ZFS: Deadlock during vnode recycling

[Fabian Keil]

Andriy Gapon <avg at FreeBSD.org> wrote:

> In fact here is a real patch that I would like to propose:
> http://people.freebsd.org/~avg/zfs-getnewvnode_reserve.diff
> 
> The patch incorporates the kib's patch for extending VFS API that helps to avoid
> entering the vnode inactive/reclaim path from getnewvnode.
> 
> The patch should fix the problem reported in this thread and the problem from
> "panic: _sx_xlock_hard: recursed on non-recursive sx zfsvfs->z_hold_mtx ..."
> thread that runs in parallel.
> 
> Reviews and testing are welcome.

I'd probably replace the intentionally empty "else if (zp->z_unlinked)"
block in zfs_freebsd_reclaim() with a comment, but other than that the
patch looks good to me.

While I'm using nullfs on a couple of jails, I never experienced
the panic above and can thus only report that I didn't notice any
regressions so far since applying the patch yesterday.

Fabian
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