Re: [patch 07/19] invalidate_complete_page() race fix

[Hugh Dickins]

On Tue, 10 Oct 2006, Greg KH wrote:

> -stable review patch.  If anyone has any objections, please let us know.
> 
> ------------------
> From: Andrew Morton <akpm@xxxxxxxx>
> 
> If a CPU faults this page into pagetables after invalidate_mapping_pages()
> checked page_mapped(), invalidate_complete_page() will still proceed to remove
> the page from pagecache.  This leaves the page-faulting process with a
> detached page.  If it was MAP_SHARED then file data loss will ensue.
> 
> Fix that up by checking the page's refcount after taking tree_lock.

I may have lost the plot, but I think this patch has already proved
to cause problems for NFS in 2.6.18: not good to put it into 2.6.17
stable while it's awaiting refinement for 2.6.18 stable.

Hugh
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