Re: [PATCH v7 00/12] Support non-lru page migration

[Sergey Senozhatsky]

On (06/16/16 13:47), Minchan Kim wrote:
[..]
> > this is what I'm getting with the [zsmalloc: keep first object offset in struct page]
> > applied:  "count:0 mapcount:-127". which may be not related to zsmalloc at this point.
> > 
> > kernel: BUG: Bad page state in process khugepaged  pfn:101db8
> > kernel: page:ffffea0004076e00 count:0 mapcount:-127 mapping:          (null) index:0x1
> 
> Hm, it seems double free.
> 
> It doen't happen if you disable zram? IOW, it seems to be related
> zsmalloc migration?

need to test more, can't confidently answer now.

> How easy can you reprodcue it? Could you bisect it?

it takes some (um.. random) time to trigger the bug.
I'll try to come up with more details.

	-ss

> > kernel: flags: 0x8000000000000000()
> > kernel: page dumped because: nonzero mapcount
> > kernel: Modules linked in: lzo zram zsmalloc mousedev coretemp hwmon crc32c_intel snd_hda_codec_realtek i2c_i801 snd_hda_codec_generic r8169 mii snd_hda_intel snd_hda_codec snd_hda_core acpi_cpufreq snd_pcm snd_timer snd soundcore lpc_ich processor mfd_core sch_fq_codel sd_mod hid_generic usb
> > kernel: CPU: 3 PID: 38 Comm: khugepaged Not tainted 4.7.0-rc3-next-20160615-dbg-00005-gfd11984-dirty #491
> > kernel:  0000000000000000 ffff8801124c73f8 ffffffff814d69b0 ffffea0004076e00
> > kernel:  ffffffff81e658a0 ffff8801124c7420 ffffffff811e9b63 0000000000000000
> > kernel:  ffffea0004076e00 ffffffff81e658a0 ffff8801124c7440 ffffffff811e9ca9
> > kernel: Call Trace:
> > kernel:  [<ffffffff814d69b0>] dump_stack+0x68/0x92
> > kernel:  [<ffffffff811e9b63>] bad_page+0x158/0x1a2
> > kernel:  [<ffffffff811e9ca9>] free_pages_check_bad+0xfc/0x101
> > kernel:  [<ffffffff811ee516>] free_hot_cold_page+0x135/0x5de
> > kernel:  [<ffffffff811eea26>] __free_pages+0x67/0x72
> > kernel:  [<ffffffff81227c63>] release_freepages+0x13a/0x191
> > kernel:  [<ffffffff8122b3c2>] compact_zone+0x845/0x1155
> > kernel:  [<ffffffff8122ab7d>] ? compaction_suitable+0x76/0x76
> > kernel:  [<ffffffff8122bdb2>] compact_zone_order+0xe0/0x167
> > kernel:  [<ffffffff8122bcd2>] ? compact_zone+0x1155/0x1155
> > kernel:  [<ffffffff8122ce88>] try_to_compact_pages+0x2f1/0x648
> > kernel:  [<ffffffff8122ce88>] ? try_to_compact_pages+0x2f1/0x648
> > kernel:  [<ffffffff8122cb97>] ? compaction_zonelist_suitable+0x3a6/0x3a6
> > kernel:  [<ffffffff811ef1ea>] ? get_page_from_freelist+0x2c0/0x133c
> > kernel:  [<ffffffff811f0350>] __alloc_pages_direct_compact+0xea/0x30d
> > kernel:  [<ffffffff811f0266>] ? get_page_from_freelist+0x133c/0x133c
> > kernel:  [<ffffffff811ee3b2>] ? drain_all_pages+0x1d6/0x205
> > kernel:  [<ffffffff811f21a8>] __alloc_pages_nodemask+0x143d/0x16b6
> > kernel:  [<ffffffff8111f405>] ? debug_show_all_locks+0x226/0x226
> > kernel:  [<ffffffff811f0d6b>] ? warn_alloc_failed+0x24c/0x24c
> > kernel:  [<ffffffff81110ffc>] ? finish_wait+0x1a4/0x1b0
> > kernel:  [<ffffffff81122faf>] ? lock_acquire+0xec/0x147
> > kernel:  [<ffffffff81d32ed0>] ? _raw_spin_unlock_irqrestore+0x3b/0x5c
> > kernel:  [<ffffffff81d32edc>] ? _raw_spin_unlock_irqrestore+0x47/0x5c
> > kernel:  [<ffffffff81110ffc>] ? finish_wait+0x1a4/0x1b0
> > kernel:  [<ffffffff8128f73a>] khugepaged+0x1d4/0x484f
> > kernel:  [<ffffffff8128f566>] ? hugepage_vma_revalidate+0xef/0xef
> > kernel:  [<ffffffff810d5bcc>] ? finish_task_switch+0x3de/0x484
> > kernel:  [<ffffffff81d32f18>] ? _raw_spin_unlock_irq+0x27/0x45
> > kernel:  [<ffffffff8111d13f>] ? trace_hardirqs_on_caller+0x3d2/0x492
> > kernel:  [<ffffffff81111487>] ? prepare_to_wait_event+0x3f7/0x3f7
> > kernel:  [<ffffffff81d28bf5>] ? __schedule+0xa4d/0xd16
> > kernel:  [<ffffffff810cd0de>] kthread+0x252/0x261
> > kernel:  [<ffffffff8128f566>] ? hugepage_vma_revalidate+0xef/0xef
> > kernel:  [<ffffffff810cce8c>] ? kthread_create_on_node+0x377/0x377
> > kernel:  [<ffffffff81d3387f>] ret_from_fork+0x1f/0x40
> > kernel:  [<ffffffff810cce8c>] ? kthread_create_on_node+0x377/0x377
> > -- Reboot --