Hi Trond-
> On Mar 3, 2019, at 7:19 PM, Trond Myklebust <trondmy@xxxxxxxxx> wrote:
>
> 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.
Is this a required change for transports, or simply an optimization?
Wondering if a similar change is needed for RPC-over-RDMA.
> Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
> ---
> net/sunrpc/backchannel_rqst.c | 41 +++++++++++++++++++++--------------
> 1 file changed, 25 insertions(+), 16 deletions(-)
>
> diff --git a/net/sunrpc/backchannel_rqst.c b/net/sunrpc/backchannel_rqst.c
> index b9313c15ee3a..c47d82622fd1 100644
> --- a/net/sunrpc/backchannel_rqst.c
> +++ b/net/sunrpc/backchannel_rqst.c
> @@ -235,7 +235,8 @@ void xprt_destroy_bc(struct rpc_xprt *xprt, unsigned int max_reqs)
> 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;
> }
>
> --
> 2.20.1
>
--
Chuck Lever
