Re: [Qemu-devel] [PATCH 14/20] nbd: Support BDRV_REQ_FUA

From: Max Reitz <mreitz@redhat.com>
To: Kevin Wolf <kwolf@redhat.com>, qemu-block@nongnu.org
Cc: qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [PATCH 14/20] nbd: Support BDRV_REQ_FUA
Date: Sat, 26 Mar 2016 21:46:56 +0100	[thread overview]
Message-ID: <56F6F540.1030003@redhat.com> (raw)
In-Reply-To: <1458325289-17848-15-git-send-email-kwolf@redhat.com>

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On 18.03.2016 19:21, Kevin Wolf wrote:
> The NBD server already used to send a FUA flag when the writethrough
> mode was set. This code was a remnant from the times where protocol
> drivers actually had to implement writethrough modes. Since nowadays the
> block layer sends flushes in writethrough mode and non-root nodes are
> always writeback, this was mostly dead code - only mostly because if NBD
> was configured to be used without a format, we sent _both_ FUA and an
> explicit flush afterwards, which makes the code not technically dead,
> but useless overhead.
> 
> This patch changes the code so that the block layer's FUA flag is
> recognised and translated into a NBD FUA flag. The additional flush is
> avoided now.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  block/nbd-client.c | 13 +++++++------
>  block/nbd-client.h |  2 +-
>  block/nbd.c        | 26 +++++++++++++++++++++-----
>  3 files changed, 29 insertions(+), 12 deletions(-)

Looks good, but I have the same issue as with patch 13.

Max

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