lustre/obdecho/echo.c

   1 /*
   2  * GPL HEADER START
   3  *
   4  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 only,
   8  * as published by the Free Software Foundation.
   9  *
  10  * This program is distributed in the hope that it will be useful, but
  11  * WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  * General Public License version 2 for more details (a copy is included
  14  * in the LICENSE file that accompanied this code).
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * version 2 along with this program; If not, see
  18  * http://www.sun.com/software/products/lustre/docs/GPLv2.pdf
  19  *
  20  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
  21  * CA 95054 USA or visit www.sun.com if you need additional information or
  22  * have any questions.
  23  *
  24  * GPL HEADER END
  25  */
  26 /*
  27  * Copyright (c) 2002, 2010, Oracle and/or its affiliates. All rights reserved.
  28  * Use is subject to license terms.
  29  *
  30  * Copyright (c) 2010, 2015, Intel Corporation.
  31  */
  32 /*
  33  * This file is part of Lustre, http://www.lustre.org/
  34  * Lustre is a trademark of Sun Microsystems, Inc.
  35  *
  36  * lustre/obdecho/echo.c
  37  *
  38  * Author: Peter Braam <braam@clusterfs.com>
  39  * Author: Andreas Dilger <adilger@clusterfs.com>
  40  */
  41
  42 #define DEBUG_SUBSYSTEM S_ECHO
  43
  44 #include <obd_support.h>
  45 #include <obd_class.h>
  46 #include <lustre_debug.h>
  47 #include <lustre_dlm.h>
  48 #include <lprocfs_status.h>
  49
  50 #include "echo_internal.h"
  51
  52 /* The echo objid needs to be below 2^32, because regular FID numbers are
  53  * limited to 2^32 objects in f_oid for the FID_SEQ_ECHO range. b=23335 */
  54 #define ECHO_INIT_OID        0x10000000ULL
  55 #define ECHO_HANDLE_MAGIC    0xabcd0123fedc9876ULL
  56
  57 #define ECHO_PERSISTENT_PAGES (ECHO_PERSISTENT_SIZE >> PAGE_CACHE_SHIFT)
  58 static struct page *echo_persistent_pages[ECHO_PERSISTENT_PAGES];
  59
  60 enum {
  61         LPROC_ECHO_READ_BYTES = 1,
  62         LPROC_ECHO_WRITE_BYTES = 2,
  63         LPROC_ECHO_LAST = LPROC_ECHO_WRITE_BYTES +1
  64 };
  65
  66 static int echo_connect(const struct lu_env *env,
  67                         struct obd_export **exp, struct obd_device *obd,
  68                         struct obd_uuid *cluuid, struct obd_connect_data *data,
  69                         void *localdata)
  70 {
  71         struct lustre_handle conn = { 0 };
  72         int rc;
  73
  74         data->ocd_connect_flags &= ECHO_CONNECT_SUPPORTED;
  75         data->ocd_connect_flags2 &= ECHO_CONNECT_SUPPORTED2;
  76         rc = class_connect(&conn, obd, cluuid);
  77         if (rc) {
  78                 CERROR("can't connect %d\n", rc);
  79                 return rc;
  80         }
  81         *exp = class_conn2export(&conn);
  82
  83         return 0;
  84 }
  85
  86 static int echo_disconnect(struct obd_export *exp)
  87 {
  88         LASSERT (exp != NULL);
  89
  90         return server_disconnect_export(exp);
  91 }
  92
  93 static int echo_init_export(struct obd_export *exp)
  94 {
  95         return ldlm_init_export(exp);
  96 }
  97
  98 static int echo_destroy_export(struct obd_export *exp)
  99 {
 100         ENTRY;
 101
 102         target_destroy_export(exp);
 103         ldlm_destroy_export(exp);
 104
 105         RETURN(0);
 106 }
 107
 108 static u64 echo_next_id(struct obd_device *obddev)
 109 {
 110         u64 id;
 111
 112         spin_lock(&obddev->u.echo.eo_lock);
 113         id = ++obddev->u.echo.eo_lastino;
 114         spin_unlock(&obddev->u.echo.eo_lock);
 115
 116         return id;
 117 }
 118
 119 static int echo_create(const struct lu_env *env, struct obd_export *exp,
 120                        struct obdo *oa)
 121 {
 122         struct obd_device *obd = class_exp2obd(exp);
 123
 124         if (!obd) {
 125                 CERROR("invalid client cookie "LPX64"\n",
 126                        exp->exp_handle.h_cookie);
 127                 return -EINVAL;
 128         }
 129
 130         if (!(oa->o_mode & S_IFMT)) {
 131                 CERROR("echo obd: no type!\n");
 132                 return -ENOENT;
 133         }
 134
 135         if (!(oa->o_valid & OBD_MD_FLTYPE)) {
 136                 CERROR("invalid o_valid "LPX64"\n", oa->o_valid);
 137                 return -EINVAL;
 138         }
 139
 140         ostid_set_seq_echo(&oa->o_oi);
 141         ostid_set_id(&oa->o_oi, echo_next_id(obd));
 142         oa->o_valid = OBD_MD_FLID;
 143
 144         return 0;
 145 }
 146
 147 static int echo_destroy(const struct lu_env *env, struct obd_export *exp,
 148                         struct obdo *oa)
 149 {
 150         struct obd_device *obd = class_exp2obd(exp);
 151
 152         ENTRY;
 153         if (!obd) {
 154                 CERROR("invalid client cookie "LPX64"\n",
 155                        exp->exp_handle.h_cookie);
 156                 RETURN(-EINVAL);
 157         }
 158
 159         if (!(oa->o_valid & OBD_MD_FLID)) {
 160                 CERROR("obdo missing FLID valid flag: "LPX64"\n", oa->o_valid);
 161                 RETURN(-EINVAL);
 162         }
 163
 164         if (ostid_id(&oa->o_oi) > obd->u.echo.eo_lastino ||
 165             ostid_id(&oa->o_oi) < ECHO_INIT_OID) {
 166                 CERROR("bad destroy objid: "DOSTID"\n", POSTID(&oa->o_oi));
 167                 RETURN(-EINVAL);
 168         }
 169
 170         RETURN(0);
 171 }
 172
 173 static int echo_getattr(const struct lu_env *env, struct obd_export *exp,
 174                         struct obdo *oa)
 175 {
 176         struct obd_device *obd = class_exp2obd(exp);
 177         u64 id = ostid_id(&oa->o_oi);
 178
 179         ENTRY;
 180         if (!obd) {
 181                 CERROR("invalid client cookie "LPX64"\n",
 182                        exp->exp_handle.h_cookie);
 183                 RETURN(-EINVAL);
 184         }
 185
 186         if (!(oa->o_valid & OBD_MD_FLID)) {
 187                 CERROR("obdo missing FLID valid flag: "LPX64"\n", oa->o_valid);
 188                 RETURN(-EINVAL);
 189         }
 190
 191         obdo_cpy_md(oa, &obd->u.echo.eo_oa, oa->o_valid);
 192         ostid_set_seq_echo(&oa->o_oi);
 193         ostid_set_id(&oa->o_oi, id);
 194
 195         RETURN(0);
 196 }
 197
 198 static int echo_setattr(const struct lu_env *env, struct obd_export *exp,
 199                         struct obdo *oa)
 200 {
 201         struct obd_device *obd = class_exp2obd(exp);
 202
 203         ENTRY;
 204         if (!obd) {
 205                 CERROR("invalid client cookie "LPX64"\n",
 206                        exp->exp_handle.h_cookie);
 207                 RETURN(-EINVAL);
 208         }
 209
 210         if (!(oa->o_valid & OBD_MD_FLID)) {
 211                 CERROR("obdo missing FLID valid flag: "LPX64"\n", oa->o_valid);
 212                 RETURN(-EINVAL);
 213         }
 214
 215         obd->u.echo.eo_oa = *oa;
 216
 217         RETURN(0);
 218 }
 219
 220 static void
 221 echo_page_debug_setup(struct page *page, int rw, u64 id,
 222                       __u64 offset, int len)
 223 {
 224         int   page_offset = offset & ~PAGE_MASK;
 225         char *addr        = ((char *)kmap(page)) + page_offset;
 226
 227         if (len % OBD_ECHO_BLOCK_SIZE != 0)
 228                 CERROR("Unexpected block size %d\n", len);
 229
 230         while (len > 0) {
 231                 if (rw & OBD_BRW_READ)
 232                         block_debug_setup(addr, OBD_ECHO_BLOCK_SIZE,
 233                                           offset, id);
 234                 else
 235                         block_debug_setup(addr, OBD_ECHO_BLOCK_SIZE,
 236                                           0xecc0ecc0ecc0ecc0ULL,
 237                                           0xecc0ecc0ecc0ecc0ULL);
 238
 239                 addr   += OBD_ECHO_BLOCK_SIZE;
 240                 offset += OBD_ECHO_BLOCK_SIZE;
 241                 len    -= OBD_ECHO_BLOCK_SIZE;
 242         }
 243
 244         kunmap(page);
 245 }
 246
 247 static int
 248 echo_page_debug_check(struct page *page, u64 id,
 249                       __u64 offset, int len)
 250 {
 251         int   page_offset = offset & ~PAGE_MASK;
 252         char *addr        = ((char *)kmap(page)) + page_offset;
 253         int   rc          = 0;
 254         int   rc2;
 255
 256         if (len % OBD_ECHO_BLOCK_SIZE != 0)
 257                 CERROR("Unexpected block size %d\n", len);
 258
 259         while (len > 0) {
 260                 rc2 = block_debug_check("echo", addr, OBD_ECHO_BLOCK_SIZE,
 261                                         offset, id);
 262
 263                 if (rc2 != 0 && rc == 0)
 264                         rc = rc2;
 265
 266                 addr   += OBD_ECHO_BLOCK_SIZE;
 267                 offset += OBD_ECHO_BLOCK_SIZE;
 268                 len    -= OBD_ECHO_BLOCK_SIZE;
 269         }
 270
 271         kunmap(page);
 272
 273         return rc;
 274 }
 275
 276 static int echo_map_nb_to_lb(struct obdo *oa, struct obd_ioobj *obj,
 277                              struct niobuf_remote *nb, int *pages,
 278                              struct niobuf_local *lb, int cmd, int *left)
 279 {
 280         gfp_t gfp_mask = (ostid_id(&obj->ioo_oid) & 1) ?
 281                         GFP_HIGHUSER : GFP_KERNEL;
 282         int ispersistent = ostid_id(&obj->ioo_oid) == ECHO_PERSISTENT_OBJID;
 283         int debug_setup = (!ispersistent &&
 284                            (oa->o_valid & OBD_MD_FLFLAGS) != 0 &&
 285                            (oa->o_flags & OBD_FL_DEBUG_CHECK) != 0);
 286         struct niobuf_local *res = lb;
 287         u64 offset = nb->rnb_offset;
 288         int len = nb->rnb_len;
 289
 290         while (len > 0) {
 291                 int plen = PAGE_CACHE_SIZE - (offset & (PAGE_CACHE_SIZE-1));
 292                 if (len < plen)
 293                         plen = len;
 294
 295                 /* check for local buf overflow */
 296                 if (*left == 0)
 297                         return -EINVAL;
 298
 299                 res->lnb_file_offset = offset;
 300                 res->lnb_len = plen;
 301                 LASSERT((res->lnb_file_offset & ~PAGE_MASK) +
 302                         res->lnb_len <= PAGE_CACHE_SIZE);
 303
 304                 if (ispersistent &&
 305                     ((res->lnb_file_offset >> PAGE_CACHE_SHIFT) <
 306                       ECHO_PERSISTENT_PAGES)) {
 307                         res->lnb_page =
 308                                 echo_persistent_pages[res->lnb_file_offset >>
 309                                                       PAGE_CACHE_SHIFT];
 310                         /* Take extra ref so __free_pages() can be called OK */
 311                         get_page(res->lnb_page);
 312                 } else {
 313                         res->lnb_page = alloc_page(gfp_mask);
 314                         if (res->lnb_page == NULL) {
 315                                 CERROR("can't get page for id " DOSTID"\n",
 316                                        POSTID(&obj->ioo_oid));
 317                                 return -ENOMEM;
 318                         }
 319                 }
 320
 321                 CDEBUG(D_PAGE, "$$$$ get page %p @ "LPU64" for %d\n",
 322                        res->lnb_page, res->lnb_file_offset, res->lnb_len);
 323
 324                 if (cmd & OBD_BRW_READ)
 325                         res->lnb_rc = res->lnb_len;
 326
 327                 if (debug_setup)
 328                         echo_page_debug_setup(res->lnb_page, cmd,
 329                                               ostid_id(&obj->ioo_oid),
 330                                               res->lnb_file_offset,
 331                                               res->lnb_len);
 332
 333                 offset += plen;
 334                 len -= plen;
 335                 res++;
 336
 337                 (*left)--;
 338                 (*pages)++;
 339         }
 340
 341         return 0;
 342 }
 343
 344 static int echo_finalize_lb(struct obdo *oa, struct obd_ioobj *obj,
 345                             struct niobuf_remote *rb, int *pgs,
 346                             struct niobuf_local *lb, int verify)
 347 {
 348         struct niobuf_local *res = lb;
 349         u64 start = rb->rnb_offset >> PAGE_CACHE_SHIFT;
 350         u64 end   = (rb->rnb_offset + rb->rnb_len + PAGE_CACHE_SIZE - 1) >>
 351                     PAGE_CACHE_SHIFT;
 352         int     count  = (int)(end - start);
 353         int     rc     = 0;
 354         int     i;
 355
 356         for (i = 0; i < count; i++, (*pgs) ++, res++) {
 357                 struct page *page = res->lnb_page;
 358                 void       *addr;
 359
 360                 if (page == NULL) {
 361                         CERROR("null page objid "LPU64":%p, buf %d/%d\n",
 362                                ostid_id(&obj->ioo_oid), page, i,
 363                                obj->ioo_bufcnt);
 364                         return -EFAULT;
 365                 }
 366
 367                 addr = kmap(page);
 368
 369                 CDEBUG(D_PAGE, "$$$$ use page %p, addr %p@"LPU64"\n",
 370                        res->lnb_page, addr, res->lnb_file_offset);
 371
 372                 if (verify) {
 373                         int vrc = echo_page_debug_check(page,
 374                                                         ostid_id(&obj->ioo_oid),
 375                                                         res->lnb_file_offset,
 376                                                         res->lnb_len);
 377                         /* check all the pages always */
 378                         if (vrc != 0 && rc == 0)
 379                                 rc = vrc;
 380                 }
 381
 382                 kunmap(page);
 383                 /* NB see comment above regarding persistent pages */
 384                 __free_page(page);
 385         }
 386
 387         return rc;
 388 }
 389
 390 static int echo_preprw(const struct lu_env *env, int cmd,
 391                        struct obd_export *export, struct obdo *oa,
 392                        int objcount, struct obd_ioobj *obj,
 393                        struct niobuf_remote *nb, int *pages,
 394                        struct niobuf_local *res)
 395 {
 396         struct obd_device *obd;
 397         int tot_bytes = 0;
 398         int rc = 0;
 399         int i, left;
 400         ENTRY;
 401
 402         obd = export->exp_obd;
 403         if (obd == NULL)
 404                 RETURN(-EINVAL);
 405
 406         /* Temp fix to stop falling foul of osc_announce_cached() */
 407         oa->o_valid &= ~(OBD_MD_FLBLOCKS | OBD_MD_FLGRANT);
 408
 409         memset(res, 0, sizeof(*res) * *pages);
 410
 411         CDEBUG(D_PAGE, "%s %d obdos with %d IOs\n",
 412                cmd == OBD_BRW_READ ? "reading" : "writing", objcount, *pages);
 413
 414         left = *pages;
 415         *pages = 0;
 416
 417         for (i = 0; i < objcount; i++, obj++) {
 418                 int j;
 419
 420                 for (j = 0 ; j < obj->ioo_bufcnt ; j++, nb++) {
 421
 422                         rc = echo_map_nb_to_lb(oa, obj, nb, pages,
 423                                                res + *pages, cmd, &left);
 424                         if (rc)
 425                                 GOTO(preprw_cleanup, rc);
 426
 427                         tot_bytes += nb->rnb_len;
 428                 }
 429         }
 430
 431         atomic_add(*pages, &obd->u.echo.eo_prep);
 432
 433         if (cmd & OBD_BRW_READ)
 434                 lprocfs_counter_add(obd->obd_stats, LPROC_ECHO_READ_BYTES,
 435                                     tot_bytes);
 436         else
 437                 lprocfs_counter_add(obd->obd_stats, LPROC_ECHO_WRITE_BYTES,
 438                                     tot_bytes);
 439
 440         CDEBUG(D_PAGE, "%d pages allocated after prep\n",
 441                atomic_read(&obd->u.echo.eo_prep));
 442
 443         RETURN(0);
 444
 445 preprw_cleanup:
 446         /* It is possible that we would rather handle errors by  allow
 447          * any already-set-up pages to complete, rather than tearing them
 448          * all down again.  I believe that this is what the in-kernel
 449          * prep/commit operations do.
 450          */
 451         CERROR("cleaning up %u pages (%d obdos)\n", *pages, objcount);
 452         for (i = 0; i < *pages; i++) {
 453                 kunmap(res[i].lnb_page);
 454                 /* NB if this is a persistent page, __free_page() will just
 455                  * lose the extra ref gained above */
 456                 __free_page(res[i].lnb_page);
 457                 res[i].lnb_page = NULL;
 458                 atomic_dec(&obd->u.echo.eo_prep);
 459         }
 460
 461         return rc;
 462 }
 463
 464 static int echo_commitrw(const struct lu_env *env, int cmd,
 465                          struct obd_export *export, struct obdo *oa,
 466                          int objcount, struct obd_ioobj *obj,
 467                          struct niobuf_remote *rb, int niocount,
 468                          struct niobuf_local *res, int rc)
 469 {
 470         struct obd_device *obd;
 471         int pgs = 0;
 472         int i;
 473         ENTRY;
 474
 475         obd = export->exp_obd;
 476         if (obd == NULL)
 477                 RETURN(-EINVAL);
 478
 479         if (rc)
 480                 GOTO(commitrw_cleanup, rc);
 481
 482         if ((cmd & OBD_BRW_RWMASK) == OBD_BRW_READ) {
 483                 CDEBUG(D_PAGE, "reading %d obdos with %d IOs\n",
 484                        objcount, niocount);
 485         } else {
 486                 CDEBUG(D_PAGE, "writing %d obdos with %d IOs\n",
 487                        objcount, niocount);
 488         }
 489
 490         if (niocount && res == NULL) {
 491                 CERROR("NULL res niobuf with niocount %d\n", niocount);
 492                 RETURN(-EINVAL);
 493         }
 494
 495         for (i = 0; i < objcount; i++, obj++) {
 496                 int verify = (rc == 0 &&
 497                              ostid_id(&obj->ioo_oid) != ECHO_PERSISTENT_OBJID &&
 498                               (oa->o_valid & OBD_MD_FLFLAGS) != 0 &&
 499                               (oa->o_flags & OBD_FL_DEBUG_CHECK) != 0);
 500                 int j;
 501
 502                 for (j = 0 ; j < obj->ioo_bufcnt ; j++, rb++) {
 503                         int vrc = echo_finalize_lb(oa, obj, rb, &pgs, &res[pgs],
 504                                                    verify);
 505                         if (vrc == 0)
 506                                 continue;
 507
 508                         if (vrc == -EFAULT)
 509                                 GOTO(commitrw_cleanup, rc = vrc);
 510
 511                         if (rc == 0)
 512                                 rc = vrc;
 513                 }
 514
 515         }
 516
 517         atomic_sub(pgs, &obd->u.echo.eo_prep);
 518
 519         CDEBUG(D_PAGE, "%d pages remain after commit\n",
 520                atomic_read(&obd->u.echo.eo_prep));
 521         RETURN(rc);
 522
 523 commitrw_cleanup:
 524         atomic_sub(pgs, &obd->u.echo.eo_prep);
 525
 526         CERROR("cleaning up %d pages (%d obdos)\n",
 527                niocount - pgs - 1, objcount);
 528
 529         while (pgs < niocount) {
 530                 struct page *page = res[pgs++].lnb_page;
 531
 532                 if (page == NULL)
 533                         continue;
 534
 535                 /* NB see comment above regarding persistent pages */
 536                 __free_page(page);
 537                 atomic_dec(&obd->u.echo.eo_prep);
 538         }
 539         return rc;
 540 }
 541
 542 LPROC_SEQ_FOPS_RO_TYPE(echo, uuid);
 543 static struct lprocfs_vars lprocfs_echo_obd_vars[] = {
 544         { .name =       "uuid",
 545           .fops =       &echo_uuid_fops         },
 546         { NULL }
 547 };
 548
 549 static int echo_setup(struct obd_device *obd, struct lustre_cfg *lcfg)
 550 {
 551         int                     rc;
 552         __u64                   lock_flags = 0;
 553         struct ldlm_res_id      res_id = {.name = {1}};
 554         char                    ns_name[48];
 555         ENTRY;
 556
 557         obd->u.echo.eo_obt.obt_magic = OBT_MAGIC;
 558         spin_lock_init(&obd->u.echo.eo_lock);
 559         obd->u.echo.eo_lastino = ECHO_INIT_OID;
 560
 561         sprintf(ns_name, "echotgt-%s", obd->obd_uuid.uuid);
 562         obd->obd_namespace = ldlm_namespace_new(obd, ns_name,
 563                                                 LDLM_NAMESPACE_SERVER,
 564                                                 LDLM_NAMESPACE_MODEST,
 565                                                 LDLM_NS_TYPE_OST);
 566         if (obd->obd_namespace == NULL) {
 567                 LBUG();
 568                 RETURN(-ENOMEM);
 569         }
 570
 571         rc = ldlm_cli_enqueue_local(obd->obd_namespace, &res_id, LDLM_PLAIN,
 572                                     NULL, LCK_NL, &lock_flags, NULL,
 573                                     ldlm_completion_ast, NULL, NULL, 0,
 574                                     LVB_T_NONE, NULL, &obd->u.echo.eo_nl_lock);
 575         LASSERT (rc == ELDLM_OK);
 576
 577         obd->obd_vars = lprocfs_echo_obd_vars;
 578         if (lprocfs_obd_setup(obd) == 0 &&
 579             lprocfs_alloc_obd_stats(obd, LPROC_ECHO_LAST) == 0) {
 580                 lprocfs_counter_init(obd->obd_stats, LPROC_ECHO_READ_BYTES,
 581                                      LPROCFS_CNTR_AVGMINMAX,
 582                                      "read_bytes", "bytes");
 583                 lprocfs_counter_init(obd->obd_stats, LPROC_ECHO_WRITE_BYTES,
 584                                      LPROCFS_CNTR_AVGMINMAX,
 585                                      "write_bytes", "bytes");
 586         }
 587
 588         ptlrpc_init_client(LDLM_CB_REQUEST_PORTAL, LDLM_CB_REPLY_PORTAL,
 589                            "echo_ldlm_cb_client", &obd->obd_ldlm_client);
 590         RETURN(0);
 591 }
 592
 593 static int echo_cleanup(struct obd_device *obd)
 594 {
 595         int leaked;
 596         ENTRY;
 597
 598         lprocfs_obd_cleanup(obd);
 599         lprocfs_free_obd_stats(obd);
 600
 601         ldlm_lock_decref(&obd->u.echo.eo_nl_lock, LCK_NL);
 602
 603         /* XXX Bug 3413; wait for a bit to ensure the BL callback has
 604          * happened before calling ldlm_namespace_free() */
 605         set_current_state(TASK_UNINTERRUPTIBLE);
 606         schedule_timeout(cfs_time_seconds(1));
 607
 608         ldlm_namespace_free(obd->obd_namespace, NULL, obd->obd_force);
 609         obd->obd_namespace = NULL;
 610
 611         leaked = atomic_read(&obd->u.echo.eo_prep);
 612         if (leaked != 0)
 613                 CERROR("%d prep/commitrw pages leaked\n", leaked);
 614
 615         RETURN(0);
 616 }
 617
 618 struct obd_ops echo_obd_ops = {
 619         .o_owner           = THIS_MODULE,
 620         .o_connect         = echo_connect,
 621         .o_disconnect      = echo_disconnect,
 622         .o_init_export     = echo_init_export,
 623         .o_destroy_export  = echo_destroy_export,
 624         .o_create          = echo_create,
 625         .o_destroy         = echo_destroy,
 626         .o_getattr         = echo_getattr,
 627         .o_setattr         = echo_setattr,
 628         .o_preprw          = echo_preprw,
 629         .o_commitrw        = echo_commitrw,
 630         .o_setup           = echo_setup,
 631         .o_cleanup         = echo_cleanup
 632 };
 633
 634 void echo_persistent_pages_fini(void)
 635 {
 636         int i;
 637
 638         for (i = 0; i < ECHO_PERSISTENT_PAGES; i++)
 639                 if (echo_persistent_pages[i] != NULL) {
 640                         __free_page(echo_persistent_pages[i]);
 641                         echo_persistent_pages[i] = NULL;
 642                 }
 643 }
 644
 645 int echo_persistent_pages_init(void)
 646 {
 647         struct page *pg;
 648         int          i;
 649
 650         for (i = 0; i < ECHO_PERSISTENT_PAGES; i++) {
 651                 gfp_t gfp_mask = (i < ECHO_PERSISTENT_PAGES/2) ?
 652                         GFP_KERNEL : GFP_HIGHUSER;
 653
 654                 pg = alloc_page(gfp_mask);
 655                 if (pg == NULL) {
 656                         echo_persistent_pages_fini();
 657                         return -ENOMEM;
 658                 }
 659
 660                 memset (kmap (pg), 0, PAGE_CACHE_SIZE);
 661                 kunmap (pg);
 662
 663                 echo_persistent_pages[i] = pg;
 664         }
 665
 666         return 0;
 667 }