Re: [PATCH v3 RESEND] cgroup/kmemcheck: Annotate alloc_page() for cgroup allocations

[Steven Rostedt <rostedt@goodmis.org>]

Andrew,

On Tue, 2011-07-26 at 22:10 -0400, Steven Rostedt wrote:
> [ Resending with CGROUP maintainers Cc'd this time ]

Paul sent me a note saying that these patches usually go through -mm,
want to take them?

Thanks,

-- Steve

> 
> When the cgroup base was allocated with kmalloc, it was necessary to
> annotate the variable with kmemcheck_not_leak(). But because it has
> recently been changed to be allocated with alloc_page() (which skips
> kmemleak checks) causes a warning on boot up.
> 
> I was triggering this output:
> 
> allocated 8388608 bytes of page_cgroup
> please try 'cgroup_disable=memory' option if you don't want memory cgroups
> kmemleak: Trying to color unknown object at 0xf5840000 as Grey
> Pid: 0, comm: swapper Not tainted 3.0.0-test #12
> Call Trace:
>  [<c17e34e6>] ? printk+0x1d/0x1f^M
>  [<c10e2941>] paint_ptr+0x4f/0x78
>  [<c178ab57>] kmemleak_not_leak+0x58/0x7d
>  [<c108ae9f>] ? __rcu_read_unlock+0x9/0x7d
>  [<c1cdb462>] kmemleak_init+0x19d/0x1e9
>  [<c1cbf771>] start_kernel+0x346/0x3ec
>  [<c1cbf1b4>] ? loglevel+0x18/0x18
>  [<c1cbf0aa>] i386_start_kernel+0xaa/0xb0
> 
> After a bit of debugging I tracked the object 0xf840000 (and others)
> down to the cgroup code. The change from allocating base with kmalloc to
> alloc_page() has the base not calling kmemleak_alloc() which adds the
> pointer to the object_tree_root, but kmemleak_not_leak() adds it to the
> crt_early_log[] table. On kmemleak_init(), the entry is found in the
> early_log[] but not the object_tree_root, and this error message is
> displayed.
> 
> If alloc_page() fails then it defaults back to vmalloc() which still
> uses the kmemleak_alloc() which makes us still need the
> kmemleak_not_leak() call. The solution is to call the kmemleak_alloc()
> directly if the alloc_page() succeeds.
> 
> Reviewed-by: Michal Hocko <mhocko@suse.cz>
> Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
> Acked-by: Johannes Weiner <hannes@cmpxchg.org>
> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
> 
> diff --git a/mm/page_cgroup.c b/mm/page_cgroup.c
> index 53bffc6..1eb534a 100644
> --- a/mm/page_cgroup.c
> +++ b/mm/page_cgroup.c
> @@ -133,10 +133,13 @@ struct page *lookup_cgroup_page(struct page_cgroup *pc)
>  static void *__meminit alloc_page_cgroup(size_t size, int nid)
>  {
>  	void *addr = NULL;
> +	gfp_t flags = GFP_KERNEL | __GFP_NOWARN;
>  
> -	addr = alloc_pages_exact_nid(nid, size, GFP_KERNEL | __GFP_NOWARN);
> -	if (addr)
> +	addr = alloc_pages_exact_nid(nid, size, flags);
> +	if (addr) {
> +		kmemleak_alloc(addr, size, 1, flags);
>  		return addr;
> +	}
>  
>  	if (node_state(nid, N_HIGH_MEMORY))
>  		addr = vmalloc_node(size, nid);
> 
>