On Mon, May 15, 2017 at 11:09:06AM -0400, Chuck Lever wrote:
>
> > On May 15, 2017, at 10:57 AM, Leon Romanovsky <leon@xxxxxxxxxx> wrote:
> >
> > On Mon, May 15, 2017 at 10:52:44AM -0400, Chuck Lever wrote:
> >> The fourth parameter of the module_param_named macro is a set of
> >> file permissions. Passing 0 there means that module parameter is
> >> not created and that adding "options ib_core force_mr=1" to a
> >> modprobe.conf file has no effect.
> >>
> >> The default setting of rdma_rw_force_mr continues to be 0, or false.
> >>
> >> Fixes: a060b5629ab0 ("IB/core: generic RDMA READ/WRITE API")
> >> Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
> >
> > Chuck,
> >
> > Do we really need this parameter?
>
> Hi Leon-
>
> Christoph and Sagi introduced this with the new rdma_rw API.
> The default behavior is to avoid the use of FRWR, even for
> devices that can support FRWR but also work without. FRWR is
> used only for iWARP devices, which require it; but FRWR can
> have a (slight) negative performance impact, which is why it
> is not the default.
>
> The purpose of this module parameter is to enable the use of
> FRWR for devices that can go either way, as a way to test the
> FRWR capability when using those devices.
>
> I'm not sure we _need_ to have the module parameter. But I've
> certainly used it while developing the NFSD conversion to use
> the rdma_rw API, since I have no iWARP devices here.
I asked that question because commit a060b5629ab0 was added a year ago
and since then no one noticed that it is not usable, including authors.
I think that we can safely remove it and for development, we can set
rdma_rw_force_mr internally in the code.
Thanks
>
>
> >> ---
> >> drivers/infiniband/core/rw.c | 2 +-
> >> 1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/infiniband/core/rw.c b/drivers/infiniband/core/rw.c
> >> index dbfd854..1cc8f07 100644
> >> --- a/drivers/infiniband/core/rw.c
> >> +++ b/drivers/infiniband/core/rw.c
> >> @@ -23,7 +23,7 @@ enum {
> >> };
> >>
> >> static bool rdma_rw_force_mr;
> >> -module_param_named(force_mr, rdma_rw_force_mr, bool, 0);
> >> +module_param_named(force_mr, rdma_rw_force_mr, bool, 0644);
> >> MODULE_PARM_DESC(force_mr, "Force usage of MRs for RDMA READ/WRITE operations");
> >>
> >> /*
> >>
> >> --
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>
> --
> Chuck Lever
>
>
>
> --
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