backchannel_rqst.c revision 9e00abc3c20904fd6a5d888bb7023925799ec8a5
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 28#ifdef RPC_DEBUG 29#define RPCDBG_FACILITY RPCDBG_TRANS 30#endif 31 32/* 33 * Helper routines that track the number of preallocation elements 34 * on the transport. 35 */ 36static inline int xprt_need_to_requeue(struct rpc_xprt *xprt) 37{ 38 return xprt->bc_alloc_count > 0; 39} 40 41static inline void xprt_inc_alloc_count(struct rpc_xprt *xprt, unsigned int n) 42{ 43 xprt->bc_alloc_count += n; 44} 45 46static inline int xprt_dec_alloc_count(struct rpc_xprt *xprt, unsigned int n) 47{ 48 return xprt->bc_alloc_count -= n; 49} 50 51/* 52 * Free the preallocated rpc_rqst structure and the memory 53 * buffers hanging off of it. 54 */ 55static void xprt_free_allocation(struct rpc_rqst *req) 56{ 57 struct xdr_buf *xbufp; 58 59 dprintk("RPC: free allocations for req= %p\n", req); 60 BUG_ON(test_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state)); 61 xbufp = &req->rq_private_buf; 62 free_page((unsigned long)xbufp->head[0].iov_base); 63 xbufp = &req->rq_snd_buf; 64 free_page((unsigned long)xbufp->head[0].iov_base); 65 list_del(&req->rq_bc_pa_list); 66 kfree(req); 67} 68 69/* 70 * Preallocate up to min_reqs structures and related buffers for use 71 * by the backchannel. This function can be called multiple times 72 * when creating new sessions that use the same rpc_xprt. The 73 * preallocated buffers are added to the pool of resources used by 74 * the rpc_xprt. Anyone of these resources may be used used by an 75 * incoming callback request. It's up to the higher levels in the 76 * stack to enforce that the maximum number of session slots is not 77 * being exceeded. 78 * 79 * Some callback arguments can be large. For example, a pNFS server 80 * using multiple deviceids. The list can be unbound, but the client 81 * has the ability to tell the server the maximum size of the callback 82 * requests. Each deviceID is 16 bytes, so allocate one page 83 * for the arguments to have enough room to receive a number of these 84 * deviceIDs. The NFS client indicates to the pNFS server that its 85 * callback requests can be up to 4096 bytes in size. 86 */ 87int xprt_setup_backchannel(struct rpc_xprt *xprt, unsigned int min_reqs) 88{ 89 struct page *page_rcv = NULL, *page_snd = NULL; 90 struct xdr_buf *xbufp = NULL; 91 struct rpc_rqst *req, *tmp; 92 struct list_head tmp_list; 93 int i; 94 95 dprintk("RPC: setup backchannel transport\n"); 96 97 /* 98 * We use a temporary list to keep track of the preallocated 99 * buffers. Once we're done building the list we splice it 100 * into the backchannel preallocation list off of the rpc_xprt 101 * struct. This helps minimize the amount of time the list 102 * lock is held on the rpc_xprt struct. It also makes cleanup 103 * easier in case of memory allocation errors. 104 */ 105 INIT_LIST_HEAD(&tmp_list); 106 for (i = 0; i < min_reqs; i++) { 107 /* Pre-allocate one backchannel rpc_rqst */ 108 req = kzalloc(sizeof(struct rpc_rqst), GFP_KERNEL); 109 if (req == NULL) { 110 printk(KERN_ERR "Failed to create bc rpc_rqst\n"); 111 goto out_free; 112 } 113 114 /* Add the allocated buffer to the tmp list */ 115 dprintk("RPC: adding req= %p\n", req); 116 list_add(&req->rq_bc_pa_list, &tmp_list); 117 118 req->rq_xprt = xprt; 119 INIT_LIST_HEAD(&req->rq_list); 120 INIT_LIST_HEAD(&req->rq_bc_list); 121 122 /* Preallocate one XDR receive buffer */ 123 page_rcv = alloc_page(GFP_KERNEL); 124 if (page_rcv == NULL) { 125 printk(KERN_ERR "Failed to create bc receive xbuf\n"); 126 goto out_free; 127 } 128 xbufp = &req->rq_rcv_buf; 129 xbufp->head[0].iov_base = page_address(page_rcv); 130 xbufp->head[0].iov_len = PAGE_SIZE; 131 xbufp->tail[0].iov_base = NULL; 132 xbufp->tail[0].iov_len = 0; 133 xbufp->page_len = 0; 134 xbufp->len = PAGE_SIZE; 135 xbufp->buflen = PAGE_SIZE; 136 137 /* Preallocate one XDR send buffer */ 138 page_snd = alloc_page(GFP_KERNEL); 139 if (page_snd == NULL) { 140 printk(KERN_ERR "Failed to create bc snd xbuf\n"); 141 goto out_free; 142 } 143 144 xbufp = &req->rq_snd_buf; 145 xbufp->head[0].iov_base = page_address(page_snd); 146 xbufp->head[0].iov_len = 0; 147 xbufp->tail[0].iov_base = NULL; 148 xbufp->tail[0].iov_len = 0; 149 xbufp->page_len = 0; 150 xbufp->len = 0; 151 xbufp->buflen = PAGE_SIZE; 152 } 153 154 /* 155 * Add the temporary list to the backchannel preallocation list 156 */ 157 spin_lock_bh(&xprt->bc_pa_lock); 158 list_splice(&tmp_list, &xprt->bc_pa_list); 159 xprt_inc_alloc_count(xprt, min_reqs); 160 spin_unlock_bh(&xprt->bc_pa_lock); 161 162 dprintk("RPC: setup backchannel transport done\n"); 163 return 0; 164 165out_free: 166 /* 167 * Memory allocation failed, free the temporary list 168 */ 169 list_for_each_entry_safe(req, tmp, &tmp_list, rq_bc_pa_list) 170 xprt_free_allocation(req); 171 172 dprintk("RPC: setup backchannel transport failed\n"); 173 return -1; 174} 175EXPORT_SYMBOL(xprt_setup_backchannel); 176 177/* 178 * Destroys the backchannel preallocated structures. 179 * Since these structures may have been allocated by multiple calls 180 * to xprt_setup_backchannel, we only destroy up to the maximum number 181 * of reqs specified by the caller. 182 * @xprt: the transport holding the preallocated strucures 183 * @max_reqs the maximum number of preallocated structures to destroy 184 */ 185void xprt_destroy_backchannel(struct rpc_xprt *xprt, unsigned int max_reqs) 186{ 187 struct rpc_rqst *req = NULL, *tmp = NULL; 188 189 dprintk("RPC: destroy backchannel transport\n"); 190 191 BUG_ON(max_reqs == 0); 192 spin_lock_bh(&xprt->bc_pa_lock); 193 xprt_dec_alloc_count(xprt, max_reqs); 194 list_for_each_entry_safe(req, tmp, &xprt->bc_pa_list, rq_bc_pa_list) { 195 dprintk("RPC: req=%p\n", req); 196 xprt_free_allocation(req); 197 if (--max_reqs == 0) 198 break; 199 } 200 spin_unlock_bh(&xprt->bc_pa_lock); 201 202 dprintk("RPC: backchannel list empty= %s\n", 203 list_empty(&xprt->bc_pa_list) ? "true" : "false"); 204} 205EXPORT_SYMBOL(xprt_destroy_backchannel); 206 207/* 208 * One or more rpc_rqst structure have been preallocated during the 209 * backchannel setup. Buffer space for the send and private XDR buffers 210 * has been preallocated as well. Use xprt_alloc_bc_request to allocate 211 * to this request. Use xprt_free_bc_request to return it. 212 * 213 * We know that we're called in soft interrupt context, grab the spin_lock 214 * since there is no need to grab the bottom half spin_lock. 215 * 216 * Return an available rpc_rqst, otherwise NULL if non are available. 217 */ 218struct rpc_rqst *xprt_alloc_bc_request(struct rpc_xprt *xprt) 219{ 220 struct rpc_rqst *req; 221 222 dprintk("RPC: allocate a backchannel request\n"); 223 spin_lock(&xprt->bc_pa_lock); 224 if (!list_empty(&xprt->bc_pa_list)) { 225 req = list_first_entry(&xprt->bc_pa_list, struct rpc_rqst, 226 rq_bc_pa_list); 227 list_del(&req->rq_bc_pa_list); 228 } else { 229 req = NULL; 230 } 231 spin_unlock(&xprt->bc_pa_lock); 232 233 if (req != NULL) { 234 set_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state); 235 req->rq_reply_bytes_recvd = 0; 236 req->rq_bytes_sent = 0; 237 memcpy(&req->rq_private_buf, &req->rq_rcv_buf, 238 sizeof(req->rq_private_buf)); 239 } 240 dprintk("RPC: backchannel req=%p\n", req); 241 return req; 242} 243 244/* 245 * Return the preallocated rpc_rqst structure and XDR buffers 246 * associated with this rpc_task. 247 */ 248void xprt_free_bc_request(struct rpc_rqst *req) 249{ 250 struct rpc_xprt *xprt = req->rq_xprt; 251 252 dprintk("RPC: free backchannel req=%p\n", req); 253 254 smp_mb__before_clear_bit(); 255 BUG_ON(!test_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state)); 256 clear_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state); 257 smp_mb__after_clear_bit(); 258 259 if (!xprt_need_to_requeue(xprt)) { 260 /* 261 * The last remaining session was destroyed while this 262 * entry was in use. Free the entry and don't attempt 263 * to add back to the list because there is no need to 264 * have anymore preallocated entries. 265 */ 266 dprintk("RPC: Last session removed req=%p\n", req); 267 xprt_free_allocation(req); 268 return; 269 } 270 271 /* 272 * Return it to the list of preallocations so that it 273 * may be reused by a new callback request. 274 */ 275 spin_lock_bh(&xprt->bc_pa_lock); 276 list_add(&req->rq_bc_pa_list, &xprt->bc_pa_list); 277 spin_unlock_bh(&xprt->bc_pa_lock); 278} 279 280