Re: INFO: possible circular locking dependency detected

[Nick Piggin <nickpiggin@yahoo.com.au>]

Andrew Morton wrote:
> On Tue, 17 Oct 2006 00:32:44 +1000
> Nick Piggin <nickpiggin@yahoo.com.au> wrote:
>
>
> > alpha @ steudten Engineering wrote:
> >
> > > =======================================================
> > > [ INFO: possible circular locking dependency detected ]
> > > 2.6.18-1.2189self #1
> > > -------------------------------------------------------
> > > kswapd0/186 is trying to acquire lock:
> > > (&inode->i_mutex){--..}, at: [<c0326e32>] mutex_lock+0x21/0x24
> > >
> > > but task is already holding lock:
> > > (iprune_mutex){--..}, at: [<c0326e32>] mutex_lock+0x21/0x24
> > >
> > > which lock already depends on the new lock.
> >
> > Thanks. __grab_cache_page wants to clear __GFP_FS, because it is
> > holding the i_mutex so we don't want to reenter the filesystem in
> > page reclaim.
>
>
> We want to be able to enter page reclaim while holding i_mutex.  Think what
> the effect of not doing this would be upon write() (!)
>
> This warning is more fallout from ntfs's insistence on taking i_mutex in
> its clear_inode().  See lengthy and unproductive discussion at
> http://lkml.org/lkml/2006/7/26/185 .

Yeah you're right. It will be a hot allocation + reclaim path for high
bandwidth writes.

--
SUSE Labs, Novell Inc.
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