Re: WARNING: at mm/page_alloc.c:1159 get_page_from_freelist+0x325/0x655()

[Catalin Marinas <catalin.marinas@arm.com>]

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:

diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index 58ec86c..46c9c93 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -462,7 +462,7 @@ static void create_object(unsigned long ptr, size_t size, int min_count,
 	struct prio_tree_node *node;
 	struct stack_trace trace;
 
-	object = kmem_cache_alloc(object_cache, gfp & ~GFP_SLAB_BUG_MASK);
+	object = kmem_cache_alloc(object_cache, gfp & (GFP_KERNEL | GFP_ATOMIC));
 	if (!object) {
 		kmemleak_panic("kmemleak: Cannot allocate a kmemleak_object "
 			       "structure\n");
@@ -636,7 +636,7 @@ static void add_scan_area(unsigned long ptr, unsigned long offset,
 		return;
 	}
 
-	area = kmem_cache_alloc(scan_area_cache, gfp & ~GFP_SLAB_BUG_MASK);
+	area = kmem_cache_alloc(scan_area_cache, gfp & (GFP_KERNEL | GFP_ATOMIC));
 	if (!area) {
 		kmemleak_warn("kmemleak: Cannot allocate a scan area\n");
 		goto out;

-- 
Catalin