Re: [PATCH] flush_cache_page while pte valid

From: David S. Miller (
Date: Tue Nov 12 2002 - 16:45:52 EST

   From: Rik van Riel <>
   Date: Tue, 12 Nov 2002 12:49:50 -0200 (BRST)

   On Mon, 11 Nov 2002, David S. Miller wrote:
> The flush merely writes back the data, a copy-back operation, fully L2
> cache coherent. All cpus will see correct data if an intermittant
> store occurs.
   The CPUs will, but the harddisk might not.
   We really need to get this right in the swapout path.

We do get it right, watch:

1) remove last mapping instance of page

   -> MM level cache flush pushes it permanently to ram
      in full view of DMA activity

2) remove last mapping, but new one appears as we swap out

   -> no problem we'll see one of several instances of the
      page and we'll need to reswap it out later anyways
      if someone currently writes to it

I know this because I tested this extensively ages ago on sparc32
where it really mattered.
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