[PATCH] nvme: implement the DEAC bit for the Write Zeroes command

[Martin K. Petersen]

Keith,

> The device must return all 0's for the range covered by a write zeroes
> command no matter what. The controller shall not deallocate the
> logical blocks if it can't guarantee reading deallocated blocks will
> return 0's, so I think it's okay to skip checking the lower dlfeat
> bits.

The spec is sufficiently vague for the does-not-return-zeroes case that
I'm concerned about "shall not deallocate" being interpreted by vendors
as "free to ignore" based on past ATA/SCSI experience.

But we can always quirk it. Devices that return all-Fs are rare.

-- 
Martin K. Petersen	Oracle Linux Engineering