From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jens Axboe Subject: Re: More virtio users Date: Tue, 12 Jun 2007 09:56:10 +0200 Message-ID: <20070612075610.GU18832@kernel.dk> References: <466BA965.6050208@qumranet.com> <1181463220.16428.24.camel@localhost.localdomain> <466BB34B.9050105@qumranet.com> <1181479060.16428.37.camel@localhost.localdomain> <20070611064107.GA7341@kernel.dk> <1181546953.16428.96.camel@localhost.localdomain> <20070611073300.GB21969@kernel.dk> <1181608287.16428.127.camel@localhost.localdomain> <20070612062451.GN18832@kernel.dk> <1181634747.6237.79.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1181634747.6237.79.camel@localhost.localdomain> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Rusty Russell Cc: kvm-devel , Tejun Heo , xen-devel , virtualization List-Id: virtualization@lists.linuxfoundation.org On Tue, Jun 12 2007, Rusty Russell wrote: > On Tue, 2007-06-12 at 08:24 +0200, Jens Axboe wrote: > > On Tue, Jun 12 2007, Rusty Russell wrote: > > > On Mon, 2007-06-11 at 09:33 +0200, Jens Axboe wrote: > > > > The other main request type is blk_pc_request(). In the data setup it's > > > > indentical to blk_fs_request(), there's a bio chain off ->bio. It's a > > > > byte granularity entity though, so you should check ->data_len for the > > > > size of it. ->cmd[] holds a SCSI cdb, which is the command you are > > > > supposed to handle. > > > > > > SCSI? I'm even more lost now. > > > > > > Q: So what *are* the commands? > > > > They are SCSI commands! > > > > > Q: Who puts them in my queue? > > > > If you want to support SG_IO for instance, you'd have to deal with SCSI > > commands. > > I do not. If someone wants to implement a SCSI layer over virtio, I > think that's wonderful. Fortunately, that's not the problem I'm trying > to solve. Then you can blissfully ignore blk_pc_request() and just keep your current code for rejecting !blk_fs_request(). > > -o barrier=1 for ext3, it doesn't use barriers by default. > > That's, um, a little disturbing. > > But, it works. Thanks! Well, feel free to send a patch making barrier=1 the default, then I'll make sure that mails from users that are confused because performance is suddenly much worse get redirected to you :-) Kudos to XFS for making it the default, though! -- Jens Axboe