net/sunrpc/backchannel_rqst.c

   1 /******************************************************************************
   2
   3 (c) 2007 Network Appliance, Inc.  All Rights Reserved.
   4 (c) 2009 NetApp.  All Rights Reserved.
   5
   6 NetApp provides this source code under the GPL v2 License.
   7 The GPL v2 license is available at
   8 http://opensource.org/licenses/gpl-license.php.
   9
  10 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  11 "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  12 LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  13 A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
  14 CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  15 EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  16 PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  17 PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
  18 LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
  19 NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  20 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  21
  22 ******************************************************************************/
  23
  24 #include <linux/tcp.h>
  25 #include <linux/slab.h>
  26 #include <linux/sunrpc/xprt.h>
  27 #include <linux/export.h>
  28
  29 #ifdef RPC_DEBUG
  30 #define RPCDBG_FACILITY RPCDBG_TRANS
  31 #endif
  32
  33 /*
  34  * Helper routines that track the number of preallocation elements
  35  * on the transport.
  36  */
  37 static inline int xprt_need_to_requeue(struct rpc_xprt *xprt)
  38 {
  39         return xprt->bc_alloc_count > 0;
  40 }
  41
  42 static inline void xprt_inc_alloc_count(struct rpc_xprt *xprt, unsigned int n)
  43 {
  44         xprt->bc_alloc_count += n;
  45 }
  46
  47 static 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  */
  56 static 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_rcv_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  */
  88 int 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
 166 out_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 }
 176 EXPORT_SYMBOL_GPL(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  */
 186 void 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 }
 206 EXPORT_SYMBOL_GPL(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  */
 219 struct 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  */
 249 void 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