Messages in this thread | | | Date | Wed, 12 Oct 2011 13:21:30 -0400 | From | Konrad Rzeszutek Wilk <> | Subject | Re: [Xen-devel] [PATCH 3/3] xen/blk[front|back]: Enhance discard support with secure erasing support. |
| |
> > if (operation != REQ_DISCARD) > > /* Check that the number of segments is sane. */ > > nseg = req->nr_segments; > > else > > nseg = 0; > > Right above this hunk is a switch statement over the req->operation. The > value of req->operation precisely defines the semantics/validity or > otherwise of the req->nr_segments field and whether or not it contains > the nr of segments or (due to the aliasing) something else. Why not set > nsegs inside that switch statement (and explicitly zero it in the other > cases) so that this obvious connection is retained?
Sure. > > > > > if (unlikely(nseg == 0 && operation != WRITE_FLUSH && > > > > operation != REQ_DISCARD) || > > > > And I guess we can also skip the REQ_DISCARD test here. > > I don't think so, if nseg == 0 and operation == REQ_DISCARD that is > fine, right? The fact that there is all this "operation != xx &&
<nods>
..snip.. > (I think I'm right that BLKIF_OP_FLUSH_DISKCACHE can have associated > data or not)
You are right. > > However do discard and r/w really have so much in common that handling > them all in dispatch_rw_block_io() and relying on nsegs == 0 when the > operation is discard makes sense? > > Would it be clearer if the caller (__do_block_io_op) had this switch > over req->operation and called dispatch_rw_block_io(req, WRITE_FLUSH, > nsegs), dispatch_discard(req) etc as appropriate?
Potentially. It would cut down on this functions bloated size so that is a definite plus.
| |