From: Andy Grover <agrover@redhat.com>
To: "Nicholas A. Bellinger" <nab@linux-iscsi.org>
Cc: majianpeng <majianpeng@gmail.com>,
linux-scsi <linux-scsi@vger.kernel.org>,
target-devel <target-devel@vger.kernel.org>
Subject: Re: [PATCH] target: For iblock at default writecache enable.
Date: Tue, 29 Jan 2013 15:04:45 -0800 [thread overview]
Message-ID: <5108558D.6000408@redhat.com> (raw)
In-Reply-To: <1359486198.23290.1409.camel@haakon2.linux-iscsi.org>
On 01/29/2013 11:03 AM, Nicholas A. Bellinger wrote:
> So enabling emulate_write_cache=1 in the case when the underlying device
> has not enabled it is incorrect.
>
> I'd like to enable this bit when we know the underlying device has WCE=1
> set, but currently there is not a way to determine this (generically)
> from struct block_device.
>
> So NACK for applying this until there is a method to determine what the
> hardware below is doing.
This should be possible from userspace though. I'm planning on looking
up underlying scsi device(s?) using libblkid, and then query the sense
data using libsgutils when adding a block backstore in targetcli.
It's kind of a hassle, but isn't it a huge performance win if we can
enable this?
Regards -- Andy
next prev parent reply other threads:[~2013-01-29 23:04 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-25 1:58 [PATCH] target: For iblock at default writecache enable majianpeng
2013-01-29 19:03 ` Nicholas A. Bellinger
2013-01-29 23:04 ` Andy Grover [this message]
2013-01-29 23:14 ` Nicholas A. Bellinger
2013-01-30 1:19 ` majianpeng
2013-01-30 7:29 ` Nicholas A. Bellinger
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