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Date:      Wed, 18 Mar 2009 12:09:18 -0400
From:      John Baldwin <jhb@freebsd.org>
To:        Pawel Jakub Dawidek <pjd@freebsd.org>
Cc:        "freebsd-current@freebsd.org" <freebsd-current@freebsd.org>, Attilio Rao <attilio@freebsd.org>, Tim Kientzle <kientzle@freebsd.org>, Mark Powell <M.S.Powell@salford.ac.uk>, Anonymous <swell.k@gmail.com>, Peter Schuller <peter.schuller@infidyne.com>
Subject:   Re: repeatable ZFS panic: share->excl
Message-ID:  <200903181209.18970.jhb@freebsd.org>
In-Reply-To: <20090317070440.GE2012@garage.freebsd.pl>
References:  <20090312175345.Y80227@rust.salford.ac.uk> <49BAA103.2060508@FreeBSD.org> <20090317070440.GE2012@garage.freebsd.pl>

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On Tuesday 17 March 2009 3:04:40 am Pawel Jakub Dawidek wrote:
> On Fri, Mar 13, 2009 at 02:08:03PM -0400, John Baldwin wrote:
> > John Baldwin wrote:
> > >Yes, I think that is the real bug.  Looking at this further I think
> > >zfs_get_xattrdir() will return the vnode locked if it has to create a
> > >new node via zfs_make_attrdir() but only returns it held and unlocked if
> > >it finds an existing one.  So my new patch is to just fix
> > >zfs_get_xattrdir() to unlock the vnode if it creates a new one like so:
> > >
> > >(Sorry, TBird is probably going to butcher all the whitespace):
> > >
> > >---
> > 
>//depot/user/jhb/lock/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_dir.c
> > >+++
> > 
>/Users/jhb/work/p4/lock/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_dir.c 
> > >
> > >@@ -940,6 +940,7 @@
> > >         /* NB: we already did dmu_tx_wait() if necessary */
> > >         goto top;
> > >     }
> > >+    VOP_UNLOCK(*xvpp, 0);
> > >
> > >     return (error);
> > > }
> > >
> > >A non-butchered version is at www.FreeBSD.org/~jhb/patches/zfs_ea.patch.
> > 
> > So lulf@ reports success with this patch.  Pawel, can you review it?
> 
> Yes, it works for me too and looks good. The only thing we need to
> change is to check for error beeing 0 before unlocking the vnode.
> The zfs_make_xattrdir() function can still return with EIO, so I'd add
> something like this:
> 
> 	if (error == 0)
> 		VOP_UNLOCK(*xvpp, 0);

Yes, I realized this about 30 minutes after I sent this e-mail. :-P  I will 
commit a version with the error check today.

> Thank you John for spending time on tracking this one down.

Sure, was good to read a bit of the ZFS code.

-- 
John Baldwin



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