mm: Make use of the anon_vma ref count
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From: Christian Ehrhardt on 9 Apr 2010 03:10 Hi, On Thu, Apr 08, 2010 at 09:17:42PM +0200, Peter Zijlstra wrote: > @@ -302,23 +307,33 @@ again: > goto out; > > anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON); > - spin_lock(&anon_vma->lock); > + if (!atomic_inc_not_zero(&anon_vma->ref)) > + anon_vma = NULL; > > if (page_rmapping(page) != anon_vma) { > - spin_unlock(&anon_vma->lock); > + anon_vma_put(anon_vma); > goto again; > } AFAICS anon_vma_put might be called with anon_vma == NULL here which will oops on the ref count. Not sure if page_rmapping(page) == anon_vma == NULL is possible, too. regards Christian -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Peter Zijlstra on 9 Apr 2010 06:00
On Fri, 2010-04-09 at 09:04 +0200, Christian Ehrhardt wrote: > Hi, > > On Thu, Apr 08, 2010 at 09:17:42PM +0200, Peter Zijlstra wrote: > > @@ -302,23 +307,33 @@ again: > > goto out; > > > > anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON); > > - spin_lock(&anon_vma->lock); > > + if (!atomic_inc_not_zero(&anon_vma->ref)) > > + anon_vma = NULL; > > > > if (page_rmapping(page) != anon_vma) { > > - spin_unlock(&anon_vma->lock); > > + anon_vma_put(anon_vma); > > goto again; > > } > > AFAICS anon_vma_put might be called with anon_vma == NULL here which > will oops on the ref count. Not sure if > > page_rmapping(page) == anon_vma == NULL > > is possible, too. Gah, you're right, thanks! -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |