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