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