> On Feb 2, 2021, at 2:18 PM, Tom Talpey <tom@xxxxxxxxxx> wrote:
>
> What's not to like about a log that uses the words "with aplomb"? :)
>
> 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?
Ah, well the "if no page" part is now obsolete.
I suppose it should be set to "offset_in_page(vec->iov_base)" ?
--
Chuck Lever
