[deliverable/linux.git] / net / sunrpc / backchannel_rqst.c

/******************************************************************************

(c) 2007 Network Appliance, Inc.  All Rights Reserved.
(c) 2009 NetApp.  All Rights Reserved.

NetApp provides this source code under the GPL v2 License.
The GPL v2 license is available at
http://opensource.org/licenses/gpl-license.php.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

******************************************************************************/

#include <linux/tcp.h>
#include <linux/slab.h>
#include <linux/sunrpc/xprt.h>
#include <linux/export.h>
#include <linux/sunrpc/bc_xprt.h>

#ifdef RPC_DEBUG
#define RPCDBG_FACILITY	RPCDBG_TRANS
#endif

/*
 * Helper routines that track the number of preallocation elements
 * on the transport.
 */
static inline int xprt_need_to_requeue(struct rpc_xprt *xprt)
{
	return xprt->bc_alloc_count > 0;
}

static inline void xprt_inc_alloc_count(struct rpc_xprt *xprt, unsigned int n)
{
	xprt->bc_alloc_count += n;
}

static inline int xprt_dec_alloc_count(struct rpc_xprt *xprt, unsigned int n)
{
	return xprt->bc_alloc_count -= n;
}

/*
 * Free the preallocated rpc_rqst structure and the memory
 * buffers hanging off of it.
 */
static void xprt_free_allocation(struct rpc_rqst *req)
{
	struct xdr_buf *xbufp;

	dprintk("RPC:        free allocations for req= %p\n", req);
	WARN_ON_ONCE(test_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state));
	xbufp = &req->rq_private_buf;
	free_page((unsigned long)xbufp->head[0].iov_base);
	xbufp = &req->rq_snd_buf;
	free_page((unsigned long)xbufp->head[0].iov_base);
	kfree(req);
}

/*
 * Preallocate up to min_reqs structures and related buffers for use
 * by the backchannel.  This function can be called multiple times
 * when creating new sessions that use the same rpc_xprt.  The
 * preallocated buffers are added to the pool of resources used by
 * the rpc_xprt.  Anyone of these resources may be used used by an
 * incoming callback request.  It's up to the higher levels in the
 * stack to enforce that the maximum number of session slots is not
 * being exceeded.
 *
 * Some callback arguments can be large.  For example, a pNFS server
 * using multiple deviceids.  The list can be unbound, but the client
 * has the ability to tell the server the maximum size of the callback
 * requests.  Each deviceID is 16 bytes, so allocate one page
 * for the arguments to have enough room to receive a number of these
 * deviceIDs.  The NFS client indicates to the pNFS server that its
 * callback requests can be up to 4096 bytes in size.
 */
int xprt_setup_backchannel(struct rpc_xprt *xprt, unsigned int min_reqs)
{
	struct page *page_rcv = NULL, *page_snd = NULL;
	struct xdr_buf *xbufp = NULL;
	struct rpc_rqst *req, *tmp;
	struct list_head tmp_list;
	int i;

	dprintk("RPC:       setup backchannel transport\n");

	/*
	 * We use a temporary list to keep track of the preallocated
	 * buffers.  Once we're done building the list we splice it
	 * into the backchannel preallocation list off of the rpc_xprt
	 * struct.  This helps minimize the amount of time the list
	 * lock is held on the rpc_xprt struct.  It also makes cleanup
	 * easier in case of memory allocation errors.
	 */
	INIT_LIST_HEAD(&tmp_list);
	for (i = 0; i < min_reqs; i++) {
		/* Pre-allocate one backchannel rpc_rqst */
		req = kzalloc(sizeof(struct rpc_rqst), GFP_KERNEL);
		if (req == NULL) {
			printk(KERN_ERR "Failed to create bc rpc_rqst\n");
			goto out_free;
		}

		/* Add the allocated buffer to the tmp list */
		dprintk("RPC:       adding req= %p\n", req);
		list_add(&req->rq_bc_pa_list, &tmp_list);

		req->rq_xprt = xprt;
		INIT_LIST_HEAD(&req->rq_list);
		INIT_LIST_HEAD(&req->rq_bc_list);

		/* Preallocate one XDR receive buffer */
		page_rcv = alloc_page(GFP_KERNEL);
		if (page_rcv == NULL) {
			printk(KERN_ERR "Failed to create bc receive xbuf\n");
			goto out_free;
		}
		xbufp = &req->rq_rcv_buf;
		xbufp->head[0].iov_base = page_address(page_rcv);
		xbufp->head[0].iov_len = PAGE_SIZE;
		xbufp->tail[0].iov_base = NULL;
		xbufp->tail[0].iov_len = 0;
		xbufp->page_len = 0;
		xbufp->len = PAGE_SIZE;
		xbufp->buflen = PAGE_SIZE;

		/* Preallocate one XDR send buffer */
		page_snd = alloc_page(GFP_KERNEL);
		if (page_snd == NULL) {
			printk(KERN_ERR "Failed to create bc snd xbuf\n");
			goto out_free;
		}

		xbufp = &req->rq_snd_buf;
		xbufp->head[0].iov_base = page_address(page_snd);
		xbufp->head[0].iov_len = 0;
		xbufp->tail[0].iov_base = NULL;
		xbufp->tail[0].iov_len = 0;
		xbufp->page_len = 0;
		xbufp->len = 0;
		xbufp->buflen = PAGE_SIZE;
	}

	/*
	 * Add the temporary list to the backchannel preallocation list
	 */
	spin_lock_bh(&xprt->bc_pa_lock);
	list_splice(&tmp_list, &xprt->bc_pa_list);
	xprt_inc_alloc_count(xprt, min_reqs);
	spin_unlock_bh(&xprt->bc_pa_lock);

	dprintk("RPC:       setup backchannel transport done\n");
	return 0;

out_free:
	/*
	 * Memory allocation failed, free the temporary list
	 */
	list_for_each_entry_safe(req, tmp, &tmp_list, rq_bc_pa_list) {
		list_del(&req->rq_bc_pa_list);
		xprt_free_allocation(req);
	}

	dprintk("RPC:       setup backchannel transport failed\n");
	return -ENOMEM;
}
EXPORT_SYMBOL_GPL(xprt_setup_backchannel);

/**
 * xprt_destroy_backchannel - Destroys the backchannel preallocated structures.
 * @xprt:	the transport holding the preallocated strucures
 * @max_reqs	the maximum number of preallocated structures to destroy
 *
 * Since these structures may have been allocated by multiple calls
 * to xprt_setup_backchannel, we only destroy up to the maximum number
 * of reqs specified by the caller.
 */
void xprt_destroy_backchannel(struct rpc_xprt *xprt, unsigned int max_reqs)
{
	struct rpc_rqst *req = NULL, *tmp = NULL;

	dprintk("RPC:        destroy backchannel transport\n");

	if (max_reqs == 0)
		goto out;

	spin_lock_bh(&xprt->bc_pa_lock);
	xprt_dec_alloc_count(xprt, max_reqs);
	list_for_each_entry_safe(req, tmp, &xprt->bc_pa_list, rq_bc_pa_list) {
		dprintk("RPC:        req=%p\n", req);
		list_del(&req->rq_bc_pa_list);
		xprt_free_allocation(req);
		if (--max_reqs == 0)
			break;
	}
	spin_unlock_bh(&xprt->bc_pa_lock);

out:
	dprintk("RPC:        backchannel list empty= %s\n",
		list_empty(&xprt->bc_pa_list) ? "true" : "false");
}
EXPORT_SYMBOL_GPL(xprt_destroy_backchannel);

static struct rpc_rqst *xprt_alloc_bc_request(struct rpc_xprt *xprt, __be32 xid)
{
	struct rpc_rqst *req = NULL;

	dprintk("RPC:       allocate a backchannel request\n");
	if (list_empty(&xprt->bc_pa_list))
		goto not_found;

	req = list_first_entry(&xprt->bc_pa_list, struct rpc_rqst,
				rq_bc_pa_list);
	req->rq_reply_bytes_recvd = 0;
	req->rq_bytes_sent = 0;
	memcpy(&req->rq_private_buf, &req->rq_rcv_buf,
			sizeof(req->rq_private_buf));
	req->rq_xid = xid;
	req->rq_connect_cookie = xprt->connect_cookie;
not_found:
	dprintk("RPC:       backchannel req=%p\n", req);
	return req;
}

/*
 * Return the preallocated rpc_rqst structure and XDR buffers
 * associated with this rpc_task.
 */
void xprt_free_bc_request(struct rpc_rqst *req)
{
	struct rpc_xprt *xprt = req->rq_xprt;

	dprintk("RPC:       free backchannel req=%p\n", req);

	req->rq_connect_cookie = xprt->connect_cookie - 1;
	smp_mb__before_atomic();
	WARN_ON_ONCE(!test_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state));
	clear_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state);
	smp_mb__after_atomic();

	if (!xprt_need_to_requeue(xprt)) {
		/*
		 * The last remaining session was destroyed while this
		 * entry was in use.  Free the entry and don't attempt
		 * to add back to the list because there is no need to
		 * have anymore preallocated entries.
		 */
		dprintk("RPC:       Last session removed req=%p\n", req);
		xprt_free_allocation(req);
		return;
	}

	/*
	 * Return it to the list of preallocations so that it
	 * may be reused by a new callback request.
	 */
	spin_lock_bh(&xprt->bc_pa_lock);
	list_add_tail(&req->rq_bc_pa_list, &xprt->bc_pa_list);
	spin_unlock_bh(&xprt->bc_pa_lock);
}

/*
 * One or more rpc_rqst structure have been preallocated during the
 * backchannel setup.  Buffer space for the send and private XDR buffers
 * has been preallocated as well.  Use xprt_alloc_bc_request to allocate
 * to this request.  Use xprt_free_bc_request to return it.
 *
 * We know that we're called in soft interrupt context, grab the spin_lock
 * since there is no need to grab the bottom half spin_lock.
 *
 * Return an available rpc_rqst, otherwise NULL if non are available.
 */
struct rpc_rqst *xprt_lookup_bc_request(struct rpc_xprt *xprt, __be32 xid)
{
	struct rpc_rqst *req;

	spin_lock(&xprt->bc_pa_lock);
	list_for_each_entry(req, &xprt->bc_pa_list, rq_bc_pa_list) {
		if (req->rq_connect_cookie != xprt->connect_cookie)
			continue;
		if (req->rq_xid == xid)
			goto found;
	}
	req = xprt_alloc_bc_request(xprt, xid);
found:
	spin_unlock(&xprt->bc_pa_lock);
	return req;
}

/*
 * Add callback request to callback list.  The callback
 * service sleeps on the sv_cb_waitq waiting for new
 * requests.  Wake it up after adding enqueing the
 * request.
 */
void xprt_complete_bc_request(struct rpc_rqst *req, uint32_t copied)
{
	struct rpc_xprt *xprt = req->rq_xprt;
	struct svc_serv *bc_serv = xprt->bc_serv;

	req->rq_private_buf.len = copied;
	set_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state);

	dprintk("RPC:       add callback request to list\n");
	spin_lock(&bc_serv->sv_cb_lock);
	list_del(&req->rq_bc_pa_list);
	list_add(&req->rq_bc_list, &bc_serv->sv_cb_list);
	wake_up(&bc_serv->sv_cb_waitq);
	spin_unlock(&bc_serv->sv_cb_lock);
}
Commit	Line	Data
fb7a0b9a RL	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>
5a0e3ad6	25	#include <linux/slab.h>
fb7a0b9a	26	#include <linux/sunrpc/xprt.h>
bc3b2d7f	27	#include <linux/export.h>
09acfea5	28	#include <linux/sunrpc/bc_xprt.h>
fb7a0b9a RL	29
	30	#ifdef RPC_DEBUG
	31	#define RPCDBG_FACILITY RPCDBG_TRANS
	32	#endif
	33
fb7a0b9a RL	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);
f30dfbba	62	WARN_ON_ONCE(test_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state));
fb7a0b9a RL	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);
fb7a0b9a RL	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	*/
62835679 TM	170	list_for_each_entry_safe(req, tmp, &tmp_list, rq_bc_pa_list) {
62835679 TM	171	list_del(&req->rq_bc_pa_list);
fb7a0b9a	172	xprt_free_allocation(req);
62835679	173	}
fb7a0b9a RL	174
fb7a0b9a RL	175	dprintk("RPC: setup backchannel transport failed\n");
d24bab93	176	return -ENOMEM;
fb7a0b9a	177	}
0d961aa9	178	EXPORT_SYMBOL_GPL(xprt_setup_backchannel);
fb7a0b9a	179
2c53040f BH	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	*
fb7a0b9a RL	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.
fb7a0b9a RL	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
c4ded8d9 WAA	195	if (max_reqs == 0)
	196	goto out;
	197
fb7a0b9a RL	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);
62835679	202	list_del(&req->rq_bc_pa_list);
fb7a0b9a RL	203	xprt_free_allocation(req);
	204	if (--max_reqs == 0)
	205	break;
	206	}
	207	spin_unlock_bh(&xprt->bc_pa_lock);
	208
c4ded8d9	209	out:
fb7a0b9a RL	210	dprintk("RPC: backchannel list empty= %s\n",
	211	list_empty(&xprt->bc_pa_list) ? "true" : "false");
	212	}
0d961aa9	213	EXPORT_SYMBOL_GPL(xprt_destroy_backchannel);
fb7a0b9a	214
2ea24497	215	static struct rpc_rqst xprt_alloc_bc_request(struct rpc_xprt xprt, __be32 xid)
fb7a0b9a	216	{
2ea24497	217	struct rpc_rqst *req = NULL;
fb7a0b9a RL	218
fb7a0b9a RL	219	dprintk("RPC: allocate a backchannel request\n");
2ea24497 TM	220	if (list_empty(&xprt->bc_pa_list))
2ea24497 TM	221	goto not_found;
fb7a0b9a	222
2ea24497 TM	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,
fb7a0b9a	228	sizeof(req->rq_private_buf));
2ea24497 TM	229	req->rq_xid = xid;
	230	req->rq_connect_cookie = xprt->connect_cookie;
	231	not_found:
fb7a0b9a RL	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
2ea24497	246	req->rq_connect_cookie = xprt->connect_cookie - 1;
4e857c58	247	smp_mb__before_atomic();
f30dfbba	248	WARN_ON_ONCE(!test_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state));
fb7a0b9a	249	clear_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state);
4e857c58	250	smp_mb__after_atomic();
fb7a0b9a RL	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);
2ea24497	269	list_add_tail(&req->rq_bc_pa_list, &xprt->bc_pa_list);
fb7a0b9a RL	270	spin_unlock_bh(&xprt->bc_pa_lock);
	271	}
	272
2ea24497 TM	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