[Gluster-devel] dht mkdir preop check, afr and (non-)readable afr subvols

Raghavendra Gowdappa rgowdapp at redhat.com
Tue May 31 05:05:19 UTC 2016


+gluster-devel, +Xavi

Hi all,

The context is [1], where bricks do pre-operation checks before doing a fop and proceed with fop only if pre-op check is successful.

@Xavi,

We need your inputs on behavior of EC subvolumes as well.

[1] http://review.gluster.org/13885

regards,
Raghavendra

----- Original Message -----
> From: "Pranith Kumar Karampuri" <pkarampu at redhat.com>
> To: "Raghavendra Gowdappa" <rgowdapp at redhat.com>
> Cc: "team-quine-afr" <team-quine-afr at redhat.com>, "rhs-zteam" <rhs-zteam at redhat.com>
> Sent: Tuesday, May 31, 2016 10:22:49 AM
> Subject: Re: dht mkdir preop check, afr and (non-)readable afr subvols
> 
> I think you should start a discussion on gluster-devel so that Xavi gets a
> chance to respond on the mails as well.
> 
> On Tue, May 31, 2016 at 10:21 AM, Raghavendra Gowdappa <rgowdapp at redhat.com>
> wrote:
> 
> > Also note that we've plans to extend this pre-op check to all dentry
> > operations which also depend parent layout. So, the discussion need to
> > cover all dentry operations like:
> >
> > 1. create
> > 2. mkdir
> > 3. rmdir
> > 4. mknod
> > 5. symlink
> > 6. unlink
> > 7. rename
> >
> > We also plan to have similar checks in lock codepath for directories too
> > (planning to use hashed-subvolume as lock-subvolume for directories). So,
> > more fops :)
> > 8. lk (posix locks)
> > 9. inodelk
> > 10. entrylk
> >
> > regards,
> > Raghavendra
> >
> > ----- Original Message -----
> > > From: "Raghavendra Gowdappa" <rgowdapp at redhat.com>
> > > To: "team-quine-afr" <team-quine-afr at redhat.com>
> > > Cc: "rhs-zteam" <rhs-zteam at redhat.com>
> > > Sent: Tuesday, May 31, 2016 10:15:04 AM
> > > Subject: dht mkdir preop check, afr and (non-)readable afr subvols
> > >
> > > Hi all,
> > >
> > > I have some queries related to the behavior of afr_mkdir with respect to
> > > readable subvols.
> > >
> > > 1. While winding mkdir to subvols does afr check whether the subvolume is
> > > good/readable? Or does it wind to all subvols irrespective of whether a
> > > subvol is good/bad? In the latter case, what if
> > >    a. mkdir succeeds on non-readable subvolume
> > >    b. fails on readable subvolume
> > >
> > >   What is the result reported to higher layers in the above scenario? If
> > >   mkdir is failed, is it cleaned up on non-readable subvolume where it
> > >   failed?
> > >
> > > I am interested in this case as dht-preop check relies on layout xattrs
> > and I
> > > assume layout xattrs in particular (and all xattrs in general) are
> > > guaranteed to be correct only on a readable subvolume of afr. So, in
> > essence
> > > we shouldn't be winding down mkdir on non-readable subvols as whatever
> > the
> > > decision brick makes as part of pre-op check is inherently flawed.
> > >
> > > regards,
> > > Raghavendra
> --
> Pranith
> 


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