Re: [BUG] non-swapcache page in end_swap_bio_read()

[Minchan Kim]

Hello Artem,

On Fri, Jun 07, 2013 at 04:59:09PM +0400, Artem Savkov wrote:
> Hello all,
> 
> I'm hitting the following BUG_ON during boot when
> CONFIG_PM_STD_PARTITION or "resume" kernel boot option are set. Looks
> like this issue was introduced in (or brought up to light by)
> "mm: remove compressed copy from zram in-memory"
> (84e5bb4f06e6d6f0c4dfc033b4700702ed8aaccc in linux-next.git)
> What happens is that during swsusp_check() bio is created with
> bio_end_io set to end_swap_bio_read(), but the page is not in swap
> cache.

True. I totally missed it.

> Not sure how to handle this the right way, but proceeding with the
> optimization in end_swap_bio_read() only after checking PageSwapCache
> flag does help.

I'd like to go with your way.
We already have SetPageUptodate so PageSwapCache's cost would be really
cheap from hitting from cacheline. Even, we can optimize it with unlikely
hint.

The credit should be yours so could you send a patch with your SOB?
Please write a comment in code about that why we need such check.

If you have any problem about sending a patch, I will send it for you
on Monday if others don't suggest another solution.

Thanks for the report!

> 
> [    2.065206] kernel BUG at mm/swapfile.c:2361!
> [    2.065469] invalid opcode: 0000 [#1] SMP 
> [    2.065469] Modules linked in:
> [    2.065469] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 3.10.0-rc4-next-20130607+ #61
> [    2.065469] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2007
> [    2.065469] task: ffff88001e5ccfc0 ti: ffff88001e5ea000 task.ti: ffff88001e5ea000
> [    2.065469] RIP: 0010:[<ffffffff811462eb>]  [<ffffffff811462eb>] page_swap_info+0xab/0xb0
> [    2.065469] RSP: 0000:ffff88001ec03c78  EFLAGS: 00010246
> [    2.065469] RAX: 0100000000000009 RBX: ffffea0000794780 RCX: 0000000000000c0b
> [    2.065469] RDX: 0000000000000046 RSI: 0000000000000000 RDI: 0000000000000000
> [    2.065469] RBP: ffff88001ec03c88 R08: 0000000000000000 R09: 0000000000000000
> [    2.065469] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
> [    2.065469] R13: 0000000000000001 R14: ffff88001e7f6200 R15: 0000000000001000
> [    2.065469] FS:  0000000000000000(0000) GS:ffff88001ec00000(0000) knlGS:0000000000000000
> [    2.065469] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> [    2.065469] CR2: 0000000000000000 CR3: 000000000240b000 CR4: 00000000000006e0
> [    2.065469] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> [    2.065469] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
> [    2.065469] Stack:
> [    2.065469]  ffffea0000794780 ffff88001e7f6200 ffff88001ec03cb8 ffffffff81145486
> [    2.065469]  ffff88001e5cd5c0 ffff88001c02cd20 0000000000001000 0000000000000000
> [    2.065469]  ffff88001ec03cc8 ffffffff81199518 ffff88001ec03d28 ffffffff81518ec3
> [    2.065469] Call Trace:
> [    2.065469]  <IRQ> 
> [    2.065469]  [<ffffffff81145486>] end_swap_bio_read+0x96/0x130
> [    2.065469]  [<ffffffff81199518>] bio_endio+0x18/0x40
> [    2.065469]  [<ffffffff81518ec3>] blk_update_request+0x213/0x540
> [    2.065469]  [<ffffffff81518fa0>] ? blk_update_request+0x2f0/0x540
> [    2.065469]  [<ffffffff817986a6>] ? ata_hsm_qc_complete+0x46/0x130
> [    2.065469]  [<ffffffff81519212>] blk_update_bidi_request+0x22/0x90
> [    2.065469]  [<ffffffff8151b9ea>] blk_end_bidi_request+0x2a/0x80
> [    2.065469]  [<ffffffff8151ba8b>] blk_end_request+0xb/0x10
> [    2.065469]  [<ffffffff817693aa>] scsi_io_completion+0xaa/0x6b0
> [    2.065469]  [<ffffffff817608d8>] scsi_finish_command+0xc8/0x130
> [    2.065469]  [<ffffffff81769aff>] scsi_softirq_done+0x13f/0x160
> [    2.065469]  [<ffffffff81521ebc>] blk_done_softirq+0x7c/0x90
> [    2.065469]  [<ffffffff81049030>] __do_softirq+0x130/0x3f0
> [    2.065469]  [<ffffffff810d454e>] ? handle_irq_event+0x4e/0x70
> [    2.065469]  [<ffffffff81049405>] irq_exit+0xa5/0xb0
> [    2.065469]  [<ffffffff81003cb1>] do_IRQ+0x61/0xe0
> [    2.065469]  [<ffffffff81c2832f>] common_interrupt+0x6f/0x6f
> [    2.065469]  <EOI> 
> [    2.065469]  [<ffffffff8107ebff>] ? local_clock+0x4f/0x60
> [    2.065469]  [<ffffffff81c27f85>] ? _raw_spin_unlock_irq+0x35/0x50
> [    2.065469]  [<ffffffff81c27f7b>] ? _raw_spin_unlock_irq+0x2b/0x50
> [    2.065469]  [<ffffffff81078bd0>] finish_task_switch+0x80/0x110
> [    2.065469]  [<ffffffff81078b93>] ? finish_task_switch+0x43/0x110
> [    2.065469]  [<ffffffff81c2525c>] __schedule+0x32c/0x8c0
> [    2.065469]  [<ffffffff81c2c010>] ? notifier_call_chain+0x150/0x150
> [    2.065469]  [<ffffffff81c259d4>] schedule+0x24/0x70
> [    2.065469]  [<ffffffff81c25d42>] schedule_preempt_disabled+0x22/0x30
> [    2.065469]  [<ffffffff81093645>] cpu_startup_entry+0x335/0x380
> [    2.065469]  [<ffffffff81c1ed7e>] start_secondary+0x217/0x219
> [    2.065469] Code: 69 bc 16 82 48 c7 c7 77 bc 16 82 31 c0 49 c1 ec 39 49 c1 e9 10 41 83 e1 01 e8 6c d2 ad 00 5b 4a 8b 04 e5 e0 bf 14 83 41 5c c9 c3 <0f> 0b eb fe 90 48 8b 07 55 48 89 e5 a9 00 00 01 00 74 12 e8 3d 
> [    2.065469] RIP  [<ffffffff811462eb>] page_swap_info+0xab/0xb0
> [    2.065469]  RSP <ffff88001ec03c78>
> 
> -- 
> Regards,
>     Artem
> 
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-- 
Kind regards,
Minchan Kim
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