xprtrdma: Replace send and receive arrays

[ Proposed for upstream v4.4 ]

The rb_send_bufs and rb_recv_bufs arrays are used to implement a
pair of stacks for keeping track of free rpcrdma_req and rpcrdma_rep
structs. Replace those arrays with free lists.

To allow more than 512 RPCs in-flight at once, each of these arrays
would be larger than a page (assuming 8-byte addresses and 4KB
pages). Allowing up to 64K in-flight RPCs (as TCP now does), each
buffer array would have to be 128 pages. That's an order-6
allocation. (Not that we're going there.)

A list is easier to expand dynamically. Instead of allocating a
larger array of pointers and copying the existing pointers to the
new array, simply append more buffers to each list.

This also makes it simpler to manage receive buffers that might
catch backwards-direction calls, or to post receive buffers in
bulk to amortize the overhead of ib_post_recv.

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

diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c
index 3e5453facb9bce2726763ba4a32bef89c142cb10..c38d5027312b17d6211c6f59a0f8114ad7844375 100644 (file)
--- a/net/sunrpc/xprtrdma/verbs.c
+++ b/net/sunrpc/xprtrdma/verbs.c
@@ -1107,44 +1107,18 @@ rpcrdma_buffer_create(struct rpcrdma_xprt *r_xprt)
 {
        struct rpcrdma_buffer *buf = &r_xprt->rx_buf;
        struct rpcrdma_ia *ia = &r_xprt->rx_ia;
-       struct rpcrdma_create_data_internal *cdata = &r_xprt->rx_data;
-       char *p;
-       size_t len;
        int i, rc;
 
-       buf->rb_max_requests = cdata->max_requests;
+       buf->rb_max_requests = r_xprt->rx_data.max_requests;
        spin_lock_init(&buf->rb_lock);
 
-       /* Need to allocate:
-        *   1.  arrays for send and recv pointers
-        *   2.  arrays of struct rpcrdma_req to fill in pointers
-        *   3.  array of struct rpcrdma_rep for replies
-        * Send/recv buffers in req/rep need to be registered
-        */
-       len = buf->rb_max_requests *
-               (sizeof(struct rpcrdma_req *) + sizeof(struct rpcrdma_rep *));
-
-       p = kzalloc(len, GFP_KERNEL);
-       if (p == NULL) {
-               dprintk("RPC:       %s: req_t/rep_t/pad kzalloc(%zd) failed\n",
-                       __func__, len);
-               rc = -ENOMEM;
-               goto out;
-       }
-       buf->rb_pool = p;       /* for freeing it later */
-
-       buf->rb_send_bufs = (struct rpcrdma_req **) p;
-       p = (char *) &buf->rb_send_bufs[buf->rb_max_requests];
-       buf->rb_recv_bufs = (struct rpcrdma_rep **) p;
-       p = (char *) &buf->rb_recv_bufs[buf->rb_max_requests];
-
        rc = ia->ri_ops->ro_init(r_xprt);
        if (rc)
                goto out;
 
+       INIT_LIST_HEAD(&buf->rb_send_bufs);
        for (i = 0; i < buf->rb_max_requests; i++) {
                struct rpcrdma_req *req;
-               struct rpcrdma_rep *rep;
 
                req = rpcrdma_create_req(r_xprt);
                if (IS_ERR(req)) {
@@ -1153,7 +1127,12 @@ rpcrdma_buffer_create(struct rpcrdma_xprt *r_xprt)
                        rc = PTR_ERR(req);
                        goto out;
                }
-               buf->rb_send_bufs[i] = req;
+               list_add(&req->rl_free, &buf->rb_send_bufs);
+       }
+
+       INIT_LIST_HEAD(&buf->rb_recv_bufs);
+       for (i = 0; i < buf->rb_max_requests + 2; i++) {
+               struct rpcrdma_rep *rep;
 
                rep = rpcrdma_create_rep(r_xprt);
                if (IS_ERR(rep)) {
@@ -1162,7 +1141,7 @@ rpcrdma_buffer_create(struct rpcrdma_xprt *r_xprt)
                        rc = PTR_ERR(rep);
                        goto out;
                }
-               buf->rb_recv_bufs[i] = rep;
+               list_add(&rep->rr_list, &buf->rb_recv_bufs);
        }
 
        return 0;
@@ -1196,25 +1175,26 @@ void
 rpcrdma_buffer_destroy(struct rpcrdma_buffer *buf)
 {
        struct rpcrdma_ia *ia = rdmab_to_ia(buf);
-       int i;
 
-       /* clean up in reverse order from create
-        *   1.  recv mr memory (mr free, then kfree)
-        *   2.  send mr memory (mr free, then kfree)
-        *   3.  MWs
-        */
-       dprintk("RPC:       %s: entering\n", __func__);
+       while (!list_empty(&buf->rb_recv_bufs)) {
+               struct rpcrdma_rep *rep = list_entry(buf->rb_recv_bufs.next,
+                                                    struct rpcrdma_rep,
+                                                    rr_list);
 
-       for (i = 0; i < buf->rb_max_requests; i++) {
-               if (buf->rb_recv_bufs)
-                       rpcrdma_destroy_rep(ia, buf->rb_recv_bufs[i]);
-               if (buf->rb_send_bufs)
-                       rpcrdma_destroy_req(ia, buf->rb_send_bufs[i]);
+               list_del(&rep->rr_list);
+               rpcrdma_destroy_rep(ia, rep);
        }
 
-       ia->ri_ops->ro_destroy(buf);
+       while (!list_empty(&buf->rb_send_bufs)) {
+               struct rpcrdma_req *req = list_entry(buf->rb_send_bufs.next,
+                                                    struct rpcrdma_req,
+                                                    rl_free);
 
-       kfree(buf->rb_pool);
+               list_del(&req->rl_free);
+               rpcrdma_destroy_req(ia, req);
+       }
+
+       ia->ri_ops->ro_destroy(buf);
 }
 
 struct rpcrdma_mw *
@@ -1247,24 +1227,27 @@ rpcrdma_put_mw(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mw *mw)
 }
 
 static void
-rpcrdma_buffer_put_sendbuf(struct rpcrdma_req *req, struct rpcrdma_buffer *buf)
+rpcrdma_buffer_put_locked(struct rpcrdma_rep *rep, struct rpcrdma_buffer *buf)
 {
-       buf->rb_send_bufs[--buf->rb_send_index] = req;
-       req->rl_niovs = 0;
-       if (req->rl_reply) {
-               buf->rb_recv_bufs[--buf->rb_recv_index] = req->rl_reply;
-               req->rl_reply = NULL;
-       }
+       list_add_tail(&rep->rr_list, &buf->rb_recv_bufs);
+}
+
+static struct rpcrdma_rep *
+rpcrdma_buffer_get_locked(struct rpcrdma_buffer *buf)
+{
+       struct rpcrdma_rep *rep;
+
+       rep = list_first_entry(&buf->rb_recv_bufs,
+                              struct rpcrdma_rep, rr_list);
+       list_del(&rep->rr_list);
+
+       return rep;
 }
 
 /*
  * Get a set of request/reply buffers.
  *
- * Reply buffer (if needed) is attached to send buffer upon return.
- * Rule:
- *    rb_send_index and rb_recv_index MUST always be pointing to the
- *    *next* available buffer (non-NULL). They are incremented after
- *    removing buffers, and decremented *before* returning them.
+ * Reply buffer (if available) is attached to send buffer upon return.
  */
 struct rpcrdma_req *
 rpcrdma_buffer_get(struct rpcrdma_buffer *buffers)
@@ -1274,25 +1257,22 @@ rpcrdma_buffer_get(struct rpcrdma_buffer *buffers)
 
        spin_lock_irqsave(&buffers->rb_lock, flags);
 
-       if (buffers->rb_send_index == buffers->rb_max_requests) {
+       if (list_empty(&buffers->rb_send_bufs)) {
                spin_unlock_irqrestore(&buffers->rb_lock, flags);
-               dprintk("RPC:       %s: out of request buffers\n", __func__);
-               return ((struct rpcrdma_req *)NULL);
-       }
-
-       req = buffers->rb_send_bufs[buffers->rb_send_index];
-       if (buffers->rb_send_index < buffers->rb_recv_index) {
-               dprintk("RPC:       %s: %d extra receives outstanding (ok)\n",
-                       __func__,
-                       buffers->rb_recv_index - buffers->rb_send_index);
-               req->rl_reply = NULL;
-       } else {
-               req->rl_reply = buffers->rb_recv_bufs[buffers->rb_recv_index];
-               buffers->rb_recv_bufs[buffers->rb_recv_index++] = NULL;
+               pr_warn("RPC:       %s: out of request buffers\n", __func__);
+               return NULL;
        }
-       buffers->rb_send_bufs[buffers->rb_send_index++] = NULL;
+       req = list_first_entry(&buffers->rb_send_bufs,
+                              struct rpcrdma_req, rl_free);
+       list_del(&req->rl_free);
 
+       req->rl_reply = NULL;
+       if (!list_empty(&buffers->rb_recv_bufs))
+               req->rl_reply = rpcrdma_buffer_get_locked(buffers);
        spin_unlock_irqrestore(&buffers->rb_lock, flags);
+
+       if (!req->rl_reply)
+               pr_warn("RPC:       %s: out of reply buffers\n", __func__);
        return req;
 }
 
@@ -1304,17 +1284,22 @@ void
 rpcrdma_buffer_put(struct rpcrdma_req *req)
 {
        struct rpcrdma_buffer *buffers = req->rl_buffer;
+       struct rpcrdma_rep *rep = req->rl_reply;
        unsigned long flags;
 
+       req->rl_niovs = 0;
+       req->rl_reply = NULL;
+
        spin_lock_irqsave(&buffers->rb_lock, flags);
-       rpcrdma_buffer_put_sendbuf(req, buffers);
+       list_add_tail(&req->rl_free, &buffers->rb_send_bufs);
+       if (rep)
+               rpcrdma_buffer_put_locked(rep, buffers);
        spin_unlock_irqrestore(&buffers->rb_lock, flags);
 }
 
 /*
  * Recover reply buffers from pool.
- * This happens when recovering from error conditions.
- * Post-increment counter/array index.
+ * This happens when recovering from disconnect.
  */
 void
 rpcrdma_recv_buffer_get(struct rpcrdma_req *req)
@@ -1323,10 +1308,8 @@ rpcrdma_recv_buffer_get(struct rpcrdma_req *req)
        unsigned long flags;
 
        spin_lock_irqsave(&buffers->rb_lock, flags);
-       if (buffers->rb_recv_index < buffers->rb_max_requests) {
-               req->rl_reply = buffers->rb_recv_bufs[buffers->rb_recv_index];
-               buffers->rb_recv_bufs[buffers->rb_recv_index++] = NULL;
-       }
+       if (!list_empty(&buffers->rb_recv_bufs))
+               req->rl_reply = rpcrdma_buffer_get_locked(buffers);
        spin_unlock_irqrestore(&buffers->rb_lock, flags);
 }
 
@@ -1341,7 +1324,7 @@ rpcrdma_recv_buffer_put(struct rpcrdma_rep *rep)
        unsigned long flags;
 
        spin_lock_irqsave(&buffers->rb_lock, flags);
-       buffers->rb_recv_bufs[--buffers->rb_recv_index] = rep;
+       rpcrdma_buffer_put_locked(rep, buffers);
        spin_unlock_irqrestore(&buffers->rb_lock, flags);
 }
 

diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
index 08a65c0bca240b68f4a97ca6c7558e7acc919611..4aca779eba7a81ad9dc89ea4f2258e15e06d27a1 100644 (file)
--- a/net/sunrpc/xprtrdma/xprt_rdma.h
+++ b/net/sunrpc/xprtrdma/xprt_rdma.h
@@ -259,6 +259,7 @@ struct rpcrdma_mr_seg {             /* chunk descriptors */
 #define RPCRDMA_MAX_IOVS       (2)
 
 struct rpcrdma_req {
+       struct list_head        rl_free;
        unsigned int            rl_niovs;
        unsigned int            rl_nchunks;
        unsigned int            rl_connect_cookie;
@@ -292,12 +293,10 @@ struct rpcrdma_buffer {
        struct list_head        rb_all;
        char                    *rb_pool;
 
-       spinlock_t              rb_lock;        /* protect buf arrays */
+       spinlock_t              rb_lock;        /* protect buf lists */
+       struct list_head        rb_send_bufs;
+       struct list_head        rb_recv_bufs;
        u32                     rb_max_requests;
-       int                     rb_send_index;
-       int                     rb_recv_index;
-       struct rpcrdma_req      **rb_send_bufs;
-       struct rpcrdma_rep      **rb_recv_bufs;
 };
 #define rdmab_to_ia(b) (&container_of((b), struct rpcrdma_xprt, rx_buf)->rx_ia)