Re: Application error handling with write-back caching

[Paolo Bonzini <pbonzini@redhat.com>]

On 10/05/2016 16:16, James Bottomley wrote:
> > If "is performed" just means "completes", maybe with an error, the
> > application would have to resubmit write requests and then try to 
> > flush the write cache again.
> > 
> > I'm not aware of applications that keep acknowledged write data 
> > around until the cache flush completion in order to retry writes.
> 
> I think you may be misunderstanding the nature of the returned error. 
> It will be permanent and fatal and usually signal that the device has
> a failed sector that can't be remapped and so the device itself has for
> most purposes failed.  The only recovery is if you happen to have RAID,
> in which case the RAID layer will mostly take care of it.

What about a SPACE ALLOCATION FAILED error or a similar error that can
be fixed by administrator actions (or just by a concurrent process doing
an UNMAP)?  Would a subsequent cache flush cause data loss?

Paolo