Re: [PATCH] block/sd: Return -EREMOTEIO when WRITE SAME and DISCARD are disabled

["Martin K. Petersen" <martin.petersen@oracle.com>]

>>>>> "Yiwen" == jiangyiwen  <jiangyiwen@huawei.com> writes:

Yiwen,

Yiwen> First, I don't understand why blk_peek_request() return
Yiwen> EREMOTEIO, as I know, in this situation we only prepare scsi
Yiwen> command without sending to device, and I think EREMOTEIO should
Yiwen> be returned only when IO has already sent to device, maybe I
Yiwen> don't understand definition of EREMOTEIO.  So, Why don't return
Yiwen> the errno with EOPNOTSUPP?

DM currently has special handling for EREMOTEIO failures (because that's
what we'd return when a device responds with ILLEGAL REQUEST).

I am not opposed to returning EOPNOTSUPP but it would require more
changes and since this is a bugfix for stable I want to keep it as small
as possible.

Yiwen> In addition, I still worried with whether there has other
Yiwen> situations which will return EIO or other error. In this way,
Yiwen> MD/DM still can happen this type of problem, so I think may be in
Yiwen> multipath we still needs a protection to avoid it.

There are various error scenarios where we can end up bailing with a
BLKPREP_KILL. But the general rule of thumb is that these conditions all
demand a retry. The optional commands like WRITE SAME and UNMAP are
special in that they are irrecoverable.

Yiwen> At last, I have a additional problem, I remember that you
Yiwen> previously send a series of patches about XCOPY, why don't have
Yiwen> any news latter later? I very much expect that I can see these
Yiwen> patches which are merged into kernel.

I am working on a refresh of the series that includes token-based copy
offload support in addition to EXTENDED COPY. The patches depend on Mike
Christie's request flag patch series which has yet to be merged.

-- 
Martin K. Petersen	Oracle Linux Engineering