Re: BTRFS constantly reports "No space left on device" even with a huge unallocated space

[Jeff Mahoney <jeffm@suse.com>]

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On 9/18/16 10:38 PM, Wang Xiaoguang wrote:
> hi,
> 
> On 09/14/2016 10:25 PM, Jeff Mahoney wrote:
>> On 9/13/16 10:24 PM, Josef Bacik wrote:
>>> On 09/08/2016 07:02 PM, Jeff Mahoney wrote:
>>>> On 9/8/16 2:49 PM, Jeff Mahoney wrote:
>>>>> On 9/8/16 2:24 PM, Ronan Arraes Jardim Chagas wrote:
>>>>>> Hi all!
>>>>>>
>>>>>> Em Seg, 2016-09-05 às 16:49 +0800, Qu Wenruo escreveu:
>>>>>>> Just like what Wang has mentioned, would you please paste all the
>>>>>>> output
>>>>>>> of the contents of /sys/fs/btrfs/<your fs uuid>/allocation?
>>>>>>>
>>>>>>> It's recommended to use "grep . -IR <path>" to get all the data as
>>>>>>> it
>>>>>>> will show the file name.
>>>>>> So, one more time, I see the problem. This time I was just using
>>>>>> Firefox and I cannot recover using `btrfs balance`. I think that, one
>>>>>> more time, I will need to reboot this machine. This problem is really
>>>>>> causing me a lot of troubles :(
>>>>> I have a hunch the list is about to be flooded with similar reports if
>>>>> we don't find this one before 4.8.
>>>>>
>>>>> commit d555b6c380c644af63dbdaa7cc14bba041a4e4dd
>>>>> Author: Josef Bacik <jbacik@fb.com>
>>>>> Date:   Fri Mar 25 13:25:51 2016 -0400
>>>>>
>>>>>      Btrfs: warn_on for unaccounted spaces
>>>>>
>>>>> This commit isn't the source of the bug, but it's making it a lot more
>>>>> noisy.  I spent a few hours last night trying to track down why
>>>>> xfstests
>>>>> was throwing these warnings and I was able to reproduce them at
>>>>> least as
>>>>> far back as 4.4-vanilla with -oenospc_debug enabled.
>>>>>
>>>>> Speaking of which, can you turn on mounting with -oenospc_debug if you
>>>>> haven't already?
>>>>>
>>>>> In my case, space_info->bytes_may_use was getting accounted
>>>>> incorrectly.
>>>>>
>>>>> I am able to reproduce that even with the following commit:
>>>>> commit 18513091af9483ba84328d42092bd4d42a3c958f
>>>>> Author: Wang Xiaoguang <wangxg.fnst@cn.fujitsu.com>
>>>>> Date:   Mon Jul 25 15:51:40 2016 +0800
>>>>>
>>>>>      btrfs: update btrfs_space_info's bytes_may_use timely
>>>> And the btrfs_free_reserved_data_space_noquota WARN_ON I was seeing is
>>>> fixed by:
>>>>
>>>> commit ed7a6948394305b810d0c6203268648715e5006f
>>>> Author: Wang Xiaoguang <wangxg.fnst@cn.fujitsu.com>
>>>> Date:   Fri Aug 26 11:33:14 2016 +0800
>>>>
>>>>      btrfs: do not decrease bytes_may_use when replaying extents
>>>>
>>>> ... which shouldn't change anything for your issue, unfortunately.
>>>>
>>>> I still see these:
>>>> WARNING: CPU: 2 PID: 8166 at ../fs/btrfs/extent-tree.c:9582
>>>> btrfs_free_block_groups+0x2a8/0x400 [btrfs]()
>>>> Modules linked in: loop dm_flakey af_packet iscsi_ibft iscsi_boot_sysfs
>>>> msr ext4 crc16 mbcache jbd2 ipmi_ssif dm_mod igb ptp pps_core
>>>> acpi_cpufreq tpm_infineon kvm_amd ipmi_si kvm dca pcspkr
>>>> ipmi_msghandler
>>>> 8250_fintek sp5100_tco fjes irqbypass i2c_piix4 shpchp processor button
>>>> amd64_edac_mod edac_mce_amd edac_core k10temp btrfs xor raid6_pq sd_mod
>>>> ata_generic mgag200 i2c_algo_bit drm_kms_helper syscopyarea sysfillrect
>>>> ohci_pci sysimgblt ehci_pci serio_raw ohci_hcd fb_sys_fops pata_atiixp
>>>> ehci_hcd ttm ahci libahci drm usbcore libata usb_common sg scsi_mod
>>>> autofs4
>>>> CPU: 2 PID: 8166 Comm: umount Tainted: G        W
>>>> 4.4.19-11.g81405db-vanilla #1
>>>> Hardware name: HP ProLiant DL165 G7, BIOS O37 10/17/2012
>>>>   0000000000000000 ffff880230317d10 ffffffff813170ec 0000000000000000
>>>>   ffffffffa0472528 ffff880230317d48 ffffffff8107d816 0000000000000000
>>>>   ffff88009ab03600 ffff8800ba106288 ffff8800ab75a000 ffff8800ba106200
>>>> Call Trace:
>>>>   [<ffffffff813170ec>] dump_stack+0x63/0x87
>>>>   [<ffffffff8107d816>] warn_slowpath_common+0x86/0xc0
>>>>   [<ffffffff8107d90a>] warn_slowpath_null+0x1a/0x20
>>>>   [<ffffffffa03de3a8>] btrfs_free_block_groups+0x2a8/0x400 [btrfs]
>>>>   [<ffffffffa03ef24b>] close_ctree+0x15b/0x330 [btrfs]
>>>>   [<ffffffffa03bfeb9>] btrfs_put_super+0x19/0x20 [btrfs]
>>>>   [<ffffffff811fe5bf>] generic_shutdown_super+0x6f/0x100
>>>>   [<ffffffff811fe662>] kill_anon_super+0x12/0x20
>>>>   [<ffffffffa03c4fa8>] btrfs_kill_super+0x18/0x120 [btrfs]
>>>>   [<ffffffff811fe003>] deactivate_locked_super+0x43/0x70
>>>>   [<ffffffff811fe076>] deactivate_super+0x46/0x60
>>>>   [<ffffffff81219dcf>] cleanup_mnt+0x3f/0x80
>>>>   [<ffffffff81219e62>] __cleanup_mnt+0x12/0x20
>>>>   [<ffffffff81099fb6>] task_work_run+0x86/0xb0
>>>>   [<ffffffff81078806>] exit_to_usermode_loop+0x73/0xa2
>>>>   [<ffffffff81003b2d>] syscall_return_slowpath+0x8d/0xa0
>>>>   [<ffffffff815f928c>] int_ret_from_sys_call+0x25/0x8f
>>>> ---[ end trace 09a0cc2892b6305c ]---
>>>> BTRFS: space_info 1 has 7946240 free, is not full
>>>> BTRFS: space_info total=8388608, used=442368, pinned=0, reserved=0,
>>>> may_use=4096, readonly=0
>>>>
>>>> ... where the value of may_use varies.
>>>>
>>> What test are you seeing this with?  Thanks,
>> btrfs/022 hits it every time for me.
> btrfs/022 is not related to this enospc error.
> Qu wenruo's patch “ btrfs: Fix leaking bytes_may_use after hitting
> EDQUOTA” has
> fixed this warning, please check his patch for detailed commit message.

Yep, that's understood.  This was just something I happened to encounter
while looking at this.

-Jeff


-- 
Jeff Mahoney
SUSE Labs


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