xref: /openbmc/linux/net/rds/ib_rdma.c (revision 9d56dd3b083a3bec56e9da35ce07baca81030b03)
1 /*
2  * Copyright (c) 2006 Oracle.  All rights reserved.
3  *
4  * This software is available to you under a choice of one of two
5  * licenses.  You may choose to be licensed under the terms of the GNU
6  * General Public License (GPL) Version 2, available from the file
7  * COPYING in the main directory of this source tree, or the
8  * OpenIB.org BSD license below:
9  *
10  *     Redistribution and use in source and binary forms, with or
11  *     without modification, are permitted provided that the following
12  *     conditions are met:
13  *
14  *      - Redistributions of source code must retain the above
15  *        copyright notice, this list of conditions and the following
16  *        disclaimer.
17  *
18  *      - Redistributions in binary form must reproduce the above
19  *        copyright notice, this list of conditions and the following
20  *        disclaimer in the documentation and/or other materials
21  *        provided with the distribution.
22  *
23  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
24  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
25  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
26  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
27  * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
28  * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
29  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
30  * SOFTWARE.
31  *
32  */
33 #include <linux/kernel.h>
34 
35 #include "rds.h"
36 #include "rdma.h"
37 #include "ib.h"
38 
39 
40 /*
41  * This is stored as mr->r_trans_private.
42  */
43 struct rds_ib_mr {
44 	struct rds_ib_device	*device;
45 	struct rds_ib_mr_pool	*pool;
46 	struct ib_fmr		*fmr;
47 	struct list_head	list;
48 	unsigned int		remap_count;
49 
50 	struct scatterlist	*sg;
51 	unsigned int		sg_len;
52 	u64			*dma;
53 	int			sg_dma_len;
54 };
55 
56 /*
57  * Our own little FMR pool
58  */
59 struct rds_ib_mr_pool {
60 	struct mutex		flush_lock;		/* serialize fmr invalidate */
61 	struct work_struct	flush_worker;		/* flush worker */
62 
63 	spinlock_t		list_lock;		/* protect variables below */
64 	atomic_t		item_count;		/* total # of MRs */
65 	atomic_t		dirty_count;		/* # dirty of MRs */
66 	struct list_head	drop_list;		/* MRs that have reached their max_maps limit */
67 	struct list_head	free_list;		/* unused MRs */
68 	struct list_head	clean_list;		/* unused & unamapped MRs */
69 	atomic_t		free_pinned;		/* memory pinned by free MRs */
70 	unsigned long		max_items;
71 	unsigned long		max_items_soft;
72 	unsigned long		max_free_pinned;
73 	struct ib_fmr_attr	fmr_attr;
74 };
75 
76 static int rds_ib_flush_mr_pool(struct rds_ib_mr_pool *pool, int free_all);
77 static void rds_ib_teardown_mr(struct rds_ib_mr *ibmr);
78 static void rds_ib_mr_pool_flush_worker(struct work_struct *work);
79 
80 static struct rds_ib_device *rds_ib_get_device(__be32 ipaddr)
81 {
82 	struct rds_ib_device *rds_ibdev;
83 	struct rds_ib_ipaddr *i_ipaddr;
84 
85 	list_for_each_entry(rds_ibdev, &rds_ib_devices, list) {
86 		spin_lock_irq(&rds_ibdev->spinlock);
87 		list_for_each_entry(i_ipaddr, &rds_ibdev->ipaddr_list, list) {
88 			if (i_ipaddr->ipaddr == ipaddr) {
89 				spin_unlock_irq(&rds_ibdev->spinlock);
90 				return rds_ibdev;
91 			}
92 		}
93 		spin_unlock_irq(&rds_ibdev->spinlock);
94 	}
95 
96 	return NULL;
97 }
98 
99 static int rds_ib_add_ipaddr(struct rds_ib_device *rds_ibdev, __be32 ipaddr)
100 {
101 	struct rds_ib_ipaddr *i_ipaddr;
102 
103 	i_ipaddr = kmalloc(sizeof *i_ipaddr, GFP_KERNEL);
104 	if (!i_ipaddr)
105 		return -ENOMEM;
106 
107 	i_ipaddr->ipaddr = ipaddr;
108 
109 	spin_lock_irq(&rds_ibdev->spinlock);
110 	list_add_tail(&i_ipaddr->list, &rds_ibdev->ipaddr_list);
111 	spin_unlock_irq(&rds_ibdev->spinlock);
112 
113 	return 0;
114 }
115 
116 static void rds_ib_remove_ipaddr(struct rds_ib_device *rds_ibdev, __be32 ipaddr)
117 {
118 	struct rds_ib_ipaddr *i_ipaddr, *next;
119 
120 	spin_lock_irq(&rds_ibdev->spinlock);
121 	list_for_each_entry_safe(i_ipaddr, next, &rds_ibdev->ipaddr_list, list) {
122 		if (i_ipaddr->ipaddr == ipaddr) {
123 			list_del(&i_ipaddr->list);
124 			kfree(i_ipaddr);
125 			break;
126 		}
127 	}
128 	spin_unlock_irq(&rds_ibdev->spinlock);
129 }
130 
131 int rds_ib_update_ipaddr(struct rds_ib_device *rds_ibdev, __be32 ipaddr)
132 {
133 	struct rds_ib_device *rds_ibdev_old;
134 
135 	rds_ibdev_old = rds_ib_get_device(ipaddr);
136 	if (rds_ibdev_old)
137 		rds_ib_remove_ipaddr(rds_ibdev_old, ipaddr);
138 
139 	return rds_ib_add_ipaddr(rds_ibdev, ipaddr);
140 }
141 
142 void rds_ib_add_conn(struct rds_ib_device *rds_ibdev, struct rds_connection *conn)
143 {
144 	struct rds_ib_connection *ic = conn->c_transport_data;
145 
146 	/* conn was previously on the nodev_conns_list */
147 	spin_lock_irq(&ib_nodev_conns_lock);
148 	BUG_ON(list_empty(&ib_nodev_conns));
149 	BUG_ON(list_empty(&ic->ib_node));
150 	list_del(&ic->ib_node);
151 
152 	spin_lock_irq(&rds_ibdev->spinlock);
153 	list_add_tail(&ic->ib_node, &rds_ibdev->conn_list);
154 	spin_unlock_irq(&rds_ibdev->spinlock);
155 	spin_unlock_irq(&ib_nodev_conns_lock);
156 
157 	ic->rds_ibdev = rds_ibdev;
158 }
159 
160 void rds_ib_remove_conn(struct rds_ib_device *rds_ibdev, struct rds_connection *conn)
161 {
162 	struct rds_ib_connection *ic = conn->c_transport_data;
163 
164 	/* place conn on nodev_conns_list */
165 	spin_lock(&ib_nodev_conns_lock);
166 
167 	spin_lock_irq(&rds_ibdev->spinlock);
168 	BUG_ON(list_empty(&ic->ib_node));
169 	list_del(&ic->ib_node);
170 	spin_unlock_irq(&rds_ibdev->spinlock);
171 
172 	list_add_tail(&ic->ib_node, &ib_nodev_conns);
173 
174 	spin_unlock(&ib_nodev_conns_lock);
175 
176 	ic->rds_ibdev = NULL;
177 }
178 
179 void __rds_ib_destroy_conns(struct list_head *list, spinlock_t *list_lock)
180 {
181 	struct rds_ib_connection *ic, *_ic;
182 	LIST_HEAD(tmp_list);
183 
184 	/* avoid calling conn_destroy with irqs off */
185 	spin_lock_irq(list_lock);
186 	list_splice(list, &tmp_list);
187 	INIT_LIST_HEAD(list);
188 	spin_unlock_irq(list_lock);
189 
190 	list_for_each_entry_safe(ic, _ic, &tmp_list, ib_node)
191 		rds_conn_destroy(ic->conn);
192 }
193 
194 struct rds_ib_mr_pool *rds_ib_create_mr_pool(struct rds_ib_device *rds_ibdev)
195 {
196 	struct rds_ib_mr_pool *pool;
197 
198 	pool = kzalloc(sizeof(*pool), GFP_KERNEL);
199 	if (!pool)
200 		return ERR_PTR(-ENOMEM);
201 
202 	INIT_LIST_HEAD(&pool->free_list);
203 	INIT_LIST_HEAD(&pool->drop_list);
204 	INIT_LIST_HEAD(&pool->clean_list);
205 	mutex_init(&pool->flush_lock);
206 	spin_lock_init(&pool->list_lock);
207 	INIT_WORK(&pool->flush_worker, rds_ib_mr_pool_flush_worker);
208 
209 	pool->fmr_attr.max_pages = fmr_message_size;
210 	pool->fmr_attr.max_maps = rds_ibdev->fmr_max_remaps;
211 	pool->fmr_attr.page_shift = PAGE_SHIFT;
212 	pool->max_free_pinned = rds_ibdev->max_fmrs * fmr_message_size / 4;
213 
214 	/* We never allow more than max_items MRs to be allocated.
215 	 * When we exceed more than max_items_soft, we start freeing
216 	 * items more aggressively.
217 	 * Make sure that max_items > max_items_soft > max_items / 2
218 	 */
219 	pool->max_items_soft = rds_ibdev->max_fmrs * 3 / 4;
220 	pool->max_items = rds_ibdev->max_fmrs;
221 
222 	return pool;
223 }
224 
225 void rds_ib_get_mr_info(struct rds_ib_device *rds_ibdev, struct rds_info_rdma_connection *iinfo)
226 {
227 	struct rds_ib_mr_pool *pool = rds_ibdev->mr_pool;
228 
229 	iinfo->rdma_mr_max = pool->max_items;
230 	iinfo->rdma_mr_size = pool->fmr_attr.max_pages;
231 }
232 
233 void rds_ib_destroy_mr_pool(struct rds_ib_mr_pool *pool)
234 {
235 	flush_workqueue(rds_wq);
236 	rds_ib_flush_mr_pool(pool, 1);
237 	BUG_ON(atomic_read(&pool->item_count));
238 	BUG_ON(atomic_read(&pool->free_pinned));
239 	kfree(pool);
240 }
241 
242 static inline struct rds_ib_mr *rds_ib_reuse_fmr(struct rds_ib_mr_pool *pool)
243 {
244 	struct rds_ib_mr *ibmr = NULL;
245 	unsigned long flags;
246 
247 	spin_lock_irqsave(&pool->list_lock, flags);
248 	if (!list_empty(&pool->clean_list)) {
249 		ibmr = list_entry(pool->clean_list.next, struct rds_ib_mr, list);
250 		list_del_init(&ibmr->list);
251 	}
252 	spin_unlock_irqrestore(&pool->list_lock, flags);
253 
254 	return ibmr;
255 }
256 
257 static struct rds_ib_mr *rds_ib_alloc_fmr(struct rds_ib_device *rds_ibdev)
258 {
259 	struct rds_ib_mr_pool *pool = rds_ibdev->mr_pool;
260 	struct rds_ib_mr *ibmr = NULL;
261 	int err = 0, iter = 0;
262 
263 	while (1) {
264 		ibmr = rds_ib_reuse_fmr(pool);
265 		if (ibmr)
266 			return ibmr;
267 
268 		/* No clean MRs - now we have the choice of either
269 		 * allocating a fresh MR up to the limit imposed by the
270 		 * driver, or flush any dirty unused MRs.
271 		 * We try to avoid stalling in the send path if possible,
272 		 * so we allocate as long as we're allowed to.
273 		 *
274 		 * We're fussy with enforcing the FMR limit, though. If the driver
275 		 * tells us we can't use more than N fmrs, we shouldn't start
276 		 * arguing with it */
277 		if (atomic_inc_return(&pool->item_count) <= pool->max_items)
278 			break;
279 
280 		atomic_dec(&pool->item_count);
281 
282 		if (++iter > 2) {
283 			rds_ib_stats_inc(s_ib_rdma_mr_pool_depleted);
284 			return ERR_PTR(-EAGAIN);
285 		}
286 
287 		/* We do have some empty MRs. Flush them out. */
288 		rds_ib_stats_inc(s_ib_rdma_mr_pool_wait);
289 		rds_ib_flush_mr_pool(pool, 0);
290 	}
291 
292 	ibmr = kzalloc(sizeof(*ibmr), GFP_KERNEL);
293 	if (!ibmr) {
294 		err = -ENOMEM;
295 		goto out_no_cigar;
296 	}
297 
298 	ibmr->fmr = ib_alloc_fmr(rds_ibdev->pd,
299 			(IB_ACCESS_LOCAL_WRITE |
300 			 IB_ACCESS_REMOTE_READ |
301 			 IB_ACCESS_REMOTE_WRITE),
302 			&pool->fmr_attr);
303 	if (IS_ERR(ibmr->fmr)) {
304 		err = PTR_ERR(ibmr->fmr);
305 		ibmr->fmr = NULL;
306 		printk(KERN_WARNING "RDS/IB: ib_alloc_fmr failed (err=%d)\n", err);
307 		goto out_no_cigar;
308 	}
309 
310 	rds_ib_stats_inc(s_ib_rdma_mr_alloc);
311 	return ibmr;
312 
313 out_no_cigar:
314 	if (ibmr) {
315 		if (ibmr->fmr)
316 			ib_dealloc_fmr(ibmr->fmr);
317 		kfree(ibmr);
318 	}
319 	atomic_dec(&pool->item_count);
320 	return ERR_PTR(err);
321 }
322 
323 static int rds_ib_map_fmr(struct rds_ib_device *rds_ibdev, struct rds_ib_mr *ibmr,
324 	       struct scatterlist *sg, unsigned int nents)
325 {
326 	struct ib_device *dev = rds_ibdev->dev;
327 	struct scatterlist *scat = sg;
328 	u64 io_addr = 0;
329 	u64 *dma_pages;
330 	u32 len;
331 	int page_cnt, sg_dma_len;
332 	int i, j;
333 	int ret;
334 
335 	sg_dma_len = ib_dma_map_sg(dev, sg, nents,
336 				 DMA_BIDIRECTIONAL);
337 	if (unlikely(!sg_dma_len)) {
338 		printk(KERN_WARNING "RDS/IB: dma_map_sg failed!\n");
339 		return -EBUSY;
340 	}
341 
342 	len = 0;
343 	page_cnt = 0;
344 
345 	for (i = 0; i < sg_dma_len; ++i) {
346 		unsigned int dma_len = ib_sg_dma_len(dev, &scat[i]);
347 		u64 dma_addr = ib_sg_dma_address(dev, &scat[i]);
348 
349 		if (dma_addr & ~PAGE_MASK) {
350 			if (i > 0)
351 				return -EINVAL;
352 			else
353 				++page_cnt;
354 		}
355 		if ((dma_addr + dma_len) & ~PAGE_MASK) {
356 			if (i < sg_dma_len - 1)
357 				return -EINVAL;
358 			else
359 				++page_cnt;
360 		}
361 
362 		len += dma_len;
363 	}
364 
365 	page_cnt += len >> PAGE_SHIFT;
366 	if (page_cnt > fmr_message_size)
367 		return -EINVAL;
368 
369 	dma_pages = kmalloc(sizeof(u64) * page_cnt, GFP_ATOMIC);
370 	if (!dma_pages)
371 		return -ENOMEM;
372 
373 	page_cnt = 0;
374 	for (i = 0; i < sg_dma_len; ++i) {
375 		unsigned int dma_len = ib_sg_dma_len(dev, &scat[i]);
376 		u64 dma_addr = ib_sg_dma_address(dev, &scat[i]);
377 
378 		for (j = 0; j < dma_len; j += PAGE_SIZE)
379 			dma_pages[page_cnt++] =
380 				(dma_addr & PAGE_MASK) + j;
381 	}
382 
383 	ret = ib_map_phys_fmr(ibmr->fmr,
384 				   dma_pages, page_cnt, io_addr);
385 	if (ret)
386 		goto out;
387 
388 	/* Success - we successfully remapped the MR, so we can
389 	 * safely tear down the old mapping. */
390 	rds_ib_teardown_mr(ibmr);
391 
392 	ibmr->sg = scat;
393 	ibmr->sg_len = nents;
394 	ibmr->sg_dma_len = sg_dma_len;
395 	ibmr->remap_count++;
396 
397 	rds_ib_stats_inc(s_ib_rdma_mr_used);
398 	ret = 0;
399 
400 out:
401 	kfree(dma_pages);
402 
403 	return ret;
404 }
405 
406 void rds_ib_sync_mr(void *trans_private, int direction)
407 {
408 	struct rds_ib_mr *ibmr = trans_private;
409 	struct rds_ib_device *rds_ibdev = ibmr->device;
410 
411 	switch (direction) {
412 	case DMA_FROM_DEVICE:
413 		ib_dma_sync_sg_for_cpu(rds_ibdev->dev, ibmr->sg,
414 			ibmr->sg_dma_len, DMA_BIDIRECTIONAL);
415 		break;
416 	case DMA_TO_DEVICE:
417 		ib_dma_sync_sg_for_device(rds_ibdev->dev, ibmr->sg,
418 			ibmr->sg_dma_len, DMA_BIDIRECTIONAL);
419 		break;
420 	}
421 }
422 
423 static void __rds_ib_teardown_mr(struct rds_ib_mr *ibmr)
424 {
425 	struct rds_ib_device *rds_ibdev = ibmr->device;
426 
427 	if (ibmr->sg_dma_len) {
428 		ib_dma_unmap_sg(rds_ibdev->dev,
429 				ibmr->sg, ibmr->sg_len,
430 				DMA_BIDIRECTIONAL);
431 		ibmr->sg_dma_len = 0;
432 	}
433 
434 	/* Release the s/g list */
435 	if (ibmr->sg_len) {
436 		unsigned int i;
437 
438 		for (i = 0; i < ibmr->sg_len; ++i) {
439 			struct page *page = sg_page(&ibmr->sg[i]);
440 
441 			/* FIXME we need a way to tell a r/w MR
442 			 * from a r/o MR */
443 			set_page_dirty(page);
444 			put_page(page);
445 		}
446 		kfree(ibmr->sg);
447 
448 		ibmr->sg = NULL;
449 		ibmr->sg_len = 0;
450 	}
451 }
452 
453 static void rds_ib_teardown_mr(struct rds_ib_mr *ibmr)
454 {
455 	unsigned int pinned = ibmr->sg_len;
456 
457 	__rds_ib_teardown_mr(ibmr);
458 	if (pinned) {
459 		struct rds_ib_device *rds_ibdev = ibmr->device;
460 		struct rds_ib_mr_pool *pool = rds_ibdev->mr_pool;
461 
462 		atomic_sub(pinned, &pool->free_pinned);
463 	}
464 }
465 
466 static inline unsigned int rds_ib_flush_goal(struct rds_ib_mr_pool *pool, int free_all)
467 {
468 	unsigned int item_count;
469 
470 	item_count = atomic_read(&pool->item_count);
471 	if (free_all)
472 		return item_count;
473 
474 	return 0;
475 }
476 
477 /*
478  * Flush our pool of MRs.
479  * At a minimum, all currently unused MRs are unmapped.
480  * If the number of MRs allocated exceeds the limit, we also try
481  * to free as many MRs as needed to get back to this limit.
482  */
483 static int rds_ib_flush_mr_pool(struct rds_ib_mr_pool *pool, int free_all)
484 {
485 	struct rds_ib_mr *ibmr, *next;
486 	LIST_HEAD(unmap_list);
487 	LIST_HEAD(fmr_list);
488 	unsigned long unpinned = 0;
489 	unsigned long flags;
490 	unsigned int nfreed = 0, ncleaned = 0, free_goal;
491 	int ret = 0;
492 
493 	rds_ib_stats_inc(s_ib_rdma_mr_pool_flush);
494 
495 	mutex_lock(&pool->flush_lock);
496 
497 	spin_lock_irqsave(&pool->list_lock, flags);
498 	/* Get the list of all MRs to be dropped. Ordering matters -
499 	 * we want to put drop_list ahead of free_list. */
500 	list_splice_init(&pool->free_list, &unmap_list);
501 	list_splice_init(&pool->drop_list, &unmap_list);
502 	if (free_all)
503 		list_splice_init(&pool->clean_list, &unmap_list);
504 	spin_unlock_irqrestore(&pool->list_lock, flags);
505 
506 	free_goal = rds_ib_flush_goal(pool, free_all);
507 
508 	if (list_empty(&unmap_list))
509 		goto out;
510 
511 	/* String all ib_mr's onto one list and hand them to ib_unmap_fmr */
512 	list_for_each_entry(ibmr, &unmap_list, list)
513 		list_add(&ibmr->fmr->list, &fmr_list);
514 	ret = ib_unmap_fmr(&fmr_list);
515 	if (ret)
516 		printk(KERN_WARNING "RDS/IB: ib_unmap_fmr failed (err=%d)\n", ret);
517 
518 	/* Now we can destroy the DMA mapping and unpin any pages */
519 	list_for_each_entry_safe(ibmr, next, &unmap_list, list) {
520 		unpinned += ibmr->sg_len;
521 		__rds_ib_teardown_mr(ibmr);
522 		if (nfreed < free_goal || ibmr->remap_count >= pool->fmr_attr.max_maps) {
523 			rds_ib_stats_inc(s_ib_rdma_mr_free);
524 			list_del(&ibmr->list);
525 			ib_dealloc_fmr(ibmr->fmr);
526 			kfree(ibmr);
527 			nfreed++;
528 		}
529 		ncleaned++;
530 	}
531 
532 	spin_lock_irqsave(&pool->list_lock, flags);
533 	list_splice(&unmap_list, &pool->clean_list);
534 	spin_unlock_irqrestore(&pool->list_lock, flags);
535 
536 	atomic_sub(unpinned, &pool->free_pinned);
537 	atomic_sub(ncleaned, &pool->dirty_count);
538 	atomic_sub(nfreed, &pool->item_count);
539 
540 out:
541 	mutex_unlock(&pool->flush_lock);
542 	return ret;
543 }
544 
545 static void rds_ib_mr_pool_flush_worker(struct work_struct *work)
546 {
547 	struct rds_ib_mr_pool *pool = container_of(work, struct rds_ib_mr_pool, flush_worker);
548 
549 	rds_ib_flush_mr_pool(pool, 0);
550 }
551 
552 void rds_ib_free_mr(void *trans_private, int invalidate)
553 {
554 	struct rds_ib_mr *ibmr = trans_private;
555 	struct rds_ib_device *rds_ibdev = ibmr->device;
556 	struct rds_ib_mr_pool *pool = rds_ibdev->mr_pool;
557 	unsigned long flags;
558 
559 	rdsdebug("RDS/IB: free_mr nents %u\n", ibmr->sg_len);
560 
561 	/* Return it to the pool's free list */
562 	spin_lock_irqsave(&pool->list_lock, flags);
563 	if (ibmr->remap_count >= pool->fmr_attr.max_maps)
564 		list_add(&ibmr->list, &pool->drop_list);
565 	else
566 		list_add(&ibmr->list, &pool->free_list);
567 
568 	atomic_add(ibmr->sg_len, &pool->free_pinned);
569 	atomic_inc(&pool->dirty_count);
570 	spin_unlock_irqrestore(&pool->list_lock, flags);
571 
572 	/* If we've pinned too many pages, request a flush */
573 	if (atomic_read(&pool->free_pinned) >= pool->max_free_pinned ||
574 	    atomic_read(&pool->dirty_count) >= pool->max_items / 10)
575 		queue_work(rds_wq, &pool->flush_worker);
576 
577 	if (invalidate) {
578 		if (likely(!in_interrupt())) {
579 			rds_ib_flush_mr_pool(pool, 0);
580 		} else {
581 			/* We get here if the user created a MR marked
582 			 * as use_once and invalidate at the same time. */
583 			queue_work(rds_wq, &pool->flush_worker);
584 		}
585 	}
586 }
587 
588 void rds_ib_flush_mrs(void)
589 {
590 	struct rds_ib_device *rds_ibdev;
591 
592 	list_for_each_entry(rds_ibdev, &rds_ib_devices, list) {
593 		struct rds_ib_mr_pool *pool = rds_ibdev->mr_pool;
594 
595 		if (pool)
596 			rds_ib_flush_mr_pool(pool, 0);
597 	}
598 }
599 
600 void *rds_ib_get_mr(struct scatterlist *sg, unsigned long nents,
601 		    struct rds_sock *rs, u32 *key_ret)
602 {
603 	struct rds_ib_device *rds_ibdev;
604 	struct rds_ib_mr *ibmr = NULL;
605 	int ret;
606 
607 	rds_ibdev = rds_ib_get_device(rs->rs_bound_addr);
608 	if (!rds_ibdev) {
609 		ret = -ENODEV;
610 		goto out;
611 	}
612 
613 	if (!rds_ibdev->mr_pool) {
614 		ret = -ENODEV;
615 		goto out;
616 	}
617 
618 	ibmr = rds_ib_alloc_fmr(rds_ibdev);
619 	if (IS_ERR(ibmr))
620 		return ibmr;
621 
622 	ret = rds_ib_map_fmr(rds_ibdev, ibmr, sg, nents);
623 	if (ret == 0)
624 		*key_ret = ibmr->fmr->rkey;
625 	else
626 		printk(KERN_WARNING "RDS/IB: map_fmr failed (errno=%d)\n", ret);
627 
628 	ibmr->device = rds_ibdev;
629 
630  out:
631 	if (ret) {
632 		if (ibmr)
633 			rds_ib_free_mr(ibmr, 0);
634 		ibmr = ERR_PTR(ret);
635 	}
636 	return ibmr;
637 }
638