net/sunrpc/xprtrdma/fmr_ops.c

   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
  38 static int
  39 fmr_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  */
  47 static size_t
  48 fmr_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
  54 static int
  55 fmr_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
  97 out_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);
 101 out_free:
 102         kfree(r);
 103 out:
 104         return rc;
 105 }
 106
 107 static 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  */
 119 static int
 120 fmr_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
 173 out_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
 182 static 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  */
 202 static void
 203 fmr_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  */
 248 static int
 249 fmr_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
 267 out_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
 275 static void
 276 fmr_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
 295 const 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 };