Re: bcache detach lead to xfs force shutdown

[Nix <nix@esperi.org.uk>]

On 2 Mar 2022, Coly Li verbalised:

> On 2/23/22 8:26 PM, Zhang Zhen wrote:
>> The reproduce opreation as follows:
>> 1. mount a bcache disk with xfs
>>
>> /dev/bcache1 on /media/disk1 type xfs
>>
>> 2. run ls in background
>> #!/bin/bash
>>
>> while true
>> do
>>   echo 2 > /proc/sys/vm/drop_caches
>>   ls -R /media/disk1 > /dev/null
>> done
>>
>>
>> 3. remove cache disk sdc
>> echo 1 >/sys/block/sdc/device/delete
>>
>> 4. dmesg should get xfs error
>>
>> I write a patch to improve，please help to review it, thanks.
>
> Hold on. Why do you think it should be fixed? As I said, it is as-designed behavior.

I was thinking exactly as you were... but, y'know, this might be a
genuine resiliency improvement, *if* done only when the cache is
writearound (or none, I suppose!). Obviously if writes are being cached
a cache device failure must trigger I/O failures visible to userspace...
but if it's just speeding up the underlying device, having it fail would
ideally just fail it out and cause all I/Os to proceed uncached,
including the one that was underway when the cache I/O error was
encountered.

-- 
NULL && (void)