Re: [Nbd] [PATCH 1/3] nbd: support FLUSH requests
- To: Paolo Bonzini <pbonzini@...696...>
- Cc: Andrew Morton <akpm@...133...>, nbd-general@...72..., Paul Clements <Paul.Clements@...124...>, linux-kernel@...25...
- Subject: Re: [Nbd] [PATCH 1/3] nbd: support FLUSH requests
- From: Alex Bligh <alex@...872...>
- Date: Tue, 12 Feb 2013 17:37:04 +0000
- Message-id: <115932E2-48BE-406E-9E75-61D12EB5937A@...872...>
- In-reply-to: <1360685171-3792-2-git-send-email-pbonzini@...696...>
- References: <1360685171-3792-1-git-send-email-pbonzini@...696...> <1360685171-3792-2-git-send-email-pbonzini@...696...>
Paolo,
> Add support for a new flag that the server can pass. If the flag is
> enabled, we translate REQ_FLUSH requests into the NBD_CMD_FLUSH
> command.
>
> Cc: <nbd-general@...72...>
> Cc: Paul Clements <Paul.Clements@...124...>
> Cc: Andrew Morton <akpm@...133...>
> Signed-off-by: Alex Bligh <alex@...872...>
> [ Removed FUA support for reasons similar to those outlined in
> https://lkml.org/lkml/2010/8/17/234 for virtio - Paolo ]
> Signed-off-by: Paolo Bonzini <pbonzini@...696...>
For my education, why remove the FUA stuff? The link you posted
was for virtio drivers, and says:
> > Hmmm... the underlying storage could be md/dm RAIDs in which case FUA
> > should be cheaper than FLUSH.
>
> If someone ever wrote a virtio-blk backend that sits directly ontop
> of the Linux block layer that would be true.
In this case we don't know what the backend is sitting on top of
a-priori. It might be the current nbd server code, but it might
not be.
--
Alex Bligh
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