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         WARN_ON_ONCE(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         kfree(req);
  68 }
  69
  70 /*
  71  * Preallocate up to min_reqs structures and related buffers for use
  72  * by the backchannel.  This function can be called multiple times
  73  * when creating new sessions that use the same rpc_xprt.  The
  74  * preallocated buffers are added to the pool of resources used by
  75  * the rpc_xprt.  Anyone of these resources may be used used by an
  76  * incoming callback request.  It's up to the higher levels in the
  77  * stack to enforce that the maximum number of session slots is not
  78  * being exceeded.
  79  *
  80  * Some callback arguments can be large.  For example, a pNFS server
  81  * using multiple deviceids.  The list can be unbound, but the client
  82  * has the ability to tell the server the maximum size of the callback
  83  * requests.  Each deviceID is 16 bytes, so allocate one page
  84  * for the arguments to have enough room to receive a number of these
  85  * deviceIDs.  The NFS client indicates to the pNFS server that its
  86  * callback requests can be up to 4096 bytes in size.
  87  */
  88 int xprt_setup_backchannel(struct rpc_xprt *xprt, unsigned int min_reqs)
  89 {
  90         struct page *page_rcv = NULL, *page_snd = NULL;
  91         struct xdr_buf *xbufp = NULL;
  92         struct rpc_rqst *req, *tmp;
  93         struct list_head tmp_list;
  94         int i;
  95
  96         dprintk("RPC:       setup backchannel transport\n");
  97
  98         /*
  99          * We use a temporary list to keep track of the preallocated
 100          * buffers.  Once we're done building the list we splice it
 101          * into the backchannel preallocation list off of the rpc_xprt
 102          * struct.  This helps minimize the amount of time the list
 103          * lock is held on the rpc_xprt struct.  It also makes cleanup
 104          * easier in case of memory allocation errors.
 105          */
 106         INIT_LIST_HEAD(&tmp_list);
 107         for (i = 0; i < min_reqs; i++) {
 108                 /* Pre-allocate one backchannel rpc_rqst */
 109                 req = kzalloc(sizeof(struct rpc_rqst), GFP_KERNEL);
 110                 if (req == NULL) {
 111                         printk(KERN_ERR "Failed to create bc rpc_rqst\n");
 112                         goto out_free;
 113                 }
 114
 115                 /* Add the allocated buffer to the tmp list */
 116                 dprintk("RPC:       adding req= %p\n", req);
 117                 list_add(&req->rq_bc_pa_list, &tmp_list);
 118
 119                 req->rq_xprt = xprt;
 120                 INIT_LIST_HEAD(&req->rq_list);
 121                 INIT_LIST_HEAD(&req->rq_bc_list);
 122
 123                 /* Preallocate one XDR receive buffer */
 124                 page_rcv = alloc_page(GFP_KERNEL);
 125                 if (page_rcv == NULL) {
 126                         printk(KERN_ERR "Failed to create bc receive xbuf\n");
 127                         goto out_free;
 128                 }
 129                 xbufp = &req->rq_rcv_buf;
 130                 xbufp->head[0].iov_base = page_address(page_rcv);
 131                 xbufp->head[0].iov_len = PAGE_SIZE;
 132                 xbufp->tail[0].iov_base = NULL;
 133                 xbufp->tail[0].iov_len = 0;
 134                 xbufp->page_len = 0;
 135                 xbufp->len = PAGE_SIZE;
 136                 xbufp->buflen = PAGE_SIZE;
 137
 138                 /* Preallocate one XDR send buffer */
 139                 page_snd = alloc_page(GFP_KERNEL);
 140                 if (page_snd == NULL) {
 141                         printk(KERN_ERR "Failed to create bc snd xbuf\n");
 142                         goto out_free;
 143                 }
 144
 145                 xbufp = &req->rq_snd_buf;
 146                 xbufp->head[0].iov_base = page_address(page_snd);
 147                 xbufp->head[0].iov_len = 0;
 148                 xbufp->tail[0].iov_base = NULL;
 149                 xbufp->tail[0].iov_len = 0;
 150                 xbufp->page_len = 0;
 151                 xbufp->len = 0;
 152                 xbufp->buflen = PAGE_SIZE;
 153         }
 154
 155         /*
 156          * Add the temporary list to the backchannel preallocation list
 157          */
 158         spin_lock_bh(&xprt->bc_pa_lock);
 159         list_splice(&tmp_list, &xprt->bc_pa_list);
 160         xprt_inc_alloc_count(xprt, min_reqs);
 161         spin_unlock_bh(&xprt->bc_pa_lock);
 162
 163         dprintk("RPC:       setup backchannel transport done\n");
 164         return 0;
 165
 166 out_free:
 167         /*
 168          * Memory allocation failed, free the temporary list
 169          */
 170         list_for_each_entry_safe(req, tmp, &tmp_list, rq_bc_pa_list) {
 171                 list_del(&req->rq_bc_pa_list);
 172                 xprt_free_allocation(req);
 173         }
 174
 175         dprintk("RPC:       setup backchannel transport failed\n");
 176         return -ENOMEM;
 177 }
 178 EXPORT_SYMBOL_GPL(xprt_setup_backchannel);
 179
 180 /**
 181  * xprt_destroy_backchannel - Destroys the backchannel preallocated structures.
 182  * @xprt:       the transport holding the preallocated strucures
 183  * @max_reqs    the maximum number of preallocated structures to destroy
 184  *
 185  * Since these structures may have been allocated by multiple calls
 186  * to xprt_setup_backchannel, we only destroy up to the maximum number
 187  * of reqs specified by the caller.
 188  */
 189 void xprt_destroy_backchannel(struct rpc_xprt *xprt, unsigned int max_reqs)
 190 {
 191         struct rpc_rqst *req = NULL, *tmp = NULL;
 192
 193         dprintk("RPC:        destroy backchannel transport\n");
 194
 195         if (max_reqs == 0)
 196                 goto out;
 197
 198         spin_lock_bh(&xprt->bc_pa_lock);
 199         xprt_dec_alloc_count(xprt, max_reqs);
 200         list_for_each_entry_safe(req, tmp, &xprt->bc_pa_list, rq_bc_pa_list) {
 201                 dprintk("RPC:        req=%p\n", req);
 202                 list_del(&req->rq_bc_pa_list);
 203                 xprt_free_allocation(req);
 204                 if (--max_reqs == 0)
 205                         break;
 206         }
 207         spin_unlock_bh(&xprt->bc_pa_lock);
 208
 209 out:
 210         dprintk("RPC:        backchannel list empty= %s\n",
 211                 list_empty(&xprt->bc_pa_list) ? "true" : "false");
 212 }
 213 EXPORT_SYMBOL_GPL(xprt_destroy_backchannel);
 214
 215 /*
 216  * One or more rpc_rqst structure have been preallocated during the
 217  * backchannel setup.  Buffer space for the send and private XDR buffers
 218  * has been preallocated as well.  Use xprt_alloc_bc_request to allocate
 219  * to this request.  Use xprt_free_bc_request to return it.
 220  *
 221  * We know that we're called in soft interrupt context, grab the spin_lock
 222  * since there is no need to grab the bottom half spin_lock.
 223  *
 224  * Return an available rpc_rqst, otherwise NULL if non are available.
 225  */
 226 struct rpc_rqst *xprt_alloc_bc_request(struct rpc_xprt *xprt)
 227 {
 228         struct rpc_rqst *req;
 229
 230         dprintk("RPC:       allocate a backchannel request\n");
 231         spin_lock(&xprt->bc_pa_lock);
 232         if (!list_empty(&xprt->bc_pa_list)) {
 233                 req = list_first_entry(&xprt->bc_pa_list, struct rpc_rqst,
 234                                 rq_bc_pa_list);
 235                 list_del(&req->rq_bc_pa_list);
 236         } else {
 237                 req = NULL;
 238         }
 239         spin_unlock(&xprt->bc_pa_lock);
 240
 241         if (req != NULL) {
 242                 set_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state);
 243                 req->rq_reply_bytes_recvd = 0;
 244                 req->rq_bytes_sent = 0;
 245                 memcpy(&req->rq_private_buf, &req->rq_rcv_buf,
 246                         sizeof(req->rq_private_buf));
 247         }
 248         dprintk("RPC:       backchannel req=%p\n", req);
 249         return req;
 250 }
 251
 252 /*
 253  * Return the preallocated rpc_rqst structure and XDR buffers
 254  * associated with this rpc_task.
 255  */
 256 void xprt_free_bc_request(struct rpc_rqst *req)
 257 {
 258         struct rpc_xprt *xprt = req->rq_xprt;
 259
 260         dprintk("RPC:       free backchannel req=%p\n", req);
 261
 262         smp_mb__before_clear_bit();
 263         WARN_ON_ONCE(!test_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state));
 264         clear_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state);
 265         smp_mb__after_clear_bit();
 266
 267         if (!xprt_need_to_requeue(xprt)) {
 268                 /*
 269                  * The last remaining session was destroyed while this
 270                  * entry was in use.  Free the entry and don't attempt
 271                  * to add back to the list because there is no need to
 272                  * have anymore preallocated entries.
 273                  */
 274                 dprintk("RPC:       Last session removed req=%p\n", req);
 275                 xprt_free_allocation(req);
 276                 return;
 277         }
 278
 279         /*
 280          * Return it to the list of preallocations so that it
 281          * may be reused by a new callback request.
 282          */
 283         spin_lock_bh(&xprt->bc_pa_lock);
 284         list_add(&req->rq_bc_pa_list, &xprt->bc_pa_list);
 285         spin_unlock_bh(&xprt->bc_pa_lock);
 286 }
 287