Re: [Qemu-devel] Re: [PATCH][v2] Align file accesses with cache=off (O_DIRECT)

[Laurent Vivier]

Le mercredi 21 mai 2008 à 01:54 +0100, Paul Brook a écrit :
> > > Seems like the easiest solution would be to have qcow always align its
> > > writes. We don't do on the fly compression, so it should be fairly easy
> > > to make this happen with minimal overhead.
> >
> > I did the patch you describe and post it to the mailing list on Tue, 22
> > Jan 2008 11:17:09 +0100, it was called
> > "[PATCH] snapshot=on and cache=off compatibility"
> > but was never commented.
> 
> That patch that patch messes with O_DIRECT on an open file descriptor, which 
> was generally agreed to be a bad idea.

I agree with that, it's why I sent a new patch yesterday.
But look at the second part of the (first) patch that try to align qcow
buffers (it was to answer to your comment).
Moreover we can't align all data, so we have to make some
buffer/count/offset alignment in block-raw-posix.c.

I sincerely think that the patch I sent yesterday must be apply.

Laurent
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