[PATCH] mm: move page_ext_init after all struct pages are initialized

[PATCH] mm: move page_ext_init after all struct pages are initialized

[Yang Shi]

When DEFERRED_STRUCT_PAGE_INIT is enabled, just a subset of memmap at boot
are initialized, then the rest are initialized in parallel by starting one-off
"pgdatinitX" kernel thread for each node X.

If page_ext_init is called before it, some pages will not have valid extension,
so move page_ext_init() after it.

CC: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Yang Shi <yang.shi@linaro.org>
---
 init/main.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/init/main.c b/init/main.c
index b3c6e36..2075faf 100644
--- a/init/main.c
+++ b/init/main.c
@@ -606,7 +606,6 @@ asmlinkage __visible void __init start_kernel(void)
 		initrd_start = 0;
 	}
 #endif
-	page_ext_init();
 	debug_objects_mem_init();
 	kmemleak_init();
 	setup_per_cpu_pageset();
@@ -1004,6 +1003,8 @@ static noinline void __init kernel_init_freeable(void)
 	sched_init_smp();
 
 	page_alloc_init_late();
+	/* Initialize page ext after all struct pages are initializaed */
+	page_ext_init();
 
 	do_basic_setup();
 
-- 
2.0.2

Re: [PATCH] mm: move page_ext_init after all struct pages are initialized

[Andrew Morton]

On Thu, 19 May 2016 14:29:05 -0700 Yang Shi <yang.shi@linaro.org> wrote:

> When DEFERRED_STRUCT_PAGE_INIT is enabled, just a subset of memmap at boot
> are initialized, then the rest are initialized in parallel by starting one-off
> "pgdatinitX" kernel thread for each node X.
> 
> If page_ext_init is called before it, some pages will not have valid extension,
> so move page_ext_init() after it.
> 

<stdreply>When fixing a bug, please fully describe the end-user impact
of that bug</>

Re: [PATCH] mm: move page_ext_init after all struct pages are initialized

[Shi, Yang]

On 5/19/2016 3:30 PM, Andrew Morton wrote:
> On Thu, 19 May 2016 14:29:05 -0700 Yang Shi <yang.shi@linaro.org> wrote:
>
>> When DEFERRED_STRUCT_PAGE_INIT is enabled, just a subset of memmap at boot
>> are initialized, then the rest are initialized in parallel by starting one-off
>> "pgdatinitX" kernel thread for each node X.
>>
>> If page_ext_init is called before it, some pages will not have valid extension,
>> so move page_ext_init() after it.
>>
>
> <stdreply>When fixing a bug, please fully describe the end-user impact
> of that bug</>

The kernel ran into the below oops which is same with the oops reported 
in 
http://ozlabs.org/~akpm/mmots/broken-out/mm-page_is_guard-return-false-when-page_ext-arrays-are-not-allocated-yet.patch.

BUG: unable to handle kernel NULL pointer dereference at           (null)
IP: [<ffffffff8118d982>] free_pcppages_bulk+0x2d2/0x8d0
PGD 0
Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
Modules linked in:
CPU: 11 PID: 106 Comm: pgdatinit1 Not tainted 4.6.0-rc5-next-20160427 #26
Hardware name: Intel Corporation S5520HC/S5520HC, BIOS 
S5500.86B.01.10.0025.030220091519 03/02/2009
task: ffff88017c080040 ti: ffff88017c084000 task.ti: ffff88017c084000
RIP: 0010:[<ffffffff8118d982>]  [<ffffffff8118d982>] 
free_pcppages_bulk+0x2d2/0x8d0
RSP: 0000:ffff88017c087c48  EFLAGS: 00010046
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000001
RDX: 0000000000000980 RSI: 0000000000000080 RDI: 0000000000660401
RBP: ffff88017c087cd0 R08: 0000000000000401 R09: 0000000000000009
R10: ffff88017c080040 R11: 000000000000000a R12: 0000000000000400
R13: ffffea0019810000 R14: ffffea0019810040 R15: ffff88066cfe6080
FS:  0000000000000000(0000) GS:ffff88066cd40000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 0000000002406000 CR4: 00000000000006e0
Stack:
  ffff88066cd5bbd8 ffff88066cfe6640 0000000000000000 0000000000000000
  0000001f0000001f ffff88066cd5bbe8 ffffea0019810000 000000008118f53e
  0000000000000009 0000000000000401 ffffffff0000000a 0000000000000001
Call Trace:
  [<ffffffff8118f602>] free_hot_cold_page+0x192/0x1d0
  [<ffffffff8118f69c>] __free_pages+0x5c/0x90
  [<ffffffff8262a676>] __free_pages_boot_core+0x11a/0x14e
  [<ffffffff8262a6fa>] deferred_free_range+0x50/0x62
  [<ffffffff8262aa46>] deferred_init_memmap+0x220/0x3c3
  [<ffffffff8262a826>] ? setup_per_cpu_pageset+0x35/0x35
  [<ffffffff8108b1f8>] kthread+0xf8/0x110
  [<ffffffff81c1b732>] ret_from_fork+0x22/0x40
  [<ffffffff8108b100>] ? kthread_create_on_node+0x200/0x200
Code: 49 89 d4 48 c1 e0 06 49 01 c5 e9 de fe ff ff 4c 89 f7 44 89 4d b8 
4c 89 45 c0 44 89 5d c8 48 89 4d d0 e8 62 c7 07 00 48 8b 4d d0 <48> 8b 
00 44 8b 5d c8 4c 8b 45 c0 44 8b 4d b8 a8 02 0f 84 05 ff
RIP  [<ffffffff8118d982>] free_pcppages_bulk+0x2d2/0x8d0
  RSP <ffff88017c087c48>
CR2: 0000000000000000


I will add the oops info into the commit log in V2.

Thanks,
Yang

>

Re: [PATCH] mm: move page_ext_init after all struct pages are initialized

[Andrew Morton]

On Thu, 19 May 2016 15:35:15 -0700 "Shi, Yang" <yang.shi@linaro.org> wrote:

> On 5/19/2016 3:30 PM, Andrew Morton wrote:
> > On Thu, 19 May 2016 14:29:05 -0700 Yang Shi <yang.shi@linaro.org> wrote:
> >
> >> When DEFERRED_STRUCT_PAGE_INIT is enabled, just a subset of memmap at boot
> >> are initialized, then the rest are initialized in parallel by starting one-off
> >> "pgdatinitX" kernel thread for each node X.
> >>
> >> If page_ext_init is called before it, some pages will not have valid extension,
> >> so move page_ext_init() after it.
> >>
> >
> > <stdreply>When fixing a bug, please fully describe the end-user impact
> > of that bug</>
> 
> The kernel ran into the below oops which is same with the oops reported 
> in 
> http://ozlabs.org/~akpm/mmots/broken-out/mm-page_is_guard-return-false-when-page_ext-arrays-are-not-allocated-yet.patch.

So this patch makes
mm-page_is_guard-return-false-when-page_ext-arrays-are-not-allocated-yet.patch
obsolete?

Re: [PATCH] mm: move page_ext_init after all struct pages are initialized

[Shi, Yang]

On 5/19/2016 4:21 PM, Andrew Morton wrote:
> On Thu, 19 May 2016 15:35:15 -0700 "Shi, Yang" <yang.shi@linaro.org> wrote:
>
>> On 5/19/2016 3:30 PM, Andrew Morton wrote:
>>> On Thu, 19 May 2016 14:29:05 -0700 Yang Shi <yang.shi@linaro.org> wrote:
>>>
>>>> When DEFERRED_STRUCT_PAGE_INIT is enabled, just a subset of memmap at boot
>>>> are initialized, then the rest are initialized in parallel by starting one-off
>>>> "pgdatinitX" kernel thread for each node X.
>>>>
>>>> If page_ext_init is called before it, some pages will not have valid extension,
>>>> so move page_ext_init() after it.
>>>>
>>>
>>> <stdreply>When fixing a bug, please fully describe the end-user impact
>>> of that bug</>
>>
>> The kernel ran into the below oops which is same with the oops reported
>> in
>> http://ozlabs.org/~akpm/mmots/broken-out/mm-page_is_guard-return-false-when-page_ext-arrays-are-not-allocated-yet.patch.
>
> So this patch makes
> mm-page_is_guard-return-false-when-page_ext-arrays-are-not-allocated-yet.patch
> obsolete?

Actually, no. Checking the return value for lookup_page_ext() is still 
needed. But, the commit log need to be amended since that bootup oops 
won't happen anymore with this patch applied.

Thanks,
Yang

>