Re: 3.14.0-rc3 btrfs scrub is preventing my laptop from going to sleep

[Josef Bacik <jbacik@fb.com>]

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On 02/27/2014 02:06 PM, Marc MERLIN wrote:
> This does not happen consistently, but sometimes:
> 
> PM: Preparing system for mem sleep Freezing user space processes
> ... (...) Freezing of tasks failed after 20.002 seconds (1 tasks
> refusing to freeze, wq_busy=0): btrfs           D ffff88017639c800
> 0 12239  12224 0x00000084 ffff880165ec1960 0000000000000086
> ffff880165ec1fd8 ffff88017639c2d0 00000000000141c0 ffff88017639c2d0
> ffff88007b874000 ffff8804062fa480 0000000000000000 ffff880175837ec0
> ffff88007b874220 ffff880165ec1970 Call Trace: [<ffffffff8160b0d9>]
> schedule+0x73/0x75 [<ffffffff8126e94c>] scrub_pages+0x27e/0x426 
> [<ffffffff81085062>] ? finish_wait+0x65/0x65 [<ffffffff81271732>]
> scrub_stripe+0xada/0xc9e [<ffffffff812719cc>]
> scrub_chunk.isra.9+0xd6/0x10d [<ffffffff81271c77>]
> scrub_enumerate_chunks+0x274/0x418 [<ffffffff81085000>] ?
> finish_wait+0x3/0x65 [<ffffffff812723bb>]
> btrfs_scrub_dev+0x254/0x3cb [<ffffffff8116ddab>] ?
> __mnt_want_write+0x62/0x78 [<ffffffff81255c68>]
> btrfs_ioctl+0x1114/0x24b1 [<ffffffff81140698>] ?
> ____cache_alloc+0x1c/0x29b [<ffffffff81140a06>] ?
> kmem_cache_alloc_node+0xef/0x179 [<ffffffff8160d7b3>] ?
> _raw_spin_unlock+0x17/0x2a [<ffffffff81163ade>]
> do_vfs_ioctl+0x3d2/0x41d [<ffffffff8116bd00>] ? __fget+0x6f/0x79 
> [<ffffffff81163b80>] SyS_ioctl+0x57/0x82 [<ffffffff8161426d>]
> system_call_fastpath+0x1a/0x1f
> 
> 
> And then I end up with a hot laptop and a mostly dead battery in my
> backpack.
> 
> As far as I know, this was not happening with 3.13, unless I'm
> doing something differently without knowing.
> 
> My laptop went to sleep just fine while I was typing this Email, so
> I'm guessing it's only btrfs scrub that causes the problem with
> sleep.
> 

We probably need to put something in ->fs_freeze() to pause scrubbing
(and this probably applies to snapshot deletion too) so you can
hibernate.  Should be easy enough to do, I'll look into it after
quotas unless somebody beats me to it.  Thanks,

Josef

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