linux-kernel - Re: [PATCH] Fix inconsistent lock state in inotify

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Message-Id: <20090415133104.5f248c1b.akpm@linux-foundation.org>
Date:	Wed, 15 Apr 2009 13:31:04 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Eric Paris <eparis@...hat.com>
Cc:	kronos.it@...il.com, linux-kernel@...r.kernel.org,
	john@...nmccutchan.com, rlove@...ve.org
Subject: Re: [PATCH] Fix inconsistent lock state in inotify

On Wed, 15 Apr 2009 15:31:35 -0400
Eric Paris <eparis@...hat.com> wrote:

> On Wed, 2009-04-15 at 12:25 -0700, Andrew Morton wrote:
> > On Wed, 15 Apr 2009 13:59:29 +0200
> > Luca Tettamanti <kronos.it@...il.com> wrote:
> > 
> > > >> +++ b/fs/notify/inotify/inotify_user.c
> > > >> @@ -220,7 +220,7 @@ static struct inotify_kernel_event * kernel_event(s32 wd, u32 mask, u32 cookie,
> > > >>                               rem = 0;
> > > >>               }
> > > >>
> > > >> -             kevent->name = kmalloc(len + rem, GFP_KERNEL);
> > > >> +             kevent->name = kmalloc(len + rem, GFP_NOFS);
> > > >>               if (unlikely(!kevent->name)) {
> > > >>                       kmem_cache_free(event_cachep, kevent);
> > > >>                       return NULL;
> > > >
> > > > Thanks.
> > > >
> > > > This is in fact a false positive and we plan to fix it via lockdep
> > > > annotation.
> > > 
> > > Well, I trust you on the "false positive", but a few line before there this:
> > > 
> > >   kevent = kmem_cache_alloc(event_cachep, GFP_NOFS);
> > > 
> > > so can kmem_cache_alloc also use GFP_KERNEL?
> > 
> > Yes, it looks that way.
> > 
> > umm, I think I'll merge your original patch as a reminder-to-self.
> > If the problem doesn't get fixed in a better way for 2.6.30 then I
> > might end up going with the GFP_NOFS approach.
> > 
> > But it's bad to weaken the memory allocation mode just to plug a lockdep
> > warning.
> 
> I swear, I'm fighting with my machines trying to get one to work so I
> can test my lockdep fix today (and found a separate oddity/bug in the
> process)
> 

heh, thanks.  No rush, it's a tiny problem.  Some time this week or
next would be OK.

I get all paranoid about things falling through cracks.
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