From owner-freebsd-current@FreeBSD.ORG  Wed Jul 17 17:19:04 2013
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Subject: Re: Deadlock in nullfs/zfs somewhere
From: Adrian Chadd <adrian@freebsd.org>
To: Andriy Gapon <avg@freebsd.org>
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On 17 July 2013 04:26, Andriy Gapon <avg@freebsd.org> wrote:
> on 16/07/2013 22:40 Adrian Chadd said the following:
>> :(  So it's a deadlock. Ok, so what's next?
>
> A creative process...

Wonderful. :)

> 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...

Well, what do others think? This seems like a showstopper for systems
with lots and lots of ZFS filesystems doing lots and lots of activity.



-adrian