RE: Trying to reduce NFSv4 timeouts to a few seconds on an established connection

[Andrew Klaassen <andrew.klaassen@boatrocker.com>]

> From: Andrew Klaassen <andrew.klaassen@boatrocker.com>
> Sent: Monday, February 6, 2023 10:28 AM
> 

> [snipping for readability; hope that's okay]
> 
>  - I'm allocating memory.  I assume that means I should free it somewhere.
> But where?  In xprt_destroy(), which appears to do cleanup?  Or in
> xprt_destroy_cb(), which is called from xprt_destroy() and which frees xprt-
> >servername?  Or somewhere else completely?
>  - If I free the allocated memory, will that cause any problems in the cases
> where no timeout is passed in via the args and the static const struct
> xs_tcp_default_timeout is assigned to xprt->timeout?
>  - If freeing the static const struct default will cause a problem, what should I
> do instead?  Allocate and memcpy even when assigning the default?  And
> would that mean doing the same thing for all the other transports that are
> setting timeouts (local, udp, tcp, and bc_tcp)?

Here's my best guess as the answer to my questions.  Any advice/feedback appreciated.

diff --git a/include/linux/sunrpc/xprt.h b/include/linux/sunrpc/xprt.h
index b9f59aabee53..4543ec07cc12 100644
--- a/include/linux/sunrpc/xprt.h
+++ b/include/linux/sunrpc/xprt.h
@@ -333,6 +333,7 @@ struct xprt_create {
        struct svc_xprt         *bc_xprt;       /* NFSv4.1 backchannel */
        struct rpc_xprt_switch  *bc_xps;
        unsigned int            flags;
+       const struct rpc_timeout *timeout;      /* timeout parms */
 };

 struct xprt_class {
@@ -373,6 +374,8 @@ void                        xprt_release_xprt_cong(struct rpc_xprt *xprt, struct rpc_task *task);
 void                   xprt_release(struct rpc_task *task);
 struct rpc_xprt *      xprt_get(struct rpc_xprt *xprt);
 void                   xprt_put(struct rpc_xprt *xprt);
+struct rpc_timeout *   xprt_alloc_timeout(const struct rpc_timeout * timeo,
+                               const struct rpc_timeout *default_timeo);
 struct rpc_xprt *      xprt_alloc(struct net *net, size_t size,
                                unsigned int num_prealloc,
                                unsigned int max_req);
diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index 0b0b9f1eed46..1350c1f489f7 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -532,6 +532,7 @@ struct rpc_clnt *rpc_create(struct rpc_create_args *args)
                .addrlen = args->addrsize,
                .servername = args->servername,
                .bc_xprt = args->bc_xprt,
+               .timeout = args->timeout,
        };
        char servername[48];
        struct rpc_clnt *clnt;
diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
index ab453ede54f0..1065b76ddff4 100644
--- a/net/sunrpc/xprt.c
+++ b/net/sunrpc/xprt.c
@@ -1801,6 +1801,26 @@ static void xprt_free_id(struct rpc_xprt *xprt)
        ida_free(&rpc_xprt_ids, xprt->id);
 }

+struct rpc_timeout *xprt_alloc_timeout(const struct rpc_timeout *timeo,
+               const struct rpc_timeout *default_timeo)
+{
+       struct rpc_timeout *timeout;
+       timeout = kzalloc(sizeof(struct rpc_timeout), GFP_KERNEL);
+       if (timeout == NULL)
+               return ERR_PTR(-ENOMEM);
+       if (timeo)
+               memcpy(timeout, timeo, sizeof(struct rpc_timeout));
+       else
+               memcpy(timeout, default_timeo, sizeof(struct rpc_timeout));
+       return timeout;
+}
+
+static void xprt_free_timeout(struct rpc_xprt *xprt)
+{
+       if (xprt->timeout != NULL)
+               kfree(xprt->timeout);
+}
+
 struct rpc_xprt *xprt_alloc(struct net *net, size_t size,
                unsigned int num_prealloc,
                unsigned int max_alloc)
@@ -1837,6 +1857,7 @@ EXPORT_SYMBOL_GPL(xprt_alloc);

 void xprt_free(struct rpc_xprt *xprt)
 {
+       xprt_free_timeout(xprt);
        put_net_track(xprt->xprt_net, &xprt->ns_tracker);
        xprt_free_all_slots(xprt);
        xprt_free_id(xprt);
diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index aaa5b2741b79..ba05258509fa 100644
--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -3003,7 +3003,11 @@ static struct rpc_xprt *xs_setup_tcp(struct xprt_create *args)
        xprt->idle_timeout = XS_IDLE_DISC_TO;

        xprt->ops = &xs_tcp_ops;
-       xprt->timeout = &xs_tcp_default_timeout;
+
+       xprt->timeout = xprt_alloc_timeout(args->timeout, &xs_tcp_default_timeout);
+
+       if (IS_ERR(xprt->timeout))
+               goto out_err;

        xprt->max_reconnect_timeout = xprt->timeout->to_maxval;
        xprt->connect_timeout = xprt->timeout->to_initval *