linux-kernel - Re: [PATCH] make inotify event handles use GFP

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Date:	Fri, 03 Apr 2009 16:34:00 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Eric Paris <eparis@...hat.com>, linux-kernel@...r.kernel.org,
	mingo@...e.hu, balbir@...ux.vnet.ibm.com,
	linux-fsdevel@...r.kernel.org, aviro@...hat.com
Subject: Re: [PATCH] make inotify event handles use GFP_NOFS

On Mon, 2009-03-30 at 23:33 +0200, Peter Zijlstra wrote:
> On Mon, 2009-03-30 at 14:26 -0700, Andrew Morton wrote:
> > On Wed, 18 Mar 2009 14:27:32 -0400
> > Eric Paris <eparis@...hat.com> wrote:
> > 
> > > I think this is a bandaide to shut up lockdep.  I could either figure
> > > out lockdep classes and figure out how to reclassify inotify locks since
> > > I believe Nick is correct when he says inotify watches pin the inode in
> > > core so memory pressure can't evict it.
> > 
> > It's pretty sad to degrading the strength of the memory allocation just
> > to squish a lockdep report.
> 
> Yeah, I agree, its the wrong thing to do. lockdep annotations really
> aren't that hard -- also, you could also talk me through it.

static struct lock_class_key inotify_mutex_free;


     /*
      * here the inotify mutex gets moved to a different
      * data structure with different locking semantics while
      * holding inotify_mutex.
      */
     lock_set_class(&foo->inotify_mutex.dep_map, "inotify_mutex_free",
                     &inotify_mutex_free, 0, _THIS_IP_);


Or when done without holding the inotify_mutex


     /*
      * here the inotify mutex gets moved to a different
      * data structure with different locking semantics.
      */
     lockdep_set_class(&foo->inotify_mutex, &inotify_mutex_free);


Is all there should be to it.
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