Subject: Re: time traveling with physio
To: Stephan Uphoff <>
From: Chuck Silvers <>
List: tech-kern
Date: 07/13/2003 17:08:55

the bit that should handle this is where uvm_fault() calls pmap_enter()
with access_type that includes VM_PROT_WRITE in the case of writable
wiring faults.  pmap_enter() is supposed to force the page to be
marked dirty in this case.  is there a bug in there somewhere?


On Fri, Jul 11, 2003 at 02:52:26PM -0400, Stephan Uphoff wrote:
> Read operations from devices using physio will not cause
> pages associated with the buffer to be marked dirty.
> Because of this changed state (data read from the device) can get 
> lost later.
> Fortunately data loss will not happen with anonymous memory as wiring releases
> any swap space owned by an anonymous page. (physio wires the pages)
> This can however cause problems for programs using device reads into
> mmaped files.
> 	Stephan