Re: More virtio users

On Tue, Jun 12 2007, Rusty Russell wrote:

On Tue, 2007-06-12 at 08:24 +0200, Jens Axboe wrote:

quoted

On Tue, Jun 12 2007, Rusty Russell wrote:

quoted

On Mon, 2007-06-11 at 09:33 +0200, Jens Axboe wrote:

quoted

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!

quoted

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().

quoted

-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