On Thu, Nov 12, 2020 at 08:59:45PM +0100, Klaus Jensen wrote:
> From: Klaus Jensen <k.jen...@samsung.com>
>
> Add support for the Dataset Management command and the Deallocate
> attribute. Deallocation results in discards being sent to the underlying
> block device. Whether of not the blocks are actually deallocated is
> affected by the same factors as Write Zeroes (see previous commit).
>
> format | discard | dsm (512B) dsm (4KiB) dsm (64KiB)
> --------------------------------------------------------
> qcow2 ignore n n n
> qcow2 unmap n n y
> raw ignore n n n
> raw unmap n y y
>
> Again, a raw format and 4KiB LBAs are preferable.
>
> In order to set the Namespace Preferred Deallocate Granularity and
> Alignment fields (NPDG and NPDA), choose a sane minimum discard
> granularity of 4KiB. If we are using a passthru device supporting
> discard at a 512B granularity, user should set the discard_granularity
> property explicitly. NPDG and NPDA will also account for the
> cluster_size of the block driver if required (i.e. for QCOW2).
>
> See NVM Express 1.3d, Section 6.7 ("Dataset Management command").
Looks good to me.
Reviewed-by: Keith Busch <kbu...@kernel.org>
