[saturnero@freesbie.org: Weird behaviour of mount_unionfs with executables]

Dario Freni saturnero at freesbie.org
Mon Jul 4 09:54:17 GMT 2005


On Sun, Jul 03, 2005 at 08:43:01PM -0400, Stephan Uphoff wrote:
> On Sun, 2005-07-03 at 20:21, Scott Long wrote:
> > 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.
> 
> YES - and it looks like just specifying noatime for the union mount
> should fix the copy problem for FreeSBIE.

Correct. Using -o noatime when mounting the unionfs resolves all above
problems. Thank you very much.

-- 
Dario Freni (saturnero at freesbie.org)
FreeSBIE developer (http://www.freesbie.org)
GPG Public key at http://www.saturnero.net/saturnero.asc
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 187 bytes
Desc: not available
Url : http://lists.freebsd.org/pipermail/freebsd-fs/attachments/20050704/c5f62dff/attachment.bin


More information about the freebsd-fs mailing list