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Subject: Re: [PATCH] Fix inconsistent lock state in inotify
From: Eric Paris <eparis@redhat.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Luca Tettamanti <kronos.it@gmail.com>, linux-kernel@vger.kernel.org,
       john@johnmccutchan.com, rlove@rlove.org
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Date: Wed, 15 Apr 2009 15:31:35 -0400
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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@gmail.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)

-Eric