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Date: Wed, 03 Oct 2012 11:42:03 +0300
From: Andriy Gapon <avg@FreeBSD.org>
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Cc: Baptiste Daroussin <bapt@FreeBSD.org>, Florian Smeets <flo@smeets.im>,
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Subject: Re: panic: _sx_xlock_hard: recursed on non-recursive sx
 zfsvfs->z_hold_mtx[i]
 @ ...cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_znode.c:1407
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on 30/09/2012 15:24 Konstantin Belousov said the following:
> The postponing of the reclaim when vnode reserve goes low to the vnlru 
> process does not solve anything, since you only change the recursion into 
> the deadlock.
> 
> I discussed an approach for this issue with avg. Basic idea is presented in
> the untested patch below. You can specify that some count of the free
> vnodes must be present for some dynamic scope, started by 
> getnewvnode_reserve() function. While staying inside the reserved pool,
> getnewvnode() calls would not recurse into vnlru(). The scope is finished
> with getnewvnode_drop_reserve().
> 
> The getnewvnode_reserve() shall be called while no locks are held.
> 
> What do you think ?

Here is a patch that makes use of the getnewvnode_reserve API in ZFS:
http://people.freebsd.org/~avg/zfs-getnewvnode.diff

-- 
Andriy Gapon