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