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?
From: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Subject: mm-more-checks-on-free_pages_prepare-for-tail-pages-fix
Make it conditional on CONFIG_DEBUG_VM, make free_tail_pages_check()
return void.
Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)
diff -puN mm/page_alloc.c~mm-more-checks-on-free_pages_prepare-for-tail-pages-fix mm/page_alloc.c
--- a/mm/page_alloc.c~mm-more-checks-on-free_pages_prepare-for-tail-pages-fix
+++ a/mm/page_alloc.c
@@ -764,20 +764,26 @@ 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)
+#ifdef CONFIG_DEBUG_VM
+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;
}
+#else
+static inline void free_tail_pages_check(struct page *head_page,
+ struct page *page)
+{
+}
+#endif
static bool free_pages_prepare(struct page *page, unsigned int order)
{
_
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