xprtrdma: Manage MRs in context of a single connection

MRs are now allocated on demand so we can safely throw them away on
disconnect. This way an idle transport can disconnect and it won't
pin hardware MR resources.

Two additional changes:

- Now that all MRs are destroyed on disconnect, there's no need to
  check during header marshaling if a req has MRs to recycle. Each
  req is sent only once per connection, and now rl_registered is
  guaranteed to be empty when rpcrdma_marshal_req is invoked.

- Because MRs are now destroyed in a WQ_MEM_RECLAIM context, they
  also must be allocated in a WQ_MEM_RECLAIM context. This reduces
  the likelihood that device driver memory allocation will trigger
  memory reclaim during NFS writeback.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

1 files changed, 2 insertions, 22 deletions

diff --git a/net/sunrpc/xprtrdma/frwr_ops.c b/net/sunrpc/xprtrdma/frwr_ops.c
index 9901a811f598..37ba82dc2474 100644
--- a/net/sunrpc/xprtrdma/frwr_ops.c
+++ b/net/sunrpc/xprtrdma/frwr_ops.c
@@ -36,8 +36,8 @@
  * connect worker from running concurrently.
  *
  * When the underlying transport disconnects, MRs that are in flight
- * are flushed and are likely unusable. Thus all flushed MRs are
- * destroyed. New MRs are created on demand.
+ * are flushed and are likely unusable. Thus all MRs are destroyed.
+ * New MRs are created on demand.
  */
 
 #include <linux/sunrpc/rpc_rdma.h>
@@ -119,20 +119,6 @@ frwr_mr_recycle_worker(struct work_struct *work)
 	frwr_mr_recycle(mr->mr_xprt, mr);
 }
 
-/* frwr_recycle - Discard MRs
- * @req: request to reset
- *
- * Used after a reconnect. These MRs could be in flight, we can't
- * tell. Safe thing to do is release them.
- */
-void frwr_recycle(struct rpcrdma_req *req)
-{
-	struct rpcrdma_mr *mr;
-
-	while ((mr = rpcrdma_mr_pop(&req->rl_registered)))
-		frwr_mr_recycle(mr->mr_xprt, mr);
-}
-
 /* frwr_reset - Place MRs back on the free list
  * @req: request to reset
  *
@@ -166,9 +152,6 @@ int frwr_init_mr(struct rpcrdma_ia *ia, struct rpcrdma_mr *mr)
 	struct ib_mr *frmr;
 	int rc;
 
-	/* NB: ib_alloc_mr and device drivers typically allocate
-	 *     memory with GFP_KERNEL.
-	 */
 	frmr = ib_alloc_mr(ia->ri_pd, ia->ri_mrtype, depth);
 	if (IS_ERR(frmr))
 		goto out_mr_err;
@@ -440,9 +423,6 @@ int frwr_send(struct rpcrdma_ia *ia, struct rpcrdma_req *req)
 		post_wr = &frwr->fr_regwr.wr;
 	}
 
-	/* If ib_post_send fails, the next ->send_request for
-	 * @req will queue these MRs for recovery.
-	 */
 	return ib_post_send(ia->ri_id->qp, post_wr, NULL);
 }