Re: advice on bad_page instance

[Luigi Semenzato <semenzato@google.com>]

Thank you for your replies!  Actually I don't see anything that makes
me suspect zram as the culprit.  I mentioned it just in case you folks
knew of any bug that would result in that behavior.

Thank you for the suggestion to backport---I'll look into it.  Of
course I would prefer to backport code that I actually know fixes this
mm problem.


On Wed, Apr 15, 2015 at 1:22 AM, Sergey Senozhatsky
<sergey.senozhatsky.work@gmail.com> wrote:
> On (04/15/15 16:16), Minchan Kim wrote:
>> On Tue, Apr 14, 2015 at 11:36:57AM -0700, Luigi Semenzato wrote:
>> > We are seeing several instances of these things (often with different
>> > but plausible values in the struct page) in kernel 3.8.11, followed by
>> > a panic() in release_pages a few seconds later.
>> >
>> > I realize it's an old kernel and probably of little interest here, but
>> > I would be most grateful for any pointers on how to proceed.  In
>> > particular, I suspect that many such bugs may have been fixed by now,
>> > but I am not sure how to find the right fix (which I would backport).
>> >
>> > Also, this happens under heavy swap, and we're using zram.  I wonder
>> > if there may be a race condition related to zram which may have been
>> > fixed since then, and which may result in these symptoms.
>>
>> I didn't see such bug until now. Sorry. However, I might miss something
>> because zram has changed a lot since then.
>> What I recommend is just to use recent zram/zsmalloc.
>> I think it's not hard to backport it because they are almost isolated
>> from other parts in kernel.
>> If you don't see any problem any more with recent zram, yay, your
>> system doesn't have any problem. But if you see the problem still,
>> it means you should suspect another stuffs as culprits as well as
>> zram.
>>
>> Thanks.
>>
>
> assuming that you use zram0, does 'mkswap -c /dev/zram0' show any bad
> pages right after the swap creation/activation?
>
>         -ss
>
>> > <1>[ 5392.106074] BUG: Bad page state in process CompositorTileW  pfn:57a7e
>> > <1>[ 5392.106109] page:ffffea00015e9f80 count:0 mapcount:0 mapping:
>> >       (null) index:0x2
>> > <1>[ 5392.106122] page flags: 0x4000000000000004(referenced)
>> > <5>[ 5392.106139] Modules linked in: i2c_dev uinput
>> > snd_hda_codec_realtek memconsole snd_hda_codec_hdmi uvcvideo
>> > videobuf2_vmalloc videobuf2_memops videobuf2_core videodev
>> > snd_hda_intel snd_hda_codec snd_hwdep snd_pcm snd_page_alloc snd_timer
>> > zram(C) lzo_compress zsmalloc(C) fuse nf_conntrack_ipv6 nf_defrag_ipv6
>> > ip6table_filter ip6_tables ath9k_btcoex ath9k_common_btcoex
>> > ath9k_hw_btcoex ath mac80211 cfg80211 option usb_wwan cdc_ether usbnet
>> > ath3k btusb bluetooth joydev ppp_async ppp_generic slhc tun
>> > <5>[ 5392.106333] Pid: 27363, comm: CompositorTileW Tainted: G    B
>> > C   3.8.11 #1
>> > <5>[ 5392.106344] Call Trace:
>> > <5>[ 5392.106357]  [<ffffffff978ba5bb>] bad_page+0xcf/0xe3
>> > <5>[ 5392.106370]  [<ffffffff978bb181>] get_page_from_freelist+0x21a/0x46c
>> > <5>[ 5392.106383]  [<ffffffff978beb74>] ? release_pages+0x19b/0x1be
>> > <5>[ 5392.106394]  [<ffffffff978bb5da>] __alloc_pages_nodemask+0x207/0x685
>> > <5>[ 5392.106407]  [<ffffffff97cb8caf>] ? _cond_resched+0xe/0x1e
>> > <5>[ 5392.106421]  [<ffffffff978d215a>] handle_pte_fault+0x305/0x500
>> > <5>[ 5392.106433]  [<ffffffff978d4f5e>] ? __vma_link_file+0x65/0x67
>> > <5>[ 5392.106445]  [<ffffffff978d30d0>] handle_mm_fault+0x97/0xbb
>> > <5>[ 5392.106459]  [<ffffffff97828616>] __do_page_fault+0x1d4/0x38c
>> > <5>[ 5392.106470]  [<ffffffff978d7803>] ? do_mmap_pgoff+0x284/0x2c0
>> > <5>[ 5392.106482]  [<ffffffff978ca82c>] ? vm_mmap_pgoff+0x7d/0x8e
>> > <5>[ 5392.106495]  [<ffffffff97828800>] do_page_fault+0xe/0x10
>> > <5>[ 5392.106506]  [<ffffffff97cb9d32>] page_fault+0x22/0x30

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