SUNRPC: Allow dynamic allocation of back channel slots

Now that the reads happen in a process context rather than a softirq,
it is safe to allocate back channel slots using a reclaiming
allocation.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

diff --git a/net/sunrpc/backchannel_rqst.c b/net/sunrpc/backchannel_rqst.c
index b9313c1..c47d826 100644 (file)
--- a/net/sunrpc/backchannel_rqst.c
+++ b/net/sunrpc/backchannel_rqst.c
@@ -235,7 +235,8 @@ out:
                list_empty(&xprt->bc_pa_list) ? "true" : "false");
 }
 
-static struct rpc_rqst *xprt_alloc_bc_request(struct rpc_xprt *xprt, __be32 xid)
+static struct rpc_rqst *xprt_get_bc_request(struct rpc_xprt *xprt, __be32 xid,
+               struct rpc_rqst *new)
 {
        struct rpc_rqst *req = NULL;
 
@@ -243,10 +244,9 @@ static struct rpc_rqst *xprt_alloc_bc_request(struct rpc_xprt *xprt, __be32 xid)
        if (atomic_read(&xprt->bc_free_slots) <= 0)
                goto not_found;
        if (list_empty(&xprt->bc_pa_list)) {
-               req = xprt_alloc_bc_req(xprt, GFP_ATOMIC);
-               if (!req)
+               if (!new)
                        goto not_found;
-               list_add_tail(&req->rq_bc_pa_list, &xprt->bc_pa_list);
+               list_add_tail(&new->rq_bc_pa_list, &xprt->bc_pa_list);
                xprt->bc_alloc_count++;
        }
        req = list_first_entry(&xprt->bc_pa_list, struct rpc_rqst,
@@ -256,8 +256,8 @@ static struct rpc_rqst *xprt_alloc_bc_request(struct rpc_xprt *xprt, __be32 xid)
                        sizeof(req->rq_private_buf));
        req->rq_xid = xid;
        req->rq_connect_cookie = xprt->connect_cookie;
-not_found:
        dprintk("RPC:       backchannel req=%p\n", req);
+not_found:
        return req;
 }
 
@@ -320,18 +320,27 @@ void xprt_free_bc_rqst(struct rpc_rqst *req)
  */
 struct rpc_rqst *xprt_lookup_bc_request(struct rpc_xprt *xprt, __be32 xid)
 {
-       struct rpc_rqst *req;
-
-       spin_lock(&xprt->bc_pa_lock);
-       list_for_each_entry(req, &xprt->bc_pa_list, rq_bc_pa_list) {
-               if (req->rq_connect_cookie != xprt->connect_cookie)
-                       continue;
-               if (req->rq_xid == xid)
-                       goto found;
-       }
-       req = xprt_alloc_bc_request(xprt, xid);
+       struct rpc_rqst *req, *new = NULL;
+
+       do {
+               spin_lock(&xprt->bc_pa_lock);
+               list_for_each_entry(req, &xprt->bc_pa_list, rq_bc_pa_list) {
+                       if (req->rq_connect_cookie != xprt->connect_cookie)
+                               continue;
+                       if (req->rq_xid == xid)
+                               goto found;
+               }
+               req = xprt_get_bc_request(xprt, xid, new);
 found:
-       spin_unlock(&xprt->bc_pa_lock);
+               spin_unlock(&xprt->bc_pa_lock);
+               if (new) {
+                       if (req != new)
+                               xprt_free_bc_rqst(new);
+                       break;
+               } else if (req)
+                       break;
+               new = xprt_alloc_bc_req(xprt, GFP_KERNEL);
+       } while (new);
        return req;
 }