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

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Date:	Fri, 3 Apr 2009 10:56:31 -0400 (EDT)
From:	eparis@...hat.com
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"mingo@...e.hu" <mingo@...e.hu>,
	"balbir@...ux.vnet.ibm.com" <balbir@...ux.vnet.ibm.com>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	"aviro@...hat.com" <aviro@...hat.com>
Subject: Re: [PATCH] make inotify event handles use GFP_NOFS





On Apr 3, 2009, at 10:33 AM, Peter Zijlstra <peterz@...radead.org>  
wrote:

> 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.

Thanks I'll try to send something soon.

-Eric
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