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