Re: [blktests] zbd/012: Test requeuing of zoned writes and queue freezing

[Damien Le Moal <dlemoal@kernel.org>]

On 11/28/24 08:36, Bart Van Assche wrote:
> 
> On 11/27/24 3:18 PM, Damien Le Moal wrote:
>> The BIO that failed is not recovered. The user will see the failure. The error
>> recovery report zones is all about avoiding more failures of plugged zone append
>> BIOs behind that failed BIO. These can succeed with the error recovery.
>>
>> So sure, we can fail all BIOs. The user will see more failures. If that is OK,
>> that's easy to do. But in the end, that is not a solution because we still need
>> to get an updated zone write pointer to be able to restart zone append
>> emulation. Otherwise, we are in the dark and will not know where to send the
>> regular writes emulating zone append. That means that we still need to issue a
>> zone report and that is racing with queue freeze and reception of a new BIO. We
>> cannot have new BIOs "wait" for the zone report as that would create a hang
>> situation again if a queue freeze is started between reception of the new BIO
>> and the zone report. Do we fail these new BIOs too ? That seems extreme.
> 
> This patch removes the disk->fops->report_zones() call from the
> blk-zoned.c code:
> https://lore.kernel.org/linux-block/20241119002815.600608-6-bvanassche@acm.org/. 
> Is it really not possible to get that
> approach working for SAS SMR drives? If a torn write happens, is the
> residual information in the response from the drive reliable?

Let me dig into this again and see if that can work.


-- 
Damien Le Moal
Western Digital Research