linux-kernel - Re: WARNING: at mm/page_alloc.c:1159 get_page_from

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Date:	Wed, 17 Jun 2009 13:40:34 +0100
From:	Mel Gorman <mel@....ul.ie>
To:	Catalin Marinas <catalin.marinas@....com>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	torvalds@...ux-foundation.org, fengguang.wu@...el.com,
	Pekka Enberg <penberg@...helsinki.fi>,
	linux-kernel@...r.kernel.org
Subject: Re: WARNING: at mm/page_alloc.c:1159
	get_page_from_freelist+0x325/0x655()

On Wed, Jun 17, 2009 at 01:36:00PM +0100, Catalin Marinas wrote:
> On Wed, 2009-06-17 at 13:28 +0100, Mel Gorman wrote:
> > On Wed, Jun 17, 2009 at 01:11:17PM +0100, Catalin Marinas wrote:
> > > On Wed, 2009-06-17 at 13:31 +0200, Ingo Molnar wrote:
> > > > a new warning started popping up today, in the new page allocator 
> > > > code. The allocation came from kmemleak:
> > > > 
> > > > WARNING: at mm/page_alloc.c:1159 get_page_from_freelist+0x325/0x655()
> > > > Hardware name: System Product Name
> > > > Modules linked in:
> > > > Pid: 4367, comm: ifup Not tainted 2.6.30-tip-04303-g5ada65e-dirty #54431
> > > > Call Trace:
> > > >  [<ffffffff810dba73>] ? get_page_from_freelist+0x325/0x655
> > > >  [<ffffffff8106f140>] warn_slowpath_common+0x88/0xcb
> > > >  [<ffffffff8106f1a5>] warn_slowpath_null+0x22/0x38
> > > >  [<ffffffff810dba73>] get_page_from_freelist+0x325/0x655
> > > >  [<ffffffff810dc18c>] __alloc_pages_nodemask+0x14c/0x5b0
> > > >  [<ffffffff811063e1>] ? deactivate_slab+0xce/0x16b
> > > >  [<ffffffff8103b1c8>] ? native_sched_clock+0x40/0x79
> > > >  [<ffffffff811063e1>] ? deactivate_slab+0xce/0x16b
> > > >  [<ffffffff811063e1>] ? deactivate_slab+0xce/0x16b
> > > >  [<ffffffff81102417>] alloc_pages_current+0xcc/0xeb
> > > >  [<ffffffff81107a78>] alloc_slab_page+0x2a/0x7e
> > > >  [<ffffffff81107b27>] new_slab+0x5b/0x210
> > > >  [<ffffffff811063fa>] ? deactivate_slab+0xe7/0x16b
> > > >  [<ffffffff81108253>] __slab_alloc+0x214/0x3da
> > > >  [<ffffffff8110f58d>] ? kmemleak_alloc+0x83/0x35a
> > > >  [<ffffffff8110f58d>] ? kmemleak_alloc+0x83/0x35a
> > > >  [<ffffffff8110863c>] kmem_cache_alloc+0xac/0x14e
> > > >  [<ffffffff8110f58d>] kmemleak_alloc+0x83/0x35a
> > > >  [<ffffffff812b6436>] ? cfq_get_queue+0x101/0x231
> > > >  [<ffffffff81108511>] kmem_cache_alloc_node+0xf8/0x177
> > > >  [<ffffffff812b6436>] ? cfq_get_queue+0x101/0x231
> > > >  [<ffffffff812b6436>] cfq_get_queue+0x101/0x231
> > > 
> > > Kmemleak needs to allocate memory for the pointer tracing and it
> > > currently passes the same gfp flags as those used by the original
> > > caller. In this case cfq_find_alloc_queue uses __GFP_NOFAIL.
> > > 
> > > The reason for this was to avoid GFP_ATOMIC if the caller wasn't
> > > requiring it. I think the approach below is better:
> > > 
> > 
> > How about defining a GFP_SLAB_KMEMLEAK_MASK the subset of flags that kmemleak
> > should use? Based on this patch, the following appears to be it's definition.
> > 
> > __GFP_WAIT | __GFP_IO | __GFP_FS | __GFP_HIGH
> 
> Do you mean defining one in the gfp.h file? I think this would be better
> placed in the kmemleak.c file as no other part of Linux would be using
> it.
> 

Yes, I meant placing it in the gfp.h file but I don't feel super strongly
about it. Defining it in kmemleak.c is fine too and is easier to read than
placing the mask directly at the call site.

> I personally find defining the GFP_KMEMLEAK_MASK as (GFP_KERNEL |
> GFP_ATOMIC) more readable than using the individual bits since this
> states clearly what type of allocations would be allowed (and safer if
> someone later decides to improve the GFP_KERNEL or GFP_ATOMIC
> definitions).
> 

That's fair enough.

-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab
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