On Tue, Feb 2, 2021 at 2:24 PM Tom Talpey <tom@xxxxxxxxxx> wrote:
>
> What's not to like about a log that uses the words "with aplomb"? :)
As far as I can tell, it'll be the first use of "aplomb" in the entire
kernel git history
>
> Minor related comment/question below.
>
> On 2/2/2021 9:42 AM, Chuck Lever wrote:
> > Clean up.
> >
> > Support for FMR was removed by commit ba69cd122ece ("xprtrdma:
> > Remove support for FMR memory registration") [Dec 2018]. That means
> > the buffer-splitting behavior of rpcrdma_convert_kvec(), added by
> > commit 821c791a0bde ("xprtrdma: Segment head and tail XDR buffers
> > on page boundaries") [Mar 2016], is no longer necessary. FRWR
> > memory registration handles this case with aplomb.
> >
> > A related simplification removes an extra conditional branch from
> > the SGL set-up loop in frwr_map(): Instead of using either
> > sg_set_page() or sg_set_buf(), initialize the mr_page field properly
> > when rpcrdma_convert_kvec() converts the kvec to an SGL entry.
> > frwr_map() can then invoke sg_set_page() unconditionally.
> >
> > Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
> > ---
> > net/sunrpc/xprtrdma/frwr_ops.c | 10 ++--------
> > net/sunrpc/xprtrdma/rpc_rdma.c | 21 +++++----------------
> > net/sunrpc/xprtrdma/xprt_rdma.h | 2 +-
> > 3 files changed, 8 insertions(+), 25 deletions(-)
> >
> > diff --git a/net/sunrpc/xprtrdma/frwr_ops.c b/net/sunrpc/xprtrdma/frwr_ops.c
> > index baca49fe83af..5eb044a5f0be 100644
> > --- a/net/sunrpc/xprtrdma/frwr_ops.c
> > +++ b/net/sunrpc/xprtrdma/frwr_ops.c
> > @@ -306,14 +306,8 @@ struct rpcrdma_mr_seg *frwr_map(struct rpcrdma_xprt *r_xprt,
> > if (nsegs > ep->re_max_fr_depth)
> > nsegs = ep->re_max_fr_depth;
> > for (i = 0; i < nsegs;) {
> > - if (seg->mr_page)
> > - sg_set_page(&mr->mr_sg[i],
> > - seg->mr_page,
> > - seg->mr_len,
> > - offset_in_page(seg->mr_offset));
> > - else
> > - sg_set_buf(&mr->mr_sg[i], seg->mr_offset,
> > - seg->mr_len);
> > + sg_set_page(&mr->mr_sg[i], seg->mr_page,
> > + seg->mr_len, offset_in_page(seg->mr_offset));
> >
> > ++seg;
> > ++i;
> > diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c b/net/sunrpc/xprtrdma/rpc_rdma.c
> > index 8f5d0cb68360..529adb6ad4db 100644
> > --- a/net/sunrpc/xprtrdma/rpc_rdma.c
> > +++ b/net/sunrpc/xprtrdma/rpc_rdma.c
> > @@ -204,9 +204,7 @@ rpcrdma_alloc_sparse_pages(struct xdr_buf *buf)
> > return 0;
> > }
> >
> > -/* Split @vec on page boundaries into SGEs. FMR registers pages, not
> > - * a byte range. Other modes coalesce these SGEs into a single MR
> > - * when they can.
> > +/* Convert @vec to a single SGL element.
> > *
> > * Returns pointer to next available SGE, and bumps the total number
> > * of SGEs consumed.
> > @@ -215,21 +213,12 @@ static struct rpcrdma_mr_seg *
> > rpcrdma_convert_kvec(struct kvec *vec, struct rpcrdma_mr_seg *seg,
> > unsigned int *n)
> > {
> > - u32 remaining, page_offset;
> > - char *base;
> > -
> > - base = vec->iov_base;
> > - page_offset = offset_in_page(base);
> > - remaining = vec->iov_len;
> > - while (remaining) {
> > - seg->mr_page = NULL;
> > - seg->mr_offset = base;
> > - seg->mr_len = min_t(u32, PAGE_SIZE - page_offset, remaining);
> > - remaining -= seg->mr_len;
> > - base += seg->mr_len;
> > + if (vec->iov_len) {
> > + seg->mr_page = virt_to_page(vec->iov_base);
> > + seg->mr_offset = vec->iov_base;
> > + seg->mr_len = vec->iov_len;
> > ++seg;
> > ++(*n);
> > - page_offset = 0;
> > }
> > return seg;
> > }
> > diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
> > index 94b28657aeeb..4a9fe6592795 100644
> > --- a/net/sunrpc/xprtrdma/xprt_rdma.h
> > +++ b/net/sunrpc/xprtrdma/xprt_rdma.h
> > @@ -285,7 +285,7 @@ enum {
> >
> > struct rpcrdma_mr_seg { /* chunk descriptors */
> > u32 mr_len; /* length of chunk or segment */
> > - struct page *mr_page; /* owning page, if any */
> > + struct page *mr_page; /* underlying struct page */
> > char *mr_offset; /* kva if no page, else offset */
>
> Is this comment ("kva if no page") actually correct? The hunk just
> above is an example of a case where mr_page is set, yet mr_offset
> is an iov_base. Is iov_base not a kva?
>
> Tom.
>
> > };
> >
> >
> >
> >
