drivers/staging/lustre/lustre/llite/vvp_dev.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) 2008, 2010, Oracle and/or its affiliates. All rights reserved.
  28  * Use is subject to license terms.
  29  *
  30  * Copyright (c) 2012, 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  * cl_device and cl_device_type implementation for VVP layer.
  37  *
  38  *   Author: Nikita Danilov <nikita.danilov@sun.com>
  39  *   Author: Jinshan Xiong <jinshan.xiong@intel.com>
  40  */
  41
  42 #define DEBUG_SUBSYSTEM S_LLITE
  43
  44 #include "../include/obd.h"
  45 #include "../include/lustre_lite.h"
  46 #include "llite_internal.h"
  47 #include "vvp_internal.h"
  48
  49 /*****************************************************************************
  50  *
  51  * Vvp device and device type functions.
  52  *
  53  */
  54
  55 /*
  56  * vvp_ prefix stands for "Vfs Vm Posix". It corresponds to historical
  57  * "llite_" (var. "ll_") prefix.
  58  */
  59
  60 static struct kmem_cache *ll_thread_kmem;
  61 struct kmem_cache *vvp_lock_kmem;
  62 struct kmem_cache *vvp_object_kmem;
  63 struct kmem_cache *vvp_req_kmem;
  64 static struct kmem_cache *vvp_session_kmem;
  65 static struct kmem_cache *vvp_thread_kmem;
  66
  67 static struct lu_kmem_descr vvp_caches[] = {
  68         {
  69                 .ckd_cache = &ll_thread_kmem,
  70                 .ckd_name  = "ll_thread_kmem",
  71                 .ckd_size  = sizeof(struct ll_thread_info),
  72         },
  73         {
  74                 .ckd_cache = &vvp_lock_kmem,
  75                 .ckd_name  = "vvp_lock_kmem",
  76                 .ckd_size  = sizeof(struct vvp_lock),
  77         },
  78         {
  79                 .ckd_cache = &vvp_object_kmem,
  80                 .ckd_name  = "vvp_object_kmem",
  81                 .ckd_size  = sizeof(struct vvp_object),
  82         },
  83         {
  84                 .ckd_cache = &vvp_req_kmem,
  85                 .ckd_name  = "vvp_req_kmem",
  86                 .ckd_size  = sizeof(struct vvp_req),
  87         },
  88         {
  89                 .ckd_cache = &vvp_session_kmem,
  90                 .ckd_name  = "vvp_session_kmem",
  91                 .ckd_size  = sizeof(struct vvp_session)
  92         },
  93         {
  94                 .ckd_cache = &vvp_thread_kmem,
  95                 .ckd_name  = "vvp_thread_kmem",
  96                 .ckd_size  = sizeof(struct vvp_thread_info),
  97         },
  98         {
  99                 .ckd_cache = NULL
 100         }
 101 };
 102
 103 static void *ll_thread_key_init(const struct lu_context *ctx,
 104                                 struct lu_context_key *key)
 105 {
 106         struct vvp_thread_info *info;
 107
 108         info = kmem_cache_zalloc(ll_thread_kmem, GFP_NOFS);
 109         if (!info)
 110                 info = ERR_PTR(-ENOMEM);
 111         return info;
 112 }
 113
 114 static void ll_thread_key_fini(const struct lu_context *ctx,
 115                                struct lu_context_key *key, void *data)
 116 {
 117         struct vvp_thread_info *info = data;
 118
 119         kmem_cache_free(ll_thread_kmem, info);
 120 }
 121
 122 struct lu_context_key ll_thread_key = {
 123         .lct_tags = LCT_CL_THREAD,
 124         .lct_init = ll_thread_key_init,
 125         .lct_fini = ll_thread_key_fini
 126 };
 127
 128 static void *vvp_session_key_init(const struct lu_context *ctx,
 129                                   struct lu_context_key *key)
 130 {
 131         struct vvp_session *session;
 132
 133         session = kmem_cache_zalloc(vvp_session_kmem, GFP_NOFS);
 134         if (!session)
 135                 session = ERR_PTR(-ENOMEM);
 136         return session;
 137 }
 138
 139 static void vvp_session_key_fini(const struct lu_context *ctx,
 140                                  struct lu_context_key *key, void *data)
 141 {
 142         struct vvp_session *session = data;
 143
 144         kmem_cache_free(vvp_session_kmem, session);
 145 }
 146
 147 struct lu_context_key vvp_session_key = {
 148         .lct_tags = LCT_SESSION,
 149         .lct_init = vvp_session_key_init,
 150         .lct_fini = vvp_session_key_fini
 151 };
 152
 153 void *vvp_thread_key_init(const struct lu_context *ctx,
 154                           struct lu_context_key *key)
 155 {
 156         struct vvp_thread_info *vti;
 157
 158         vti = kmem_cache_zalloc(vvp_thread_kmem, GFP_NOFS);
 159         if (!vti)
 160                 vti = ERR_PTR(-ENOMEM);
 161         return vti;
 162 }
 163
 164 void vvp_thread_key_fini(const struct lu_context *ctx,
 165                          struct lu_context_key *key, void *data)
 166 {
 167         struct vvp_thread_info *vti = data;
 168
 169         kmem_cache_free(vvp_thread_kmem, vti);
 170 }
 171
 172 struct lu_context_key vvp_thread_key = {
 173         .lct_tags = LCT_CL_THREAD,
 174         .lct_init = vvp_thread_key_init,
 175         .lct_fini = vvp_thread_key_fini
 176 };
 177
 178 /* type constructor/destructor: vvp_type_{init,fini,start,stop}(). */
 179 LU_TYPE_INIT_FINI(vvp, &vvp_thread_key, &ll_thread_key, &vvp_session_key);
 180
 181 static const struct lu_device_operations vvp_lu_ops = {
 182         .ldo_object_alloc      = vvp_object_alloc
 183 };
 184
 185 static const struct cl_device_operations vvp_cl_ops = {
 186         .cdo_req_init = vvp_req_init
 187 };
 188
 189 static struct lu_device *vvp_device_free(const struct lu_env *env,
 190                                          struct lu_device *d)
 191 {
 192         struct vvp_device *vdv  = lu2vvp_dev(d);
 193         struct cl_site    *site = lu2cl_site(d->ld_site);
 194         struct lu_device  *next = cl2lu_dev(vdv->vdv_next);
 195
 196         if (d->ld_site) {
 197                 cl_site_fini(site);
 198                 kfree(site);
 199         }
 200         cl_device_fini(lu2cl_dev(d));
 201         kfree(vdv);
 202         return next;
 203 }
 204
 205 static struct lu_device *vvp_device_alloc(const struct lu_env *env,
 206                                           struct lu_device_type *t,
 207                                           struct lustre_cfg *cfg)
 208 {
 209         struct vvp_device *vdv;
 210         struct lu_device  *lud;
 211         struct cl_site    *site;
 212         int rc;
 213
 214         vdv = kzalloc(sizeof(*vdv), GFP_NOFS);
 215         if (!vdv)
 216                 return ERR_PTR(-ENOMEM);
 217
 218         lud = &vdv->vdv_cl.cd_lu_dev;
 219         cl_device_init(&vdv->vdv_cl, t);
 220         vvp2lu_dev(vdv)->ld_ops = &vvp_lu_ops;
 221         vdv->vdv_cl.cd_ops = &vvp_cl_ops;
 222
 223         site = kzalloc(sizeof(*site), GFP_NOFS);
 224         if (site) {
 225                 rc = cl_site_init(site, &vdv->vdv_cl);
 226                 if (rc == 0) {
 227                         rc = lu_site_init_finish(&site->cs_lu);
 228                 } else {
 229                         LASSERT(!lud->ld_site);
 230                         CERROR("Cannot init lu_site, rc %d.\n", rc);
 231                         kfree(site);
 232                 }
 233         } else {
 234                 rc = -ENOMEM;
 235         }
 236         if (rc != 0) {
 237                 vvp_device_free(env, lud);
 238                 lud = ERR_PTR(rc);
 239         }
 240         return lud;
 241 }
 242
 243 static int vvp_device_init(const struct lu_env *env, struct lu_device *d,
 244                            const char *name, struct lu_device *next)
 245 {
 246         struct vvp_device  *vdv;
 247         int rc;
 248
 249         vdv = lu2vvp_dev(d);
 250         vdv->vdv_next = lu2cl_dev(next);
 251
 252         LASSERT(d->ld_site && next->ld_type);
 253         next->ld_site = d->ld_site;
 254         rc = next->ld_type->ldt_ops->ldto_device_init(env, next,
 255                                                       next->ld_type->ldt_name,
 256                                                       NULL);
 257         if (rc == 0) {
 258                 lu_device_get(next);
 259                 lu_ref_add(&next->ld_reference, "lu-stack", &lu_site_init);
 260         }
 261         return rc;
 262 }
 263
 264 static struct lu_device *vvp_device_fini(const struct lu_env *env,
 265                                          struct lu_device *d)
 266 {
 267         return cl2lu_dev(lu2vvp_dev(d)->vdv_next);
 268 }
 269
 270 static const struct lu_device_type_operations vvp_device_type_ops = {
 271         .ldto_init = vvp_type_init,
 272         .ldto_fini = vvp_type_fini,
 273
 274         .ldto_start = vvp_type_start,
 275         .ldto_stop  = vvp_type_stop,
 276
 277         .ldto_device_alloc = vvp_device_alloc,
 278         .ldto_device_free       = vvp_device_free,
 279         .ldto_device_init       = vvp_device_init,
 280         .ldto_device_fini       = vvp_device_fini,
 281 };
 282
 283 struct lu_device_type vvp_device_type = {
 284         .ldt_tags     = LU_DEVICE_CL,
 285         .ldt_name     = LUSTRE_VVP_NAME,
 286         .ldt_ops      = &vvp_device_type_ops,
 287         .ldt_ctx_tags = LCT_CL_THREAD
 288 };
 289
 290 /**
 291  * A mutex serializing calls to vvp_inode_fini() under extreme memory
 292  * pressure, when environments cannot be allocated.
 293  */
 294 int vvp_global_init(void)
 295 {
 296         int rc;
 297
 298         rc = lu_kmem_init(vvp_caches);
 299         if (rc != 0)
 300                 return rc;
 301
 302         rc = lu_device_type_init(&vvp_device_type);
 303         if (rc != 0)
 304                 goto out_kmem;
 305
 306         return 0;
 307
 308 out_kmem:
 309         lu_kmem_fini(vvp_caches);
 310
 311         return rc;
 312 }
 313
 314 void vvp_global_fini(void)
 315 {
 316         lu_device_type_fini(&vvp_device_type);
 317         lu_kmem_fini(vvp_caches);
 318 }
 319
 320 /*****************************************************************************
 321  *
 322  * mirror obd-devices into cl devices.
 323  *
 324  */
 325
 326 int cl_sb_init(struct super_block *sb)
 327 {
 328         struct ll_sb_info *sbi;
 329         struct cl_device  *cl;
 330         struct lu_env     *env;
 331         int rc = 0;
 332         int refcheck;
 333
 334         sbi  = ll_s2sbi(sb);
 335         env = cl_env_get(&refcheck);
 336         if (!IS_ERR(env)) {
 337                 cl = cl_type_setup(env, NULL, &vvp_device_type,
 338                                    sbi->ll_dt_exp->exp_obd->obd_lu_dev);
 339                 if (!IS_ERR(cl)) {
 340                         cl2vvp_dev(cl)->vdv_sb = sb;
 341                         sbi->ll_cl = cl;
 342                         sbi->ll_site = cl2lu_dev(cl)->ld_site;
 343                 }
 344                 cl_env_put(env, &refcheck);
 345         } else {
 346                 rc = PTR_ERR(env);
 347         }
 348         return rc;
 349 }
 350
 351 int cl_sb_fini(struct super_block *sb)
 352 {
 353         struct ll_sb_info *sbi;
 354         struct lu_env     *env;
 355         struct cl_device  *cld;
 356         int             refcheck;
 357         int             result;
 358
 359         sbi = ll_s2sbi(sb);
 360         env = cl_env_get(&refcheck);
 361         if (!IS_ERR(env)) {
 362                 cld = sbi->ll_cl;
 363
 364                 if (cld) {
 365                         cl_stack_fini(env, cld);
 366                         sbi->ll_cl = NULL;
 367                         sbi->ll_site = NULL;
 368                 }
 369                 cl_env_put(env, &refcheck);
 370                 result = 0;
 371         } else {
 372                 CERROR("Cannot cleanup cl-stack due to memory shortage.\n");
 373                 result = PTR_ERR(env);
 374         }
 375         /*
 376          * If mount failed (sbi->ll_cl == NULL), and this there are no other
 377          * mounts, stop device types manually (this usually happens
 378          * automatically when last device is destroyed).
 379          */
 380         lu_types_stop();
 381         return result;
 382 }
 383
 384 /****************************************************************************
 385  *
 386  * debugfs/lustre/llite/$MNT/dump_page_cache
 387  *
 388  ****************************************************************************/
 389
 390 /*
 391  * To represent contents of a page cache as a byte stream, following
 392  * information if encoded in 64bit offset:
 393  *
 394  *       - file hash bucket in lu_site::ls_hash[]       28bits
 395  *
 396  *       - how far file is from bucket head           4bits
 397  *
 398  *       - page index                              32bits
 399  *
 400  * First two data identify a file in the cache uniquely.
 401  */
 402
 403 #define PGC_OBJ_SHIFT (32 + 4)
 404 #define PGC_DEPTH_SHIFT (32)
 405
 406 struct vvp_pgcache_id {
 407         unsigned                 vpi_bucket;
 408         unsigned                 vpi_depth;
 409         uint32_t                 vpi_index;
 410
 411         unsigned                 vpi_curdep;
 412         struct lu_object_header *vpi_obj;
 413 };
 414
 415 static void vvp_pgcache_id_unpack(loff_t pos, struct vvp_pgcache_id *id)
 416 {
 417         CLASSERT(sizeof(pos) == sizeof(__u64));
 418
 419         id->vpi_index  = pos & 0xffffffff;
 420         id->vpi_depth  = (pos >> PGC_DEPTH_SHIFT) & 0xf;
 421         id->vpi_bucket = (unsigned long long)pos >> PGC_OBJ_SHIFT;
 422 }
 423
 424 static loff_t vvp_pgcache_id_pack(struct vvp_pgcache_id *id)
 425 {
 426         return
 427                 ((__u64)id->vpi_index) |
 428                 ((__u64)id->vpi_depth  << PGC_DEPTH_SHIFT) |
 429                 ((__u64)id->vpi_bucket << PGC_OBJ_SHIFT);
 430 }
 431
 432 static int vvp_pgcache_obj_get(struct cfs_hash *hs, struct cfs_hash_bd *bd,
 433                                struct hlist_node *hnode, void *data)
 434 {
 435         struct vvp_pgcache_id   *id  = data;
 436         struct lu_object_header *hdr = cfs_hash_object(hs, hnode);
 437
 438         if (id->vpi_curdep-- > 0)
 439                 return 0; /* continue */
 440
 441         if (lu_object_is_dying(hdr))
 442                 return 1;
 443
 444         cfs_hash_get(hs, hnode);
 445         id->vpi_obj = hdr;
 446         return 1;
 447 }
 448
 449 static struct cl_object *vvp_pgcache_obj(const struct lu_env *env,
 450                                          struct lu_device *dev,
 451                                          struct vvp_pgcache_id *id)
 452 {
 453         LASSERT(lu_device_is_cl(dev));
 454
 455         id->vpi_depth &= 0xf;
 456         id->vpi_obj    = NULL;
 457         id->vpi_curdep = id->vpi_depth;
 458
 459         cfs_hash_hlist_for_each(dev->ld_site->ls_obj_hash, id->vpi_bucket,
 460                                 vvp_pgcache_obj_get, id);
 461         if (id->vpi_obj) {
 462                 struct lu_object *lu_obj;
 463
 464                 lu_obj = lu_object_locate(id->vpi_obj, dev->ld_type);
 465                 if (lu_obj) {
 466                         lu_object_ref_add(lu_obj, "dump", current);
 467                         return lu2cl(lu_obj);
 468                 }
 469                 lu_object_put(env, lu_object_top(id->vpi_obj));
 470
 471         } else if (id->vpi_curdep > 0) {
 472                 id->vpi_depth = 0xf;
 473         }
 474         return NULL;
 475 }
 476
 477 static loff_t vvp_pgcache_find(const struct lu_env *env,
 478                                struct lu_device *dev, loff_t pos)
 479 {
 480         struct cl_object     *clob;
 481         struct lu_site       *site;
 482         struct vvp_pgcache_id id;
 483
 484         site = dev->ld_site;
 485         vvp_pgcache_id_unpack(pos, &id);
 486
 487         while (1) {
 488                 if (id.vpi_bucket >= CFS_HASH_NHLIST(site->ls_obj_hash))
 489                         return ~0ULL;
 490                 clob = vvp_pgcache_obj(env, dev, &id);
 491                 if (clob) {
 492                         struct inode *inode = vvp_object_inode(clob);
 493                         struct page *vmpage;
 494                         int nr;
 495
 496                         nr = find_get_pages_contig(inode->i_mapping,
 497                                                    id.vpi_index, 1, &vmpage);
 498                         if (nr > 0) {
 499                                 id.vpi_index = vmpage->index;
 500                                 /* Cant support over 16T file */
 501                                 nr = !(vmpage->index > 0xffffffff);
 502                                 put_page(vmpage);
 503                         }
 504
 505                         lu_object_ref_del(&clob->co_lu, "dump", current);
 506                         cl_object_put(env, clob);
 507                         if (nr > 0)
 508                                 return vvp_pgcache_id_pack(&id);
 509                 }
 510                 /* to the next object. */
 511                 ++id.vpi_depth;
 512                 id.vpi_depth &= 0xf;
 513                 if (id.vpi_depth == 0 && ++id.vpi_bucket == 0)
 514                         return ~0ULL;
 515                 id.vpi_index = 0;
 516         }
 517 }
 518
 519 #define seq_page_flag(seq, page, flag, has_flags) do {            \
 520         if (test_bit(PG_##flag, &(page)->flags)) {                \
 521                 seq_printf(seq, "%s"#flag, has_flags ? "|" : "");       \
 522                 has_flags = 1;                                    \
 523         }                                                              \
 524 } while (0)
 525
 526 static void vvp_pgcache_page_show(const struct lu_env *env,
 527                                   struct seq_file *seq, struct cl_page *page)
 528 {
 529         struct vvp_page *vpg;
 530         struct page      *vmpage;
 531         int           has_flags;
 532
 533         vpg = cl2vvp_page(cl_page_at(page, &vvp_device_type));
 534         vmpage = vpg->vpg_page;
 535         seq_printf(seq, " %5i | %p %p %s %s %s %s | %p "DFID"(%p) %lu %u [",
 536                    0 /* gen */,
 537                    vpg, page,
 538                    "none",
 539                    vpg->vpg_write_queued ? "wq" : "- ",
 540                    vpg->vpg_defer_uptodate ? "du" : "- ",
 541                    PageWriteback(vmpage) ? "wb" : "-",
 542                    vmpage, PFID(ll_inode2fid(vmpage->mapping->host)),
 543                    vmpage->mapping->host, vmpage->index,
 544                    page_count(vmpage));
 545         has_flags = 0;
 546         seq_page_flag(seq, vmpage, locked, has_flags);
 547         seq_page_flag(seq, vmpage, error, has_flags);
 548         seq_page_flag(seq, vmpage, referenced, has_flags);
 549         seq_page_flag(seq, vmpage, uptodate, has_flags);
 550         seq_page_flag(seq, vmpage, dirty, has_flags);
 551         seq_page_flag(seq, vmpage, writeback, has_flags);
 552         seq_printf(seq, "%s]\n", has_flags ? "" : "-");
 553 }
 554
 555 static int vvp_pgcache_show(struct seq_file *f, void *v)
 556 {
 557         loff_t             pos;
 558         struct ll_sb_info       *sbi;
 559         struct cl_object        *clob;
 560         struct lu_env      *env;
 561         struct vvp_pgcache_id    id;
 562         int                   refcheck;
 563         int                   result;
 564
 565         env = cl_env_get(&refcheck);
 566         if (!IS_ERR(env)) {
 567                 pos = *(loff_t *) v;
 568                 vvp_pgcache_id_unpack(pos, &id);
 569                 sbi = f->private;
 570                 clob = vvp_pgcache_obj(env, &sbi->ll_cl->cd_lu_dev, &id);
 571                 if (clob) {
 572                         struct inode *inode = vvp_object_inode(clob);
 573                         struct cl_page *page = NULL;
 574                         struct page *vmpage;
 575
 576                         result = find_get_pages_contig(inode->i_mapping,
 577                                                        id.vpi_index, 1,
 578                                                        &vmpage);
 579                         if (result > 0) {
 580                                 lock_page(vmpage);
 581                                 page = cl_vmpage_page(vmpage, clob);
 582                                 unlock_page(vmpage);
 583                                 put_page(vmpage);
 584                         }
 585
 586                         seq_printf(f, "%8x@" DFID ": ", id.vpi_index,
 587                                    PFID(lu_object_fid(&clob->co_lu)));
 588                         if (page) {
 589                                 vvp_pgcache_page_show(env, f, page);
 590                                 cl_page_put(env, page);
 591                         } else {
 592                                 seq_puts(f, "missing\n");
 593                         }
 594                         lu_object_ref_del(&clob->co_lu, "dump", current);
 595                         cl_object_put(env, clob);
 596                 } else {
 597                         seq_printf(f, "%llx missing\n", pos);
 598                 }
 599                 cl_env_put(env, &refcheck);
 600                 result = 0;
 601         } else {
 602                 result = PTR_ERR(env);
 603         }
 604         return result;
 605 }
 606
 607 static void *vvp_pgcache_start(struct seq_file *f, loff_t *pos)
 608 {
 609         struct ll_sb_info *sbi;
 610         struct lu_env     *env;
 611         int             refcheck;
 612
 613         sbi = f->private;
 614
 615         env = cl_env_get(&refcheck);
 616         if (!IS_ERR(env)) {
 617                 sbi = f->private;
 618                 if (sbi->ll_site->ls_obj_hash->hs_cur_bits > 64 - PGC_OBJ_SHIFT)
 619                         pos = ERR_PTR(-EFBIG);
 620                 else {
 621                         *pos = vvp_pgcache_find(env, &sbi->ll_cl->cd_lu_dev,
 622                                                 *pos);
 623                         if (*pos == ~0ULL)
 624                                 pos = NULL;
 625                 }
 626                 cl_env_put(env, &refcheck);
 627         }
 628         return pos;
 629 }
 630
 631 static void *vvp_pgcache_next(struct seq_file *f, void *v, loff_t *pos)
 632 {
 633         struct ll_sb_info *sbi;
 634         struct lu_env     *env;
 635         int             refcheck;
 636
 637         env = cl_env_get(&refcheck);
 638         if (!IS_ERR(env)) {
 639                 sbi = f->private;
 640                 *pos = vvp_pgcache_find(env, &sbi->ll_cl->cd_lu_dev, *pos + 1);
 641                 if (*pos == ~0ULL)
 642                         pos = NULL;
 643                 cl_env_put(env, &refcheck);
 644         }
 645         return pos;
 646 }
 647
 648 static void vvp_pgcache_stop(struct seq_file *f, void *v)
 649 {
 650         /* Nothing to do */
 651 }
 652
 653 static const struct seq_operations vvp_pgcache_ops = {
 654         .start = vvp_pgcache_start,
 655         .next  = vvp_pgcache_next,
 656         .stop  = vvp_pgcache_stop,
 657         .show  = vvp_pgcache_show
 658 };
 659
 660 static int vvp_dump_pgcache_seq_open(struct inode *inode, struct file *filp)
 661 {
 662         struct seq_file *seq;
 663         int rc;
 664
 665         rc = seq_open(filp, &vvp_pgcache_ops);
 666         if (rc)
 667                 return rc;
 668
 669         seq = filp->private_data;
 670         seq->private = inode->i_private;
 671
 672         return 0;
 673 }
 674
 675 const struct file_operations vvp_dump_pgcache_file_ops = {
 676         .owner   = THIS_MODULE,
 677         .open    = vvp_dump_pgcache_seq_open,
 678         .read    = seq_read,
 679         .llseek  = seq_lseek,
 680         .release = seq_release,
 681 };