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From: Paul Brook <paul@codesourcery.com>
Subject: Re: [Qemu-devel] [PATCH] Asynchronous reliable and configurable cache
	flush
Date: Thu, 3 Apr 2008 01:40:33 +0100
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To: qemu-devel@nongnu.org
Cc: Ian Jackson <Ian.Jackson@eu.citrix.com>

> > > + =A0 =A0if (ret) {
> > > + =A0 =A0 =A0 =A0BADF("scsi-disc: IO error on flush: %s\n", strerror(=
=2Dret));
> >
> > This is wrong for two reasons: BADF already adds a suitable prefix,
> > and is for reporting qemu bugs (i.e. missing features or things that
> > should never happen). This is just a normal IO error, which we
> > correctly report to the guest.
>
> I don't think flush failures are a normal IO error.  They can only
> occur when the corresponding host block device is having serious
> trouble.  Normally (if it's actually a host disk) this is very bad.

In practice any IO error indicates that the target device is pretty screwed.
I don't see why flushes should be special. When caches are enabled I'd be=20
fairly surprised if normal write operations ever returned an error.

Paul