From: Wei Yang <richard.weiyang@gmail.com>
To: Zaslonko Mikhail <zaslonko@linux.bm.com>
Cc: Wei Yang <richard.weiyang@gmail.com>,
Mikhail Zaslonko <zaslonko@linux.ibm.com>,
akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, mhocko@kernel.org,
Pavel.Tatashin@microsoft.com, schwidefsky@de.ibm.com,
heiko.carstens@de.ibm.com, gerald.schaefer@de.ibm.com
Subject: Re: [PATCH v2 1/1] mm, memory_hotplug: Initialize struct pages for the full memory section
Date: Thu, 13 Dec 2018 15:12:09 +0000 [thread overview]
Message-ID: <20181213151209.hmrhrr5gvb256bzm@master> (raw)
In-Reply-To: <e4cebbae-3fcb-f03c-3d0e-a1a44ff0675a@linux.bm.com>
On Thu, Dec 13, 2018 at 01:37:16PM +0100, Zaslonko Mikhail wrote:
>On 13.12.2018 04:46, Wei Yang wrote:
>> On Wed, Dec 12, 2018 at 06:27:12PM +0100, Mikhail Zaslonko wrote:
>>> If memory end is not aligned with the sparse memory section boundary, the
>>> mapping of such a section is only partly initialized. This may lead to
>>> VM_BUG_ON due to uninitialized struct page access from
>>> is_mem_section_removable() or test_pages_in_a_zone() function triggered by
>>> memory_hotplug sysfs handlers:
>>>
>>> Here are the the panic examples:
>>> CONFIG_DEBUG_VM=y
>>> CONFIG_DEBUG_VM_PGFLAGS=y
>>>
>>> kernel parameter mem=2050M
>>> --------------------------
>>> page:000003d082008000 is uninitialized and poisoned
>>> page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p))
>>> Call Trace:
>>> ([<0000000000385b26>] test_pages_in_a_zone+0xde/0x160)
>>> [<00000000008f15c4>] show_valid_zones+0x5c/0x190
>>> [<00000000008cf9c4>] dev_attr_show+0x34/0x70
>>> [<0000000000463ad0>] sysfs_kf_seq_show+0xc8/0x148
>>> [<00000000003e4194>] seq_read+0x204/0x480
>>> [<00000000003b53ea>] __vfs_read+0x32/0x178
>>> [<00000000003b55b2>] vfs_read+0x82/0x138
>>> [<00000000003b5be2>] ksys_read+0x5a/0xb0
>>> [<0000000000b86ba0>] system_call+0xdc/0x2d8
>>> Last Breaking-Event-Address:
>>> [<0000000000385b26>] test_pages_in_a_zone+0xde/0x160
>>> Kernel panic - not syncing: Fatal exception: panic_on_oops
>>>
>>> kernel parameter mem=3075M
>>> --------------------------
>>> page:000003d08300c000 is uninitialized and poisoned
>>> page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p))
>>> Call Trace:
>>> ([<000000000038596c>] is_mem_section_removable+0xb4/0x190)
>>> [<00000000008f12fa>] show_mem_removable+0x9a/0xd8
>>> [<00000000008cf9c4>] dev_attr_show+0x34/0x70
>>> [<0000000000463ad0>] sysfs_kf_seq_show+0xc8/0x148
>>> [<00000000003e4194>] seq_read+0x204/0x480
>>> [<00000000003b53ea>] __vfs_read+0x32/0x178
>>> [<00000000003b55b2>] vfs_read+0x82/0x138
>>> [<00000000003b5be2>] ksys_read+0x5a/0xb0
>>> [<0000000000b86ba0>] system_call+0xdc/0x2d8
>>> Last Breaking-Event-Address:
>>> [<000000000038596c>] is_mem_section_removable+0xb4/0x190
>>> Kernel panic - not syncing: Fatal exception: panic_on_oops
>>>
>>> Fix the problem by initializing the last memory section of each zone
>>> in memmap_init_zone() till the very end, even if it goes beyond the zone
>>> end.
>>>
>>> Signed-off-by: Mikhail Zaslonko <zaslonko@linux.ibm.com>
>>> Reviewed-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
>>> Cc: <stable@vger.kernel.org>
>>> ---
>>> mm/page_alloc.c | 12 ++++++++++++
>>> 1 file changed, 12 insertions(+)
>>>
>>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>>> index 2ec9cc407216..e2afdb2dc2c5 100644
>>> --- a/mm/page_alloc.c
>>> +++ b/mm/page_alloc.c
>>> @@ -5542,6 +5542,18 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
>>> cond_resched();
>>> }
>>> }
>>> +#ifdef CONFIG_SPARSEMEM
>>> + /*
>>> + * If the zone does not span the rest of the section then
>>> + * we should at least initialize those pages. Otherwise we
>>> + * could blow up on a poisoned page in some paths which depend
>>> + * on full sections being initialized (e.g. memory hotplug).
>>> + */
>>> + while (end_pfn % PAGES_PER_SECTION) {
>>> + __init_single_page(pfn_to_page(end_pfn), end_pfn, zone, nid);
>>> + end_pfn++;
>>> + }
>>> +#endif
>>> }
>>
>> What will happen if the end_pfn is PAGES_PER_SECTION aligned, but there
>> is invalid pfn? For example, the page is skipped in the for loop of
>> memmap_init_zone()?
>>
>
>If the end_pfn is PAGES_PER_SECTION aligned, we do not do any extra
>initialization.
>If the page is skipped in the loop, it will remain uninitialized for
>the reason (e.g. a memory hole). The behavior has not been changed here.
>
I may not describe my question clearly.
If the page is skipped, then it is uninitialized. Then would this page
trigger the call trace when read the removable sysfs?
>>>
>>> #ifdef CONFIG_ZONE_DEVICE
>>> --
>>> 2.16.4
>>
--
Wei Yang
Help you, Help me
next prev parent reply other threads:[~2018-12-13 15:12 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-12 17:27 [PATCH v2 0/1] Initialize struct pages for the full section Mikhail Zaslonko
2018-12-12 17:27 ` [PATCH v2 1/1] mm, memory_hotplug: Initialize struct pages for the full memory section Mikhail Zaslonko
2018-12-13 3:46 ` Wei Yang
[not found] ` <e4cebbae-3fcb-f03c-3d0e-a1a44ff0675a@linux.bm.com>
2018-12-13 15:12 ` Wei Yang [this message]
[not found] ` <674c53e2-e4b3-f21f-4613-b149acef7e53@linux.bm.com>
2018-12-14 10:19 ` Michal Hocko
2018-12-15 0:26 ` Wei Yang
2018-12-13 12:59 ` Michal Hocko
2018-12-14 15:22 ` David Hildenbrand
2018-12-14 15:49 ` David Hildenbrand
2018-12-14 19:23 ` Gerald Schaefer
2018-12-17 9:38 ` David Hildenbrand
2018-12-17 12:28 ` Michal Hocko
2018-12-17 13:29 ` David Hildenbrand
2018-12-17 13:35 ` Michal Hocko
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