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 #if IS_ENABLED(CONFIG_SUNRPC_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 < atomic_read(&xprt->bc_free_slots);
  41 }
  42
  43 static inline void xprt_inc_alloc_count(struct rpc_xprt *xprt, unsigned int n)
  44 {
  45         atomic_add(n, &xprt->bc_free_slots);
  46         xprt->bc_alloc_count += n;
  47 }
  48
  49 static inline int xprt_dec_alloc_count(struct rpc_xprt *xprt, unsigned int n)
  50 {
  51         atomic_sub(n, &xprt->bc_free_slots);
  52         return xprt->bc_alloc_count -= n;
  53 }
  54
  55 /*
  56  * Free the preallocated rpc_rqst structure and the memory
  57  * buffers hanging off of it.
  58  */
  59 static void xprt_free_allocation(struct rpc_rqst *req)
  60 {
  61         struct xdr_buf *xbufp;
  62
  63         dprintk("RPC:        free allocations for req= %p\n", req);
  64         WARN_ON_ONCE(test_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state));
  65         xbufp = &req->rq_rcv_buf;
  66         free_page((unsigned long)xbufp->head[0].iov_base);
  67         xbufp = &req->rq_snd_buf;
  68         free_page((unsigned long)xbufp->head[0].iov_base);
  69         kfree(req);
  70 }
  71
  72 static int xprt_alloc_xdr_buf(struct xdr_buf *buf, gfp_t gfp_flags)
  73 {
  74         struct page *page;
  75         /* Preallocate one XDR receive buffer */
  76         page = alloc_page(gfp_flags);
  77         if (page == NULL)
  78                 return -ENOMEM;
  79         buf->head[0].iov_base = page_address(page);
  80         buf->head[0].iov_len = PAGE_SIZE;
  81         buf->tail[0].iov_base = NULL;
  82         buf->tail[0].iov_len = 0;
  83         buf->page_len = 0;
  84         buf->len = 0;
  85         buf->buflen = PAGE_SIZE;
  86         return 0;
  87 }
  88
  89 static
  90 struct rpc_rqst *xprt_alloc_bc_req(struct rpc_xprt *xprt, gfp_t gfp_flags)
  91 {
  92         struct rpc_rqst *req;
  93
  94         /* Pre-allocate one backchannel rpc_rqst */
  95         req = kzalloc(sizeof(*req), gfp_flags);
  96         if (req == NULL)
  97                 return NULL;
  98
  99         req->rq_xprt = xprt;
 100         INIT_LIST_HEAD(&req->rq_list);
 101         INIT_LIST_HEAD(&req->rq_bc_list);
 102
 103         /* Preallocate one XDR receive buffer */
 104         if (xprt_alloc_xdr_buf(&req->rq_rcv_buf, gfp_flags) < 0) {
 105                 printk(KERN_ERR "Failed to create bc receive xbuf\n");
 106                 goto out_free;
 107         }
 108         req->rq_rcv_buf.len = PAGE_SIZE;
 109
 110         /* Preallocate one XDR send buffer */
 111         if (xprt_alloc_xdr_buf(&req->rq_snd_buf, gfp_flags) < 0) {
 112                 printk(KERN_ERR "Failed to create bc snd xbuf\n");
 113                 goto out_free;
 114         }
 115         return req;
 116 out_free:
 117         xprt_free_allocation(req);
 118         return NULL;
 119 }
 120
 121 /*
 122  * Preallocate up to min_reqs structures and related buffers for use
 123  * by the backchannel.  This function can be called multiple times
 124  * when creating new sessions that use the same rpc_xprt.  The
 125  * preallocated buffers are added to the pool of resources used by
 126  * the rpc_xprt.  Anyone of these resources may be used used by an
 127  * incoming callback request.  It's up to the higher levels in the
 128  * stack to enforce that the maximum number of session slots is not
 129  * being exceeded.
 130  *
 131  * Some callback arguments can be large.  For example, a pNFS server
 132  * using multiple deviceids.  The list can be unbound, but the client
 133  * has the ability to tell the server the maximum size of the callback
 134  * requests.  Each deviceID is 16 bytes, so allocate one page
 135  * for the arguments to have enough room to receive a number of these
 136  * deviceIDs.  The NFS client indicates to the pNFS server that its
 137  * callback requests can be up to 4096 bytes in size.
 138  */
 139 int xprt_setup_backchannel(struct rpc_xprt *xprt, unsigned int min_reqs)
 140 {
 141         if (!xprt->ops->bc_setup)
 142                 return 0;
 143         return xprt->ops->bc_setup(xprt, min_reqs);
 144 }
 145 EXPORT_SYMBOL_GPL(xprt_setup_backchannel);
 146
 147 int xprt_setup_bc(struct rpc_xprt *xprt, unsigned int min_reqs)
 148 {
 149         struct rpc_rqst *req;
 150         struct list_head tmp_list;
 151         int i;
 152
 153         dprintk("RPC:       setup backchannel transport\n");
 154
 155         /*
 156          * We use a temporary list to keep track of the preallocated
 157          * buffers.  Once we're done building the list we splice it
 158          * into the backchannel preallocation list off of the rpc_xprt
 159          * struct.  This helps minimize the amount of time the list
 160          * lock is held on the rpc_xprt struct.  It also makes cleanup
 161          * easier in case of memory allocation errors.
 162          */
 163         INIT_LIST_HEAD(&tmp_list);
 164         for (i = 0; i < min_reqs; i++) {
 165                 /* Pre-allocate one backchannel rpc_rqst */
 166                 req = xprt_alloc_bc_req(xprt, GFP_KERNEL);
 167                 if (req == NULL) {
 168                         printk(KERN_ERR "Failed to create bc rpc_rqst\n");
 169                         goto out_free;
 170                 }
 171
 172                 /* Add the allocated buffer to the tmp list */
 173                 dprintk("RPC:       adding req= %p\n", req);
 174                 list_add(&req->rq_bc_pa_list, &tmp_list);
 175         }
 176
 177         /*
 178          * Add the temporary list to the backchannel preallocation list
 179          */
 180         spin_lock_bh(&xprt->bc_pa_lock);
 181         list_splice(&tmp_list, &xprt->bc_pa_list);
 182         xprt_inc_alloc_count(xprt, min_reqs);
 183         spin_unlock_bh(&xprt->bc_pa_lock);
 184
 185         dprintk("RPC:       setup backchannel transport done\n");
 186         return 0;
 187
 188 out_free:
 189         /*
 190          * Memory allocation failed, free the temporary list
 191          */
 192         while (!list_empty(&tmp_list)) {
 193                 req = list_first_entry(&tmp_list,
 194                                 struct rpc_rqst,
 195                                 rq_bc_pa_list);
 196                 list_del(&req->rq_bc_pa_list);
 197                 xprt_free_allocation(req);
 198         }
 199
 200         dprintk("RPC:       setup backchannel transport failed\n");
 201         return -ENOMEM;
 202 }
 203
 204 /**
 205  * xprt_destroy_backchannel - Destroys the backchannel preallocated structures.
 206  * @xprt:       the transport holding the preallocated strucures
 207  * @max_reqs    the maximum number of preallocated structures to destroy
 208  *
 209  * Since these structures may have been allocated by multiple calls
 210  * to xprt_setup_backchannel, we only destroy up to the maximum number
 211  * of reqs specified by the caller.
 212  */
 213 void xprt_destroy_backchannel(struct rpc_xprt *xprt, unsigned int max_reqs)
 214 {
 215         if (xprt->ops->bc_destroy)
 216                 xprt->ops->bc_destroy(xprt, max_reqs);
 217 }
 218 EXPORT_SYMBOL_GPL(xprt_destroy_backchannel);
 219
 220 void xprt_destroy_bc(struct rpc_xprt *xprt, unsigned int max_reqs)
 221 {
 222         struct rpc_rqst *req = NULL, *tmp = NULL;
 223
 224         dprintk("RPC:        destroy backchannel transport\n");
 225
 226         if (max_reqs == 0)
 227                 goto out;
 228
 229         spin_lock_bh(&xprt->bc_pa_lock);
 230         xprt_dec_alloc_count(xprt, max_reqs);
 231         list_for_each_entry_safe(req, tmp, &xprt->bc_pa_list, rq_bc_pa_list) {
 232                 dprintk("RPC:        req=%p\n", req);
 233                 list_del(&req->rq_bc_pa_list);
 234                 xprt_free_allocation(req);
 235                 if (--max_reqs == 0)
 236                         break;
 237         }
 238         spin_unlock_bh(&xprt->bc_pa_lock);
 239
 240 out:
 241         dprintk("RPC:        backchannel list empty= %s\n",
 242                 list_empty(&xprt->bc_pa_list) ? "true" : "false");
 243 }
 244
 245 static struct rpc_rqst *xprt_alloc_bc_request(struct rpc_xprt *xprt, __be32 xid)
 246 {
 247         struct rpc_rqst *req = NULL;
 248
 249         dprintk("RPC:       allocate a backchannel request\n");
 250         if (atomic_read(&xprt->bc_free_slots) <= 0)
 251                 goto not_found;
 252         if (list_empty(&xprt->bc_pa_list)) {
 253                 req = xprt_alloc_bc_req(xprt, GFP_ATOMIC);
 254                 if (!req)
 255                         goto not_found;
 256                 list_add_tail(&req->rq_bc_pa_list, &xprt->bc_pa_list);
 257                 xprt->bc_alloc_count++;
 258         }
 259         req = list_first_entry(&xprt->bc_pa_list, struct rpc_rqst,
 260                                 rq_bc_pa_list);
 261         req->rq_reply_bytes_recvd = 0;
 262         req->rq_bytes_sent = 0;
 263         memcpy(&req->rq_private_buf, &req->rq_rcv_buf,
 264                         sizeof(req->rq_private_buf));
 265         req->rq_xid = xid;
 266         req->rq_connect_cookie = xprt->connect_cookie;
 267 not_found:
 268         dprintk("RPC:       backchannel req=%p\n", req);
 269         return req;
 270 }
 271
 272 /*
 273  * Return the preallocated rpc_rqst structure and XDR buffers
 274  * associated with this rpc_task.
 275  */
 276 void xprt_free_bc_request(struct rpc_rqst *req)
 277 {
 278         struct rpc_xprt *xprt = req->rq_xprt;
 279
 280         xprt->ops->bc_free_rqst(req);
 281 }
 282
 283 void xprt_free_bc_rqst(struct rpc_rqst *req)
 284 {
 285         struct rpc_xprt *xprt = req->rq_xprt;
 286
 287         dprintk("RPC:       free backchannel req=%p\n", req);
 288
 289         req->rq_connect_cookie = xprt->connect_cookie - 1;
 290         smp_mb__before_atomic();
 291         clear_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state);
 292         smp_mb__after_atomic();
 293
 294         /*
 295          * Return it to the list of preallocations so that it
 296          * may be reused by a new callback request.
 297          */
 298         spin_lock_bh(&xprt->bc_pa_lock);
 299         if (xprt_need_to_requeue(xprt)) {
 300                 list_add_tail(&req->rq_bc_pa_list, &xprt->bc_pa_list);
 301                 xprt->bc_alloc_count++;
 302                 req = NULL;
 303         }
 304         spin_unlock_bh(&xprt->bc_pa_lock);
 305         if (req != NULL) {
 306                 /*
 307                  * The last remaining session was destroyed while this
 308                  * entry was in use.  Free the entry and don't attempt
 309                  * to add back to the list because there is no need to
 310                  * have anymore preallocated entries.
 311                  */
 312                 dprintk("RPC:       Last session removed req=%p\n", req);
 313                 xprt_free_allocation(req);
 314                 return;
 315         }
 316 }
 317
 318 /*
 319  * One or more rpc_rqst structure have been preallocated during the
 320  * backchannel setup.  Buffer space for the send and private XDR buffers
 321  * has been preallocated as well.  Use xprt_alloc_bc_request to allocate
 322  * to this request.  Use xprt_free_bc_request to return it.
 323  *
 324  * We know that we're called in soft interrupt context, grab the spin_lock
 325  * since there is no need to grab the bottom half spin_lock.
 326  *
 327  * Return an available rpc_rqst, otherwise NULL if non are available.
 328  */
 329 struct rpc_rqst *xprt_lookup_bc_request(struct rpc_xprt *xprt, __be32 xid)
 330 {
 331         struct rpc_rqst *req;
 332
 333         spin_lock(&xprt->bc_pa_lock);
 334         list_for_each_entry(req, &xprt->bc_pa_list, rq_bc_pa_list) {
 335                 if (req->rq_connect_cookie != xprt->connect_cookie)
 336                         continue;
 337                 if (req->rq_xid == xid)
 338                         goto found;
 339         }
 340         req = xprt_alloc_bc_request(xprt, xid);
 341 found:
 342         spin_unlock(&xprt->bc_pa_lock);
 343         return req;
 344 }
 345
 346 /*
 347  * Add callback request to callback list.  The callback
 348  * service sleeps on the sv_cb_waitq waiting for new
 349  * requests.  Wake it up after adding enqueing the
 350  * request.
 351  */
 352 void xprt_complete_bc_request(struct rpc_rqst *req, uint32_t copied)
 353 {
 354         struct rpc_xprt *xprt = req->rq_xprt;
 355         struct svc_serv *bc_serv = xprt->bc_serv;
 356
 357         spin_lock(&xprt->bc_pa_lock);
 358         list_del(&req->rq_bc_pa_list);
 359         xprt_dec_alloc_count(xprt, 1);
 360         spin_unlock(&xprt->bc_pa_lock);
 361
 362         req->rq_private_buf.len = copied;
 363         set_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state);
 364
 365         dprintk("RPC:       add callback request to list\n");
 366         spin_lock(&bc_serv->sv_cb_lock);
 367         list_add(&req->rq_bc_list, &bc_serv->sv_cb_list);
 368         wake_up(&bc_serv->sv_cb_waitq);
 369         spin_unlock(&bc_serv->sv_cb_lock);
 370 }
 371