xref: /openbmc/linux/net/sunrpc/backchannel_rqst.c (revision b34e08d5)
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 static struct rpc_rqst *xprt_alloc_bc_request(struct rpc_xprt *xprt, __be32 xid)
216 {
217 	struct rpc_rqst *req = NULL;
218 
219 	dprintk("RPC:       allocate a backchannel request\n");
220 	if (list_empty(&xprt->bc_pa_list))
221 		goto not_found;
222 
223 	req = list_first_entry(&xprt->bc_pa_list, struct rpc_rqst,
224 				rq_bc_pa_list);
225 	req->rq_reply_bytes_recvd = 0;
226 	req->rq_bytes_sent = 0;
227 	memcpy(&req->rq_private_buf, &req->rq_rcv_buf,
228 			sizeof(req->rq_private_buf));
229 	req->rq_xid = xid;
230 	req->rq_connect_cookie = xprt->connect_cookie;
231 not_found:
232 	dprintk("RPC:       backchannel req=%p\n", req);
233 	return req;
234 }
235 
236 /*
237  * Return the preallocated rpc_rqst structure and XDR buffers
238  * associated with this rpc_task.
239  */
240 void xprt_free_bc_request(struct rpc_rqst *req)
241 {
242 	struct rpc_xprt *xprt = req->rq_xprt;
243 
244 	dprintk("RPC:       free backchannel req=%p\n", req);
245 
246 	req->rq_connect_cookie = xprt->connect_cookie - 1;
247 	smp_mb__before_clear_bit();
248 	WARN_ON_ONCE(!test_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state));
249 	clear_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state);
250 	smp_mb__after_clear_bit();
251 
252 	if (!xprt_need_to_requeue(xprt)) {
253 		/*
254 		 * The last remaining session was destroyed while this
255 		 * entry was in use.  Free the entry and don't attempt
256 		 * to add back to the list because there is no need to
257 		 * have anymore preallocated entries.
258 		 */
259 		dprintk("RPC:       Last session removed req=%p\n", req);
260 		xprt_free_allocation(req);
261 		return;
262 	}
263 
264 	/*
265 	 * Return it to the list of preallocations so that it
266 	 * may be reused by a new callback request.
267 	 */
268 	spin_lock_bh(&xprt->bc_pa_lock);
269 	list_add_tail(&req->rq_bc_pa_list, &xprt->bc_pa_list);
270 	spin_unlock_bh(&xprt->bc_pa_lock);
271 }
272 
273 /*
274  * One or more rpc_rqst structure have been preallocated during the
275  * backchannel setup.  Buffer space for the send and private XDR buffers
276  * has been preallocated as well.  Use xprt_alloc_bc_request to allocate
277  * to this request.  Use xprt_free_bc_request to return it.
278  *
279  * We know that we're called in soft interrupt context, grab the spin_lock
280  * since there is no need to grab the bottom half spin_lock.
281  *
282  * Return an available rpc_rqst, otherwise NULL if non are available.
283  */
284 struct rpc_rqst *xprt_lookup_bc_request(struct rpc_xprt *xprt, __be32 xid)
285 {
286 	struct rpc_rqst *req;
287 
288 	spin_lock(&xprt->bc_pa_lock);
289 	list_for_each_entry(req, &xprt->bc_pa_list, rq_bc_pa_list) {
290 		if (req->rq_connect_cookie != xprt->connect_cookie)
291 			continue;
292 		if (req->rq_xid == xid)
293 			goto found;
294 	}
295 	req = xprt_alloc_bc_request(xprt, xid);
296 found:
297 	spin_unlock(&xprt->bc_pa_lock);
298 	return req;
299 }
300 
301 /*
302  * Add callback request to callback list.  The callback
303  * service sleeps on the sv_cb_waitq waiting for new
304  * requests.  Wake it up after adding enqueing the
305  * request.
306  */
307 void xprt_complete_bc_request(struct rpc_rqst *req, uint32_t copied)
308 {
309 	struct rpc_xprt *xprt = req->rq_xprt;
310 	struct svc_serv *bc_serv = xprt->bc_serv;
311 
312 	req->rq_private_buf.len = copied;
313 	set_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state);
314 
315 	dprintk("RPC:       add callback request to list\n");
316 	spin_lock(&bc_serv->sv_cb_lock);
317 	list_del(&req->rq_bc_pa_list);
318 	list_add(&req->rq_bc_list, &bc_serv->sv_cb_list);
319 	wake_up(&bc_serv->sv_cb_waitq);
320 	spin_unlock(&bc_serv->sv_cb_lock);
321 }
322 
323