Re: [PATCH 0/7] Discard requests, v2

[Jens Axboe <jens.axboe@oracle.com>]

On Wed, Aug 13 2008, David Woodhouse wrote:
> On Wed, 2008-08-13 at 13:32 +0200, Jens Axboe wrote:
> > On Wed, Aug 13 2008, David Woodhouse wrote:
> > > On Wed, 2008-08-13 at 13:15 +0200, Jens Axboe wrote:
> > > > On Tue, Aug 12 2008, David Woodhouse wrote:
> > > > > On Tue, 2008-08-12 at 14:04 +0100, David Woodhouse wrote:
> > > > > > > Or just match the check before -EOPNOTSUPP with bio_has_data(),
> > > > > > > since it only applies to a barrier that carries data.
> > > > > > 
> > > > > > Like this, you mean? Empty barriers don't get to there?
> > > > > 
> > > > > Seems to work, although I'm somewhat dubious about it. Still, if you're
> > > > > happy that it's correct and you really prefer it that way, then I can
> > > > > commit it.
> > > > 
> > > > Looks ok to me.
> > > 
> > > OK, that version is now in the git tree.
> > 
> > Alright, I'll pull it it.
> > 
> > > > > Anything else I need to address before you pull the tree? Any comment on
> > > > > the BLKDISCARD ioctl? I've left that one using the non-barrier version
> > > > > since it's waiting for it anyway, and shouldn't be happening
> > > > > concurrently with anything else.
> > > > > 
> > > > > (http://,git://} git.infradead.org/users/dwmw2/discard-2.6.git
> > > > 
> > > > I'm with Jamie on using the safer version for the ioctl, unless you
> > > > ensure that the block device isn't mounted before allowing it.
> > > 
> > > We don't ensure that the block device isn't mounted before we allow
> > > reads/writes -- why should we do so before we allow discard?
> > > 
> > > If the userspace tool 'owns' the block device, that's a different story
> > > -- and that's OK too, because the BLKDISCARD ioctl is synchronous. It
> > > won't return until it's actually _complete_, and userspace really
> > > shouldn't be trying to write to the same sectors until that happens.
> > 
> > Still seems a little unsafe. I guess you could make a case for making
> > the ioctl privileged. We should at least ensure that the user has write
> > access to the device before allowing a discard operation.
> 
> Er, yes. That would be a good idea, wouldn't it? :)

I'd think so :-)

> Hold off on pulling the tree for a moment; I'll do that.

I've pulled it this morning.

-- 
Jens Axboe