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Re: [Qemu-devel] [Nbd] Is NBD_CMD_FLAG_FUA valid during NBD_CMD_FLUSH?

From: Paolo Bonzini
Subject: Re: [Qemu-devel] [Nbd] Is NBD_CMD_FLAG_FUA valid during NBD_CMD_FLUSH?
Date: Tue, 5 Apr 2016 15:28:47 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0

On 05/04/2016 07:09, Kevin Wolf wrote:
> > TRIM is an advisory operation, so it doesn't make sense to force access
> > to the medium.
> I think it does make sense. It means that on completion there is no
> pending discard operation (i.e. either there wasn't a discard or if
> there was, it has completed) and other readers will see the final state
> of the blocks.

This is what already happens though, isn't it?


>> > The closest you could get would be to add FUA to WRITE_ZEROES.  But
>> > since WRITE_ZEROES is not a particularly common operation there isn't
>> > much to gain compared to FLUSHing after the write has completed; in
>> > fact SCSI doesn't have a FUA bit on its WRITE SAME command.
> Right, I guess this would mostly be for consistency when FUA is
> supported more or less everywhere else.

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