Had same issue on a similar (well, quite exactly same setup), on a machine in production.
But It Is more than 4 tera of data, so in the end I re-dd the image and restarted, sticking to 5.0.y branch never had problem.
I was able to replicate it. SSD Samsung, more recent version.
Not with btrfs but ext4, by the way.
I saw the discard of big initial part of lvm partition. I can't find superblocks Copy in the First half, but torwards the end of logical volume.
Sorry, i can't play with It again, but i have the whole (4 tera) dd image with the bug.
Ciao,
Gelma
Il lun 20 mag 2019, 02:38 Michael Laß <bevan@xxxxxxxxx> ha scritto:
CC'ing dm-devel, as this seems to be a dm-related issue. Short summary for new readers:
On Linux 5.1 (tested up to 5.1.3), fstrim may discard too many blocks, leading to data loss. I have the following storage stack:
btrfs
dm-crypt (LUKS)
LVM logical volume
LVM single physical volume
MBR partition
Samsung 830 SSD
The mapping between logical volumes and physical segments is a bit mixed up. See below for the output for “pvdisplay -m”. When I issue fstrim on the mounted btrfs volume, I get the following kernel messages:
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
At the same time, other logical volumes on the same physical volume are destroyed. Also the btrfs volume itself may be damaged (this seems to depend on the actual usage).
I can easily reproduce this issue locally and I’m currently bisecting. So far I could narrow down the range of commits to:
Good: 92fff53b7191cae566be9ca6752069426c7f8241
Bad: 225557446856448039a9e495da37b72c20071ef2
In this range of commits, there are only dm-related changes.
So far, I have not reproduced the issue with other file systems or a simplified stack. I first want to continue bisecting but this may take another day.
> Am 18.05.2019 um 12:26 schrieb Qu Wenruo <quwenruo.btrfs@xxxxxxx>:
> On 2019/5/18 下午5:18, Michael Laß wrote:
>>
>>> Am 18.05.2019 um 06:09 schrieb Chris Murphy <lists@xxxxxxxxxxxxxxxxx>:
>>>
>>> On Fri, May 17, 2019 at 11:37 AM Michael Laß <bevan@xxxxxxxxx> 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.
Indeed, bisecting the issue led me to a range of commits that only contains dm-related and no btrfs-related changes. So I assume this is a bug in dm.
>> 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.
That sounds like a plan! However, I first want to continue bisecting as I am afraid to lose my reproducer by changing parts of my storage stack.
Cheers,
Michael
>
> Thanks,
> Qu
>>
>> Cheers,
>> Michael
>>
>> PS: Current state of bisection: It looks like the error was introduced somewhere between b5dd0c658c31b469ccff1b637e5124851e7a4a1c and v5.1.
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