On Fri, Jan 09, 2015 at 05:06:42PM -0800, Andrew Morton wrote:
> On Sat, 10 Jan 2015 02:41:43 +0200 "Kirill A. Shutemov" <kirill@xxxxxxxxxxxxx> wrote:
>
> > On Fri, Jan 09, 2015 at 04:24:19PM -0800, Andrew Morton wrote:
> > > On Thu, 8 Jan 2015 16:10:04 +0200 (EET) "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> wrote:
> > >
> > > > Something like this?
> > > >
> > > > >From 5fd481c1c521112e9cea407f5a2644c9f93d0e14 Mon Sep 17 00:00:00 2001
> > > > From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
> > > > Date: Thu, 8 Jan 2015 15:59:23 +0200
> > > > Subject: [PATCH] mm: more checks on free_pages_prepare() for tail pages
> > > >
> > > > Apart form being dead, destroy_compound_page() did some potentially
> > > > useful checks. Let's re-introduce them in free_pages_prepare(), where
> > > > they can be acctually triggered.
> > > >
> > > > compound_order() assert is already in free_pages_prepare(). We have few
> > > > checks for tail pages left.
> > > >
> > >
> > > I'm thinking we avoid the overhead unless CONFIG_DEBUG_VM?
> >
> > That's why there's "if (!IS_ENABLED(CONFIG_DEBUG_VM))". Is it wrong in
> > some way?
> > I didn't check, but I assume compiler is smart enough to get rid of
> > free_tail_pages_check() if CONFIG_DEBUG_VM is not defined. No?
>
> doh, OK. I updated the
> mm-more-checks-on-free_pages_prepare-for-tail-pages.patch changelog to
> reflect this and did
>
> --- a/mm/page_alloc.c~mm-more-checks-on-free_pages_prepare-for-tail-pages-fix
> +++ a/mm/page_alloc.c
> @@ -764,19 +764,18 @@ static void free_one_page(struct zone *z
> spin_unlock(&zone->lock);
> }
>
> -static int free_tail_pages_check(struct page *head_page, struct page *page)
> +static void free_tail_pages_check(struct page *head_page, struct page *page)
> {
> if (!IS_ENABLED(CONFIG_DEBUG_VM))
> - return 0;
> + return;
> if (unlikely(!PageTail(page))) {
> bad_page(page, "PageTail not set", 0);
> - return 1;
> + return;
> }
> if (unlikely(page->first_page != head_page)) {
> bad_page(page, "first_page not consistent", 0);
> - return 1;
> + return;
> }
> - return 0;
> }
>
> static bool free_pages_prepare(struct page *page, unsigned int order)
> _
Oops. I wanted this return code to be accounted into 'bad' in
free_pages_prepare() instead. Incremental patch:
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index cf327e2eea6f..ee37d1e0c969 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -798,7 +798,7 @@ static bool free_pages_prepare(struct page *page, unsigned int order)
bad += free_pages_check(page);
for (i = 1; i < (1 << order); i++) {
if (compound)
- free_tail_pages_check(page, page + i);
+ bad += free_tail_pages_check(page, page + i);
bad += free_pages_check(page + i);
}
if (bad)
--
Kirill A. Shutemov
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