[linux-2.6-block.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>

#if IS_ENABLED(CONFIG_SUNRPC_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 < atomic_read(&xprt->bc_free_slots);
}

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

static inline int xprt_dec_alloc_count(struct rpc_xprt *xprt, unsigned int n)
{
	atomic_sub(n, &xprt->bc_free_slots);
	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_rcv_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);
}

static int xprt_alloc_xdr_buf(struct xdr_buf *buf, gfp_t gfp_flags)
{
	struct page *page;
	/* Preallocate one XDR receive buffer */
	page = alloc_page(gfp_flags);
	if (page == NULL)
		return -ENOMEM;
	xdr_buf_init(buf, page_address(page), PAGE_SIZE);
	return 0;
}

static
struct rpc_rqst *xprt_alloc_bc_req(struct rpc_xprt *xprt, gfp_t gfp_flags)
{
	struct rpc_rqst *req;

	/* Pre-allocate one backchannel rpc_rqst */
	req = kzalloc(sizeof(*req), gfp_flags);
	if (req == NULL)
		return NULL;

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

	/* Preallocate one XDR receive buffer */
	if (xprt_alloc_xdr_buf(&req->rq_rcv_buf, gfp_flags) < 0) {
		printk(KERN_ERR "Failed to create bc receive xbuf\n");
		goto out_free;
	}
	req->rq_rcv_buf.len = PAGE_SIZE;

	/* Preallocate one XDR send buffer */
	if (xprt_alloc_xdr_buf(&req->rq_snd_buf, gfp_flags) < 0) {
		printk(KERN_ERR "Failed to create bc snd xbuf\n");
		goto out_free;
	}
	return req;
out_free:
	xprt_free_allocation(req);
	return NULL;
}

/*
 * 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)
{
	if (!xprt->ops->bc_setup)
		return 0;
	return xprt->ops->bc_setup(xprt, min_reqs);
}
EXPORT_SYMBOL_GPL(xprt_setup_backchannel);

int xprt_setup_bc(struct rpc_xprt *xprt, unsigned int min_reqs)
{
	struct rpc_rqst *req;
	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 = xprt_alloc_bc_req(xprt, 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);
	}

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

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

out_free:
	/*
	 * Memory allocation failed, free the temporary list
	 */
	while (!list_empty(&tmp_list)) {
		req = list_first_entry(&tmp_list,
				struct rpc_rqst,
				rq_bc_pa_list);
		list_del(&req->rq_bc_pa_list);
		xprt_free_allocation(req);
	}

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

/**
 * 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)
{
	if (xprt->ops->bc_destroy)
		xprt->ops->bc_destroy(xprt, max_reqs);
}
EXPORT_SYMBOL_GPL(xprt_destroy_backchannel);

void xprt_destroy_bc(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");
}

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 (atomic_read(&xprt->bc_free_slots) <= 0)
		goto not_found;
	if (list_empty(&xprt->bc_pa_list)) {
		req = xprt_alloc_bc_req(xprt, GFP_ATOMIC);
		if (!req)
			goto not_found;
		list_add_tail(&req->rq_bc_pa_list, &xprt->bc_pa_list);
		xprt->bc_alloc_count++;
	}
	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;

	xprt->ops->bc_free_rqst(req);
}

void xprt_free_bc_rqst(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();
	clear_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state);
	smp_mb__after_atomic();

	/*
	 * 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);
	if (xprt_need_to_requeue(xprt)) {
		list_add_tail(&req->rq_bc_pa_list, &xprt->bc_pa_list);
		xprt->bc_alloc_count++;
		req = NULL;
	}
	spin_unlock_bh(&xprt->bc_pa_lock);
	if (req != NULL) {
		/*
		 * 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;
	}
}

/*
 * 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;

	spin_lock(&xprt->bc_pa_lock);
	list_del(&req->rq_bc_pa_list);
	xprt_dec_alloc_count(xprt, 1);
	spin_unlock(&xprt->bc_pa_lock);

	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_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	29
f895b252	30	#if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
fb7a0b9a RL	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	{
0d2a970d	40	return xprt->bc_alloc_count < atomic_read(&xprt->bc_free_slots);
fb7a0b9a RL	41	}
	42
	43	static inline void xprt_inc_alloc_count(struct rpc_xprt *xprt, unsigned int n)
	44	{
0d2a970d	45	atomic_add(n, &xprt->bc_free_slots);
fb7a0b9a RL	46	xprt->bc_alloc_count += n;
	47	}
	48
	49	static inline int xprt_dec_alloc_count(struct rpc_xprt *xprt, unsigned int n)
	50	{
0d2a970d	51	atomic_sub(n, &xprt->bc_free_slots);
fb7a0b9a RL	52	return xprt->bc_alloc_count -= n;
	53	}
	54
	55	/*
	56	* Free the preallocated rpc_rqst structure and the memory
	57	* buffers hanging off of it.
	58	*/
	59	static void xprt_free_allocation(struct rpc_rqst *req)
	60	{
	61	struct xdr_buf *xbufp;
	62
	63	dprintk("RPC: free allocations for req= %p\n", req);
f30dfbba	64	WARN_ON_ONCE(test_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state));
88de6af2	65	xbufp = &req->rq_rcv_buf;
fb7a0b9a RL	66	free_page((unsigned long)xbufp->head[0].iov_base);
	67	xbufp = &req->rq_snd_buf;
	68	free_page((unsigned long)xbufp->head[0].iov_base);
fb7a0b9a RL	69	kfree(req);
	70	}
	71
1dddda86 TM	72	static int xprt_alloc_xdr_buf(struct xdr_buf *buf, gfp_t gfp_flags)
	73	{
	74	struct page *page;
	75	/* Preallocate one XDR receive buffer */
	76	page = alloc_page(gfp_flags);
	77	if (page == NULL)
	78	return -ENOMEM;
b9c5bc03	79	xdr_buf_init(buf, page_address(page), PAGE_SIZE);
1dddda86 TM	80	return 0;
	81	}
	82
	83	static
	84	struct rpc_rqst xprt_alloc_bc_req(struct rpc_xprt xprt, gfp_t gfp_flags)
	85	{
	86	struct rpc_rqst *req;
	87
	88	/* Pre-allocate one backchannel rpc_rqst */
	89	req = kzalloc(sizeof(*req), gfp_flags);
	90	if (req == NULL)
	91	return NULL;
	92
	93	req->rq_xprt = xprt;
1dddda86 TM	94	INIT_LIST_HEAD(&req->rq_bc_list);
	95
	96	/* Preallocate one XDR receive buffer */
	97	if (xprt_alloc_xdr_buf(&req->rq_rcv_buf, gfp_flags) < 0) {
	98	printk(KERN_ERR "Failed to create bc receive xbuf\n");
	99	goto out_free;
	100	}
	101	req->rq_rcv_buf.len = PAGE_SIZE;
	102
	103	/* Preallocate one XDR send buffer */
	104	if (xprt_alloc_xdr_buf(&req->rq_snd_buf, gfp_flags) < 0) {
	105	printk(KERN_ERR "Failed to create bc snd xbuf\n");
	106	goto out_free;
	107	}
	108	return req;
	109	out_free:
	110	xprt_free_allocation(req);
	111	return NULL;
	112	}
	113
fb7a0b9a RL	114	/*
	115	* Preallocate up to min_reqs structures and related buffers for use
	116	* by the backchannel. This function can be called multiple times
	117	* when creating new sessions that use the same rpc_xprt. The
	118	* preallocated buffers are added to the pool of resources used by
	119	* the rpc_xprt. Anyone of these resources may be used used by an
	120	* incoming callback request. It's up to the higher levels in the
	121	* stack to enforce that the maximum number of session slots is not
	122	* being exceeded.
	123	*
	124	* Some callback arguments can be large. For example, a pNFS server
	125	* using multiple deviceids. The list can be unbound, but the client
	126	* has the ability to tell the server the maximum size of the callback
	127	* requests. Each deviceID is 16 bytes, so allocate one page
	128	* for the arguments to have enough room to receive a number of these
	129	* deviceIDs. The NFS client indicates to the pNFS server that its
	130	* callback requests can be up to 4096 bytes in size.
	131	*/
	132	int xprt_setup_backchannel(struct rpc_xprt *xprt, unsigned int min_reqs)
42e5c3e2 CL	133	{
	134	if (!xprt->ops->bc_setup)
	135	return 0;
	136	return xprt->ops->bc_setup(xprt, min_reqs);
	137	}
	138	EXPORT_SYMBOL_GPL(xprt_setup_backchannel);
	139
	140	int xprt_setup_bc(struct rpc_xprt *xprt, unsigned int min_reqs)
fb7a0b9a	141	{
1dddda86	142	struct rpc_rqst *req;
fb7a0b9a RL	143	struct list_head tmp_list;
	144	int i;
	145
	146	dprintk("RPC: setup backchannel transport\n");
	147
	148	/*
	149	* We use a temporary list to keep track of the preallocated
	150	* buffers. Once we're done building the list we splice it
	151	* into the backchannel preallocation list off of the rpc_xprt
	152	* struct. This helps minimize the amount of time the list
	153	* lock is held on the rpc_xprt struct. It also makes cleanup
	154	* easier in case of memory allocation errors.
	155	*/
	156	INIT_LIST_HEAD(&tmp_list);
	157	for (i = 0; i < min_reqs; i++) {
	158	/* Pre-allocate one backchannel rpc_rqst */
1dddda86	159	req = xprt_alloc_bc_req(xprt, GFP_KERNEL);
fb7a0b9a RL	160	if (req == NULL) {
	161	printk(KERN_ERR "Failed to create bc rpc_rqst\n");
	162	goto out_free;
	163	}
	164
	165	/* Add the allocated buffer to the tmp list */
	166	dprintk("RPC: adding req= %p\n", req);
	167	list_add(&req->rq_bc_pa_list, &tmp_list);
fb7a0b9a RL	168	}
	169
	170	/*
	171	* Add the temporary list to the backchannel preallocation list
	172	*/
c89091c8	173	spin_lock(&xprt->bc_pa_lock);
fb7a0b9a RL	174	list_splice(&tmp_list, &xprt->bc_pa_list);
fb7a0b9a RL	175	xprt_inc_alloc_count(xprt, min_reqs);
c89091c8	176	spin_unlock(&xprt->bc_pa_lock);
fb7a0b9a RL	177
	178	dprintk("RPC: setup backchannel transport done\n");
	179	return 0;
	180
	181	out_free:
	182	/*
	183	* Memory allocation failed, free the temporary list
	184	*/
1dddda86 TM	185	while (!list_empty(&tmp_list)) {
	186	req = list_first_entry(&tmp_list,
	187	struct rpc_rqst,
	188	rq_bc_pa_list);
62835679	189	list_del(&req->rq_bc_pa_list);
fb7a0b9a	190	xprt_free_allocation(req);
62835679	191	}
fb7a0b9a RL	192
fb7a0b9a RL	193	dprintk("RPC: setup backchannel transport failed\n");
d24bab93	194	return -ENOMEM;
fb7a0b9a	195	}
fb7a0b9a	196
2c53040f BH	197	/**
	198	* xprt_destroy_backchannel - Destroys the backchannel preallocated structures.
	199	* @xprt: the transport holding the preallocated strucures
	200	* @max_reqs the maximum number of preallocated structures to destroy
	201	*
fb7a0b9a RL	202	* Since these structures may have been allocated by multiple calls
	203	* to xprt_setup_backchannel, we only destroy up to the maximum number
	204	* of reqs specified by the caller.
fb7a0b9a RL	205	*/
fb7a0b9a RL	206	void xprt_destroy_backchannel(struct rpc_xprt *xprt, unsigned int max_reqs)
42e5c3e2 CL	207	{
	208	if (xprt->ops->bc_destroy)
	209	xprt->ops->bc_destroy(xprt, max_reqs);
	210	}
	211	EXPORT_SYMBOL_GPL(xprt_destroy_backchannel);
	212
	213	void xprt_destroy_bc(struct rpc_xprt *xprt, unsigned int max_reqs)
fb7a0b9a RL	214	{
	215	struct rpc_rqst req = NULL, tmp = NULL;
	216
	217	dprintk("RPC: destroy backchannel transport\n");
	218
c4ded8d9 WAA	219	if (max_reqs == 0)
	220	goto out;
	221
fb7a0b9a RL	222	spin_lock_bh(&xprt->bc_pa_lock);
	223	xprt_dec_alloc_count(xprt, max_reqs);
	224	list_for_each_entry_safe(req, tmp, &xprt->bc_pa_list, rq_bc_pa_list) {
	225	dprintk("RPC: req=%p\n", req);
62835679	226	list_del(&req->rq_bc_pa_list);
fb7a0b9a RL	227	xprt_free_allocation(req);
	228	if (--max_reqs == 0)
	229	break;
	230	}
	231	spin_unlock_bh(&xprt->bc_pa_lock);
	232
c4ded8d9	233	out:
fb7a0b9a RL	234	dprintk("RPC: backchannel list empty= %s\n",
	235	list_empty(&xprt->bc_pa_list) ? "true" : "false");
	236	}
fb7a0b9a	237
2ea24497	238	static struct rpc_rqst xprt_alloc_bc_request(struct rpc_xprt xprt, __be32 xid)
fb7a0b9a	239	{
2ea24497	240	struct rpc_rqst *req = NULL;
fb7a0b9a RL	241
fb7a0b9a RL	242	dprintk("RPC: allocate a backchannel request\n");
0d2a970d	243	if (atomic_read(&xprt->bc_free_slots) <= 0)
2ea24497	244	goto not_found;
0d2a970d TM	245	if (list_empty(&xprt->bc_pa_list)) {
	246	req = xprt_alloc_bc_req(xprt, GFP_ATOMIC);
	247	if (!req)
	248	goto not_found;
68514471 TM	249	list_add_tail(&req->rq_bc_pa_list, &xprt->bc_pa_list);
68514471 TM	250	xprt->bc_alloc_count++;
0d2a970d	251	}
2ea24497 TM	252	req = list_first_entry(&xprt->bc_pa_list, struct rpc_rqst,
	253	rq_bc_pa_list);
	254	req->rq_reply_bytes_recvd = 0;
	255	req->rq_bytes_sent = 0;
	256	memcpy(&req->rq_private_buf, &req->rq_rcv_buf,
fb7a0b9a	257	sizeof(req->rq_private_buf));
2ea24497 TM	258	req->rq_xid = xid;
	259	req->rq_connect_cookie = xprt->connect_cookie;
	260	not_found:
fb7a0b9a RL	261	dprintk("RPC: backchannel req=%p\n", req);
	262	return req;
	263	}
	264
	265	/*
	266	* Return the preallocated rpc_rqst structure and XDR buffers
	267	* associated with this rpc_task.
	268	*/
	269	void xprt_free_bc_request(struct rpc_rqst *req)
	270	{
	271	struct rpc_xprt *xprt = req->rq_xprt;
	272
42e5c3e2 CL	273	xprt->ops->bc_free_rqst(req);
	274	}
	275
	276	void xprt_free_bc_rqst(struct rpc_rqst *req)
	277	{
	278	struct rpc_xprt *xprt = req->rq_xprt;
	279
fb7a0b9a RL	280	dprintk("RPC: free backchannel req=%p\n", req);
fb7a0b9a RL	281
2ea24497	282	req->rq_connect_cookie = xprt->connect_cookie - 1;
4e857c58	283	smp_mb__before_atomic();
fb7a0b9a	284	clear_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state);
4e857c58	285	smp_mb__after_atomic();
fb7a0b9a	286
0d2a970d TM	287	/*
	288	* Return it to the list of preallocations so that it
	289	* may be reused by a new callback request.
	290	*/
	291	spin_lock_bh(&xprt->bc_pa_lock);
	292	if (xprt_need_to_requeue(xprt)) {
	293	list_add_tail(&req->rq_bc_pa_list, &xprt->bc_pa_list);
	294	xprt->bc_alloc_count++;
	295	req = NULL;
	296	}
	297	spin_unlock_bh(&xprt->bc_pa_lock);
	298	if (req != NULL) {
fb7a0b9a RL	299	/*
	300	* The last remaining session was destroyed while this
	301	* entry was in use. Free the entry and don't attempt
	302	* to add back to the list because there is no need to
	303	* have anymore preallocated entries.
	304	*/
	305	dprintk("RPC: Last session removed req=%p\n", req);
	306	xprt_free_allocation(req);
	307	return;
	308	}
fb7a0b9a RL	309	}
fb7a0b9a RL	310
2ea24497 TM	311	/*
	312	* One or more rpc_rqst structure have been preallocated during the
	313	* backchannel setup. Buffer space for the send and private XDR buffers
	314	* has been preallocated as well. Use xprt_alloc_bc_request to allocate
	315	* to this request. Use xprt_free_bc_request to return it.
	316	*
	317	* We know that we're called in soft interrupt context, grab the spin_lock
	318	* since there is no need to grab the bottom half spin_lock.
	319	*
	320	* Return an available rpc_rqst, otherwise NULL if non are available.
	321	*/
	322	struct rpc_rqst xprt_lookup_bc_request(struct rpc_xprt xprt, __be32 xid)
	323	{
	324	struct rpc_rqst *req;
	325
	326	spin_lock(&xprt->bc_pa_lock);
	327	list_for_each_entry(req, &xprt->bc_pa_list, rq_bc_pa_list) {
	328	if (req->rq_connect_cookie != xprt->connect_cookie)
	329	continue;
	330	if (req->rq_xid == xid)
	331	goto found;
	332	}
	333	req = xprt_alloc_bc_request(xprt, xid);
	334	found:
	335	spin_unlock(&xprt->bc_pa_lock);
	336	return req;
	337	}
	338
	339	/*
	340	* Add callback request to callback list. The callback
	341	* service sleeps on the sv_cb_waitq waiting for new
	342	* requests. Wake it up after adding enqueing the
	343	* request.
	344	*/
	345	void xprt_complete_bc_request(struct rpc_rqst *req, uint32_t copied)
	346	{
	347	struct rpc_xprt *xprt = req->rq_xprt;
	348	struct svc_serv *bc_serv = xprt->bc_serv;
	349
813b00d6 CL	350	spin_lock(&xprt->bc_pa_lock);
813b00d6 CL	351	list_del(&req->rq_bc_pa_list);
1980bd4d	352	xprt_dec_alloc_count(xprt, 1);
813b00d6 CL	353	spin_unlock(&xprt->bc_pa_lock);
813b00d6 CL	354
2ea24497 TM	355	req->rq_private_buf.len = copied;
	356	set_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state);
	357
	358	dprintk("RPC: add callback request to list\n");
	359	spin_lock(&bc_serv->sv_cb_lock);
2ea24497 TM	360	list_add(&req->rq_bc_list, &bc_serv->sv_cb_list);
	361	wake_up(&bc_serv->sv_cb_waitq);
	362	spin_unlock(&bc_serv->sv_cb_lock);
	363	}