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Date: Wed, 17 Jul 2013 14:26:12 +0300
From: Andriy Gapon <avg@FreeBSD.org>
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To: Adrian Chadd <adrian@FreeBSD.org>
Subject: Re: Deadlock in nullfs/zfs somewhere
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on 16/07/2013 22:40 Adrian Chadd said the following:
> :(  So it's a deadlock. Ok, so what's next?

A creative process...

One possibility is to add getnewvnode_reserve() calls before the ZFS transaction
beginnings in the places where a new vnode/znode may have to be allocated within
a transaction.
This looks like a quick and cheap solution but it makes the code somewhat messier.

Another possibility is to change something in VFS machinery, so that VOP_RECLAIM
getting blocked for one filesystem does not prevent vnode allocation for other
filesystems.

I could think of other possible solutions via infrastructural changes in VFS or
ZFS...

-- 
Andriy Gapon