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 https://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 #define BC_MAX_SLOTS    64U
  35
  36 unsigned int xprt_bc_max_slots(struct rpc_xprt *xprt)
  37 {
  38         return BC_MAX_SLOTS;
  39 }
  40
  41 /*
  42  * Helper routines that track the number of preallocation elements
  43  * on the transport.
  44  */
  45 static inline int xprt_need_to_requeue(struct rpc_xprt *xprt)
  46 {
  47         return xprt->bc_alloc_count < xprt->bc_alloc_max;
  48 }
  49
  50 /*
  51  * Free the preallocated rpc_rqst structure and the memory
  52  * buffers hanging off of it.
  53  */
  54 static void xprt_free_allocation(struct rpc_rqst *req)
  55 {
  56         struct xdr_buf *xbufp;
  57
  58         dprintk("RPC:        free allocations for req= %p\n", req);
  59         WARN_ON_ONCE(test_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state));
  60         xbufp = &req->rq_rcv_buf;
  61         free_page((unsigned long)xbufp->head[0].iov_base);
  62         xbufp = &req->rq_snd_buf;
  63         free_page((unsigned long)xbufp->head[0].iov_base);
  64         kfree(req);
  65 }
  66
  67 static int xprt_alloc_xdr_buf(struct xdr_buf *buf, gfp_t gfp_flags)
  68 {
  69         struct page *page;
  70         /* Preallocate one XDR receive buffer */
  71         page = alloc_page(gfp_flags);
  72         if (page == NULL)
  73                 return -ENOMEM;
  74         xdr_buf_init(buf, page_address(page), PAGE_SIZE);
  75         return 0;
  76 }
  77
  78 static
  79 struct rpc_rqst *xprt_alloc_bc_req(struct rpc_xprt *xprt, gfp_t gfp_flags)
  80 {
  81         struct rpc_rqst *req;
  82
  83         /* Pre-allocate one backchannel rpc_rqst */
  84         req = kzalloc(sizeof(*req), gfp_flags);
  85         if (req == NULL)
  86                 return NULL;
  87
  88         req->rq_xprt = xprt;
  89         INIT_LIST_HEAD(&req->rq_bc_list);
  90
  91         /* Preallocate one XDR receive buffer */
  92         if (xprt_alloc_xdr_buf(&req->rq_rcv_buf, gfp_flags) < 0) {
  93                 printk(KERN_ERR "Failed to create bc receive xbuf\n");
  94                 goto out_free;
  95         }
  96         req->rq_rcv_buf.len = PAGE_SIZE;
  97
  98         /* Preallocate one XDR send buffer */
  99         if (xprt_alloc_xdr_buf(&req->rq_snd_buf, gfp_flags) < 0) {
 100                 printk(KERN_ERR "Failed to create bc snd xbuf\n");
 101                 goto out_free;
 102         }
 103         return req;
 104 out_free:
 105         xprt_free_allocation(req);
 106         return NULL;
 107 }
 108
 109 /*
 110  * Preallocate up to min_reqs structures and related buffers for use
 111  * by the backchannel.  This function can be called multiple times
 112  * when creating new sessions that use the same rpc_xprt.  The
 113  * preallocated buffers are added to the pool of resources used by
 114  * the rpc_xprt.  Any one of these resources may be used by an
 115  * incoming callback request.  It's up to the higher levels in the
 116  * stack to enforce that the maximum number of session slots is not
 117  * being exceeded.
 118  *
 119  * Some callback arguments can be large.  For example, a pNFS server
 120  * using multiple deviceids.  The list can be unbound, but the client
 121  * has the ability to tell the server the maximum size of the callback
 122  * requests.  Each deviceID is 16 bytes, so allocate one page
 123  * for the arguments to have enough room to receive a number of these
 124  * deviceIDs.  The NFS client indicates to the pNFS server that its
 125  * callback requests can be up to 4096 bytes in size.
 126  */
 127 int xprt_setup_backchannel(struct rpc_xprt *xprt, unsigned int min_reqs)
 128 {
 129         if (!xprt->ops->bc_setup)
 130                 return 0;
 131         return xprt->ops->bc_setup(xprt, min_reqs);
 132 }
 133 EXPORT_SYMBOL_GPL(xprt_setup_backchannel);
 134
 135 int xprt_setup_bc(struct rpc_xprt *xprt, unsigned int min_reqs)
 136 {
 137         struct rpc_rqst *req;
 138         struct list_head tmp_list;
 139         int i;
 140
 141         dprintk("RPC:       setup backchannel transport\n");
 142
 143         if (min_reqs > BC_MAX_SLOTS)
 144                 min_reqs = BC_MAX_SLOTS;
 145
 146         /*
 147          * We use a temporary list to keep track of the preallocated
 148          * buffers.  Once we're done building the list we splice it
 149          * into the backchannel preallocation list off of the rpc_xprt
 150          * struct.  This helps minimize the amount of time the list
 151          * lock is held on the rpc_xprt struct.  It also makes cleanup
 152          * easier in case of memory allocation errors.
 153          */
 154         INIT_LIST_HEAD(&tmp_list);
 155         for (i = 0; i < min_reqs; i++) {
 156                 /* Pre-allocate one backchannel rpc_rqst */
 157                 req = xprt_alloc_bc_req(xprt, GFP_KERNEL);
 158                 if (req == NULL) {
 159                         printk(KERN_ERR "Failed to create bc rpc_rqst\n");
 160                         goto out_free;
 161                 }
 162
 163                 /* Add the allocated buffer to the tmp list */
 164                 dprintk("RPC:       adding req= %p\n", req);
 165                 list_add(&req->rq_bc_pa_list, &tmp_list);
 166         }
 167
 168         /*
 169          * Add the temporary list to the backchannel preallocation list
 170          */
 171         spin_lock(&xprt->bc_pa_lock);
 172         list_splice(&tmp_list, &xprt->bc_pa_list);
 173         xprt->bc_alloc_count += min_reqs;
 174         xprt->bc_alloc_max += min_reqs;
 175         atomic_add(min_reqs, &xprt->bc_slot_count);
 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->bc_alloc_max -= min(max_reqs, xprt->bc_alloc_max);
 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                 xprt->bc_alloc_count--;
 229                 atomic_dec(&xprt->bc_slot_count);
 230                 if (--max_reqs == 0)
 231                         break;
 232         }
 233         spin_unlock_bh(&xprt->bc_pa_lock);
 234
 235 out:
 236         dprintk("RPC:        backchannel list empty= %s\n",
 237                 list_empty(&xprt->bc_pa_list) ? "true" : "false");
 238 }
 239
 240 static struct rpc_rqst *xprt_get_bc_request(struct rpc_xprt *xprt, __be32 xid,
 241                 struct rpc_rqst *new)
 242 {
 243         struct rpc_rqst *req = NULL;
 244
 245         dprintk("RPC:       allocate a backchannel request\n");
 246         if (list_empty(&xprt->bc_pa_list)) {
 247                 if (!new)
 248                         goto not_found;
 249                 if (atomic_read(&xprt->bc_slot_count) >= BC_MAX_SLOTS)
 250                         goto not_found;
 251                 list_add_tail(&new->rq_bc_pa_list, &xprt->bc_pa_list);
 252                 xprt->bc_alloc_count++;
 253                 atomic_inc(&xprt->bc_slot_count);
 254         }
 255         req = list_first_entry(&xprt->bc_pa_list, struct rpc_rqst,
 256                                 rq_bc_pa_list);
 257         req->rq_reply_bytes_recvd = 0;
 258         memcpy(&req->rq_private_buf, &req->rq_rcv_buf,
 259                         sizeof(req->rq_private_buf));
 260         req->rq_xid = xid;
 261         req->rq_connect_cookie = xprt->connect_cookie;
 262         dprintk("RPC:       backchannel req=%p\n", req);
 263 not_found:
 264         return req;
 265 }
 266
 267 /*
 268  * Return the preallocated rpc_rqst structure and XDR buffers
 269  * associated with this rpc_task.
 270  */
 271 void xprt_free_bc_request(struct rpc_rqst *req)
 272 {
 273         struct rpc_xprt *xprt = req->rq_xprt;
 274
 275         xprt->ops->bc_free_rqst(req);
 276 }
 277
 278 void xprt_free_bc_rqst(struct rpc_rqst *req)
 279 {
 280         struct rpc_xprt *xprt = req->rq_xprt;
 281
 282         dprintk("RPC:       free backchannel req=%p\n", req);
 283
 284         req->rq_connect_cookie = xprt->connect_cookie - 1;
 285         smp_mb__before_atomic();
 286         clear_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state);
 287         smp_mb__after_atomic();
 288
 289         /*
 290          * Return it to the list of preallocations so that it
 291          * may be reused by a new callback request.
 292          */
 293         spin_lock_bh(&xprt->bc_pa_lock);
 294         if (xprt_need_to_requeue(xprt)) {
 295                 list_add_tail(&req->rq_bc_pa_list, &xprt->bc_pa_list);
 296                 xprt->bc_alloc_count++;
 297                 atomic_inc(&xprt->bc_slot_count);
 298                 req = NULL;
 299         }
 300         spin_unlock_bh(&xprt->bc_pa_lock);
 301         if (req != NULL) {
 302                 /*
 303                  * The last remaining session was destroyed while this
 304                  * entry was in use.  Free the entry and don't attempt
 305                  * to add back to the list because there is no need to
 306                  * have anymore preallocated entries.
 307                  */
 308                 dprintk("RPC:       Last session removed req=%p\n", req);
 309                 xprt_free_allocation(req);
 310         }
 311         xprt_put(xprt);
 312 }
 313
 314 /*
 315  * One or more rpc_rqst structure have been preallocated during the
 316  * backchannel setup.  Buffer space for the send and private XDR buffers
 317  * has been preallocated as well.  Use xprt_alloc_bc_request to allocate
 318  * to this request.  Use xprt_free_bc_request to return it.
 319  *
 320  * We know that we're called in soft interrupt context, grab the spin_lock
 321  * since there is no need to grab the bottom half spin_lock.
 322  *
 323  * Return an available rpc_rqst, otherwise NULL if non are available.
 324  */
 325 struct rpc_rqst *xprt_lookup_bc_request(struct rpc_xprt *xprt, __be32 xid)
 326 {
 327         struct rpc_rqst *req, *new = NULL;
 328
 329         do {
 330                 spin_lock(&xprt->bc_pa_lock);
 331                 list_for_each_entry(req, &xprt->bc_pa_list, rq_bc_pa_list) {
 332                         if (req->rq_connect_cookie != xprt->connect_cookie)
 333                                 continue;
 334                         if (req->rq_xid == xid)
 335                                 goto found;
 336                 }
 337                 req = xprt_get_bc_request(xprt, xid, new);
 338 found:
 339                 spin_unlock(&xprt->bc_pa_lock);
 340                 if (new) {
 341                         if (req != new)
 342                                 xprt_free_allocation(new);
 343                         break;
 344                 } else if (req)
 345                         break;
 346                 new = xprt_alloc_bc_req(xprt, GFP_KERNEL);
 347         } while (new);
 348         return req;
 349 }
 350
 351 /*
 352  * Add callback request to callback list.  The callback
 353  * service sleeps on the sv_cb_waitq waiting for new
 354  * requests.  Wake it up after adding enqueing the
 355  * request.
 356  */
 357 void xprt_complete_bc_request(struct rpc_rqst *req, uint32_t copied)
 358 {
 359         struct rpc_xprt *xprt = req->rq_xprt;
 360         struct svc_serv *bc_serv = xprt->bc_serv;
 361
 362         spin_lock(&xprt->bc_pa_lock);
 363         list_del(&req->rq_bc_pa_list);
 364         xprt->bc_alloc_count--;
 365         spin_unlock(&xprt->bc_pa_lock);
 366
 367         req->rq_private_buf.len = copied;
 368         set_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state);
 369
 370         dprintk("RPC:       add callback request to list\n");
 371         xprt_get(xprt);
 372         spin_lock(&bc_serv->sv_cb_lock);
 373         list_add(&req->rq_bc_list, &bc_serv->sv_cb_list);
 374         wake_up(&bc_serv->sv_cb_waitq);
 375         spin_unlock(&bc_serv->sv_cb_lock);
 376 }