1/*
  2 * Copyright (c) 2015 Oracle.  All rights reserved.
  3 * Copyright (c) 2003-2007 Network Appliance, Inc. All rights reserved.
  4 */
  5
  6/* Lightweight memory registration using Fast Memory Regions (FMR).
  7 * Referred to sometimes as MTHCAFMR mode.
  8 *
  9 * FMR uses synchronous memory registration and deregistration.
 10 * FMR registration is known to be fast, but FMR deregistration
 11 * can take tens of usecs to complete.
 12 */
 13
 14/* Normal operation
 15 *
 16 * A Memory Region is prepared for RDMA READ or WRITE using the
 17 * ib_map_phys_fmr verb (fmr_op_map). When the RDMA operation is
 18 * finished, the Memory Region is unmapped using the ib_unmap_fmr
 19 * verb (fmr_op_unmap).
 20 */
 21
 22/* Transport recovery
 23 *
 24 * After a transport reconnect, fmr_op_map re-uses the MR already
 25 * allocated for the RPC, but generates a fresh rkey then maps the
 26 * MR again. This process is synchronous.
 27 */
 28
 29#include "xprt_rdma.h"
 30
 31#if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
 32# define RPCDBG_FACILITY	RPCDBG_TRANS
 33#endif
 34
 35/* Maximum scatter/gather per FMR */
 36#define RPCRDMA_MAX_FMR_SGES	(64)
 37
 38static int
 39fmr_op_open(struct rpcrdma_ia *ia, struct rpcrdma_ep *ep,
 40	    struct rpcrdma_create_data_internal *cdata)
 41{
 42	return 0;
 43}
 44
 45/* FMR mode conveys up to 64 pages of payload per chunk segment.
 46 */
 47static size_t
 48fmr_op_maxpages(struct rpcrdma_xprt *r_xprt)
 49{
 50	return min_t(unsigned int, RPCRDMA_MAX_DATA_SEGS,
 51		     rpcrdma_max_segments(r_xprt) * RPCRDMA_MAX_FMR_SGES);
 52}
 53
 54static int
 55fmr_op_init(struct rpcrdma_xprt *r_xprt)
 56{
 57	struct rpcrdma_buffer *buf = &r_xprt->rx_buf;
 58	int mr_access_flags = IB_ACCESS_REMOTE_WRITE | IB_ACCESS_REMOTE_READ;
 59	struct ib_fmr_attr fmr_attr = {
 60		.max_pages	= RPCRDMA_MAX_FMR_SGES,
 61		.max_maps	= 1,
 62		.page_shift	= PAGE_SHIFT
 63	};
 64	struct ib_pd *pd = r_xprt->rx_ia.ri_pd;
 65	struct rpcrdma_mw *r;
 66	int i, rc;
 67
 68	spin_lock_init(&buf->rb_mwlock);
 69	INIT_LIST_HEAD(&buf->rb_mws);
 70	INIT_LIST_HEAD(&buf->rb_all);
 71
 72	i = max_t(int, RPCRDMA_MAX_DATA_SEGS / RPCRDMA_MAX_FMR_SGES, 1);
 73	i += 2;				/* head + tail */
 74	i *= buf->rb_max_requests;	/* one set for each RPC slot */
 75	dprintk("RPC:       %s: initalizing %d FMRs\n", __func__, i);
 76
 77	rc = -ENOMEM;
 78	while (i--) {
 79		r = kzalloc(sizeof(*r), GFP_KERNEL);
 80		if (!r)
 81			goto out;
 82
 83		r->fmr.physaddrs = kmalloc(RPCRDMA_MAX_FMR_SGES *
 84					   sizeof(u64), GFP_KERNEL);
 85		if (!r->fmr.physaddrs)
 86			goto out_free;
 87
 88		r->fmr.fmr = ib_alloc_fmr(pd, mr_access_flags, &fmr_attr);
 89		if (IS_ERR(r->fmr.fmr))
 90			goto out_fmr_err;
 91
 92		list_add(&r->mw_list, &buf->rb_mws);
 93		list_add(&r->mw_all, &buf->rb_all);
 94	}
 95	return 0;
 96
 97out_fmr_err:
 98	rc = PTR_ERR(r->fmr.fmr);
 99	dprintk("RPC:       %s: ib_alloc_fmr status %i\n", __func__, rc);
100	kfree(r->fmr.physaddrs);
101out_free:
102	kfree(r);
103out:
104	return rc;
105}
106
107static int
108__fmr_unmap(struct rpcrdma_mw *r)
109{
110	LIST_HEAD(l);
111
112	list_add(&r->fmr.fmr->list, &l);
113	return ib_unmap_fmr(&l);
114}
115
116/* Use the ib_map_phys_fmr() verb to register a memory region
117 * for remote access via RDMA READ or RDMA WRITE.
118 */
119static int
120fmr_op_map(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mr_seg *seg,
121	   int nsegs, bool writing)
122{
123	struct rpcrdma_ia *ia = &r_xprt->rx_ia;
124	struct ib_device *device = ia->ri_device;
125	enum dma_data_direction direction = rpcrdma_data_dir(writing);
126	struct rpcrdma_mr_seg *seg1 = seg;
127	int len, pageoff, i, rc;
128	struct rpcrdma_mw *mw;
129
130	mw = seg1->rl_mw;
131	seg1->rl_mw = NULL;
132	if (!mw) {
133		mw = rpcrdma_get_mw(r_xprt);
134		if (!mw)
135			return -ENOMEM;
136	} else {
137		/* this is a retransmit; generate a fresh rkey */
138		rc = __fmr_unmap(mw);
139		if (rc)
140			return rc;
141	}
142
143	pageoff = offset_in_page(seg1->mr_offset);
144	seg1->mr_offset -= pageoff;	/* start of page */
145	seg1->mr_len += pageoff;
146	len = -pageoff;
147	if (nsegs > RPCRDMA_MAX_FMR_SGES)
148		nsegs = RPCRDMA_MAX_FMR_SGES;
149	for (i = 0; i < nsegs;) {
150		rpcrdma_map_one(device, seg, direction);
151		mw->fmr.physaddrs[i] = seg->mr_dma;
152		len += seg->mr_len;
153		++seg;
154		++i;
155		/* Check for holes */
156		if ((i < nsegs && offset_in_page(seg->mr_offset)) ||
157		    offset_in_page((seg-1)->mr_offset + (seg-1)->mr_len))
158			break;
159	}
160
161	rc = ib_map_phys_fmr(mw->fmr.fmr, mw->fmr.physaddrs,
162			     i, seg1->mr_dma);
163	if (rc)
164		goto out_maperr;
165
166	seg1->rl_mw = mw;
167	seg1->mr_rkey = mw->fmr.fmr->rkey;
168	seg1->mr_base = seg1->mr_dma + pageoff;
169	seg1->mr_nsegs = i;
170	seg1->mr_len = len;
171	return i;
172
173out_maperr:
174	dprintk("RPC:       %s: ib_map_phys_fmr %u@0x%llx+%i (%d) status %i\n",
175		__func__, len, (unsigned long long)seg1->mr_dma,
176		pageoff, i, rc);
177	while (i--)
178		rpcrdma_unmap_one(device, --seg);
179	return rc;
180}
181
182static void
183__fmr_dma_unmap(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mr_seg *seg)
184{
185	struct ib_device *device = r_xprt->rx_ia.ri_device;
186	struct rpcrdma_mw *mw = seg->rl_mw;
187	int nsegs = seg->mr_nsegs;
188
189	seg->rl_mw = NULL;
190
191	while (nsegs--)
192		rpcrdma_unmap_one(device, seg++);
193
194	rpcrdma_put_mw(r_xprt, mw);
195}
196
197/* Invalidate all memory regions that were registered for "req".
198 *
199 * Sleeps until it is safe for the host CPU to access the
200 * previously mapped memory regions.
201 */
202static void
203fmr_op_unmap_sync(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req)
204{
205	struct rpcrdma_mr_seg *seg;
206	unsigned int i, nchunks;
207	struct rpcrdma_mw *mw;
208	LIST_HEAD(unmap_list);
209	int rc;
210
211	dprintk("RPC:       %s: req %p\n", __func__, req);
212
213	/* ORDER: Invalidate all of the req's MRs first
214	 *
215	 * ib_unmap_fmr() is slow, so use a single call instead
216	 * of one call per mapped MR.
217	 */
218	for (i = 0, nchunks = req->rl_nchunks; nchunks; nchunks--) {
219		seg = &req->rl_segments[i];
220		mw = seg->rl_mw;
221
222		list_add(&mw->fmr.fmr->list, &unmap_list);
223
224		i += seg->mr_nsegs;
225	}
226	rc = ib_unmap_fmr(&unmap_list);
227	if (rc)
228		pr_warn("%s: ib_unmap_fmr failed (%i)\n", __func__, rc);
229
230	/* ORDER: Now DMA unmap all of the req's MRs, and return
231	 * them to the free MW list.
232	 */
233	for (i = 0, nchunks = req->rl_nchunks; nchunks; nchunks--) {
234		seg = &req->rl_segments[i];
235
236		__fmr_dma_unmap(r_xprt, seg);
237
238		i += seg->mr_nsegs;
239		seg->mr_nsegs = 0;
240	}
241
242	req->rl_nchunks = 0;
243}
244
245/* Use the ib_unmap_fmr() verb to prevent further remote
246 * access via RDMA READ or RDMA WRITE.
247 */
248static int
249fmr_op_unmap(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mr_seg *seg)
250{
251	struct rpcrdma_ia *ia = &r_xprt->rx_ia;
252	struct rpcrdma_mr_seg *seg1 = seg;
253	struct rpcrdma_mw *mw = seg1->rl_mw;
254	int rc, nsegs = seg->mr_nsegs;
255
256	dprintk("RPC:       %s: FMR %p\n", __func__, mw);
257
258	seg1->rl_mw = NULL;
259	while (seg1->mr_nsegs--)
260		rpcrdma_unmap_one(ia->ri_device, seg++);
261	rc = __fmr_unmap(mw);
262	if (rc)
263		goto out_err;
264	rpcrdma_put_mw(r_xprt, mw);
265	return nsegs;
266
267out_err:
268	/* The FMR is abandoned, but remains in rb_all. fmr_op_destroy
269	 * will attempt to release it when the transport is destroyed.
270	 */
271	dprintk("RPC:       %s: ib_unmap_fmr status %i\n", __func__, rc);
272	return nsegs;
273}
274
275static void
276fmr_op_destroy(struct rpcrdma_buffer *buf)
277{
278	struct rpcrdma_mw *r;
279	int rc;
280
281	while (!list_empty(&buf->rb_all)) {
282		r = list_entry(buf->rb_all.next, struct rpcrdma_mw, mw_all);
283		list_del(&r->mw_all);
284		kfree(r->fmr.physaddrs);
285
286		rc = ib_dealloc_fmr(r->fmr.fmr);
287		if (rc)
288			dprintk("RPC:       %s: ib_dealloc_fmr failed %i\n",
289				__func__, rc);
290
291		kfree(r);
292	}
293}
294
295const struct rpcrdma_memreg_ops rpcrdma_fmr_memreg_ops = {
296	.ro_map				= fmr_op_map,
297	.ro_unmap_sync			= fmr_op_unmap_sync,
298	.ro_unmap			= fmr_op_unmap,
299	.ro_open			= fmr_op_open,
300	.ro_maxpages			= fmr_op_maxpages,
301	.ro_init			= fmr_op_init,
302	.ro_destroy			= fmr_op_destroy,
303	.ro_displayname			= "fmr",
304};