Messages in this thread | | | Date | Tue, 16 Jun 2009 19:40:24 +0800 | From | Wu Fengguang <> | Subject | Re: [PATCH 10/22] HWPOISON: check and isolate corrupted free pages v2 |
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On Tue, Jun 16, 2009 at 07:29:45PM +0800, Hugh Dickins wrote: > On Tue, 16 Jun 2009, Wu Fengguang wrote: > > > > Right. Then the original __ClearPageBuddy() call in bad_page() is > > questionable, I guess this line was there just for the sake of safety > > (ie. the buddy allocator itself goes wrong): > > > > sound-2.6/mm/page_alloc.c > > > > @@ -269,7 +269,6 @@ static void bad_page(struct page *page) > > dump_stack(); > > out: > > /* Leave bad fields for debug, except PageBuddy could make trouble */ > > ===> __ClearPageBuddy(page); > > add_taint(TAINT_BAD_PAGE); > > } > > I didn't put that in for the case of the buddy allocator going wrong > (not sure if there could be such a case - I don't mean that the buddy > allocator is provably perfect! but how would it get here if it were > wrong?). No, I put that in for the case when the flag bits in struct > page have themselves got corrupted somehow, and hence we arrive at > bad_page(): most of the bits are best left as they are, to provide > maximum debug info; but leaving PageBuddy set there might conceivably > allow this corrupted struct page to get paired up with its buddy later, > and so freed for reuse, when we're trying to make sure it's never reused.
Hugh, thank you for the detailed explanations! You are always informative :)
Thanks, Fengguang
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