Discard option

Hi Coli,

I assume this email is irrelevant to the patch “bcache: avoid redundant access RB tree in read_dirty”, am I correct?

Yes you are;  sorry, I picked a message and forgot to change the title

The discard option is not recommended. Indeed in next merge window I will submit a patch series to drop the discard option.

OK, I will boot on a Live USB Key to wipe the caching device and create 
a new one without discard option.

But should I keep the discard mount option in fstab for the logical 
volumes inside bcache ?

Thanks,

Regards

_______________

Le 21/10/2025 à 03:18, Coly Li a écrit :
>> 2025年10月21日 00:39，Pierre Juhen <[email protected]> 写道：
>>
>> Hi
>> I am on kernel 6.16.12.
>> I have had errors with bcache recently, And I lost my fronted 3 or 4 times :
>> oct. 20 15:37:40 pierre.juhen kernel: bcache: journal_read_bucket() 128: bad csum, 32768 bytes, offset 0
>> oct. 20 15:37:40 pierre.juhen kernel: bcache: journal_read_bucket() 64: bad csum, 22928 bytes, offset 0
>> oct. 20 15:37:40 pierre.juhen kernel: bcache: journal_read_bucket() 32: bad csum, 4848 bytes, offset 2
>> oct. 20 15:37:40 pierre.juhen kernel: bcache: journal_read_bucket() 48: bad csum, 14096 bytes, offset 0
>> oct. 20 15:37:40 pierre.juhen (udev-worker)[461]: nvme0n1p3: Process 'bcache-register /dev/nvme0n1p3' failed with exit code 1.
>> oct. 20 15:37:40 pierre.juhen kernel: bcache: prio_read() bad csum reading priorities
>> oct. 20 15:37:40 pierre.juhen kernel: bcache: bch_cache_set_error() error on 448f191c-28df-4396-bc44-14d1f77c9005: IO error reading priorities, disabling caching
>> oct. 20 15:37:40 pierre.juhen kernel: bcache: register_bcache() error : failed to register device
>>
> I assume this email is irrelevant to the patch “bcache: avoid redundant access RB tree in read_dirty”, am I correct?
>
>
>> I had to reconfigure everything after a disk problem.
>> I have been running bcache for years now, without any problems.
>> The only difference might be that I configured the frontend with the discard option.
> The discard option is not recommended. Indeed in next merge window I will submit a patch series to drop the discard option.
>
>
>> The logical volume using bcache have also a discard option in fstab.
>> The frontend is on a Samsung 980 nvme disk.
> Try not to enable discard on cache device. This option will disappear soon.
>
> I don’t know whether discard option of Samsung 980 nvme disk may change the content of discarded LBA or not, from NVMe spec, it could be zero-filled or undefined.
> Anyway in current code discard doesn’t help performance, I suggest to not enable discard and see whether the issue still shows up.
>
> My suggestion is: always use default configuration, all our test case and performance optimization are for default configurations.
>
> Thanks.
>
> Coly Li
>