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, 2014, 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         rc = class_connect(&conn, obd, cluuid);
  76         if (rc) {
  77                 CERROR("can't connect %d\n", rc);
  78                 return rc;
  79         }
  80         *exp = class_conn2export(&conn);
  81
  82         return 0;
  83 }
  84
  85 static int echo_disconnect(struct obd_export *exp)
  86 {
  87         LASSERT (exp != NULL);
  88
  89         return server_disconnect_export(exp);
  90 }
  91
  92 static int echo_init_export(struct obd_export *exp)
  93 {
  94         return ldlm_init_export(exp);
  95 }
  96
  97 static int echo_destroy_export(struct obd_export *exp)
  98 {
  99         ENTRY;
 100
 101         target_destroy_export(exp);
 102         ldlm_destroy_export(exp);
 103
 104         RETURN(0);
 105 }
 106
 107 static u64 echo_next_id(struct obd_device *obddev)
 108 {
 109         u64 id;
 110
 111         spin_lock(&obddev->u.echo.eo_lock);
 112         id = ++obddev->u.echo.eo_lastino;
 113         spin_unlock(&obddev->u.echo.eo_lock);
 114
 115         return id;
 116 }
 117
 118 static int echo_create(const struct lu_env *env, struct obd_export *exp,
 119                        struct obdo *oa)
 120 {
 121         struct obd_device *obd = class_exp2obd(exp);
 122
 123         if (!obd) {
 124                 CERROR("invalid client cookie "LPX64"\n",
 125                        exp->exp_handle.h_cookie);
 126                 return -EINVAL;
 127         }
 128
 129         if (!(oa->o_mode & S_IFMT)) {
 130                 CERROR("echo obd: no type!\n");
 131                 return -ENOENT;
 132         }
 133
 134         if (!(oa->o_valid & OBD_MD_FLTYPE)) {
 135                 CERROR("invalid o_valid "LPX64"\n", oa->o_valid);
 136                 return -EINVAL;
 137         }
 138
 139         ostid_set_seq_echo(&oa->o_oi);
 140         ostid_set_id(&oa->o_oi, echo_next_id(obd));
 141         oa->o_valid = OBD_MD_FLID;
 142
 143         return 0;
 144 }
 145
 146 static int echo_destroy(const struct lu_env *env, struct obd_export *exp,
 147                         struct obdo *oa)
 148 {
 149         struct obd_device *obd = class_exp2obd(exp);
 150
 151         ENTRY;
 152         if (!obd) {
 153                 CERROR("invalid client cookie "LPX64"\n",
 154                        exp->exp_handle.h_cookie);
 155                 RETURN(-EINVAL);
 156         }
 157
 158         if (!(oa->o_valid & OBD_MD_FLID)) {
 159                 CERROR("obdo missing FLID valid flag: "LPX64"\n", oa->o_valid);
 160                 RETURN(-EINVAL);
 161         }
 162
 163         if (ostid_id(&oa->o_oi) > obd->u.echo.eo_lastino ||
 164             ostid_id(&oa->o_oi) < ECHO_INIT_OID) {
 165                 CERROR("bad destroy objid: "DOSTID"\n", POSTID(&oa->o_oi));
 166                 RETURN(-EINVAL);
 167         }
 168
 169         RETURN(0);
 170 }
 171
 172 static int echo_getattr(const struct lu_env *env, struct obd_export *exp,
 173                         struct obdo *oa)
 174 {
 175         struct obd_device *obd = class_exp2obd(exp);
 176         u64 id = ostid_id(&oa->o_oi);
 177
 178         ENTRY;
 179         if (!obd) {
 180                 CERROR("invalid client cookie "LPX64"\n",
 181                        exp->exp_handle.h_cookie);
 182                 RETURN(-EINVAL);
 183         }
 184
 185         if (!(oa->o_valid & OBD_MD_FLID)) {
 186                 CERROR("obdo missing FLID valid flag: "LPX64"\n", oa->o_valid);
 187                 RETURN(-EINVAL);
 188         }
 189
 190         obdo_cpy_md(oa, &obd->u.echo.eo_oa, oa->o_valid);
 191         ostid_set_seq_echo(&oa->o_oi);
 192         ostid_set_id(&oa->o_oi, id);
 193
 194         RETURN(0);
 195 }
 196
 197 static int echo_setattr(const struct lu_env *env, struct obd_export *exp,
 198                         struct obdo *oa)
 199 {
 200         struct obd_device *obd = class_exp2obd(exp);
 201
 202         ENTRY;
 203         if (!obd) {
 204                 CERROR("invalid client cookie "LPX64"\n",
 205                        exp->exp_handle.h_cookie);
 206                 RETURN(-EINVAL);
 207         }
 208
 209         if (!(oa->o_valid & OBD_MD_FLID)) {
 210                 CERROR("obdo missing FLID valid flag: "LPX64"\n", oa->o_valid);
 211                 RETURN(-EINVAL);
 212         }
 213
 214         obd->u.echo.eo_oa = *oa;
 215
 216         RETURN(0);
 217 }
 218
 219 static void
 220 echo_page_debug_setup(struct page *page, int rw, u64 id,
 221                       __u64 offset, int len)
 222 {
 223         int   page_offset = offset & ~PAGE_MASK;
 224         char *addr        = ((char *)kmap(page)) + page_offset;
 225
 226         if (len % OBD_ECHO_BLOCK_SIZE != 0)
 227                 CERROR("Unexpected block size %d\n", len);
 228
 229         while (len > 0) {
 230                 if (rw & OBD_BRW_READ)
 231                         block_debug_setup(addr, OBD_ECHO_BLOCK_SIZE,
 232                                           offset, id);
 233                 else
 234                         block_debug_setup(addr, OBD_ECHO_BLOCK_SIZE,
 235                                           0xecc0ecc0ecc0ecc0ULL,
 236                                           0xecc0ecc0ecc0ecc0ULL);
 237
 238                 addr   += OBD_ECHO_BLOCK_SIZE;
 239                 offset += OBD_ECHO_BLOCK_SIZE;
 240                 len    -= OBD_ECHO_BLOCK_SIZE;
 241         }
 242
 243         kunmap(page);
 244 }
 245
 246 static int
 247 echo_page_debug_check(struct page *page, u64 id,
 248                       __u64 offset, int len)
 249 {
 250         int   page_offset = offset & ~PAGE_MASK;
 251         char *addr        = ((char *)kmap(page)) + page_offset;
 252         int   rc          = 0;
 253         int   rc2;
 254
 255         if (len % OBD_ECHO_BLOCK_SIZE != 0)
 256                 CERROR("Unexpected block size %d\n", len);
 257
 258         while (len > 0) {
 259                 rc2 = block_debug_check("echo", addr, OBD_ECHO_BLOCK_SIZE,
 260                                         offset, id);
 261
 262                 if (rc2 != 0 && rc == 0)
 263                         rc = rc2;
 264
 265                 addr   += OBD_ECHO_BLOCK_SIZE;
 266                 offset += OBD_ECHO_BLOCK_SIZE;
 267                 len    -= OBD_ECHO_BLOCK_SIZE;
 268         }
 269
 270         kunmap(page);
 271
 272         return rc;
 273 }
 274
 275 static int echo_map_nb_to_lb(struct obdo *oa, struct obd_ioobj *obj,
 276                              struct niobuf_remote *nb, int *pages,
 277                              struct niobuf_local *lb, int cmd, int *left)
 278 {
 279         gfp_t gfp_mask = (ostid_id(&obj->ioo_oid) & 1) ?
 280                         GFP_HIGHUSER : GFP_IOFS;
 281         int ispersistent = ostid_id(&obj->ioo_oid) == ECHO_PERSISTENT_OBJID;
 282         int debug_setup = (!ispersistent &&
 283                            (oa->o_valid & OBD_MD_FLFLAGS) != 0 &&
 284                            (oa->o_flags & OBD_FL_DEBUG_CHECK) != 0);
 285         struct niobuf_local *res = lb;
 286         u64 offset = nb->rnb_offset;
 287         int len = nb->rnb_len;
 288
 289         while (len > 0) {
 290                 int plen = PAGE_CACHE_SIZE - (offset & (PAGE_CACHE_SIZE-1));
 291                 if (len < plen)
 292                         plen = len;
 293
 294                 /* check for local buf overflow */
 295                 if (*left == 0)
 296                         return -EINVAL;
 297
 298                 res->lnb_file_offset = offset;
 299                 res->lnb_len = plen;
 300                 LASSERT((res->lnb_file_offset & ~PAGE_MASK) +
 301                         res->lnb_len <= PAGE_CACHE_SIZE);
 302
 303                 if (ispersistent &&
 304                     ((res->lnb_file_offset >> PAGE_CACHE_SHIFT) <
 305                       ECHO_PERSISTENT_PAGES)) {
 306                         res->lnb_page =
 307                                 echo_persistent_pages[res->lnb_file_offset >>
 308                                                       PAGE_CACHE_SHIFT];
 309                         /* Take extra ref so __free_pages() can be called OK */
 310                         get_page(res->lnb_page);
 311                 } else {
 312                         res->lnb_page = alloc_page(gfp_mask);
 313                         if (res->lnb_page == NULL) {
 314                                 CERROR("can't get page for id " DOSTID"\n",
 315                                        POSTID(&obj->ioo_oid));
 316                                 return -ENOMEM;
 317                         }
 318                 }
 319
 320                 CDEBUG(D_PAGE, "$$$$ get page %p @ "LPU64" for %d\n",
 321                        res->lnb_page, res->lnb_file_offset, res->lnb_len);
 322
 323                 if (cmd & OBD_BRW_READ)
 324                         res->lnb_rc = res->lnb_len;
 325
 326                 if (debug_setup)
 327                         echo_page_debug_setup(res->lnb_page, cmd,
 328                                               ostid_id(&obj->ioo_oid),
 329                                               res->lnb_file_offset,
 330                                               res->lnb_len);
 331
 332                 offset += plen;
 333                 len -= plen;
 334                 res++;
 335
 336                 (*left)--;
 337                 (*pages)++;
 338         }
 339
 340         return 0;
 341 }
 342
 343 static int echo_finalize_lb(struct obdo *oa, struct obd_ioobj *obj,
 344                             struct niobuf_remote *rb, int *pgs,
 345                             struct niobuf_local *lb, int verify)
 346 {
 347         struct niobuf_local *res = lb;
 348         u64 start = rb->rnb_offset >> PAGE_CACHE_SHIFT;
 349         u64 end   = (rb->rnb_offset + rb->rnb_len + PAGE_CACHE_SIZE - 1) >>
 350                     PAGE_CACHE_SHIFT;
 351         int     count  = (int)(end - start);
 352         int     rc     = 0;
 353         int     i;
 354
 355         for (i = 0; i < count; i++, (*pgs) ++, res++) {
 356                 struct page *page = res->lnb_page;
 357                 void       *addr;
 358
 359                 if (page == NULL) {
 360                         CERROR("null page objid "LPU64":%p, buf %d/%d\n",
 361                                ostid_id(&obj->ioo_oid), page, i,
 362                                obj->ioo_bufcnt);
 363                         return -EFAULT;
 364                 }
 365
 366                 addr = kmap(page);
 367
 368                 CDEBUG(D_PAGE, "$$$$ use page %p, addr %p@"LPU64"\n",
 369                        res->lnb_page, addr, res->lnb_file_offset);
 370
 371                 if (verify) {
 372                         int vrc = echo_page_debug_check(page,
 373                                                         ostid_id(&obj->ioo_oid),
 374                                                         res->lnb_file_offset,
 375                                                         res->lnb_len);
 376                         /* check all the pages always */
 377                         if (vrc != 0 && rc == 0)
 378                                 rc = vrc;
 379                 }
 380
 381                 kunmap(page);
 382                 /* NB see comment above regarding persistent pages */
 383                 __free_page(page);
 384         }
 385
 386         return rc;
 387 }
 388
 389 static int echo_preprw(const struct lu_env *env, int cmd,
 390                        struct obd_export *export, struct obdo *oa,
 391                        int objcount, struct obd_ioobj *obj,
 392                        struct niobuf_remote *nb, int *pages,
 393                        struct niobuf_local *res)
 394 {
 395         struct obd_device *obd;
 396         int tot_bytes = 0;
 397         int rc = 0;
 398         int i, left;
 399         ENTRY;
 400
 401         obd = export->exp_obd;
 402         if (obd == NULL)
 403                 RETURN(-EINVAL);
 404
 405         /* Temp fix to stop falling foul of osc_announce_cached() */
 406         oa->o_valid &= ~(OBD_MD_FLBLOCKS | OBD_MD_FLGRANT);
 407
 408         memset(res, 0, sizeof(*res) * *pages);
 409
 410         CDEBUG(D_PAGE, "%s %d obdos with %d IOs\n",
 411                cmd == OBD_BRW_READ ? "reading" : "writing", objcount, *pages);
 412
 413         left = *pages;
 414         *pages = 0;
 415
 416         for (i = 0; i < objcount; i++, obj++) {
 417                 int j;
 418
 419                 for (j = 0 ; j < obj->ioo_bufcnt ; j++, nb++) {
 420
 421                         rc = echo_map_nb_to_lb(oa, obj, nb, pages,
 422                                                res + *pages, cmd, &left);
 423                         if (rc)
 424                                 GOTO(preprw_cleanup, rc);
 425
 426                         tot_bytes += nb->rnb_len;
 427                 }
 428         }
 429
 430         atomic_add(*pages, &obd->u.echo.eo_prep);
 431
 432         if (cmd & OBD_BRW_READ)
 433                 lprocfs_counter_add(obd->obd_stats, LPROC_ECHO_READ_BYTES,
 434                                     tot_bytes);
 435         else
 436                 lprocfs_counter_add(obd->obd_stats, LPROC_ECHO_WRITE_BYTES,
 437                                     tot_bytes);
 438
 439         CDEBUG(D_PAGE, "%d pages allocated after prep\n",
 440                atomic_read(&obd->u.echo.eo_prep));
 441
 442         RETURN(0);
 443
 444 preprw_cleanup:
 445         /* It is possible that we would rather handle errors by  allow
 446          * any already-set-up pages to complete, rather than tearing them
 447          * all down again.  I believe that this is what the in-kernel
 448          * prep/commit operations do.
 449          */
 450         CERROR("cleaning up %u pages (%d obdos)\n", *pages, objcount);
 451         for (i = 0; i < *pages; i++) {
 452                 kunmap(res[i].lnb_page);
 453                 /* NB if this is a persistent page, __free_page() will just
 454                  * lose the extra ref gained above */
 455                 __free_page(res[i].lnb_page);
 456                 res[i].lnb_page = NULL;
 457                 atomic_dec(&obd->u.echo.eo_prep);
 458         }
 459
 460         return rc;
 461 }
 462
 463 static int echo_commitrw(const struct lu_env *env, int cmd,
 464                          struct obd_export *export, struct obdo *oa,
 465                          int objcount, struct obd_ioobj *obj,
 466                          struct niobuf_remote *rb, int niocount,
 467                          struct niobuf_local *res, int rc)
 468 {
 469         struct obd_device *obd;
 470         int pgs = 0;
 471         int i;
 472         ENTRY;
 473
 474         obd = export->exp_obd;
 475         if (obd == NULL)
 476                 RETURN(-EINVAL);
 477
 478         if (rc)
 479                 GOTO(commitrw_cleanup, rc);
 480
 481         if ((cmd & OBD_BRW_RWMASK) == OBD_BRW_READ) {
 482                 CDEBUG(D_PAGE, "reading %d obdos with %d IOs\n",
 483                        objcount, niocount);
 484         } else {
 485                 CDEBUG(D_PAGE, "writing %d obdos with %d IOs\n",
 486                        objcount, niocount);
 487         }
 488
 489         if (niocount && res == NULL) {
 490                 CERROR("NULL res niobuf with niocount %d\n", niocount);
 491                 RETURN(-EINVAL);
 492         }
 493
 494         for (i = 0; i < objcount; i++, obj++) {
 495                 int verify = (rc == 0 &&
 496                              ostid_id(&obj->ioo_oid) != ECHO_PERSISTENT_OBJID &&
 497                               (oa->o_valid & OBD_MD_FLFLAGS) != 0 &&
 498                               (oa->o_flags & OBD_FL_DEBUG_CHECK) != 0);
 499                 int j;
 500
 501                 for (j = 0 ; j < obj->ioo_bufcnt ; j++, rb++) {
 502                         int vrc = echo_finalize_lb(oa, obj, rb, &pgs, &res[pgs],
 503                                                    verify);
 504                         if (vrc == 0)
 505                                 continue;
 506
 507                         if (vrc == -EFAULT)
 508                                 GOTO(commitrw_cleanup, rc = vrc);
 509
 510                         if (rc == 0)
 511                                 rc = vrc;
 512                 }
 513
 514         }
 515
 516         atomic_sub(pgs, &obd->u.echo.eo_prep);
 517
 518         CDEBUG(D_PAGE, "%d pages remain after commit\n",
 519                atomic_read(&obd->u.echo.eo_prep));
 520         RETURN(rc);
 521
 522 commitrw_cleanup:
 523         atomic_sub(pgs, &obd->u.echo.eo_prep);
 524
 525         CERROR("cleaning up %d pages (%d obdos)\n",
 526                niocount - pgs - 1, objcount);
 527
 528         while (pgs < niocount) {
 529                 struct page *page = res[pgs++].lnb_page;
 530
 531                 if (page == NULL)
 532                         continue;
 533
 534                 /* NB see comment above regarding persistent pages */
 535                 __free_page(page);
 536                 atomic_dec(&obd->u.echo.eo_prep);
 537         }
 538         return rc;
 539 }
 540
 541 LPROC_SEQ_FOPS_RO_TYPE(echo, uuid);
 542 static struct lprocfs_vars lprocfs_echo_obd_vars[] = {
 543         { .name =       "uuid",
 544           .fops =       &echo_uuid_fops         },
 545         { NULL }
 546 };
 547
 548 static int echo_setup(struct obd_device *obd, struct lustre_cfg *lcfg)
 549 {
 550         int                     rc;
 551         __u64                   lock_flags = 0;
 552         struct ldlm_res_id      res_id = {.name = {1}};
 553         char                    ns_name[48];
 554         ENTRY;
 555
 556         obd->u.echo.eo_obt.obt_magic = OBT_MAGIC;
 557         spin_lock_init(&obd->u.echo.eo_lock);
 558         obd->u.echo.eo_lastino = ECHO_INIT_OID;
 559
 560         sprintf(ns_name, "echotgt-%s", obd->obd_uuid.uuid);
 561         obd->obd_namespace = ldlm_namespace_new(obd, ns_name,
 562                                                 LDLM_NAMESPACE_SERVER,
 563                                                 LDLM_NAMESPACE_MODEST,
 564                                                 LDLM_NS_TYPE_OST);
 565         if (obd->obd_namespace == NULL) {
 566                 LBUG();
 567                 RETURN(-ENOMEM);
 568         }
 569
 570         rc = ldlm_cli_enqueue_local(obd->obd_namespace, &res_id, LDLM_PLAIN,
 571                                     NULL, LCK_NL, &lock_flags, NULL,
 572                                     ldlm_completion_ast, NULL, NULL, 0,
 573                                     LVB_T_NONE, NULL, &obd->u.echo.eo_nl_lock);
 574         LASSERT (rc == ELDLM_OK);
 575
 576         obd->obd_vars = lprocfs_echo_obd_vars;
 577         if (lprocfs_obd_setup(obd) == 0 &&
 578             lprocfs_alloc_obd_stats(obd, LPROC_ECHO_LAST) == 0) {
 579                 lprocfs_counter_init(obd->obd_stats, LPROC_ECHO_READ_BYTES,
 580                                      LPROCFS_CNTR_AVGMINMAX,
 581                                      "read_bytes", "bytes");
 582                 lprocfs_counter_init(obd->obd_stats, LPROC_ECHO_WRITE_BYTES,
 583                                      LPROCFS_CNTR_AVGMINMAX,
 584                                      "write_bytes", "bytes");
 585         }
 586
 587         ptlrpc_init_client(LDLM_CB_REQUEST_PORTAL, LDLM_CB_REPLY_PORTAL,
 588                            "echo_ldlm_cb_client", &obd->obd_ldlm_client);
 589         RETURN(0);
 590 }
 591
 592 static int echo_cleanup(struct obd_device *obd)
 593 {
 594         int leaked;
 595         ENTRY;
 596
 597         lprocfs_obd_cleanup(obd);
 598         lprocfs_free_obd_stats(obd);
 599
 600         ldlm_lock_decref(&obd->u.echo.eo_nl_lock, LCK_NL);
 601
 602         /* XXX Bug 3413; wait for a bit to ensure the BL callback has
 603          * happened before calling ldlm_namespace_free() */
 604         set_current_state(TASK_UNINTERRUPTIBLE);
 605         schedule_timeout(cfs_time_seconds(1));
 606
 607         ldlm_namespace_free(obd->obd_namespace, NULL, obd->obd_force);
 608         obd->obd_namespace = NULL;
 609
 610         leaked = atomic_read(&obd->u.echo.eo_prep);
 611         if (leaked != 0)
 612                 CERROR("%d prep/commitrw pages leaked\n", leaked);
 613
 614         RETURN(0);
 615 }
 616
 617 struct obd_ops echo_obd_ops = {
 618         .o_owner           = THIS_MODULE,
 619         .o_connect         = echo_connect,
 620         .o_disconnect      = echo_disconnect,
 621         .o_init_export     = echo_init_export,
 622         .o_destroy_export  = echo_destroy_export,
 623         .o_create          = echo_create,
 624         .o_destroy         = echo_destroy,
 625         .o_getattr         = echo_getattr,
 626         .o_setattr         = echo_setattr,
 627         .o_preprw          = echo_preprw,
 628         .o_commitrw        = echo_commitrw,
 629         .o_setup           = echo_setup,
 630         .o_cleanup         = echo_cleanup
 631 };
 632
 633 void echo_persistent_pages_fini(void)
 634 {
 635         int i;
 636
 637         for (i = 0; i < ECHO_PERSISTENT_PAGES; i++)
 638                 if (echo_persistent_pages[i] != NULL) {
 639                         __free_page(echo_persistent_pages[i]);
 640                         echo_persistent_pages[i] = NULL;
 641                 }
 642 }
 643
 644 int echo_persistent_pages_init(void)
 645 {
 646         struct page *pg;
 647         int          i;
 648
 649         for (i = 0; i < ECHO_PERSISTENT_PAGES; i++) {
 650                 gfp_t gfp_mask = (i < ECHO_PERSISTENT_PAGES/2) ?
 651                         GFP_IOFS : GFP_HIGHUSER;
 652
 653                 pg = alloc_page(gfp_mask);
 654                 if (pg == NULL) {
 655                         echo_persistent_pages_fini();
 656                         return -ENOMEM;
 657                 }
 658
 659                 memset (kmap (pg), 0, PAGE_CACHE_SIZE);
 660                 kunmap (pg);
 661
 662                 echo_persistent_pages[i] = pg;
 663         }
 664
 665         return 0;
 666 }