This is a note to let you know that I've just added the patch titled xprtrdma: Reduce required number of send SGEs to the 4.10-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: xprtrdma-reduce-required-number-of-send-sges.patch and it can be found in the queue-4.10 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 16f906d66cd76fb9895cbc628f447532a7ac1faa Mon Sep 17 00:00:00 2001 From: Chuck Lever <chuck.lever@xxxxxxxxxx> Date: Wed, 8 Feb 2017 17:00:10 -0500 Subject: xprtrdma: Reduce required number of send SGEs From: Chuck Lever <chuck.lever@xxxxxxxxxx> commit 16f906d66cd76fb9895cbc628f447532a7ac1faa upstream. The MAX_SEND_SGES check introduced in commit 655fec6987be ("xprtrdma: Use gathered Send for large inline messages") fails for devices that have a small max_sge. Instead of checking for a large fixed maximum number of SGEs, check for a minimum small number. RPC-over-RDMA will switch to using a Read chunk if an xdr_buf has more pages than can fit in the device's max_sge limit. This is considerably better than failing all together to mount the server. This fix supports devices that have as few as three send SGEs available. Reported-by: Selvin Xavier <selvin.xavier@xxxxxxxxxxxx> Reported-by: Devesh Sharma <devesh.sharma@xxxxxxxxxxxx> Reported-by: Honggang Li <honli@xxxxxxxxxx> Reported-by: Ram Amrani <Ram.Amrani@xxxxxxxxxx> Fixes: 655fec6987be ("xprtrdma: Use gathered Send for large ...") Tested-by: Honggang Li <honli@xxxxxxxxxx> Tested-by: Ram Amrani <Ram.Amrani@xxxxxxxxxx> Tested-by: Steve Wise <swise@xxxxxxxxxxxxxxxxxxxxx> Reviewed-by: Parav Pandit <parav@xxxxxxxxxxxx> Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx> Signed-off-by: Anna Schumaker <Anna.Schumaker@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- net/sunrpc/xprtrdma/rpc_rdma.c | 26 +++++++++++++++++++++++--- net/sunrpc/xprtrdma/verbs.c | 13 +++++++------ net/sunrpc/xprtrdma/xprt_rdma.h | 2 ++ 3 files changed, 32 insertions(+), 9 deletions(-) --- a/net/sunrpc/xprtrdma/rpc_rdma.c +++ b/net/sunrpc/xprtrdma/rpc_rdma.c @@ -125,14 +125,34 @@ void rpcrdma_set_max_header_sizes(struct /* The client can send a request inline as long as the RPCRDMA header * plus the RPC call fit under the transport's inline limit. If the * combined call message size exceeds that limit, the client must use - * the read chunk list for this operation. + * a Read chunk for this operation. + * + * A Read chunk is also required if sending the RPC call inline would + * exceed this device's max_sge limit. */ static bool rpcrdma_args_inline(struct rpcrdma_xprt *r_xprt, struct rpc_rqst *rqst) { - struct rpcrdma_ia *ia = &r_xprt->rx_ia; + struct xdr_buf *xdr = &rqst->rq_snd_buf; + unsigned int count, remaining, offset; - return rqst->rq_snd_buf.len <= ia->ri_max_inline_write; + if (xdr->len > r_xprt->rx_ia.ri_max_inline_write) + return false; + + if (xdr->page_len) { + remaining = xdr->page_len; + offset = xdr->page_base & ~PAGE_MASK; + count = 0; + while (remaining) { + remaining -= min_t(unsigned int, + PAGE_SIZE - offset, remaining); + offset = 0; + if (++count > r_xprt->rx_ia.ri_max_send_sges) + return false; + } + } + + return true; } /* The client can't know how large the actual reply will be. Thus it --- a/net/sunrpc/xprtrdma/verbs.c +++ b/net/sunrpc/xprtrdma/verbs.c @@ -488,18 +488,19 @@ rpcrdma_ia_close(struct rpcrdma_ia *ia) */ int rpcrdma_ep_create(struct rpcrdma_ep *ep, struct rpcrdma_ia *ia, - struct rpcrdma_create_data_internal *cdata) + struct rpcrdma_create_data_internal *cdata) { struct rpcrdma_connect_private *pmsg = &ep->rep_cm_private; + unsigned int max_qp_wr, max_sge; struct ib_cq *sendcq, *recvcq; - unsigned int max_qp_wr; int rc; - if (ia->ri_device->attrs.max_sge < RPCRDMA_MAX_SEND_SGES) { - dprintk("RPC: %s: insufficient sge's available\n", - __func__); + max_sge = min(ia->ri_device->attrs.max_sge, RPCRDMA_MAX_SEND_SGES); + if (max_sge < RPCRDMA_MIN_SEND_SGES) { + pr_warn("rpcrdma: HCA provides only %d send SGEs\n", max_sge); return -ENOMEM; } + ia->ri_max_send_sges = max_sge - RPCRDMA_MIN_SEND_SGES; if (ia->ri_device->attrs.max_qp_wr <= RPCRDMA_BACKWARD_WRS) { dprintk("RPC: %s: insufficient wqe's available\n", @@ -524,7 +525,7 @@ rpcrdma_ep_create(struct rpcrdma_ep *ep, ep->rep_attr.cap.max_recv_wr = cdata->max_requests; ep->rep_attr.cap.max_recv_wr += RPCRDMA_BACKWARD_WRS; ep->rep_attr.cap.max_recv_wr += 1; /* drain cqe */ - ep->rep_attr.cap.max_send_sge = RPCRDMA_MAX_SEND_SGES; + ep->rep_attr.cap.max_send_sge = max_sge; ep->rep_attr.cap.max_recv_sge = 1; ep->rep_attr.cap.max_inline_data = 0; ep->rep_attr.sq_sig_type = IB_SIGNAL_REQ_WR; --- a/net/sunrpc/xprtrdma/xprt_rdma.h +++ b/net/sunrpc/xprtrdma/xprt_rdma.h @@ -74,6 +74,7 @@ struct rpcrdma_ia { unsigned int ri_max_frmr_depth; unsigned int ri_max_inline_write; unsigned int ri_max_inline_read; + unsigned int ri_max_send_sges; bool ri_reminv_expected; bool ri_implicit_roundup; enum ib_mr_type ri_mrtype; @@ -311,6 +312,7 @@ struct rpcrdma_mr_seg { /* chunk descri * - xdr_buf tail iovec */ enum { + RPCRDMA_MIN_SEND_SGES = 3, RPCRDMA_MAX_SEND_PAGES = PAGE_SIZE + RPCRDMA_MAX_INLINE - 1, RPCRDMA_MAX_PAGE_SGES = (RPCRDMA_MAX_SEND_PAGES >> PAGE_SHIFT) + 1, RPCRDMA_MAX_SEND_SGES = 1 + 1 + RPCRDMA_MAX_PAGE_SGES + 1, Patches currently in stable-queue which might be from chuck.lever@xxxxxxxxxx are queue-4.10/xprtrdma-disable-pad-optimization-by-default.patch queue-4.10/xprtrdma-fix-read-chunk-padding.patch queue-4.10/xprtrdma-reduce-required-number-of-send-sges.patch queue-4.10/nfsd-special-case-truncates-some-more.patch queue-4.10/xprtrdma-per-connection-pad-optimization.patch