Re: advice on bad_page instance

[Minchan Kim <minchan@kernel.org>]

Hello Luigi,

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.

> 
> Many thanks for any pointer!
> 
> Luigi
> 
> <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

-- 
Kind regards,
Minchan Kim

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