[linux-2.6-block.git] / drivers / staging / rdma / hfi1 / keys.c

/*
 *
 * This file is provided under a dual BSD/GPLv2 license.  When using or
 * redistributing this file, you may do so under either license.
 *
 * GPL LICENSE SUMMARY
 *
 * Copyright(c) 2015 Intel Corporation.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of version 2 of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * BSD LICENSE
 *
 * Copyright(c) 2015 Intel Corporation.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *  - Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *  - Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *  - Neither the name of Intel Corporation nor the names of its
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * 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 "hfi.h"

/**
 * hfi1_alloc_lkey - allocate an lkey
 * @mr: memory region that this lkey protects
 * @dma_region: 0->normal key, 1->restricted DMA key
 *
 * Returns 0 if successful, otherwise returns -errno.
 *
 * Increments mr reference count as required.
 *
 * Sets the lkey field mr for non-dma regions.
 *
 */

int hfi1_alloc_lkey(struct hfi1_mregion *mr, int dma_region)
{
	unsigned long flags;
	u32 r;
	u32 n;
	int ret = 0;
	struct hfi1_ibdev *dev = to_idev(mr->pd->device);
	struct hfi1_lkey_table *rkt = &dev->lk_table;

	hfi1_get_mr(mr);
	spin_lock_irqsave(&rkt->lock, flags);

	/* special case for dma_mr lkey == 0 */
	if (dma_region) {
		struct hfi1_mregion *tmr;

		tmr = rcu_access_pointer(dev->dma_mr);
		if (!tmr) {
			rcu_assign_pointer(dev->dma_mr, mr);
			mr->lkey_published = 1;
		} else {
			hfi1_put_mr(mr);
		}
		goto success;
	}

	/* Find the next available LKEY */
	r = rkt->next;
	n = r;
	for (;;) {
		if (!rcu_access_pointer(rkt->table[r]))
			break;
		r = (r + 1) & (rkt->max - 1);
		if (r == n)
			goto bail;
	}
	rkt->next = (r + 1) & (rkt->max - 1);
	/*
	 * Make sure lkey is never zero which is reserved to indicate an
	 * unrestricted LKEY.
	 */
	rkt->gen++;
	/*
	 * bits are capped in verbs.c to ensure enough bits for
	 * generation number
	 */
	mr->lkey = (r << (32 - hfi1_lkey_table_size)) |
		((((1 << (24 - hfi1_lkey_table_size)) - 1) & rkt->gen)
		 << 8);
	if (mr->lkey == 0) {
		mr->lkey |= 1 << 8;
		rkt->gen++;
	}
	rcu_assign_pointer(rkt->table[r], mr);
	mr->lkey_published = 1;
success:
	spin_unlock_irqrestore(&rkt->lock, flags);
out:
	return ret;
bail:
	hfi1_put_mr(mr);
	spin_unlock_irqrestore(&rkt->lock, flags);
	ret = -ENOMEM;
	goto out;
}

/**
 * hfi1_free_lkey - free an lkey
 * @mr: mr to free from tables
 */
void hfi1_free_lkey(struct hfi1_mregion *mr)
{
	unsigned long flags;
	u32 lkey = mr->lkey;
	u32 r;
	struct hfi1_ibdev *dev = to_idev(mr->pd->device);
	struct hfi1_lkey_table *rkt = &dev->lk_table;
	int freed = 0;

	spin_lock_irqsave(&rkt->lock, flags);
	if (!mr->lkey_published)
		goto out;
	if (lkey == 0)
		RCU_INIT_POINTER(dev->dma_mr, NULL);
	else {
		r = lkey >> (32 - hfi1_lkey_table_size);
		RCU_INIT_POINTER(rkt->table[r], NULL);
	}
	mr->lkey_published = 0;
	freed++;
out:
	spin_unlock_irqrestore(&rkt->lock, flags);
	if (freed) {
		synchronize_rcu();
		hfi1_put_mr(mr);
	}
}

/**
 * hfi1_lkey_ok - check IB SGE for validity and initialize
 * @rkt: table containing lkey to check SGE against
 * @pd: protection domain
 * @isge: outgoing internal SGE
 * @sge: SGE to check
 * @acc: access flags
 *
 * Return 1 if valid and successful, otherwise returns 0.
 *
 * increments the reference count upon success
 *
 * Check the IB SGE for validity and initialize our internal version
 * of it.
 */
int hfi1_lkey_ok(struct hfi1_lkey_table *rkt, struct hfi1_pd *pd,
		 struct hfi1_sge *isge, struct ib_sge *sge, int acc)
{
	struct hfi1_mregion *mr;
	unsigned n, m;
	size_t off;

	/*
	 * We use LKEY == zero for kernel virtual addresses
	 * (see hfi1_get_dma_mr and dma.c).
	 */
	rcu_read_lock();
	if (sge->lkey == 0) {
		struct hfi1_ibdev *dev = to_idev(pd->ibpd.device);

		if (pd->user)
			goto bail;
		mr = rcu_dereference(dev->dma_mr);
		if (!mr)
			goto bail;
		atomic_inc(&mr->refcount);
		rcu_read_unlock();

		isge->mr = mr;
		isge->vaddr = (void *) sge->addr;
		isge->length = sge->length;
		isge->sge_length = sge->length;
		isge->m = 0;
		isge->n = 0;
		goto ok;
	}
	mr = rcu_dereference(
		rkt->table[(sge->lkey >> (32 - hfi1_lkey_table_size))]);
	if (unlikely(!mr || mr->lkey != sge->lkey || mr->pd != &pd->ibpd))
		goto bail;

	off = sge->addr - mr->user_base;
	if (unlikely(sge->addr < mr->user_base ||
		     off + sge->length > mr->length ||
		     (mr->access_flags & acc) != acc))
		goto bail;
	atomic_inc(&mr->refcount);
	rcu_read_unlock();

	off += mr->offset;
	if (mr->page_shift) {
		/*
		page sizes are uniform power of 2 so no loop is necessary
		entries_spanned_by_off is the number of times the loop below
		would have executed.
		*/
		size_t entries_spanned_by_off;

		entries_spanned_by_off = off >> mr->page_shift;
		off -= (entries_spanned_by_off << mr->page_shift);
		m = entries_spanned_by_off / HFI1_SEGSZ;
		n = entries_spanned_by_off % HFI1_SEGSZ;
	} else {
		m = 0;
		n = 0;
		while (off >= mr->map[m]->segs[n].length) {
			off -= mr->map[m]->segs[n].length;
			n++;
			if (n >= HFI1_SEGSZ) {
				m++;
				n = 0;
			}
		}
	}
	isge->mr = mr;
	isge->vaddr = mr->map[m]->segs[n].vaddr + off;
	isge->length = mr->map[m]->segs[n].length - off;
	isge->sge_length = sge->length;
	isge->m = m;
	isge->n = n;
ok:
	return 1;
bail:
	rcu_read_unlock();
	return 0;
}

/**
 * hfi1_rkey_ok - check the IB virtual address, length, and RKEY
 * @qp: qp for validation
 * @sge: SGE state
 * @len: length of data
 * @vaddr: virtual address to place data
 * @rkey: rkey to check
 * @acc: access flags
 *
 * Return 1 if successful, otherwise 0.
 *
 * increments the reference count upon success
 */
int hfi1_rkey_ok(struct hfi1_qp *qp, struct hfi1_sge *sge,
		 u32 len, u64 vaddr, u32 rkey, int acc)
{
	struct hfi1_lkey_table *rkt = &to_idev(qp->ibqp.device)->lk_table;
	struct hfi1_mregion *mr;
	unsigned n, m;
	size_t off;

	/*
	 * We use RKEY == zero for kernel virtual addresses
	 * (see hfi1_get_dma_mr and dma.c).
	 */
	rcu_read_lock();
	if (rkey == 0) {
		struct hfi1_pd *pd = to_ipd(qp->ibqp.pd);
		struct hfi1_ibdev *dev = to_idev(pd->ibpd.device);

		if (pd->user)
			goto bail;
		mr = rcu_dereference(dev->dma_mr);
		if (!mr)
			goto bail;
		atomic_inc(&mr->refcount);
		rcu_read_unlock();

		sge->mr = mr;
		sge->vaddr = (void *) vaddr;
		sge->length = len;
		sge->sge_length = len;
		sge->m = 0;
		sge->n = 0;
		goto ok;
	}

	mr = rcu_dereference(
		rkt->table[(rkey >> (32 - hfi1_lkey_table_size))]);
	if (unlikely(!mr || mr->lkey != rkey || qp->ibqp.pd != mr->pd))
		goto bail;

	off = vaddr - mr->iova;
	if (unlikely(vaddr < mr->iova || off + len > mr->length ||
		     (mr->access_flags & acc) == 0))
		goto bail;
	atomic_inc(&mr->refcount);
	rcu_read_unlock();

	off += mr->offset;
	if (mr->page_shift) {
		/*
		page sizes are uniform power of 2 so no loop is necessary
		entries_spanned_by_off is the number of times the loop below
		would have executed.
		*/
		size_t entries_spanned_by_off;

		entries_spanned_by_off = off >> mr->page_shift;
		off -= (entries_spanned_by_off << mr->page_shift);
		m = entries_spanned_by_off / HFI1_SEGSZ;
		n = entries_spanned_by_off % HFI1_SEGSZ;
	} else {
		m = 0;
		n = 0;
		while (off >= mr->map[m]->segs[n].length) {
			off -= mr->map[m]->segs[n].length;
			n++;
			if (n >= HFI1_SEGSZ) {
				m++;
				n = 0;
			}
		}
	}
	sge->mr = mr;
	sge->vaddr = mr->map[m]->segs[n].vaddr + off;
	sge->length = mr->map[m]->segs[n].length - off;
	sge->sge_length = len;
	sge->m = m;
	sge->n = n;
ok:
	return 1;
bail:
	rcu_read_unlock();
	return 0;
}
Commit	Line	Data
77241056 MM	1	/*
	2	*
	3	* This file is provided under a dual BSD/GPLv2 license. When using or
	4	* redistributing this file, you may do so under either license.
	5	*
	6	* GPL LICENSE SUMMARY
	7	*
	8	* Copyright(c) 2015 Intel Corporation.
	9	*
	10	* This program is free software; you can redistribute it and/or modify
	11	* it under the terms of version 2 of the GNU General Public License as
	12	* published by the Free Software Foundation.
	13	*
	14	* This program is distributed in the hope that it will be useful, but
	15	* WITHOUT ANY WARRANTY; without even the implied warranty of
	16	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	17	* General Public License for more details.
	18	*
	19	* BSD LICENSE
	20	*
	21	* Copyright(c) 2015 Intel Corporation.
	22	*
	23	* Redistribution and use in source and binary forms, with or without
	24	* modification, are permitted provided that the following conditions
	25	* are met:
	26	*
	27	* - Redistributions of source code must retain the above copyright
	28	* notice, this list of conditions and the following disclaimer.
	29	* - Redistributions in binary form must reproduce the above copyright
	30	* notice, this list of conditions and the following disclaimer in
	31	* the documentation and/or other materials provided with the
	32	* distribution.
	33	* - Neither the name of Intel Corporation nor the names of its
	34	* contributors may be used to endorse or promote products derived
	35	* from this software without specific prior written permission.
	36	*
	37	* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
	38	* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
	39	* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
	40	* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
	41	* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
	42	* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
	43	* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	44	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	45	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	46	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	47	* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	48	*
	49	*/
	50
	51	#include "hfi.h"
	52
	53	/**
	54	* hfi1_alloc_lkey - allocate an lkey
	55	* @mr: memory region that this lkey protects
	56	* @dma_region: 0->normal key, 1->restricted DMA key
	57	*
	58	* Returns 0 if successful, otherwise returns -errno.
	59	*
	60	* Increments mr reference count as required.
	61	*
	62	* Sets the lkey field mr for non-dma regions.
	63	*
	64	*/
65
66	int hfi1_alloc_lkey(struct hfi1_mregion *mr, int dma_region)
67	{
68	unsigned long flags;
69	u32 r;
70	u32 n;
71	int ret = 0;
72	struct hfi1_ibdev *dev = to_idev(mr->pd->device);
73	struct hfi1_lkey_table *rkt = &dev->lk_table;
74
75	hfi1_get_mr(mr);
76	spin_lock_irqsave(&rkt->lock, flags);
77
78	/* special case for dma_mr lkey == 0 */
79	if (dma_region) {
80	struct hfi1_mregion *tmr;
81
82	tmr = rcu_access_pointer(dev->dma_mr);
83	if (!tmr) {
84	rcu_assign_pointer(dev->dma_mr, mr);
85	mr->lkey_published = 1;
86	} else {
87	hfi1_put_mr(mr);
88	}
89	goto success;
90	}
91
92	/* Find the next available LKEY */
93	r = rkt->next;
94	n = r;
95	for (;;) {
96	if (!rcu_access_pointer(rkt->table[r]))
97	break;
98	r = (r + 1) & (rkt->max - 1);
99	if (r == n)
100	goto bail;
101	}
102	rkt->next = (r + 1) & (rkt->max - 1);
103	/*
104	* Make sure lkey is never zero which is reserved to indicate an
105	* unrestricted LKEY.
106	*/
107	rkt->gen++;
108	/*
109	* bits are capped in verbs.c to ensure enough bits for
110	* generation number
111	*/
112	mr->lkey = (r << (32 - hfi1_lkey_table_size)) \|
113	((((1 << (24 - hfi1_lkey_table_size)) - 1) & rkt->gen)
114	<< 8);
115	if (mr->lkey == 0) {
116	mr->lkey \|= 1 << 8;
117	rkt->gen++;
118	}
119	rcu_assign_pointer(rkt->table[r], mr);
120	mr->lkey_published = 1;
121	success:
122	spin_unlock_irqrestore(&rkt->lock, flags);
123	out:
124	return ret;
125	bail:
126	hfi1_put_mr(mr);
127	spin_unlock_irqrestore(&rkt->lock, flags);
128	ret = -ENOMEM;
129	goto out;
130	}
131
132	/**
133	* hfi1_free_lkey - free an lkey
134	* @mr: mr to free from tables
135	*/
136	void hfi1_free_lkey(struct hfi1_mregion *mr)
137	{
138	unsigned long flags;
139	u32 lkey = mr->lkey;
140	u32 r;
141	struct hfi1_ibdev *dev = to_idev(mr->pd->device);
142	struct hfi1_lkey_table *rkt = &dev->lk_table;
143	int freed = 0;
144
145	spin_lock_irqsave(&rkt->lock, flags);
146	if (!mr->lkey_published)
147	goto out;
148	if (lkey == 0)
149	RCU_INIT_POINTER(dev->dma_mr, NULL);
150	else {
151	r = lkey >> (32 - hfi1_lkey_table_size);
152	RCU_INIT_POINTER(rkt->table[r], NULL);
153	}
154	mr->lkey_published = 0;
155	freed++;
156	out:
157	spin_unlock_irqrestore(&rkt->lock, flags);
158	if (freed) {
159	synchronize_rcu();
160	hfi1_put_mr(mr);
161	}
162	}
163
164	/**
165	* hfi1_lkey_ok - check IB SGE for validity and initialize
166	* @rkt: table containing lkey to check SGE against
167	* @pd: protection domain
168	* @isge: outgoing internal SGE
169	* @sge: SGE to check
170	* @acc: access flags
171	*
172	* Return 1 if valid and successful, otherwise returns 0.
173	*
174	* increments the reference count upon success
175	*
176	* Check the IB SGE for validity and initialize our internal version
177	* of it.
178	*/
179	int hfi1_lkey_ok(struct hfi1_lkey_table rkt, struct hfi1_pd pd,
180	struct hfi1_sge isge, struct ib_sge sge, int acc)
181	{
182	struct hfi1_mregion *mr;
183	unsigned n, m;
184	size_t off;
185
186	/*
187	* We use LKEY == zero for kernel virtual addresses
188	* (see hfi1_get_dma_mr and dma.c).
189	*/
190	rcu_read_lock();
191	if (sge->lkey == 0) {
192	struct hfi1_ibdev *dev = to_idev(pd->ibpd.device);
193
194	if (pd->user)
195	goto bail;
196	mr = rcu_dereference(dev->dma_mr);
197	if (!mr)
198	goto bail;
199	atomic_inc(&mr->refcount);
200	rcu_read_unlock();
201
202	isge->mr = mr;
203	isge->vaddr = (void *) sge->addr;
204	isge->length = sge->length;
205	isge->sge_length = sge->length;
206	isge->m = 0;
207	isge->n = 0;
208	goto ok;
209	}
210	mr = rcu_dereference(
211	rkt->table[(sge->lkey >> (32 - hfi1_lkey_table_size))]);
212	if (unlikely(!mr \|\| mr->lkey != sge->lkey \|\| mr->pd != &pd->ibpd))
213	goto bail;
214
215	off = sge->addr - mr->user_base;
216	if (unlikely(sge->addr < mr->user_base \|\|
217	off + sge->length > mr->length \|\|
218	(mr->access_flags & acc) != acc))
219	goto bail;
220	atomic_inc(&mr->refcount);
221	rcu_read_unlock();
222
223	off += mr->offset;
224	if (mr->page_shift) {
225	/*
226	page sizes are uniform power of 2 so no loop is necessary
227	entries_spanned_by_off is the number of times the loop below
228	would have executed.
229	*/
230	size_t entries_spanned_by_off;
231
232	entries_spanned_by_off = off >> mr->page_shift;
233	off -= (entries_spanned_by_off << mr->page_shift);
234	m = entries_spanned_by_off / HFI1_SEGSZ;
235	n = entries_spanned_by_off % HFI1_SEGSZ;
236	} else {
237	m = 0;
238	n = 0;
239	while (off >= mr->map[m]->segs[n].length) {
240	off -= mr->map[m]->segs[n].length;
241	n++;
242	if (n >= HFI1_SEGSZ) {
243	m++;
244	n = 0;
245	}
246	}
247	}
248	isge->mr = mr;
249	isge->vaddr = mr->map[m]->segs[n].vaddr + off;
250	isge->length = mr->map[m]->segs[n].length - off;
251	isge->sge_length = sge->length;
252	isge->m = m;
253	isge->n = n;
254	ok:
255	return 1;
256	bail:
257	rcu_read_unlock();
258	return 0;
259	}
260
261	/**
262	* hfi1_rkey_ok - check the IB virtual address, length, and RKEY
263	* @qp: qp for validation
264	* @sge: SGE state
265	* @len: length of data
266	* @vaddr: virtual address to place data
267	* @rkey: rkey to check
268	* @acc: access flags
269	*
270	* Return 1 if successful, otherwise 0.
271	*
272	* increments the reference count upon success
273	*/
274	int hfi1_rkey_ok(struct hfi1_qp qp, struct hfi1_sge sge,
275	u32 len, u64 vaddr, u32 rkey, int acc)
276	{
277	struct hfi1_lkey_table *rkt = &to_idev(qp->ibqp.device)->lk_table;
278	struct hfi1_mregion *mr;
279	unsigned n, m;
280	size_t off;
281
282	/*
283	* We use RKEY == zero for kernel virtual addresses
284	* (see hfi1_get_dma_mr and dma.c).
285	*/
286	rcu_read_lock();
287	if (rkey == 0) {
288	struct hfi1_pd *pd = to_ipd(qp->ibqp.pd);
289	struct hfi1_ibdev *dev = to_idev(pd->ibpd.device);
290
291	if (pd->user)
292	goto bail;
293	mr = rcu_dereference(dev->dma_mr);
294	if (!mr)
295	goto bail;
296	atomic_inc(&mr->refcount);
297	rcu_read_unlock();
298
299	sge->mr = mr;
300	sge->vaddr = (void *) vaddr;
301	sge->length = len;
302	sge->sge_length = len;
303	sge->m = 0;
304	sge->n = 0;
305	goto ok;
306	}
307
308	mr = rcu_dereference(
309	rkt->table[(rkey >> (32 - hfi1_lkey_table_size))]);
310	if (unlikely(!mr \|\| mr->lkey != rkey \|\| qp->ibqp.pd != mr->pd))
311	goto bail;
312
313	off = vaddr - mr->iova;
314	if (unlikely(vaddr < mr->iova \|\| off + len > mr->length \|\|
315	(mr->access_flags & acc) == 0))
316	goto bail;
317	atomic_inc(&mr->refcount);
318	rcu_read_unlock();
319
320	off += mr->offset;
321	if (mr->page_shift) {
322	/*
323	page sizes are uniform power of 2 so no loop is necessary
324	entries_spanned_by_off is the number of times the loop below
325	would have executed.
326	*/
327	size_t entries_spanned_by_off;
328
329	entries_spanned_by_off = off >> mr->page_shift;
330	off -= (entries_spanned_by_off << mr->page_shift);
331	m = entries_spanned_by_off / HFI1_SEGSZ;
332	n = entries_spanned_by_off % HFI1_SEGSZ;
333	} else {
334	m = 0;
335	n = 0;
336	while (off >= mr->map[m]->segs[n].length) {
337	off -= mr->map[m]->segs[n].length;
338	n++;
339	if (n >= HFI1_SEGSZ) {
340	m++;
341	n = 0;
342	}
343	}
344	}
345	sge->mr = mr;
346	sge->vaddr = mr->map[m]->segs[n].vaddr + off;
347	sge->length = mr->map[m]->segs[n].length - off;
348	sge->sge_length = len;
349	sge->m = m;
350	sge->n = n;
351	ok:
352	return 1;
353	bail:
354	rcu_read_unlock();
355	return 0;
356	}