Re: CVS commit: src/external/cddl/osnet/dist/uts/common/fs/zfs

[Adam Hamsik <haaaad%gmail.com@localhost>]

On Oct,Thursday 29 2009, at 8:15 PM, David Laight wrote:

> On Wed, Oct 28, 2009 at 11:44:51PM +0000, Adam Hamsik wrote:
> > Module Name:    src
> > Committed By:   haad
> > Date:           Wed Oct 28 23:44:51 UTC 2009
> >
> > Modified Files:
> > 	src/external/cddl/osnet/dist/uts/common/fs/zfs: zfs_vnops.c  
> > zfs_znode.c
> >
> > Log Message:
> > Add workaround about zfs vnode reclaiming deadlock by checking if  
> > we don't
> > ehld ZFS_MUTEX_OBJ already. If we can lock OBJ_MUTEX deffer  
> > execution of
> > zfs_zinactive to taskq. Code was inspired by FreeBSD  
> > zfs_freebsd_reclaim.
>
> This doesn't sound right at all ...
>
> If the 'If we can lock OBJ_MUTEX' test is a try_mutex_enter() then
> it may fail because another lwp owns it ...
> I hope it is only the checkin comment that is inverted!

There are 3 option which can happen

1) Our lwp already holds mutex
2) mutex is not held at all
3) Another LWP holds it

In case 1 we can call reclaim vnode, in case 2 we lock it with  
try_mutex_enter and reclaim it and in case 3 we use taskq for  
reclaiming of vnode.
Regards

Adam.