Martin K. Petersen wrote:
>>>>>> "Ric" == Ric Wheeler <ricwheeler@xxxxxxxxx> writes:
>
>>> so we're not depending on it zeroing blocks, we're just depending on
>>> it advertising correctly whether or not it -does- zero.
>
> If the relevant bits are set (ATA: DRAT and RZAT, SCSI: TPRZ) we'll set
> the bdev's discard_zeroes_data flag.
>
> [root@test ~]# lsscsi | grep SSD | awk '{ print $7 }'
> /dev/sde
> [root@test ~]# grep . /sys/block/sde/queue/discard_zeroes_data
> 1
>
> The relevant ioctl is BLKDISCARDZEROES.
which is what that patch I pointed to uses, BTW...
I really think it's on firm footing here, we're not assuming
discard == zeroed data, we are checking whether the drive
reports exactly that behavior ...
-Eric
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