struct mm_struct *mm = current->mm; > >- struct page *page, *page_head; > >+ struct page *page; > > int err, ro = 0; > > > > /* > >@@ -442,46 +442,9 @@ again: > > else > > err = 0; > > > >-#ifdef CONFIG_TRANSPARENT_HUGEPAGE > >- page_head = page; > >- if (unlikely(PageTail(page))) { > >- put_page(page); > >- /* serialize against __split_huge_page_splitting() */ > >- local_irq_disable(); > >- if (likely(__get_user_pages_fast(address, 1, !ro, &page) == 1)) > >{ > >- page_head = compound_head(page); > >- /* > >- * page_head is valid pointer but we must pin > >- * it before taking the PG_lock and/or > >- * PG_compound_lock. The moment we re-enable > >- * irqs __split_huge_page_splitting() can > >- * return and the head page can be freed from > >- * under us. We can't take the PG_lock and/or > >- * PG_compound_lock on a page that could be > >- * freed from under us. > >- */ > >- if (page != page_head) { > >- get_page(page_head); > >- put_page(page); > >- } > >- local_irq_enable(); > >- } else { > >- local_irq_enable(); > >- goto again; > >- } > >- } > >-#else > >- page_head = compound_head(page); > >- if (page != page_head) { > >- get_page(page_head); > >- put_page(page); > >- } > > Hmm, any idea why this was there? Without THP, it was already sure that > get/put_page() on tail page operates on the head page's _count, no?
I guess it's just to deal with the same page from this point forward. Pin/unpin one page, but lock other could look strange. -- Kirill A. Shutemov -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
