Re: [PATCH] make inotify event handles use GFP_NOFS

[Andrew Morton <akpm@linux-foundation.org>]

On Wed, 18 Mar 2009 14:27:32 -0400
Eric Paris <eparis@redhat.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.

>  I don't want to do that as I
> think the real fix is my next generation fsnotify which does zero
> allocations under locks and so everything can be GFP_KERNEL.

I assume that's the 13-patch series further down in my todo pile.

Perhaps this workaround is suitable for 2.6.29.x, or 2.6.30 if the
13-patch-series was too late.  But do we care enough?


>  I'm
> posting this as it is clearly safe and should fix the issue.
> 
> http://marc.info/?l=linux-kernel&m=123617147432377&w=2
> 
> includes a lockdep warning that shows while we are reclaiming FS memory
> and inode may get evicted which generates an IN_IGNORED message.  Half
> of that code path already used GFP_NOFS but a second allocation to store
> the filename was using GFP_KERNEL.  As a precaution I also moved the
> audit handle_event code path to use GFP_NOFS.
> 
> This is much the same as the precaution in f04b30de3c82528 which did
> something similar.
>