From: Bart Van Assche <Bart.VanAssche@wdc.com>
To: "shli@kernel.org" <shli@kernel.org>, "axboe@kernel.dk" <axboe@kernel.dk>
Cc: "linux-raid@vger.kernel.org" <linux-raid@vger.kernel.org>,
"kernel-team@fb.com" <kernel-team@fb.com>,
"hare@suse.de" <hare@suse.de>,
"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
"kyungchan.koh@gmail.com" <kyungchan.koh@gmail.com>,
"shli@fb.com" <shli@fb.com>
Subject: Re: [PATCH 0/5] block: a virtual block device driver for testing
Date: Tue, 8 Aug 2017 22:00:21 +0000 [thread overview]
Message-ID: <1502229619.2686.1.camel@wdc.com> (raw)
In-Reply-To: <73342715-25af-da8e-ae7e-f24015432055@kernel.dk>
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WARNING: multiple messages have this Message-ID (diff)
From: Bart Van Assche <Bart.VanAssche@wdc.com>
To: "shli@kernel.org" <shli@kernel.org>, "axboe@kernel.dk" <axboe@kernel.dk>
Cc: "linux-raid@vger.kernel.org" <linux-raid@vger.kernel.org>,
"kernel-team@fb.com" <kernel-team@fb.com>,
"hare@suse.de" <hare@suse.de>,
"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
"kyungchan.koh@gmail.com" <kyungchan.koh@gmail.com>,
"shli@fb.com" <shli@fb.com>
Subject: Re: [PATCH 0/5] block: a virtual block device driver for testing
Date: Tue, 8 Aug 2017 22:00:21 +0000 [thread overview]
Message-ID: <1502229619.2686.1.camel@wdc.com> (raw)
In-Reply-To: <73342715-25af-da8e-ae7e-f24015432055@kernel.dk>
On Tue, 2017-08-08 at 15:13 -0600, Jens Axboe wrote:
> On 08/08/2017 03:05 PM, Shaohua Li wrote:
> > > I'm curious why null_blk isn't a good fit? You'd just need to add RAM
> > > storage to it. That would just be a separate option that should be
> > > set,
> > > ram_backing=1 or something like that. That would make it less critical
> > > than using the RAM disk driver as well, since only people that want a
> > > "real"
> > > data backing would enable it.
> > >
> > > It's not that I'm extremely opposed to adding a(nother) test block
> > > driver,
> > > but we at least need some sort of reasoning behind why, which isn't
> > > just
> > > "not a good fit".
> >
> > Ah, I thought the 'null' of null_blk means we do nothing for the
> > disks. Of course we can rename it, which means this point less
> > meaningful. I think the main reason is the interface. We will
> > configure the disks with different parameters and do power on/off for
> > each disks (which is the key we can emulate disk cache and power
> > loss). The module paramter interface of null_blk doesn't work for the
> > usage. Of course, these issues can be fixed, for example, we can make
> > null_blk use the configfs interface. If you really prefer a single
> > driver for all test purpose, I can move the test_blk functionalities
> > to null_blk.
>
> The idea with null_blk is just that it's a test vehicle. As such, it
> would actually be useful to have a mode where it does store the data in
> RAM, since that enables you to do other kinds of testing as well. I'd be
> fine with augmenting it with configfs for certain things.
Hello Jens,
Would you consider it acceptable to make the mode in which null_blk stores
data the default? I know several people who got confused by null_blk by
default not retaining data ...
Thanks,
Bart.
next prev parent reply other threads:[~2017-08-08 22:00 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-05 15:51 [PATCH 0/5] block: a virtual block device driver for testing Shaohua Li
2017-08-05 15:51 ` [PATCH 1/5] testb: add interface Shaohua Li
2017-08-05 15:51 ` [PATCH 2/5] testb: implement block device operations Shaohua Li
2017-08-08 20:34 ` Jens Axboe
2017-08-05 15:51 ` [PATCH 3/5] testb: implement bandwidth control Shaohua Li
2017-08-05 15:51 ` [PATCH 4/5] testb: emulate disk cache Shaohua Li
2017-08-05 15:51 ` [PATCH 5/5] testb: badblock support Shaohua Li
2017-08-06 1:56 ` Dan Williams
2017-08-07 4:39 ` Shaohua Li
2017-08-07 8:29 ` [PATCH 0/5] block: a virtual block device driver for testing Hannes Reinecke
2017-08-07 16:36 ` Shaohua Li
2017-08-08 20:31 ` Jens Axboe
2017-08-08 21:05 ` Shaohua Li
2017-08-08 21:13 ` Jens Axboe
2017-08-08 22:00 ` Bart Van Assche [this message]
2017-08-08 22:00 ` Bart Van Assche
2017-08-08 22:07 ` Jens Axboe
2017-08-08 22:08 ` Omar Sandoval
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