[BUG] I/O timeouts and system freezes on Kingston A2000 NVME with BCACHEFS

[Mia Kanashi]

On 2024-01-19 21:22, Jens Axboe wrote:
> On 1/19/24 5:25 AM, Mia Kanashi wrote:
>> This issue was originally reported here: 
>> https://github.com/koverstreet/bcachefs/issues/628
>> 
>> Transferring large amounts of files to the bcachefs from the btrfs
>> causes I/O timeouts and freezes the whole system. This doesn't seem to
>> be related to the btrfs, but rather to the heavy I/O on the drive, as
>> it happens without btrfs being mounted. Transferring the files to the
>> HDD, and then from it to the bcachefs on the NVME sometimes doesn't
>> make the problem occur. The problem only happens on the bcachefs, not
>> on btrfs or ext4. It doesn't happen on the HDD, I can't test with
>> other NVME drives sadly. The behaviour when it is frozen is like this:
>> all drive accesses can't process, when not cached in ram, so every app
>> that is loaded in the ram, continues to function, but at the moment it
>> tries to access the drive it freezes, until the drive is reset and
>> those abort status messages appear in the dmesg, after that system is
>> unfrozen for a moment, if you keep copying the files then the problem
>> reoccurs once again.
>> 
>> This drive is known to have problems with the power management in the
>> past:
>> https://wiki.archlinux.org/title/Solid_state_drive/NVMe#Troubleshooting
>> But those problems where since fixed with kernel workarounds /
>> firmware updates. This issue is may be related, perhaps bcachefs does
>> something different from the other filesystems, and workarounds don't
>> apply, which causes the bug to occur only on it. It may be a problem
>> in the nvme subsystem, or just some edge case in the bcachefs too, who
>> knows. I tried to disable ASPM and setting latency to 0 like was
>> suggested, it didn't fix the problem, so I don't know. If this is
>> indeed related to that specific drive it would be hard to reproduce.
> 
> From a quick look, looks like a broken drive/firmware. It is suspicious
> that all failed IO is 256 blocks. You could try and limit the transfer
> size and see if that helps:
> 
> # echo 64 > /sys/block/nvme0n1/queue/max_sectors_kb
> 
> Or maybe the transfer size is just a red herring, who knows. The error
> code seems wonky:
> 
>> [  185.384762] nvme0n1: I/O Cmd(0x2) @ LBA 105272408, 256 blocks, I/O 
>> Error (sct 0x3 / sc 0x71)

Changing max_sectors_kb to 64 does indeed seem to fix the issue at the 
first glance, default value is 128.
Also tried changing bcachefs flags during the format 
--btree_node_size=64k --bucket=64k
thought maybe that is related, but that didn't help.
It is really weird that this problem only occurs on bcachefs.