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From: Guenter Roeck <linux@roeck-us.net>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Christoph Lameter <cl@linux.com>,
	akpm@linux-foundation.org, mm-commits@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	linux-fsdevel@vger.kernel.org, linux-next@vger.kernel.org,
	Stephen Rothwell <sfr@canb.auug.org.au>,
	mhocko@suse.cz
Subject: Re: mmotm 2015-01-22-15-04: qemu failure due to 'mm: memcontrol: remove unnecessary soft limit tree node test'
Date: Fri, 23 Jan 2015 18:02:29 -0800	[thread overview]
Message-ID: <54C2FD35.9070803@roeck-us.net> (raw)
In-Reply-To: <20150123173659.GB12036@phnom.home.cmpxchg.org>

On 01/23/2015 09:36 AM, Johannes Weiner wrote:
> On Fri, Jan 23, 2015 at 08:59:51AM -0800, Guenter Roeck wrote:
>> On 01/23/2015 08:02 AM, Johannes Weiner wrote:
>>> On Fri, Jan 23, 2015 at 09:17:44AM -0600, Christoph Lameter wrote:
>>>> On Fri, 23 Jan 2015, Johannes Weiner wrote:
>>>>
>>>>> Is the assumption of this patch wrong?  Does the specified node have
>>>>> to be online for the fallback to work?
>>>>
>>>> Nodes that are offline have no control structures allocated and thus
>>>> allocations will likely segfault when the address of the controls
>>>> structure for the node is accessed.
>>>>
>>>> If we wanted to prevent that then every allocation would have to add a
>>>> check to see if the nodes are online which would impact performance.
>>>
>>> Okay, that makes sense, thank you.
>>>
>>> Andrew, can you please drop this patch?
>>>
>> Problem is that there are three patches.
>>
>> 2537ffb mm: memcontrol: consolidate swap controller code
>> 2f9b346 mm: memcontrol: consolidate memory controller initialization
>> a40d0d2 mm: memcontrol: remove unnecessary soft limit tree node test
>>
>> Reverting (or dropping) a40d0d2 alone is not possible since it modifies
>> mem_cgroup_soft_limit_tree_init which is removed by 2f9b346.
>
> ("mm: memcontrol: consolidate swap controller code") gave me no issues
> when rebasing, but ("mm: memcontrol: consolidate memory controller
> initialization") needs updating.
>
> So how about this one to replace ("mm: memcontrol: remove unnecessary
> soft limit tree node test"):
>
> ---
> From: Johannes Weiner <hannes@cmpxchg.org>
> Subject: [patch] mm: memcontrol: simplify soft limit tree init code
>
> - No need to test the node for N_MEMORY.  node_online() is enough for
>    node fallback to work in slab, use NUMA_NO_NODE for everything else.
>
> - Remove the BUG_ON() for allocation failure.  A NULL pointer crash is
>    just as descriptive, and the absent return value check is obvious.
>
> - Move local variables to the inner-most blocks.
>
> - Point to the tree structure after its initialized, not before, it's
>    just more logical that way.
>
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>

The latest version in mmotm passes my ppc64 qemu test, so it works
at least in this context.

Tested-by: Guenter Roeck <linux@roeck-us.net>


  parent reply	other threads:[~2015-01-24  2:02 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-01-22 23:05 mmotm 2015-01-22-15-04 uploaded akpm
2015-01-23  5:04 ` mmotm 2015-01-22-15-04: qemu failures due to 'mm: account pmd page tables to the process' Guenter Roeck
2015-01-23 11:13   ` Kirill A. Shutemov
2015-01-23 15:07     ` Guenter Roeck
2015-01-23 21:55       ` Andrew Morton
2015-01-24  2:44         ` Guenter Roeck
2015-01-24  3:05           ` Guenter Roeck
2015-01-24  5:52         ` Guenter Roeck
2015-01-26 12:29           ` Kirill A. Shutemov
2015-01-26 14:03             ` Guenter Roeck
2015-01-26 14:17               ` Guenter Roeck
2015-01-27 16:16               ` Kirill A. Shutemov
2015-01-27 16:24                 ` Guenter Roeck
2015-01-27 21:24                   ` Andrew Morton
2015-01-28  6:16                     ` Guenter Roeck
2015-01-23  5:08 ` mmotm 2015-01-22-15-04: qemu failure due to 'mm: memcontrol: remove unnecessary soft limit tree node test' Guenter Roeck
2015-01-23 14:18   ` Johannes Weiner
2015-01-23 15:17     ` Christoph Lameter
2015-01-23 16:02       ` Johannes Weiner
2015-01-23 16:59         ` Guenter Roeck
2015-01-23 17:36           ` Johannes Weiner
2015-01-23 17:38             ` Johannes Weiner
2015-01-24  2:02             ` Guenter Roeck [this message]
2015-01-27 17:24       ` Michal Hocko
2015-01-28 15:03         ` Christoph Lameter
2015-01-23 15:46     ` Guenter Roeck
2015-01-23 16:03       ` Johannes Weiner
2015-01-23 20:20     ` Christoph Lameter
2015-01-23 20:33       ` Guenter Roeck
2015-01-23 21:09         ` Christoph Lameter
2015-01-24  7:16           ` Johannes Weiner
2015-01-25 21:36             ` Valdis.Kletnieks
2015-01-26 13:37               ` Johannes Weiner

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