Re: [PATCH v2] mm: Fix slab->page _count corruption.

From: Eric Dumazet
Date: Mon May 14 2012 - 18:34:53 EST

On Mon, 2012-05-14 at 15:29 -0700, Pravin B Shelar wrote:
> On arches that do not support this_cpu_cmpxchg_double slab_lock is used
> to do atomic cmpxchg() on double word which contains page->_count.
> page count can be changed from get_page() or put_page() without taking
> slab_lock. That corrupts page counter.
> Following patch fixes it by moving page->_count out of cmpxchg_double
> data. So that slub does no change it while updating slub meta-data in
> struct page.

I say again : Page is owned by slub, so get_page() or put_page() is not
allowed ?

How is put_page() going to work with order-1 or order-2 allocations ?

Me very confused by these Nicira patches.

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