On 2019/5/18 下午5:18, Michael Laß wrote:
> 
>> Am 18.05.2019 um 06:09 schrieb Chris Murphy <lists@colorremedies.com>:
>>
>> On Fri, May 17, 2019 at 11:37 AM Michael Laß <bevan@bi-co.net> wrote:
>>>
>>>
>>> I tried to reproduce this issue: I recreated the btrfs file system, set up a minimal system and issued fstrim again. It printed the following error message:
>>>
>>> fstrim: /: FITRIM ioctl failed: Input/output error
>>
>> Huh. Any kernel message at the same time? I would expect any fstrim
>> user space error message to also have a kernel message. Any i/o error
>> suggests some kind of storage stack failure - which could be hardware
>> or software, you can't know without seeing the kernel messages.
> 
> I missed that. The kernel messages are:
> 
> attempt to access beyond end of device
> sda1: rw=16387, want=252755893, limit=250067632
> BTRFS warning (device dm-5): failed to trim 1 device(s), last error -5
> 
> Here are some more information on the partitions and LVM physical segments:
> 
> fdisk -l /dev/sda:
> 
> Device     Boot Start       End   Sectors   Size Id Type
> /dev/sda1  *     2048 250069679 250067632 119.2G 8e Linux LVM
> 
> pvdisplay -m:
> 
>   --- Physical volume ---
>   PV Name               /dev/sda1
>   VG Name               vg_system
>   PV Size               119.24 GiB / not usable <22.34 MiB
>   Allocatable           yes (but full)
>   PE Size               32.00 MiB
>   Total PE              3815
>   Free PE               0
>   Allocated PE          3815
>   PV UUID               mqCLFy-iDnt-NfdC-lfSv-Maor-V1Ih-RlG8lP
>    
>   --- Physical Segments ---
>   Physical extent 0 to 1248:
>     Logical volume	/dev/vg_system/btrfs
>     Logical extents	2231 to 3479
>   Physical extent 1249 to 1728:
>     Logical volume	/dev/vg_system/btrfs
>     Logical extents	640 to 1119
>   Physical extent 1729 to 1760:
>     Logical volume	/dev/vg_system/grml-images
>     Logical extents	0 to 31
>   Physical extent 1761 to 2016:
>     Logical volume	/dev/vg_system/swap
>     Logical extents	0 to 255
>   Physical extent 2017 to 2047:
>     Logical volume	/dev/vg_system/btrfs
>     Logical extents	3480 to 3510
>   Physical extent 2048 to 2687:
>     Logical volume	/dev/vg_system/btrfs
>     Logical extents	0 to 639
>   Physical extent 2688 to 3007:
>     Logical volume	/dev/vg_system/btrfs
>     Logical extents	1911 to 2230
>   Physical extent 3008 to 3320:
>     Logical volume	/dev/vg_system/btrfs
>     Logical extents	1120 to 1432
>   Physical extent 3321 to 3336:
>     Logical volume	/dev/vg_system/boot
>     Logical extents	0 to 15
>   Physical extent 3337 to 3814:
>     Logical volume	/dev/vg_system/btrfs
>     Logical extents	1433 to 1910
>    
> 
> Would btrfs even be able to accidentally trim parts of other LVs or does this clearly hint towards a LVM/dm issue?

I can't speak sure, but (at least for latest kernel) btrfs has a lot of
extra mount time self check, including chunk stripe check against
underlying device, thus the possibility shouldn't be that high for btrfs.

> Is there an easy way to somehow trace the trim through the different layers so one can see where it goes wrong?

Sure, you could use dm-log-writes.
It will record all read/write (including trim) for later replay.

So in your case, you can build the storage stack like:

Btrfs
<dm-log-writes>
LUKS/dmcrypt
LVM
MBR partition
Samsung SSD

Then replay the log (using src/log-write/replay-log in fstests) with
verbose output, you can verify every trim operation against the dmcrypt
device size.

If all trim are fine, then move the dm-log-writes a layer lower, until
you find which layer is causing the problem.

Thanks,
Qu
> 
> Cheers,
> Michael
> 
> PS: Current state of bisection: It looks like the error was introduced somewhere between b5dd0c658c31b469ccff1b637e5124851e7a4a1c and v5.1.
>