[pve-devel] [PATCH pve-storage] lvm: use blkdiscard instead cstream to saferemove drive

[DERUMIER, Alexandre]

The doc from ovirt was a little bit old,

REQ_OP_WRITE_SAME is not used anymore in recent kernel,

REQ_OP_WRITE_ZEROES is used since 2017, and

/sys/block/dm-25/queue/write_zeroes_max_bytes

show if the feature is available. 

(it's was enabled on my test machine, that's why blkdiscard is a lot
faster than cstream)