Re: [dm-devel] do not disable ext4 discards on first discard failure? [was: Re: dm snapshot: ignore discards issued to the snapshot-origin target]

[Alasdair G Kergon <agk redhat com>]

On Mon, May 02, 2011 at 09:16:21AM +0200, Lukas Czerner wrote:
> However when we have dm device where part of the device supports
> discard due to underlying hardware capability we just can not return
> EOPNOTSUPP from blkdev_issue_discard, because it is just not true! 

EOPNOTSUPP from dm means the operation was not supported on that *one* bio.
It does *not* tell you anything in general about the device, or whether
you'd get the same error from different bios in future.

Alasdair