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Date: Sun, 03 Jul 2005 18:21:53 -0600
From: Scott Long <scottl@samsco.org>
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To: Stephan Uphoff <ups@tree.com>
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Cc: freebsd-fs@freebsd.org
Subject: Re: [saturnero@freesbie.org: Weird behaviour of mount_unionfs with
 executables]
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Stephan Uphoff wrote:
> On Sun, 2005-07-03 at 20:02, Scott Long wrote:
> 
>>Stephan Uphoff wrote:
>>
>>>I suspect the changes in revision 1.272 of kern_exec.c trigger the
>>>copy operation.
>>>
>>>Looks like you need a noatime option for union_fs.
>>>
>>>Stephan
>>
>>Does this mean that every vnode that gets executed gets dirtied and all
>>its pages resynced to the backing store, or just the inode block?
> 
> 
> The kernel calls VOP_SETATTR to set the access time of the file.
> union_fs detects that it does not have an upper layer copy of the file
> to modify the attributes on and decides to copy it.
> The vm layer does not (directly) come into play on this. 
> 
> Stephan
> 

Ok, so this is just a limitation of unionfs, not the vnode pager.  You
had me scared that we'd be doing a whole lot of needless disk i/o.

Scott