[pve-devel] [PATCH V3 pve-storage] lvm: use blkdiscard instead cstream to saferemove drive

[Fiona Ebner]

Am 20.10.25 um 9:56 AM schrieb DERUMIER, Alexandre:
> Hi Fiona, I'm going to fix all your comment for this patch
> 
> 
>> +                my $write_zeroes_max_bytes =
>> +                   
>> file_read_firstline("$sysdir/queue/write_zeroes_max_bytes") // 0;
> 
>>> According to the docs: "The value 0 means that REQ_OP_WRITE_ZEROES
>>> is not supported.", so it makes sense as a fallback too. But do we
>>> need
>>> to handle that somehow below, i.e. can --zeroout still be used if the
>>> reported value is 0? Or do we need to fall back to the old way of
>>> doing it?
> 
> I don't have read the code of blkdiscard yet (and don't have found
> device without write zeroes support to test), but according to redhat
> doc
> https://www.ovirt.org/develop/release-management/features/storage/wipe-volumes-using-blkdiscard.html
> 
> "There are no restrictions when using blkdiscard -z, although
> blkdiscard performs roughly the same as dd if the storage does not
> support write same."
> 

At a glance, the implementation of blkdiscard doesn't seem to have a
fallback and will just exit with error if the BLKZEROOUT ioctl() fails:
https://github.com/util-linux/util-linux/blob/stable/v2.41/sys-utils/blkdiscard.c#L303