LXR linux/net/sunrpc/backchannel

   1/******************************************************************************
   2
   3(c) 2007 Network Appliance, Inc.  All Rights Reserved.
   4(c) 2009 NetApp.  All Rights Reserved.
   5
   6NetApp provides this source code under the GPL v2 License.
   7The GPL v2 license is available at
   8http://opensource.org/licenses/gpl-license.php.
   9
  10THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  11"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  12LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  13A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
  14CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  15EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  16PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  17PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
  18LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
  19NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  20SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  21
  22******************************************************************************/
  23
  24#include <linux/tcp.h>
  25#include <linux/sunrpc/xprt.h>
  26
  27#ifdef RPC_DEBUG
  28#define RPCDBG_FACILITY RPCDBG_TRANS
  29#endif
  30
  31#if defined(CONFIG_NFS_V4_1)
  32
  33/*
  34 * Helper routines that track the number of preallocation elements
  35 * on the transport.
  36 */
  37static inline int xprt_need_to_requeue(struct rpc_xprt *xprt)
  38{
  39        return xprt->bc_alloc_count > 0;
  40}
  41
  42static inline void xprt_inc_alloc_count(struct rpc_xprt *xprt, unsigned int n)
  43{
  44        xprt->bc_alloc_count += n;
  45}
  46
  47static inline int xprt_dec_alloc_count(struct rpc_xprt *xprt, unsigned int n)
  48{
  49        return xprt->bc_alloc_count -= n;
  50}
  51
  52/*
  53 * Free the preallocated rpc_rqst structure and the memory
  54 * buffers hanging off of it.
  55 */
  56static void xprt_free_allocation(struct rpc_rqst *req)
  57{
  58        struct xdr_buf *xbufp;
  59
  60        dprintk("RPC:        free allocations for req= %p\n", req);
  61        BUG_ON(test_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state));
  62        xbufp = &req->rq_private_buf;
  63        free_page((unsigned long)xbufp->head[0].iov_base);
  64        xbufp = &req->rq_snd_buf;
  65        free_page((unsigned long)xbufp->head[0].iov_base);
  66        list_del(&req->rq_bc_pa_list);
  67        kfree(req);
  68}
  69
  70/*
  71 * Preallocate up to min_reqs structures and related buffers for use
  72 * by the backchannel.  This function can be called multiple times
  73 * when creating new sessions that use the same rpc_xprt.  The
  74 * preallocated buffers are added to the pool of resources used by
  75 * the rpc_xprt.  Anyone of these resources may be used used by an
  76 * incoming callback request.  It's up to the higher levels in the
  77 * stack to enforce that the maximum number of session slots is not
  78 * being exceeded.
  79 *
  80 * Some callback arguments can be large.  For example, a pNFS server
  81 * using multiple deviceids.  The list can be unbound, but the client
  82 * has the ability to tell the server the maximum size of the callback
  83 * requests.  Each deviceID is 16 bytes, so allocate one page
  84 * for the arguments to have enough room to receive a number of these
  85 * deviceIDs.  The NFS client indicates to the pNFS server that its
  86 * callback requests can be up to 4096 bytes in size.
  87 */
  88int xprt_setup_backchannel(struct rpc_xprt *xprt, unsigned int min_reqs)
  89{
  90        struct page *page_rcv = NULL, *page_snd = NULL;
  91        struct xdr_buf *xbufp = NULL;
  92        struct rpc_rqst *req, *tmp;
  93        struct list_head tmp_list;
  94        int i;
  95
  96        dprintk("RPC:       setup backchannel transport\n");
  97
  98        /*
  99         * We use a temporary list to keep track of the preallocated
 100         * buffers.  Once we're done building the list we splice it
 101         * into the backchannel preallocation list off of the rpc_xprt
 102         * struct.  This helps minimize the amount of time the list
 103         * lock is held on the rpc_xprt struct.  It also makes cleanup
 104         * easier in case of memory allocation errors.
 105         */
 106        INIT_LIST_HEAD(&tmp_list);
 107        for (i = 0; i < min_reqs; i++) {
 108                /* Pre-allocate one backchannel rpc_rqst */
 109                req = kzalloc(sizeof(struct rpc_rqst), GFP_KERNEL);
 110                if (req == NULL) {
 111                        printk(KERN_ERR "Failed to create bc rpc_rqst\n");
 112                        goto out_free;
 113                }
 114
 115                /* Add the allocated buffer to the tmp list */
 116                dprintk("RPC:       adding req= %p\n", req);
 117                list_add(&req->rq_bc_pa_list, &tmp_list);
 118
 119                req->rq_xprt = xprt;
 120                INIT_LIST_HEAD(&req->rq_list);
 121                INIT_LIST_HEAD(&req->rq_bc_list);
 122
 123                /* Preallocate one XDR receive buffer */
 124                page_rcv = alloc_page(GFP_KERNEL);
 125                if (page_rcv == NULL) {
 126                        printk(KERN_ERR "Failed to create bc receive xbuf\n");
 127                        goto out_free;
 128                }
 129                xbufp = &req->rq_rcv_buf;
 130                xbufp->head[0].iov_base = page_address(page_rcv);
 131                xbufp->head[0].iov_len = PAGE_SIZE;
 132                xbufp->tail[0].iov_base = NULL;
 133                xbufp->tail[0].iov_len = 0;
 134                xbufp->page_len = 0;
 135                xbufp->len = PAGE_SIZE;
 136                xbufp->buflen = PAGE_SIZE;
 137
 138                /* Preallocate one XDR send buffer */
 139                page_snd = alloc_page(GFP_KERNEL);
 140                if (page_snd == NULL) {
 141                        printk(KERN_ERR "Failed to create bc snd xbuf\n");
 142                        goto out_free;
 143                }
 144
 145                xbufp = &req->rq_snd_buf;
 146                xbufp->head[0].iov_base = page_address(page_snd);
 147                xbufp->head[0].iov_len = 0;
 148                xbufp->tail[0].iov_base = NULL;
 149                xbufp->tail[0].iov_len = 0;
 150                xbufp->page_len = 0;
 151                xbufp->len = 0;
 152                xbufp->buflen = PAGE_SIZE;
 153        }
 154
 155        /*
 156         * Add the temporary list to the backchannel preallocation list
 157         */
 158        spin_lock_bh(&xprt->bc_pa_lock);
 159        list_splice(&tmp_list, &xprt->bc_pa_list);
 160        xprt_inc_alloc_count(xprt, min_reqs);
 161        spin_unlock_bh(&xprt->bc_pa_lock);
 162
 163        dprintk("RPC:       setup backchannel transport done\n");
 164        return 0;
 165
 166out_free:
 167        /*
 168         * Memory allocation failed, free the temporary list
 169         */
 170        list_for_each_entry_safe(req, tmp, &tmp_list, rq_bc_pa_list)
 171                xprt_free_allocation(req);
 172
 173        dprintk("RPC:       setup backchannel transport failed\n");
 174        return -1;
 175}
 176EXPORT_SYMBOL(xprt_setup_backchannel);
 177
 178/*
 179 * Destroys the backchannel preallocated structures.
 180 * Since these structures may have been allocated by multiple calls
 181 * to xprt_setup_backchannel, we only destroy up to the maximum number
 182 * of reqs specified by the caller.
 183 * @xprt:       the transport holding the preallocated strucures
 184 * @max_reqs    the maximum number of preallocated structures to destroy
 185 */
 186void xprt_destroy_backchannel(struct rpc_xprt *xprt, unsigned int max_reqs)
 187{
 188        struct rpc_rqst *req = NULL, *tmp = NULL;
 189
 190        dprintk("RPC:        destroy backchannel transport\n");
 191
 192        BUG_ON(max_reqs == 0);
 193        spin_lock_bh(&xprt->bc_pa_lock);
 194        xprt_dec_alloc_count(xprt, max_reqs);
 195        list_for_each_entry_safe(req, tmp, &xprt->bc_pa_list, rq_bc_pa_list) {
 196                dprintk("RPC:        req=%p\n", req);
 197                xprt_free_allocation(req);
 198                if (--max_reqs == 0)
 199                        break;
 200        }
 201        spin_unlock_bh(&xprt->bc_pa_lock);
 202
 203        dprintk("RPC:        backchannel list empty= %s\n",
 204                list_empty(&xprt->bc_pa_list) ? "true" : "false");
 205}
 206EXPORT_SYMBOL(xprt_destroy_backchannel);
 207
 208/*
 209 * One or more rpc_rqst structure have been preallocated during the
 210 * backchannel setup.  Buffer space for the send and private XDR buffers
 211 * has been preallocated as well.  Use xprt_alloc_bc_request to allocate
 212 * to this request.  Use xprt_free_bc_request to return it.
 213 *
 214 * We know that we're called in soft interrupt context, grab the spin_lock
 215 * since there is no need to grab the bottom half spin_lock.
 216 *
 217 * Return an available rpc_rqst, otherwise NULL if non are available.
 218 */
 219struct rpc_rqst *xprt_alloc_bc_request(struct rpc_xprt *xprt)
 220{
 221        struct rpc_rqst *req;
 222
 223        dprintk("RPC:       allocate a backchannel request\n");
 224        spin_lock(&xprt->bc_pa_lock);
 225        if (!list_empty(&xprt->bc_pa_list)) {
 226                req = list_first_entry(&xprt->bc_pa_list, struct rpc_rqst,
 227                                rq_bc_pa_list);
 228                list_del(&req->rq_bc_pa_list);
 229        } else {
 230                req = NULL;
 231        }
 232        spin_unlock(&xprt->bc_pa_lock);
 233
 234        if (req != NULL) {
 235                set_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state);
 236                req->rq_reply_bytes_recvd = 0;
 237                req->rq_bytes_sent = 0;
 238                memcpy(&req->rq_private_buf, &req->rq_rcv_buf,
 239                        sizeof(req->rq_private_buf));
 240        }
 241        dprintk("RPC:       backchannel req=%p\n", req);
 242        return req;
 243}
 244
 245/*
 246 * Return the preallocated rpc_rqst structure and XDR buffers
 247 * associated with this rpc_task.
 248 */
 249void xprt_free_bc_request(struct rpc_rqst *req)
 250{
 251        struct rpc_xprt *xprt = req->rq_xprt;
 252
 253        dprintk("RPC:       free backchannel req=%p\n", req);
 254
 255        smp_mb__before_clear_bit();
 256        BUG_ON(!test_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state));
 257        clear_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state);
 258        smp_mb__after_clear_bit();
 259
 260        if (!xprt_need_to_requeue(xprt)) {
 261                /*
 262                 * The last remaining session was destroyed while this
 263                 * entry was in use.  Free the entry and don't attempt
 264                 * to add back to the list because there is no need to
 265                 * have anymore preallocated entries.
 266                 */
 267                dprintk("RPC:       Last session removed req=%p\n", req);
 268                xprt_free_allocation(req);
 269                return;
 270        }
 271
 272        /*
 273         * Return it to the list of preallocations so that it
 274         * may be reused by a new callback request.
 275         */
 276        spin_lock_bh(&xprt->bc_pa_lock);
 277        list_add(&req->rq_bc_pa_list, &xprt->bc_pa_list);
 278        spin_unlock_bh(&xprt->bc_pa_lock);
 279}
 280
 281#endif /* CONFIG_NFS_V4_1 */
 282