[lvm-devel] lvmcache lv destroy with no flush

[Zdenek Kabelac]

Dne 05. 08. 19 v 10:45 Lakshmi Narasimhan Sundararajan napsal(a):
> Thanks Zdenek, for your follow up email clarifying my questions.
> 
> I will have to check further and shall report back.
> 
> But, I also wonder why on a writeback cache even if I do submit blkdiscard to 
> the whole device, the dirty blocks do not fall to zero?
> 
> Does blkdiscard on lvmcache device not work?
> 
>  > myhome$ sudo dmsetup status --target cache
> 
>  > pxtest-pool: 0 20963328 cache 8 40/2048 2048 4096/10220 28 58 0 0 0 0 4096 
> 1 writethrough 2 migration_threshold 2048 cleaner 0 rw -
> 
>  > myhome$
> 
>  > myhome$ sudo blkdev –getsize64 /dev/pxtest/pool
> 
> <devsize>
> 
>  >myhome$ sudo blkdiscard -o 0 -l ROUND_DISCARD_ALIGN(devsize) /dev/pxtest/pool
> 
> Even after the above discard, the lvmcache device in writeback mode holds 
> dirty blocks. And has to be flushed. Can you please help explain the behavior 
> here?
> 


Are you using latest kernels ?

Original initial release of cache was (if I remeber correctly) not supporting
discard operation on such device.

On the latest kernels all should work...


Regards

Zdenek