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1// SPDX-License-Identifier: GPL-2.0-only
2/******************************************************************************
3
4(c) 2007 Network Appliance, Inc. All Rights Reserved.
5(c) 2009 NetApp. All Rights Reserved.
6
7
8******************************************************************************/
9
10#include <linux/tcp.h>
11#include <linux/slab.h>
12#include <linux/sunrpc/xprt.h>
13#include <linux/export.h>
14#include <linux/sunrpc/bc_xprt.h>
15
16#if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
17#define RPCDBG_FACILITY RPCDBG_TRANS
18#endif
19
20#define BC_MAX_SLOTS 64U
21
22unsigned int xprt_bc_max_slots(struct rpc_xprt *xprt)
23{
24 return BC_MAX_SLOTS;
25}
26
27/*
28 * Helper routines that track the number of preallocation elements
29 * on the transport.
30 */
31static inline int xprt_need_to_requeue(struct rpc_xprt *xprt)
32{
33 return xprt->bc_alloc_count < xprt->bc_alloc_max;
34}
35
36/*
37 * Free the preallocated rpc_rqst structure and the memory
38 * buffers hanging off of it.
39 */
40static void xprt_free_allocation(struct rpc_rqst *req)
41{
42 struct xdr_buf *xbufp;
43
44 dprintk("RPC: free allocations for req= %p\n", req);
45 WARN_ON_ONCE(test_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state));
46 xbufp = &req->rq_rcv_buf;
47 free_page((unsigned long)xbufp->head[0].iov_base);
48 xbufp = &req->rq_snd_buf;
49 free_page((unsigned long)xbufp->head[0].iov_base);
50 kfree(req);
51}
52
53static void xprt_bc_reinit_xdr_buf(struct xdr_buf *buf)
54{
55 buf->head[0].iov_len = PAGE_SIZE;
56 buf->tail[0].iov_len = 0;
57 buf->pages = NULL;
58 buf->page_len = 0;
59 buf->flags = 0;
60 buf->len = 0;
61 buf->buflen = PAGE_SIZE;
62}
63
64static int xprt_alloc_xdr_buf(struct xdr_buf *buf, gfp_t gfp_flags)
65{
66 struct page *page;
67 /* Preallocate one XDR receive buffer */
68 page = alloc_page(gfp_flags);
69 if (page == NULL)
70 return -ENOMEM;
71 xdr_buf_init(buf, page_address(page), PAGE_SIZE);
72 return 0;
73}
74
75static struct rpc_rqst *xprt_alloc_bc_req(struct rpc_xprt *xprt)
76{
77 gfp_t gfp_flags = GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN;
78 struct rpc_rqst *req;
79
80 /* Pre-allocate one backchannel rpc_rqst */
81 req = kzalloc(sizeof(*req), gfp_flags);
82 if (req == NULL)
83 return NULL;
84
85 req->rq_xprt = xprt;
86
87 /* Preallocate one XDR receive buffer */
88 if (xprt_alloc_xdr_buf(&req->rq_rcv_buf, gfp_flags) < 0) {
89 printk(KERN_ERR "Failed to create bc receive xbuf\n");
90 goto out_free;
91 }
92 req->rq_rcv_buf.len = PAGE_SIZE;
93
94 /* Preallocate one XDR send buffer */
95 if (xprt_alloc_xdr_buf(&req->rq_snd_buf, gfp_flags) < 0) {
96 printk(KERN_ERR "Failed to create bc snd xbuf\n");
97 goto out_free;
98 }
99 return req;
100out_free:
101 xprt_free_allocation(req);
102 return NULL;
103}
104
105/*
106 * Preallocate up to min_reqs structures and related buffers for use
107 * by the backchannel. This function can be called multiple times
108 * when creating new sessions that use the same rpc_xprt. The
109 * preallocated buffers are added to the pool of resources used by
110 * the rpc_xprt. Any one of these resources may be used by an
111 * incoming callback request. It's up to the higher levels in the
112 * stack to enforce that the maximum number of session slots is not
113 * being exceeded.
114 *
115 * Some callback arguments can be large. For example, a pNFS server
116 * using multiple deviceids. The list can be unbound, but the client
117 * has the ability to tell the server the maximum size of the callback
118 * requests. Each deviceID is 16 bytes, so allocate one page
119 * for the arguments to have enough room to receive a number of these
120 * deviceIDs. The NFS client indicates to the pNFS server that its
121 * callback requests can be up to 4096 bytes in size.
122 */
123int xprt_setup_backchannel(struct rpc_xprt *xprt, unsigned int min_reqs)
124{
125 if (!xprt->ops->bc_setup)
126 return 0;
127 return xprt->ops->bc_setup(xprt, min_reqs);
128}
129EXPORT_SYMBOL_GPL(xprt_setup_backchannel);
130
131int xprt_setup_bc(struct rpc_xprt *xprt, unsigned int min_reqs)
132{
133 struct rpc_rqst *req;
134 struct list_head tmp_list;
135 int i;
136
137 dprintk("RPC: setup backchannel transport\n");
138
139 if (min_reqs > BC_MAX_SLOTS)
140 min_reqs = BC_MAX_SLOTS;
141
142 /*
143 * We use a temporary list to keep track of the preallocated
144 * buffers. Once we're done building the list we splice it
145 * into the backchannel preallocation list off of the rpc_xprt
146 * struct. This helps minimize the amount of time the list
147 * lock is held on the rpc_xprt struct. It also makes cleanup
148 * easier in case of memory allocation errors.
149 */
150 INIT_LIST_HEAD(&tmp_list);
151 for (i = 0; i < min_reqs; i++) {
152 /* Pre-allocate one backchannel rpc_rqst */
153 req = xprt_alloc_bc_req(xprt);
154 if (req == NULL) {
155 printk(KERN_ERR "Failed to create bc rpc_rqst\n");
156 goto out_free;
157 }
158
159 /* Add the allocated buffer to the tmp list */
160 dprintk("RPC: adding req= %p\n", req);
161 list_add(&req->rq_bc_pa_list, &tmp_list);
162 }
163
164 /*
165 * Add the temporary list to the backchannel preallocation list
166 */
167 spin_lock(&xprt->bc_pa_lock);
168 list_splice(&tmp_list, &xprt->bc_pa_list);
169 xprt->bc_alloc_count += min_reqs;
170 xprt->bc_alloc_max += min_reqs;
171 atomic_add(min_reqs, &xprt->bc_slot_count);
172 spin_unlock(&xprt->bc_pa_lock);
173
174 dprintk("RPC: setup backchannel transport done\n");
175 return 0;
176
177out_free:
178 /*
179 * Memory allocation failed, free the temporary list
180 */
181 while (!list_empty(&tmp_list)) {
182 req = list_first_entry(&tmp_list,
183 struct rpc_rqst,
184 rq_bc_pa_list);
185 list_del(&req->rq_bc_pa_list);
186 xprt_free_allocation(req);
187 }
188
189 dprintk("RPC: setup backchannel transport failed\n");
190 return -ENOMEM;
191}
192
193/**
194 * xprt_destroy_backchannel - Destroys the backchannel preallocated structures.
195 * @xprt: the transport holding the preallocated strucures
196 * @max_reqs: the maximum number of preallocated structures to destroy
197 *
198 * Since these structures may have been allocated by multiple calls
199 * to xprt_setup_backchannel, we only destroy up to the maximum number
200 * of reqs specified by the caller.
201 */
202void xprt_destroy_backchannel(struct rpc_xprt *xprt, unsigned int max_reqs)
203{
204 if (xprt->ops->bc_destroy)
205 xprt->ops->bc_destroy(xprt, max_reqs);
206}
207EXPORT_SYMBOL_GPL(xprt_destroy_backchannel);
208
209void xprt_destroy_bc(struct rpc_xprt *xprt, unsigned int max_reqs)
210{
211 struct rpc_rqst *req = NULL, *tmp = NULL;
212
213 dprintk("RPC: destroy backchannel transport\n");
214
215 if (max_reqs == 0)
216 goto out;
217
218 spin_lock_bh(&xprt->bc_pa_lock);
219 xprt->bc_alloc_max -= min(max_reqs, xprt->bc_alloc_max);
220 list_for_each_entry_safe(req, tmp, &xprt->bc_pa_list, rq_bc_pa_list) {
221 dprintk("RPC: req=%p\n", req);
222 list_del(&req->rq_bc_pa_list);
223 xprt_free_allocation(req);
224 xprt->bc_alloc_count--;
225 atomic_dec(&xprt->bc_slot_count);
226 if (--max_reqs == 0)
227 break;
228 }
229 spin_unlock_bh(&xprt->bc_pa_lock);
230
231out:
232 dprintk("RPC: backchannel list empty= %s\n",
233 list_empty(&xprt->bc_pa_list) ? "true" : "false");
234}
235
236static struct rpc_rqst *xprt_get_bc_request(struct rpc_xprt *xprt, __be32 xid,
237 struct rpc_rqst *new)
238{
239 struct rpc_rqst *req = NULL;
240
241 dprintk("RPC: allocate a backchannel request\n");
242 if (list_empty(&xprt->bc_pa_list)) {
243 if (!new)
244 goto not_found;
245 if (atomic_read(&xprt->bc_slot_count) >= BC_MAX_SLOTS)
246 goto not_found;
247 list_add_tail(&new->rq_bc_pa_list, &xprt->bc_pa_list);
248 xprt->bc_alloc_count++;
249 atomic_inc(&xprt->bc_slot_count);
250 }
251 req = list_first_entry(&xprt->bc_pa_list, struct rpc_rqst,
252 rq_bc_pa_list);
253 req->rq_reply_bytes_recvd = 0;
254 memcpy(&req->rq_private_buf, &req->rq_rcv_buf,
255 sizeof(req->rq_private_buf));
256 req->rq_xid = xid;
257 req->rq_connect_cookie = xprt->connect_cookie;
258 dprintk("RPC: backchannel req=%p\n", req);
259not_found:
260 return req;
261}
262
263/*
264 * Return the preallocated rpc_rqst structure and XDR buffers
265 * associated with this rpc_task.
266 */
267void xprt_free_bc_request(struct rpc_rqst *req)
268{
269 struct rpc_xprt *xprt = req->rq_xprt;
270
271 xprt->ops->bc_free_rqst(req);
272}
273
274void xprt_free_bc_rqst(struct rpc_rqst *req)
275{
276 struct rpc_xprt *xprt = req->rq_xprt;
277
278 dprintk("RPC: free backchannel req=%p\n", req);
279
280 req->rq_connect_cookie = xprt->connect_cookie - 1;
281 smp_mb__before_atomic();
282 clear_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state);
283 smp_mb__after_atomic();
284
285 /*
286 * Return it to the list of preallocations so that it
287 * may be reused by a new callback request.
288 */
289 spin_lock_bh(&xprt->bc_pa_lock);
290 if (xprt_need_to_requeue(xprt)) {
291 xprt_bc_reinit_xdr_buf(&req->rq_snd_buf);
292 xprt_bc_reinit_xdr_buf(&req->rq_rcv_buf);
293 req->rq_rcv_buf.len = PAGE_SIZE;
294 list_add_tail(&req->rq_bc_pa_list, &xprt->bc_pa_list);
295 xprt->bc_alloc_count++;
296 atomic_inc(&xprt->bc_slot_count);
297 req = NULL;
298 }
299 spin_unlock_bh(&xprt->bc_pa_lock);
300 if (req != NULL) {
301 /*
302 * The last remaining session was destroyed while this
303 * entry was in use. Free the entry and don't attempt
304 * to add back to the list because there is no need to
305 * have anymore preallocated entries.
306 */
307 dprintk("RPC: Last session removed req=%p\n", req);
308 xprt_free_allocation(req);
309 }
310 xprt_put(xprt);
311}
312
313/*
314 * One or more rpc_rqst structure have been preallocated during the
315 * backchannel setup. Buffer space for the send and private XDR buffers
316 * has been preallocated as well. Use xprt_alloc_bc_request to allocate
317 * to this request. Use xprt_free_bc_request to return it.
318 *
319 * We know that we're called in soft interrupt context, grab the spin_lock
320 * since there is no need to grab the bottom half spin_lock.
321 *
322 * Return an available rpc_rqst, otherwise NULL if non are available.
323 */
324struct rpc_rqst *xprt_lookup_bc_request(struct rpc_xprt *xprt, __be32 xid)
325{
326 struct rpc_rqst *req, *new = NULL;
327
328 do {
329 spin_lock(&xprt->bc_pa_lock);
330 list_for_each_entry(req, &xprt->bc_pa_list, rq_bc_pa_list) {
331 if (req->rq_connect_cookie != xprt->connect_cookie)
332 continue;
333 if (req->rq_xid == xid)
334 goto found;
335 }
336 req = xprt_get_bc_request(xprt, xid, new);
337found:
338 spin_unlock(&xprt->bc_pa_lock);
339 if (new) {
340 if (req != new)
341 xprt_free_allocation(new);
342 break;
343 } else if (req)
344 break;
345 new = xprt_alloc_bc_req(xprt);
346 } while (new);
347 return req;
348}
349
350/*
351 * Add callback request to callback list. Wake a thread
352 * on the first pool (usually the only pool) to handle it.
353 */
354void xprt_complete_bc_request(struct rpc_rqst *req, uint32_t copied)
355{
356 struct rpc_xprt *xprt = req->rq_xprt;
357 struct svc_serv *bc_serv = xprt->bc_serv;
358
359 spin_lock(&xprt->bc_pa_lock);
360 list_del(&req->rq_bc_pa_list);
361 xprt->bc_alloc_count--;
362 spin_unlock(&xprt->bc_pa_lock);
363
364 req->rq_private_buf.len = copied;
365 set_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state);
366
367 dprintk("RPC: add callback request to list\n");
368 xprt_get(xprt);
369 lwq_enqueue(&req->rq_bc_list, &bc_serv->sv_cb_list);
370 svc_pool_wake_idle_thread(&bc_serv->sv_pools[0]);
371}
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 -1;
176}
177EXPORT_SYMBOL_GPL(xprt_setup_backchannel);
178
179/*
180 * Destroys the backchannel preallocated structures.
181 * Since these structures may have been allocated by multiple calls
182 * to xprt_setup_backchannel, we only destroy up to the maximum number
183 * of reqs specified by the caller.
184 * @xprt: the transport holding the preallocated strucures
185 * @max_reqs the maximum number of preallocated structures to destroy
186 */
187void xprt_destroy_backchannel(struct rpc_xprt *xprt, unsigned int max_reqs)
188{
189 struct rpc_rqst *req = NULL, *tmp = NULL;
190
191 dprintk("RPC: destroy backchannel transport\n");
192
193 BUG_ON(max_reqs == 0);
194 spin_lock_bh(&xprt->bc_pa_lock);
195 xprt_dec_alloc_count(xprt, max_reqs);
196 list_for_each_entry_safe(req, tmp, &xprt->bc_pa_list, rq_bc_pa_list) {
197 dprintk("RPC: req=%p\n", req);
198 xprt_free_allocation(req);
199 if (--max_reqs == 0)
200 break;
201 }
202 spin_unlock_bh(&xprt->bc_pa_lock);
203
204 dprintk("RPC: backchannel list empty= %s\n",
205 list_empty(&xprt->bc_pa_list) ? "true" : "false");
206}
207EXPORT_SYMBOL_GPL(xprt_destroy_backchannel);
208
209/*
210 * One or more rpc_rqst structure have been preallocated during the
211 * backchannel setup. Buffer space for the send and private XDR buffers
212 * has been preallocated as well. Use xprt_alloc_bc_request to allocate
213 * to this request. Use xprt_free_bc_request to return it.
214 *
215 * We know that we're called in soft interrupt context, grab the spin_lock
216 * since there is no need to grab the bottom half spin_lock.
217 *
218 * Return an available rpc_rqst, otherwise NULL if non are available.
219 */
220struct rpc_rqst *xprt_alloc_bc_request(struct rpc_xprt *xprt)
221{
222 struct rpc_rqst *req;
223
224 dprintk("RPC: allocate a backchannel request\n");
225 spin_lock(&xprt->bc_pa_lock);
226 if (!list_empty(&xprt->bc_pa_list)) {
227 req = list_first_entry(&xprt->bc_pa_list, struct rpc_rqst,
228 rq_bc_pa_list);
229 list_del(&req->rq_bc_pa_list);
230 } else {
231 req = NULL;
232 }
233 spin_unlock(&xprt->bc_pa_lock);
234
235 if (req != NULL) {
236 set_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state);
237 req->rq_reply_bytes_recvd = 0;
238 req->rq_bytes_sent = 0;
239 memcpy(&req->rq_private_buf, &req->rq_rcv_buf,
240 sizeof(req->rq_private_buf));
241 }
242 dprintk("RPC: backchannel req=%p\n", req);
243 return req;
244}
245
246/*
247 * Return the preallocated rpc_rqst structure and XDR buffers
248 * associated with this rpc_task.
249 */
250void xprt_free_bc_request(struct rpc_rqst *req)
251{
252 struct rpc_xprt *xprt = req->rq_xprt;
253
254 dprintk("RPC: free backchannel req=%p\n", req);
255
256 smp_mb__before_clear_bit();
257 BUG_ON(!test_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state));
258 clear_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state);
259 smp_mb__after_clear_bit();
260
261 if (!xprt_need_to_requeue(xprt)) {
262 /*
263 * The last remaining session was destroyed while this
264 * entry was in use. Free the entry and don't attempt
265 * to add back to the list because there is no need to
266 * have anymore preallocated entries.
267 */
268 dprintk("RPC: Last session removed req=%p\n", req);
269 xprt_free_allocation(req);
270 return;
271 }
272
273 /*
274 * Return it to the list of preallocations so that it
275 * may be reused by a new callback request.
276 */
277 spin_lock_bh(&xprt->bc_pa_lock);
278 list_add(&req->rq_bc_pa_list, &xprt->bc_pa_list);
279 spin_unlock_bh(&xprt->bc_pa_lock);
280}
281