Re: [PATCH] double flush_page_to_ram

David S. Miller (davem@redhat.com)
Thu, 09 May 2002 06:07:03 -0700 (PDT)


From: Hugh Dickins <hugh@veritas.com>
Date: Thu, 9 May 2002 14:18:49 +0100 (BST)

On Thu, 9 May 2002, David S. Miller wrote:
> Wrong, consider the case where we do early COW in do_no_page, you miss
> a flush on the new-new page.

Of course we do, and then we don't map it into user address space;
if it ever gets mapped into user address space later, do_no_page
does the flush_page_to_ram then.

You miss the fact that if we do an early COW and another process
recently WROTE into that page via a shared MMAP, we will potentially
copy old data into the COW page we use for the current process.

Your changes are wrong and will cause corruption.
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