[PATCHv2 4/5] nvme: use return value from blk_execute_rq()

[Yuanyuan Zhong]

On Mon, Apr 26, 2021 at 10:15 AM Keith Busch <kbusch at kernel.org> wrote:
>
> On Mon, Apr 26, 2021 at 10:10:09AM -0700, Yuanyuan Zhong wrote:
> > On Fri, Apr 23, 2021 at 3:06 PM Keith Busch <kbusch at kernel.org> wrote:
> > >
> > > We don't have an nvme status to report if the driver's .queue_rq()
> > > returns an error without dispatching the requested nvme command. Use the
> > > return value from blk_execute_rq() for all passthrough commands so the
> > > caller may know their command was not successful.
> > >
> > > If the command is from the target passthrough interface and fails to
> > > dispatch, synthesize the response back to the host as a internal target
> > > error.
> > >
> > > Signed-off-by: Keith Busch <kbusch at kernel.org>
> > > ---
> > >  drivers/nvme/host/core.c       | 16 ++++++++++++----
> > >  drivers/nvme/host/ioctl.c      |  6 +-----
> > >  drivers/nvme/host/nvme.h       |  2 +-
> > >  drivers/nvme/target/passthru.c |  8 ++++----
> > >  4 files changed, 18 insertions(+), 14 deletions(-)
> > >
> > > diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> > > index 10bb8406e067..62af5fe7a0ce 100644
> > > --- a/drivers/nvme/host/core.c
> > > +++ b/drivers/nvme/host/core.c
> > > @@ -972,12 +972,12 @@ int __nvme_submit_sync_cmd(struct request_queue *q, struct nvme_command *cmd,
> > >                         goto out;
> > >         }
> > >
> > > -       blk_execute_rq(NULL, req, at_head);
> > > +       ret = blk_execute_rq(NULL, req, at_head);
> > >         if (result)
> > >                 *result = nvme_req(req)->result;
> > >         if (nvme_req(req)->flags & NVME_REQ_CANCELLED)
> > >                 ret = -EINTR;
> > > -       else
> > > +       else if (nvme_req(req)->status)
> >
> > Since nvme_req(req)->status is uninitialized for a command failed to dispatch,
> > it's valid only if ret from blk_execute_rq() is 0.
>
> That's not quite right. If queue_rq() succeeds, but the SSD returns an
> error, blk_execute_rq() returns a non-zero value with a valid nvme_req
> status.

Agreed. But after that, freeing the req let nvme_req(req)->status from SSD stay.
If the same req get re-allocated and get dispatching failure,
shouldn't the dispatching
error take precedence over the stale nvme_req(req)->status?