I guess the client code doesn't verify that the device supports the chosen memreg mode. That's not good. Lemme fix this and respin this patch.

On 5/16/2014 2:08 AM, Devesh Sharma wrote:
Chuck

This patch is causing a CPU soft-lockup if underlying vendor reports 
devattr.max_fast_reg_pagr_list_len = 0 and ia->ri_memreg_strategy = FRMR 
(Default option).
I think there is need to refer to device capability flags. If strategy = FRMR 
is forced and devattr.max_fast_reg_pagr_list_len=0 then flash an error and fail 
RPC with -EIO.

See inline:

-----Original Message-----
From: [email protected] [mailto:linux-rdma-
[email protected]] On Behalf Of Chuck Lever
Sent: Thursday, May 01, 2014 1:00 AM
To: [email protected]; [email protected]
Cc: [email protected]
Subject: [PATCH V3 01/17] xprtrdma: mind the device's max fast register
page list depth

From: Steve Wise <[email protected]>

Some rdma devices don't support a fast register page list depth of at least
RPCRDMA_MAX_DATA_SEGS.  So xprtrdma needs to chunk its fast register
regions according to the minimum of the device max supported depth or
RPCRDMA_MAX_DATA_SEGS.

Signed-off-by: Steve Wise <[email protected]>
Reviewed-by: Chuck Lever <[email protected]>
---

  net/sunrpc/xprtrdma/rpc_rdma.c  |    4 ---
  net/sunrpc/xprtrdma/verbs.c     |   47 +++++++++++++++++++++++++++++-
---------
  net/sunrpc/xprtrdma/xprt_rdma.h |    1 +
  3 files changed, 36 insertions(+), 16 deletions(-)

diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c
b/net/sunrpc/xprtrdma/rpc_rdma.c index 96ead52..400aa1b 100644
--- a/net/sunrpc/xprtrdma/rpc_rdma.c
+++ b/net/sunrpc/xprtrdma/rpc_rdma.c
@@ -248,10 +248,6 @@ rpcrdma_create_chunks(struct rpc_rqst *rqst, struct
xdr_buf *target,
        /* success. all failures return above */
        req->rl_nchunks = nchunks;

-       BUG_ON(nchunks == 0);
-       BUG_ON((r_xprt->rx_ia.ri_memreg_strategy == RPCRDMA_FRMR)
-              && (nchunks > 3));
-
        /*
         * finish off header. If write, marshal discrim and nchunks.
         */
diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c
index 9372656..55fb09a 100644
--- a/net/sunrpc/xprtrdma/verbs.c
+++ b/net/sunrpc/xprtrdma/verbs.c
@@ -539,6 +539,11 @@ rpcrdma_ia_open(struct rpcrdma_xprt *xprt, struct
sockaddr *addr, int memreg)
                                __func__);
                        memreg = RPCRDMA_REGISTER;
  #endif
+               } else {
+                       /* Mind the ia limit on FRMR page list depth */
+                       ia->ri_max_frmr_depth = min_t(unsigned int,
+                               RPCRDMA_MAX_DATA_SEGS,
+                               devattr.max_fast_reg_page_list_len);
                }
                break;
        }
@@ -659,24 +664,42 @@ rpcrdma_ep_create(struct rpcrdma_ep *ep, struct
rpcrdma_ia *ia,
        ep->rep_attr.srq = NULL;
        ep->rep_attr.cap.max_send_wr = cdata->max_requests;
        switch (ia->ri_memreg_strategy) {
-       case RPCRDMA_FRMR:
+       case RPCRDMA_FRMR: {
+               int depth = 7;
+
                /* Add room for frmr register and invalidate WRs.
                 * 1. FRMR reg WR for head
                 * 2. FRMR invalidate WR for head
-                * 3. FRMR reg WR for pagelist
-                * 4. FRMR invalidate WR for pagelist
+                * 3. N FRMR reg WRs for pagelist
+                * 4. N FRMR invalidate WRs for pagelist
                 * 5. FRMR reg WR for tail
                 * 6. FRMR invalidate WR for tail
                 * 7. The RDMA_SEND WR
                 */
-               ep->rep_attr.cap.max_send_wr *= 7;
+
+               /* Calculate N if the device max FRMR depth is smaller than
+                * RPCRDMA_MAX_DATA_SEGS.
+                */
+               if (ia->ri_max_frmr_depth < RPCRDMA_MAX_DATA_SEGS) {
+                       int delta = RPCRDMA_MAX_DATA_SEGS -
+                                   ia->ri_max_frmr_depth;
+
+                       do {
+                               depth += 2; /* FRMR reg + invalidate */
+                               delta -= ia->ri_max_frmr_depth;
If ia->ri_max_frmr_depth is = 0. This loop becomes infinite loop.

+                       } while (delta > 0);
+
+               }
+               ep->rep_attr.cap.max_send_wr *= depth;
                if (ep->rep_attr.cap.max_send_wr > devattr.max_qp_wr) {
-                       cdata->max_requests = devattr.max_qp_wr / 7;
+                       cdata->max_requests = devattr.max_qp_wr / depth;
                        if (!cdata->max_requests)
                                return -EINVAL;
-                       ep->rep_attr.cap.max_send_wr = cdata-
max_requests * 7;
+                       ep->rep_attr.cap.max_send_wr = cdata-
max_requests *
+                                                      depth;
                }
                break;
+       }
        case RPCRDMA_MEMWINDOWS_ASYNC:
        case RPCRDMA_MEMWINDOWS:
                /* Add room for mw_binds+unbinds - overkill! */ @@ -
1043,16 +1066,16 @@ rpcrdma_buffer_create(struct rpcrdma_buffer *buf,
struct rpcrdma_ep *ep,
        case RPCRDMA_FRMR:
                for (i = buf->rb_max_requests * RPCRDMA_MAX_SEGS; i; i--
) {
                        r->r.frmr.fr_mr = ib_alloc_fast_reg_mr(ia->ri_pd,
-
RPCRDMA_MAX_SEGS);
+                                               ia->ri_max_frmr_depth);
                        if (IS_ERR(r->r.frmr.fr_mr)) {
                                rc = PTR_ERR(r->r.frmr.fr_mr);
                                dprintk("RPC:       %s: ib_alloc_fast_reg_mr"
                                        " failed %i\n", __func__, rc);
                                goto out;
                        }
-                       r->r.frmr.fr_pgl =
-                               ib_alloc_fast_reg_page_list(ia->ri_id-
device,
-
RPCRDMA_MAX_SEGS);
+                       r->r.frmr.fr_pgl = ib_alloc_fast_reg_page_list(
+                                               ia->ri_id->device,
+                                               ia->ri_max_frmr_depth);
                        if (IS_ERR(r->r.frmr.fr_pgl)) {
                                rc = PTR_ERR(r->r.frmr.fr_pgl);
                                dprintk("RPC:       %s: "
@@ -1498,8 +1521,8 @@ rpcrdma_register_frmr_external(struct
rpcrdma_mr_seg *seg,
        seg1->mr_offset -= pageoff;  /* start of page */
        seg1->mr_len += pageoff;
        len = -pageoff;
-       if (*nsegs > RPCRDMA_MAX_DATA_SEGS)
-               *nsegs = RPCRDMA_MAX_DATA_SEGS;
+       if (*nsegs > ia->ri_max_frmr_depth)
+               *nsegs = ia->ri_max_frmr_depth;
        for (page_no = i = 0; i < *nsegs;) {
                rpcrdma_map_one(ia, seg, writing);
                pa = seg->mr_dma;
diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h
b/net/sunrpc/xprtrdma/xprt_rdma.h index cc1445d..98340a3 100644
--- a/net/sunrpc/xprtrdma/xprt_rdma.h
+++ b/net/sunrpc/xprtrdma/xprt_rdma.h
@@ -66,6 +66,7 @@ struct rpcrdma_ia {
        struct completion       ri_done;
        int                     ri_async_rc;
        enum rpcrdma_memreg     ri_memreg_strategy;
+       unsigned int            ri_max_frmr_depth;
  };

  /*

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