backchannel_rqst.c revision c4ded8d9771c8e8d5d7a202d58af9c70591dd675
1/****************************************************************************** 2 3(c) 2007 Network Appliance, Inc. All Rights Reserved. 4(c) 2009 NetApp. All Rights Reserved. 5 6NetApp provides this source code under the GPL v2 License. 7The GPL v2 license is available at 8http://opensource.org/licenses/gpl-license.php. 9 10THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 11"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 12LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 13A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR 14CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 15EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 16PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 17PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 18LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING 19NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 20SOFTWARE, 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 */ 38static inline int xprt_need_to_requeue(struct rpc_xprt *xprt) 39{ 40 return xprt->bc_alloc_count > 0; 41} 42 43static inline void xprt_inc_alloc_count(struct rpc_xprt *xprt, unsigned int n) 44{ 45 xprt->bc_alloc_count += n; 46} 47 48static 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 */ 57static 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 BUG_ON(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 list_del(&req->rq_bc_pa_list); 68 kfree(req); 69} 70 71/* 72 * Preallocate up to min_reqs structures and related buffers for use 73 * by the backchannel. This function can be called multiple times 74 * when creating new sessions that use the same rpc_xprt. The 75 * preallocated buffers are added to the pool of resources used by 76 * the rpc_xprt. Anyone of these resources may be used used by an 77 * incoming callback request. It's up to the higher levels in the 78 * stack to enforce that the maximum number of session slots is not 79 * being exceeded. 80 * 81 * Some callback arguments can be large. For example, a pNFS server 82 * using multiple deviceids. The list can be unbound, but the client 83 * has the ability to tell the server the maximum size of the callback 84 * requests. Each deviceID is 16 bytes, so allocate one page 85 * for the arguments to have enough room to receive a number of these 86 * deviceIDs. The NFS client indicates to the pNFS server that its 87 * callback requests can be up to 4096 bytes in size. 88 */ 89int xprt_setup_backchannel(struct rpc_xprt *xprt, unsigned int min_reqs) 90{ 91 struct page *page_rcv = NULL, *page_snd = NULL; 92 struct xdr_buf *xbufp = NULL; 93 struct rpc_rqst *req, *tmp; 94 struct list_head tmp_list; 95 int i; 96 97 dprintk("RPC: setup backchannel transport\n"); 98 99 /* 100 * We use a temporary list to keep track of the preallocated 101 * buffers. Once we're done building the list we splice it 102 * into the backchannel preallocation list off of the rpc_xprt 103 * struct. This helps minimize the amount of time the list 104 * lock is held on the rpc_xprt struct. It also makes cleanup 105 * easier in case of memory allocation errors. 106 */ 107 INIT_LIST_HEAD(&tmp_list); 108 for (i = 0; i < min_reqs; i++) { 109 /* Pre-allocate one backchannel rpc_rqst */ 110 req = kzalloc(sizeof(struct rpc_rqst), GFP_KERNEL); 111 if (req == NULL) { 112 printk(KERN_ERR "Failed to create bc rpc_rqst\n"); 113 goto out_free; 114 } 115 116 /* Add the allocated buffer to the tmp list */ 117 dprintk("RPC: adding req= %p\n", req); 118 list_add(&req->rq_bc_pa_list, &tmp_list); 119 120 req->rq_xprt = xprt; 121 INIT_LIST_HEAD(&req->rq_list); 122 INIT_LIST_HEAD(&req->rq_bc_list); 123 124 /* Preallocate one XDR receive buffer */ 125 page_rcv = alloc_page(GFP_KERNEL); 126 if (page_rcv == NULL) { 127 printk(KERN_ERR "Failed to create bc receive xbuf\n"); 128 goto out_free; 129 } 130 xbufp = &req->rq_rcv_buf; 131 xbufp->head[0].iov_base = page_address(page_rcv); 132 xbufp->head[0].iov_len = PAGE_SIZE; 133 xbufp->tail[0].iov_base = NULL; 134 xbufp->tail[0].iov_len = 0; 135 xbufp->page_len = 0; 136 xbufp->len = PAGE_SIZE; 137 xbufp->buflen = PAGE_SIZE; 138 139 /* Preallocate one XDR send buffer */ 140 page_snd = alloc_page(GFP_KERNEL); 141 if (page_snd == NULL) { 142 printk(KERN_ERR "Failed to create bc snd xbuf\n"); 143 goto out_free; 144 } 145 146 xbufp = &req->rq_snd_buf; 147 xbufp->head[0].iov_base = page_address(page_snd); 148 xbufp->head[0].iov_len = 0; 149 xbufp->tail[0].iov_base = NULL; 150 xbufp->tail[0].iov_len = 0; 151 xbufp->page_len = 0; 152 xbufp->len = 0; 153 xbufp->buflen = PAGE_SIZE; 154 } 155 156 /* 157 * Add the temporary list to the backchannel preallocation list 158 */ 159 spin_lock_bh(&xprt->bc_pa_lock); 160 list_splice(&tmp_list, &xprt->bc_pa_list); 161 xprt_inc_alloc_count(xprt, min_reqs); 162 spin_unlock_bh(&xprt->bc_pa_lock); 163 164 dprintk("RPC: setup backchannel transport done\n"); 165 return 0; 166 167out_free: 168 /* 169 * Memory allocation failed, free the temporary list 170 */ 171 list_for_each_entry_safe(req, tmp, &tmp_list, rq_bc_pa_list) 172 xprt_free_allocation(req); 173 174 dprintk("RPC: setup backchannel transport failed\n"); 175 return -ENOMEM; 176} 177EXPORT_SYMBOL_GPL(xprt_setup_backchannel); 178 179/** 180 * xprt_destroy_backchannel - Destroys the backchannel preallocated structures. 181 * @xprt: the transport holding the preallocated strucures 182 * @max_reqs the maximum number of preallocated structures to destroy 183 * 184 * Since these structures may have been allocated by multiple calls 185 * to xprt_setup_backchannel, we only destroy up to the maximum number 186 * of reqs specified by the caller. 187 */ 188void xprt_destroy_backchannel(struct rpc_xprt *xprt, unsigned int max_reqs) 189{ 190 struct rpc_rqst *req = NULL, *tmp = NULL; 191 192 dprintk("RPC: destroy backchannel transport\n"); 193 194 if (max_reqs == 0) 195 goto out; 196 197 spin_lock_bh(&xprt->bc_pa_lock); 198 xprt_dec_alloc_count(xprt, max_reqs); 199 list_for_each_entry_safe(req, tmp, &xprt->bc_pa_list, rq_bc_pa_list) { 200 dprintk("RPC: req=%p\n", req); 201 xprt_free_allocation(req); 202 if (--max_reqs == 0) 203 break; 204 } 205 spin_unlock_bh(&xprt->bc_pa_lock); 206 207out: 208 dprintk("RPC: backchannel list empty= %s\n", 209 list_empty(&xprt->bc_pa_list) ? "true" : "false"); 210} 211EXPORT_SYMBOL_GPL(xprt_destroy_backchannel); 212 213/* 214 * One or more rpc_rqst structure have been preallocated during the 215 * backchannel setup. Buffer space for the send and private XDR buffers 216 * has been preallocated as well. Use xprt_alloc_bc_request to allocate 217 * to this request. Use xprt_free_bc_request to return it. 218 * 219 * We know that we're called in soft interrupt context, grab the spin_lock 220 * since there is no need to grab the bottom half spin_lock. 221 * 222 * Return an available rpc_rqst, otherwise NULL if non are available. 223 */ 224struct rpc_rqst *xprt_alloc_bc_request(struct rpc_xprt *xprt) 225{ 226 struct rpc_rqst *req; 227 228 dprintk("RPC: allocate a backchannel request\n"); 229 spin_lock(&xprt->bc_pa_lock); 230 if (!list_empty(&xprt->bc_pa_list)) { 231 req = list_first_entry(&xprt->bc_pa_list, struct rpc_rqst, 232 rq_bc_pa_list); 233 list_del(&req->rq_bc_pa_list); 234 } else { 235 req = NULL; 236 } 237 spin_unlock(&xprt->bc_pa_lock); 238 239 if (req != NULL) { 240 set_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state); 241 req->rq_reply_bytes_recvd = 0; 242 req->rq_bytes_sent = 0; 243 memcpy(&req->rq_private_buf, &req->rq_rcv_buf, 244 sizeof(req->rq_private_buf)); 245 } 246 dprintk("RPC: backchannel req=%p\n", req); 247 return req; 248} 249 250/* 251 * Return the preallocated rpc_rqst structure and XDR buffers 252 * associated with this rpc_task. 253 */ 254void xprt_free_bc_request(struct rpc_rqst *req) 255{ 256 struct rpc_xprt *xprt = req->rq_xprt; 257 258 dprintk("RPC: free backchannel req=%p\n", req); 259 260 smp_mb__before_clear_bit(); 261 BUG_ON(!test_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state)); 262 clear_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state); 263 smp_mb__after_clear_bit(); 264 265 if (!xprt_need_to_requeue(xprt)) { 266 /* 267 * The last remaining session was destroyed while this 268 * entry was in use. Free the entry and don't attempt 269 * to add back to the list because there is no need to 270 * have anymore preallocated entries. 271 */ 272 dprintk("RPC: Last session removed req=%p\n", req); 273 xprt_free_allocation(req); 274 return; 275 } 276 277 /* 278 * Return it to the list of preallocations so that it 279 * may be reused by a new callback request. 280 */ 281 spin_lock_bh(&xprt->bc_pa_lock); 282 list_add(&req->rq_bc_pa_list, &xprt->bc_pa_list); 283 spin_unlock_bh(&xprt->bc_pa_lock); 284} 285 286