On Thu, Oct 10, 2019 at 10:02:39AM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <[email protected]>
>
> Currently, if the loop device receives a WRITE_ZEROES request, it asks
> the underlying filesystem to punch out the range. This behavior is
> correct if unmapping is allowed. However, a NOUNMAP request means that
> the caller forbids us from freeing the storage backing the range, so
> punching out the range is incorrect behavior.
It doesn't really forbid, as most protocols don't have a way for forbid
deallocation. It requests not to.
Otherwise this looks fine, although I would have implemented it slightly
differently:
> case REQ_OP_FLUSH:
> return lo_req_flush(lo, rq);
> case REQ_OP_DISCARD:
> - case REQ_OP_WRITE_ZEROES:
> return lo_discard(lo, rq, pos);
> + case REQ_OP_WRITE_ZEROES:
> + return lo_zeroout(lo, rq, pos);
This could just become:
case REQ_OP_WRITE_ZEROES:
if (rq->cmd_flags & REQ_NOUNMAP))
return lo_zeroout(lo, rq, pos);
/*FALLTHRU*/
case REQ_OP_DISCARD:
return lo_discard(lo, rq, pos);
