xprtrdma: Reduce required number of send SGEs
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@broadcom.com>
Reported-by: Devesh Sharma <devesh.sharma@broadcom.com>
Reported-by: Honggang Li <honli@redhat.com>
Reported-by: Ram Amrani <Ram.Amrani@cavium.com>
Fixes: 655fec6987be ("xprtrdma: Use gathered Send for large ...")
Cc: stable@vger.kernel.org # v4.9+
Tested-by: Honggang Li <honli@redhat.com>
Tested-by: Ram Amrani <Ram.Amrani@cavium.com>
Tested-by: Steve Wise <swise@opengridcomputing.com>
Reviewed-by: Parav Pandit <parav@mellanox.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c b/net/sunrpc/xprtrdma/rpc_rdma.c
index c634f0f..d889883 100644
--- 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 rpcrdma_xprt *r_xprt)
/* 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