3 files changed, 280 insertions, 0 deletions

diff --git a/include/linux/sunrpc/xprt.h b/include/linux/sunrpc/xprt.h
index 703af7ebf6cf..beae030e80b5 100644
--- a/include/linux/sunrpc/xprt.h
+++ b/include/linux/sunrpc/xprt.h
@@ -183,6 +183,7 @@ struct rpc_xprt {
 #if defined(CONFIG_NFS_V4_1)
         struct svc_serv         *bc_serv;       /* The RPC service which will */
                                                 /* process the callback */
+        unsigned int            bc_alloc_count; /* Total number of preallocs */
         spinlock_t              bc_pa_lock;     /* Protects the preallocated
                                                  * items */
         struct list_head        bc_pa_list;     /* List of preallocated
diff --git a/net/sunrpc/Makefile b/net/sunrpc/Makefile
index 5369aa369b35..4a01f9684b85 100644
--- a/net/sunrpc/Makefile
+++ b/net/sunrpc/Makefile
@@ -13,5 +13,6 @@ sunrpc-y := clnt.o xprt.o socklib.o xprtsock.o sched.o \
             rpcb_clnt.o timer.o xdr.o \
             sunrpc_syms.o cache.o rpc_pipe.o \
             svc_xprt.o
+sunrpc-$(CONFIG_NFS_V4_1) += backchannel_rqst.o
 sunrpc-$(CONFIG_PROC_FS) += stats.o
 sunrpc-$(CONFIG_SYSCTL) += sysctl.o
diff --git a/net/sunrpc/backchannel_rqst.c b/net/sunrpc/backchannel_rqst.c
new file mode 100644
index 000000000000..f56e18a23498
--- /dev/null
+++ b/net/sunrpc/backchannel_rqst.c
@@ -0,0 +1,278 @@
+/******************************************************************************
+
+(c) 2007 Network Appliance, Inc.  All Rights Reserved.
+(c) 2009 NetApp.  All Rights Reserved.
+
+NetApp provides this source code under the GPL v2 License.
+The GPL v2 license is available at
+http://opensource.org/licenses/gpl-license.php.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+******************************************************************************/
+
+#include <linux/tcp.h>
+#include <linux/sunrpc/xprt.h>
+
+#ifdef RPC_DEBUG
+#define RPCDBG_FACILITY RPCDBG_TRANS
+#endif
+
+#if defined(CONFIG_NFS_V4_1)
+
+/*
+ * Helper routines that track the number of preallocation elements
+ * on the transport.
+ */
+static inline int xprt_need_to_requeue(struct rpc_xprt *xprt)
+{
+        return xprt->bc_alloc_count > 0;
+}
+
+static inline void xprt_inc_alloc_count(struct rpc_xprt *xprt, unsigned int n)
+{
+        xprt->bc_alloc_count += n;
+}
+
+static inline int xprt_dec_alloc_count(struct rpc_xprt *xprt, unsigned int n)
+{
+        return xprt->bc_alloc_count -= n;
+}
+
+/*
+ * Free the preallocated rpc_rqst structure and the memory
+ * buffers hanging off of it.
+ */
+static void xprt_free_allocation(struct rpc_rqst *req)
+{
+        struct xdr_buf *xbufp;
+
+        dprintk("RPC:        free allocations for req= %p\n", req);
+        BUG_ON(test_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state));
+        xbufp = &req->rq_private_buf;
+        free_page((unsigned long)xbufp->head[0].iov_base);
+        xbufp = &req->rq_snd_buf;
+        free_page((unsigned long)xbufp->head[0].iov_base);
+        list_del(&req->rq_bc_pa_list);
+        kfree(req);
+}
+
+/*
+ * Preallocate up to min_reqs structures and related buffers for use
+ * by the backchannel.  This function can be called multiple times
+ * when creating new sessions that use the same rpc_xprt.  The
+ * preallocated buffers are added to the pool of resources used by
+ * the rpc_xprt.  Anyone of these resources may be used used by an
+ * incoming callback request.  It's up to the higher levels in the
+ * stack to enforce that the maximum number of session slots is not
+ * being exceeded.
+ *
+ * Some callback arguments can be large.  For example, a pNFS server
+ * using multiple deviceids.  The list can be unbound, but the client
+ * has the ability to tell the server the maximum size of the callback
+ * requests.  Each deviceID is 16 bytes, so allocate one page
+ * for the arguments to have enough room to receive a number of these
+ * deviceIDs.  The NFS client indicates to the pNFS server that its
+ * callback requests can be up to 4096 bytes in size.
+ */
+int xprt_setup_backchannel(struct rpc_xprt *xprt, unsigned int min_reqs)
+{
+        struct page *page_rcv = NULL, *page_snd = NULL;
+        struct xdr_buf *xbufp = NULL;
+        struct rpc_rqst *req, *tmp;
+        struct list_head tmp_list;
+        int i;
+
+        dprintk("RPC:       setup backchannel transport\n");
+
+        /*
+         * We use a temporary list to keep track of the preallocated
+         * buffers.  Once we're done building the list we splice it
+         * into the backchannel preallocation list off of the rpc_xprt
+         * struct.  This helps minimize the amount of time the list
+         * lock is held on the rpc_xprt struct.  It also makes cleanup
+         * easier in case of memory allocation errors.
+         */
+        INIT_LIST_HEAD(&tmp_list);
+        for (i = 0; i < min_reqs; i++) {
+                /* Pre-allocate one backchannel rpc_rqst */
+                req = kzalloc(sizeof(struct rpc_rqst), GFP_KERNEL);
+                if (req == NULL) {
+                        printk(KERN_ERR "Failed to create bc rpc_rqst\n");
+                        goto out_free;
+                }
+
+                /* Add the allocated buffer to the tmp list */
+                dprintk("RPC:       adding req= %p\n", req);
+                list_add(&req->rq_bc_pa_list, &tmp_list);
+
+                req->rq_xprt = xprt;
+                INIT_LIST_HEAD(&req->rq_list);
+                INIT_LIST_HEAD(&req->rq_bc_list);
+
+                /* Preallocate one XDR receive buffer */
+                page_rcv = alloc_page(GFP_KERNEL);
+                if (page_rcv == NULL) {
+                        printk(KERN_ERR "Failed to create bc receive xbuf\n");
+                        goto out_free;
+                }
+                xbufp = &req->rq_rcv_buf;
+                xbufp->head[0].iov_base = page_address(page_rcv);
+                xbufp->head[0].iov_len = PAGE_SIZE;
+                xbufp->tail[0].iov_base = NULL;
+                xbufp->tail[0].iov_len = 0;
+                xbufp->page_len = 0;
+                xbufp->len = PAGE_SIZE;
+                xbufp->buflen = PAGE_SIZE;
+
+                /* Preallocate one XDR send buffer */
+                page_snd = alloc_page(GFP_KERNEL);
+                if (page_snd == NULL) {
+                        printk(KERN_ERR "Failed to create bc snd xbuf\n");
+                        goto out_free;
+                }
+
+                xbufp = &req->rq_snd_buf;
+                xbufp->head[0].iov_base = page_address(page_snd);
+                xbufp->head[0].iov_len = 0;
+                xbufp->tail[0].iov_base = NULL;
+                xbufp->tail[0].iov_len = 0;
+                xbufp->page_len = 0;
+                xbufp->len = 0;
+                xbufp->buflen = PAGE_SIZE;
+        }
+
+        /*
+         * Add the temporary list to the backchannel preallocation list
+         */
+        spin_lock_bh(&xprt->bc_pa_lock);
+        list_splice(&tmp_list, &xprt->bc_pa_list);
+        xprt_inc_alloc_count(xprt, min_reqs);
+        spin_unlock_bh(&xprt->bc_pa_lock);
+
+        dprintk("RPC:       setup backchannel transport done\n");
+        return 0;
+
+out_free:
+        /*
+         * Memory allocation failed, free the temporary list
+         */
+        list_for_each_entry_safe(req, tmp, &tmp_list, rq_bc_pa_list)
+                xprt_free_allocation(req);
+
+        dprintk("RPC:       setup backchannel transport failed\n");
+        return -1;
+}
+EXPORT_SYMBOL(xprt_setup_backchannel);
+
+/*
+ * Destroys the backchannel preallocated structures.
+ * Since these structures may have been allocated by multiple calls
+ * to xprt_setup_backchannel, we only destroy up to the maximum number
+ * of reqs specified by the caller.
+ * @xprt:       the transport holding the preallocated strucures
+ * @max_reqs    the maximum number of preallocated structures to destroy
+ */
+void xprt_destroy_backchannel(struct rpc_xprt *xprt, unsigned int max_reqs)
+{
+        struct rpc_rqst *req = NULL, *tmp = NULL;
+
+        dprintk("RPC:        destroy backchannel transport\n");
+
+        BUG_ON(max_reqs == 0);
+        spin_lock_bh(&xprt->bc_pa_lock);
+        xprt_dec_alloc_count(xprt, max_reqs);
+        list_for_each_entry_safe(req, tmp, &xprt->bc_pa_list, rq_bc_pa_list) {
+                dprintk("RPC:        req=%p\n", req);
+                xprt_free_allocation(req);
+                if (--max_reqs == 0)
+                        break;
+        }
+        spin_unlock_bh(&xprt->bc_pa_lock);
+
+        dprintk("RPC:        backchannel list empty= %s\n",
+                list_empty(&xprt->bc_pa_list) ? "true" : "false");
+}
+EXPORT_SYMBOL(xprt_destroy_backchannel);
+
+/*
+ * One or more rpc_rqst structure have been preallocated during the
+ * backchannel setup.  Buffer space for the send and private XDR buffers
+ * has been preallocated as well.  Use xprt_alloc_bc_request to allocate
+ * to this request.  Use xprt_free_bc_request to return it.
+ *
+ * Return an available rpc_rqst, otherwise NULL if non are available.
+ */
+struct rpc_rqst *xprt_alloc_bc_request(struct rpc_xprt *xprt)
+{
+        struct rpc_rqst *req;
+
+        dprintk("RPC:       allocate a backchannel request\n");
+        spin_lock_bh(&xprt->bc_pa_lock);
+        if (!list_empty(&xprt->bc_pa_list)) {
+                req = list_first_entry(&xprt->bc_pa_list, struct rpc_rqst,
+                                rq_bc_pa_list);
+                list_del(&req->rq_bc_pa_list);
+        } else {
+                req = NULL;
+        }
+        spin_unlock_bh(&xprt->bc_pa_lock);
+
+        if (req != NULL) {
+                set_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state);
+                req->rq_received = 0;
+                req->rq_bytes_sent = 0;
+                memcpy(&req->rq_private_buf, &req->rq_rcv_buf,
+                        sizeof(req->rq_private_buf));
+        }
+        dprintk("RPC:       backchannel req=%p\n", req);
+        return req;
+}
+
+/*
+ * Return the preallocated rpc_rqst structure and XDR buffers
+ * associated with this rpc_task.
+ */
+void xprt_free_bc_request(struct rpc_rqst *req)
+{
+        struct rpc_xprt *xprt = req->rq_xprt;
+
+        dprintk("RPC:       free backchannel req=%p\n", req);
+
+        smp_mb__before_clear_bit();
+        BUG_ON(!test_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state));
+        clear_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state);
+        smp_mb__after_clear_bit();
+
+        if (!xprt_need_to_requeue(xprt)) {
+                /*
+                 * The last remaining session was destroyed while this
+                 * entry was in use.  Free the entry and don't attempt
+                 * to add back to the list because there is no need to
+                 * have anymore preallocated entries.
+                 */
+                dprintk("RPC:       Last session removed req=%p\n", req);
+                xprt_free_allocation(req);
+                return;
+        }
+
+        /*
+         * Return it to the list of preallocations so that it
+         * may be reused by a new callback request.
+         */
+        spin_lock_bh(&xprt->bc_pa_lock);
+        list_add(&req->rq_bc_pa_list, &xprt->bc_pa_list);
+        spin_unlock_bh(&xprt->bc_pa_lock);
+}
+
+#endif /* CONFIG_NFS_V4_1 */