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Date: Sat, 13 Nov 2010 12:27:47 +0200
From: Andriy Gapon <avg@freebsd.org>
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To: Martin Matuska <mm@freebsd.org>
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Cc: freebsd-fs@freebsd.org, freebsd-stable@freebsd.org
Subject: Re: 8.1-STABLE: problem with unmounting ZFS snapshots
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on 13/11/2010 04:27 Martin Matuska said the following:
> Yes, this is indeed a leak introduced by importing onnv revision 9214
> and it exists in perforce as well - very easy to reproduce.
> 
> # mount -t zfs test@t1 /mnt
> # umount /mnt (-> hang)
> 
> http://bugs.opensolaris.org/bugdatabase/view_bug.do?bug_id=6604992
> http://bugs.opensolaris.org/bugdatabase/view_bug.do?bug_id=6810367
> 
> This is not compatible with mounting snapshots outside mounted ZFS and I
> was not able to reproduce the errors defined in 6604992 and 6810367
> (they are Solaris-specific). I suggest we comment out this code (from
> head, later MFC and p4 as well).
> 
> Patch (should work with HEAD and 8-STABLE):
> http://people.freebsd.org/~mm/patches/zfs/zfs_vfsops.c.patch

Not quite sure, but perhaps it's better to make the logic in each place match
the other.  That is, I see that the code does hold on a filesystem of a covered
vnode, but does rele on a parent ZFS filesystem.
Or is this kind of protection not needed at all for FreeBSD?

-- 
Andriy Gapon