lustre/obdclass/cl_page.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) 2011, 2013, 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  * Client Lustre Page.
  37  *
  38  *   Author: Nikita Danilov <nikita.danilov@sun.com>
  39  *   Author: Jinshan Xiong <jinshan.xiong@intel.com>
  40  */
  41
  42 #define DEBUG_SUBSYSTEM S_CLASS
  43
  44 #include <libcfs/libcfs.h>
  45 #include <obd_class.h>
  46 #include <obd_support.h>
  47 #include <libcfs/list.h>
  48
  49 #include <cl_object.h>
  50 #include "cl_internal.h"
  51
  52 static void cl_page_delete0(const struct lu_env *env, struct cl_page *pg);
  53
  54 #ifdef LIBCFS_DEBUG
  55 # define PASSERT(env, page, expr)                                       \
  56   do {                                                                    \
  57           if (unlikely(!(expr))) {                                      \
  58                   CL_PAGE_DEBUG(D_ERROR, (env), (page), #expr "\n");    \
  59                   LASSERT(0);                                           \
  60           }                                                             \
  61   } while (0)
  62 #else /* !LIBCFS_DEBUG */
  63 # define PASSERT(env, page, exp) \
  64         ((void)sizeof(env), (void)sizeof(page), (void)sizeof !!(exp))
  65 #endif /* !LIBCFS_DEBUG */
  66
  67 #ifdef CONFIG_LUSTRE_DEBUG_EXPENSIVE_CHECK
  68 # define PINVRNT(env, page, expr)                                       \
  69   do {                                                                    \
  70           if (unlikely(!(expr))) {                                      \
  71                   CL_PAGE_DEBUG(D_ERROR, (env), (page), #expr "\n");    \
  72                   LINVRNT(0);                                           \
  73           }                                                             \
  74   } while (0)
  75 #else /* !CONFIG_LUSTRE_DEBUG_EXPENSIVE_CHECK */
  76 # define PINVRNT(env, page, exp) \
  77          ((void)sizeof(env), (void)sizeof(page), (void)sizeof !!(exp))
  78 #endif /* !CONFIG_LUSTRE_DEBUG_EXPENSIVE_CHECK */
  79
  80 /* Disable page statistic by default due to huge performance penalty. */
  81 #ifdef CONFIG_DEBUG_PAGESTATE_TRACKING
  82 #define CS_PAGE_INC(o, item) \
  83         cfs_atomic_inc(&cl_object_site(o)->cs_pages.cs_stats[CS_##item])
  84 #define CS_PAGE_DEC(o, item) \
  85         cfs_atomic_dec(&cl_object_site(o)->cs_pages.cs_stats[CS_##item])
  86 #define CS_PAGESTATE_INC(o, state) \
  87         cfs_atomic_inc(&cl_object_site(o)->cs_pages_state[state])
  88 #define CS_PAGESTATE_DEC(o, state) \
  89         cfs_atomic_dec(&cl_object_site(o)->cs_pages_state[state])
  90 #else
  91 #define CS_PAGE_INC(o, item)
  92 #define CS_PAGE_DEC(o, item)
  93 #define CS_PAGESTATE_INC(o, state)
  94 #define CS_PAGESTATE_DEC(o, state)
  95 #endif
  96
  97 /**
  98  * Internal version of cl_page_top, it should be called if the page is
  99  * known to be not freed, says with page referenced, or radix tree lock held,
 100  * or page owned.
 101  */
 102 static struct cl_page *cl_page_top_trusted(struct cl_page *page)
 103 {
 104         while (page->cp_parent != NULL)
 105                 page = page->cp_parent;
 106         return page;
 107 }
 108
 109 /**
 110  * Internal version of cl_page_get().
 111  *
 112  * This function can be used to obtain initial reference to previously
 113  * unreferenced cached object. It can be called only if concurrent page
 114  * reclamation is somehow prevented, e.g., by keeping a lock on a VM page,
 115  * associated with \a page.
 116  *
 117  * Use with care! Not exported.
 118  */
 119 static void cl_page_get_trust(struct cl_page *page)
 120 {
 121         LASSERT(cfs_atomic_read(&page->cp_ref) > 0);
 122         cfs_atomic_inc(&page->cp_ref);
 123 }
 124
 125 /**
 126  * Returns a slice within a page, corresponding to the given layer in the
 127  * device stack.
 128  *
 129  * \see cl_lock_at()
 130  */
 131 static const struct cl_page_slice *
 132 cl_page_at_trusted(const struct cl_page *page,
 133                    const struct lu_device_type *dtype)
 134 {
 135         const struct cl_page_slice *slice;
 136         ENTRY;
 137
 138         page = cl_page_top_trusted((struct cl_page *)page);
 139         do {
 140                 cfs_list_for_each_entry(slice, &page->cp_layers, cpl_linkage) {
 141                         if (slice->cpl_obj->co_lu.lo_dev->ld_type == dtype)
 142                                 RETURN(slice);
 143                 }
 144                 page = page->cp_child;
 145         } while (page != NULL);
 146         RETURN(NULL);
 147 }
 148
 149 static void cl_page_free(const struct lu_env *env, struct cl_page *page)
 150 {
 151         struct cl_object *obj  = page->cp_obj;
 152         int pagesize = cl_object_header(obj)->coh_page_bufsize;
 153
 154         PASSERT(env, page, cfs_list_empty(&page->cp_batch));
 155         PASSERT(env, page, page->cp_owner == NULL);
 156         PASSERT(env, page, page->cp_req == NULL);
 157         PASSERT(env, page, page->cp_parent == NULL);
 158         PASSERT(env, page, page->cp_state == CPS_FREEING);
 159
 160         ENTRY;
 161         might_sleep();
 162         while (!cfs_list_empty(&page->cp_layers)) {
 163                 struct cl_page_slice *slice;
 164
 165                 slice = cfs_list_entry(page->cp_layers.next,
 166                                        struct cl_page_slice, cpl_linkage);
 167                 cfs_list_del_init(page->cp_layers.next);
 168                 slice->cpl_ops->cpo_fini(env, slice);
 169         }
 170         CS_PAGE_DEC(obj, total);
 171         CS_PAGESTATE_DEC(obj, page->cp_state);
 172         lu_object_ref_del_at(&obj->co_lu, &page->cp_obj_ref, "cl_page", page);
 173         cl_object_put(env, obj);
 174         lu_ref_fini(&page->cp_reference);
 175         OBD_FREE(page, pagesize);
 176         EXIT;
 177 }
 178
 179 /**
 180  * Helper function updating page state. This is the only place in the code
 181  * where cl_page::cp_state field is mutated.
 182  */
 183 static inline void cl_page_state_set_trust(struct cl_page *page,
 184                                            enum cl_page_state state)
 185 {
 186         /* bypass const. */
 187         *(enum cl_page_state *)&page->cp_state = state;
 188 }
 189
 190 struct cl_page *cl_page_alloc(const struct lu_env *env,
 191                 struct cl_object *o, pgoff_t ind, struct page *vmpage,
 192                 enum cl_page_type type)
 193 {
 194         struct cl_page          *page;
 195         struct lu_object_header *head;
 196
 197         ENTRY;
 198         OBD_ALLOC_GFP(page, cl_object_header(o)->coh_page_bufsize,
 199                         __GFP_IO);
 200         if (page != NULL) {
 201                 int result = 0;
 202                 cfs_atomic_set(&page->cp_ref, 1);
 203                 page->cp_obj = o;
 204                 cl_object_get(o);
 205                 lu_object_ref_add_at(&o->co_lu, &page->cp_obj_ref, "cl_page",
 206                                      page);
 207                 page->cp_index = ind;
 208                 cl_page_state_set_trust(page, CPS_CACHED);
 209                 page->cp_type = type;
 210                 CFS_INIT_LIST_HEAD(&page->cp_layers);
 211                 CFS_INIT_LIST_HEAD(&page->cp_batch);
 212                 CFS_INIT_LIST_HEAD(&page->cp_flight);
 213                 mutex_init(&page->cp_mutex);
 214                 lu_ref_init(&page->cp_reference);
 215                 head = o->co_lu.lo_header;
 216                 cfs_list_for_each_entry(o, &head->loh_layers,
 217                                         co_lu.lo_linkage) {
 218                         if (o->co_ops->coo_page_init != NULL) {
 219                                 result = o->co_ops->coo_page_init(env, o,
 220                                                                   page, vmpage);
 221                                 if (result != 0) {
 222                                         cl_page_delete0(env, page);
 223                                         cl_page_free(env, page);
 224                                         page = ERR_PTR(result);
 225                                         break;
 226                                 }
 227                         }
 228                 }
 229                 if (result == 0) {
 230                         CS_PAGE_INC(o, total);
 231                         CS_PAGE_INC(o, create);
 232                         CS_PAGESTATE_DEC(o, CPS_CACHED);
 233                 }
 234         } else {
 235                 page = ERR_PTR(-ENOMEM);
 236         }
 237         RETURN(page);
 238 }
 239 EXPORT_SYMBOL(cl_page_alloc);
 240
 241 /**
 242  * Returns a cl_page with index \a idx at the object \a o, and associated with
 243  * the VM page \a vmpage.
 244  *
 245  * This is the main entry point into the cl_page caching interface. First, a
 246  * cache (implemented as a per-object radix tree) is consulted. If page is
 247  * found there, it is returned immediately. Otherwise new page is allocated
 248  * and returned. In any case, additional reference to page is acquired.
 249  *
 250  * \see cl_object_find(), cl_lock_find()
 251  */
 252 struct cl_page *cl_page_find(const struct lu_env *env,
 253                              struct cl_object *o,
 254                              pgoff_t idx, struct page *vmpage,
 255                              enum cl_page_type type)
 256 {
 257         struct cl_page          *page = NULL;
 258         struct cl_object_header *hdr;
 259
 260         LASSERT(type == CPT_CACHEABLE || type == CPT_TRANSIENT);
 261         might_sleep();
 262
 263         ENTRY;
 264
 265         hdr = cl_object_header(o);
 266         CS_PAGE_INC(o, lookup);
 267
 268         CDEBUG(D_PAGE, "%lu@"DFID" %p %lx %d\n",
 269                idx, PFID(&hdr->coh_lu.loh_fid), vmpage, vmpage->private, type);
 270         /* fast path. */
 271         if (type == CPT_CACHEABLE) {
 272                 /* vmpage lock is used to protect the child/parent
 273                  * relationship */
 274                 KLASSERT(PageLocked(vmpage));
 275                 /*
 276                  * cl_vmpage_page() can be called here without any locks as
 277                  *
 278                  *     - "vmpage" is locked (which prevents ->private from
 279                  *       concurrent updates), and
 280                  *
 281                  *     - "o" cannot be destroyed while current thread holds a
 282                  *       reference on it.
 283                  */
 284                 page = cl_vmpage_page(vmpage, o);
 285                 if (page != NULL) {
 286                         CS_PAGE_INC(o, hit);
 287                         RETURN(page);
 288                 }
 289         }
 290
 291         /* allocate and initialize cl_page */
 292         page = cl_page_alloc(env, o, idx, vmpage, type);
 293         RETURN(page);
 294 }
 295 EXPORT_SYMBOL(cl_page_find);
 296
 297 static inline int cl_page_invariant(const struct cl_page *pg)
 298 {
 299         struct cl_page          *parent;
 300         struct cl_page          *child;
 301         struct cl_io            *owner;
 302
 303         /*
 304          * Page invariant is protected by a VM lock.
 305          */
 306         LINVRNT(cl_page_is_vmlocked(NULL, pg));
 307
 308         parent = pg->cp_parent;
 309         child  = pg->cp_child;
 310         owner  = pg->cp_owner;
 311
 312         return cl_page_in_use_noref(pg) &&
 313                 ergo(parent != NULL, parent->cp_child == pg) &&
 314                 ergo(child != NULL, child->cp_parent == pg) &&
 315                 ergo(child != NULL, pg->cp_obj != child->cp_obj) &&
 316                 ergo(parent != NULL, pg->cp_obj != parent->cp_obj) &&
 317                 ergo(owner != NULL && parent != NULL,
 318                      parent->cp_owner == pg->cp_owner->ci_parent) &&
 319                 ergo(owner != NULL && child != NULL,
 320                      child->cp_owner->ci_parent == owner);
 321 }
 322
 323 static void cl_page_state_set0(const struct lu_env *env,
 324                                struct cl_page *page, enum cl_page_state state)
 325 {
 326         enum cl_page_state old;
 327
 328         /*
 329          * Matrix of allowed state transitions [old][new], for sanity
 330          * checking.
 331          */
 332         static const int allowed_transitions[CPS_NR][CPS_NR] = {
 333                 [CPS_CACHED] = {
 334                         [CPS_CACHED]  = 0,
 335                         [CPS_OWNED]   = 1, /* io finds existing cached page */
 336                         [CPS_PAGEIN]  = 0,
 337                         [CPS_PAGEOUT] = 1, /* write-out from the cache */
 338                         [CPS_FREEING] = 1, /* eviction on the memory pressure */
 339                 },
 340                 [CPS_OWNED] = {
 341                         [CPS_CACHED]  = 1, /* release to the cache */
 342                         [CPS_OWNED]   = 0,
 343                         [CPS_PAGEIN]  = 1, /* start read immediately */
 344                         [CPS_PAGEOUT] = 1, /* start write immediately */
 345                         [CPS_FREEING] = 1, /* lock invalidation or truncate */
 346                 },
 347                 [CPS_PAGEIN] = {
 348                         [CPS_CACHED]  = 1, /* io completion */
 349                         [CPS_OWNED]   = 0,
 350                         [CPS_PAGEIN]  = 0,
 351                         [CPS_PAGEOUT] = 0,
 352                         [CPS_FREEING] = 0,
 353                 },
 354                 [CPS_PAGEOUT] = {
 355                         [CPS_CACHED]  = 1, /* io completion */
 356                         [CPS_OWNED]   = 0,
 357                         [CPS_PAGEIN]  = 0,
 358                         [CPS_PAGEOUT] = 0,
 359                         [CPS_FREEING] = 0,
 360                 },
 361                 [CPS_FREEING] = {
 362                         [CPS_CACHED]  = 0,
 363                         [CPS_OWNED]   = 0,
 364                         [CPS_PAGEIN]  = 0,
 365                         [CPS_PAGEOUT] = 0,
 366                         [CPS_FREEING] = 0,
 367                 }
 368         };
 369
 370         ENTRY;
 371         old = page->cp_state;
 372         PASSERT(env, page, allowed_transitions[old][state]);
 373         CL_PAGE_HEADER(D_TRACE, env, page, "%d -> %d\n", old, state);
 374         for (; page != NULL; page = page->cp_child) {
 375                 PASSERT(env, page, page->cp_state == old);
 376                 PASSERT(env, page,
 377                         equi(state == CPS_OWNED, page->cp_owner != NULL));
 378
 379                 CS_PAGESTATE_DEC(page->cp_obj, page->cp_state);
 380                 CS_PAGESTATE_INC(page->cp_obj, state);
 381                 cl_page_state_set_trust(page, state);
 382         }
 383         EXIT;
 384 }
 385
 386 static void cl_page_state_set(const struct lu_env *env,
 387                               struct cl_page *page, enum cl_page_state state)
 388 {
 389         cl_page_state_set0(env, page, state);
 390 }
 391
 392 /**
 393  * Acquires an additional reference to a page.
 394  *
 395  * This can be called only by caller already possessing a reference to \a
 396  * page.
 397  *
 398  * \see cl_object_get(), cl_lock_get().
 399  */
 400 void cl_page_get(struct cl_page *page)
 401 {
 402         ENTRY;
 403         cl_page_get_trust(page);
 404         EXIT;
 405 }
 406 EXPORT_SYMBOL(cl_page_get);
 407
 408 /**
 409  * Releases a reference to a page.
 410  *
 411  * When last reference is released, page is returned to the cache, unless it
 412  * is in cl_page_state::CPS_FREEING state, in which case it is immediately
 413  * destroyed.
 414  *
 415  * \see cl_object_put(), cl_lock_put().
 416  */
 417 void cl_page_put(const struct lu_env *env, struct cl_page *page)
 418 {
 419         PASSERT(env, page, cfs_atomic_read(&page->cp_ref) > !!page->cp_parent);
 420
 421         ENTRY;
 422         CL_PAGE_HEADER(D_TRACE, env, page, "%d\n",
 423                        cfs_atomic_read(&page->cp_ref));
 424
 425         if (cfs_atomic_dec_and_test(&page->cp_ref)) {
 426                 LASSERT(page->cp_state == CPS_FREEING);
 427
 428                 LASSERT(cfs_atomic_read(&page->cp_ref) == 0);
 429                 PASSERT(env, page, page->cp_owner == NULL);
 430                 PASSERT(env, page, cfs_list_empty(&page->cp_batch));
 431                 /*
 432                  * Page is no longer reachable by other threads. Tear
 433                  * it down.
 434                  */
 435                 cl_page_free(env, page);
 436         }
 437
 438         EXIT;
 439 }
 440 EXPORT_SYMBOL(cl_page_put);
 441
 442 /**
 443  * Returns a VM page associated with a given cl_page.
 444  */
 445 struct page *cl_page_vmpage(const struct lu_env *env, struct cl_page *page)
 446 {
 447         const struct cl_page_slice *slice;
 448
 449         /*
 450          * Find uppermost layer with ->cpo_vmpage() method, and return its
 451          * result.
 452          */
 453         page = cl_page_top(page);
 454         do {
 455                 cfs_list_for_each_entry(slice, &page->cp_layers, cpl_linkage) {
 456                         if (slice->cpl_ops->cpo_vmpage != NULL)
 457                                 RETURN(slice->cpl_ops->cpo_vmpage(env, slice));
 458                 }
 459                 page = page->cp_child;
 460         } while (page != NULL);
 461         LBUG(); /* ->cpo_vmpage() has to be defined somewhere in the stack */
 462 }
 463 EXPORT_SYMBOL(cl_page_vmpage);
 464
 465 /**
 466  * Returns a cl_page associated with a VM page, and given cl_object.
 467  */
 468 struct cl_page *cl_vmpage_page(struct page *vmpage, struct cl_object *obj)
 469 {
 470         struct cl_page *top;
 471         struct cl_page *page;
 472
 473         ENTRY;
 474         KLASSERT(PageLocked(vmpage));
 475
 476         /*
 477          * NOTE: absence of races and liveness of data are guaranteed by page
 478          *       lock on a "vmpage". That works because object destruction has
 479          *       bottom-to-top pass.
 480          */
 481
 482         /*
 483          * This loop assumes that ->private points to the top-most page. This
 484          * can be rectified easily.
 485          */
 486         top = (struct cl_page *)vmpage->private;
 487         if (top == NULL)
 488                 RETURN(NULL);
 489
 490         for (page = top; page != NULL; page = page->cp_child) {
 491                 if (cl_object_same(page->cp_obj, obj)) {
 492                         cl_page_get_trust(page);
 493                         break;
 494                 }
 495         }
 496         LASSERT(ergo(page, page->cp_type == CPT_CACHEABLE));
 497         RETURN(page);
 498 }
 499 EXPORT_SYMBOL(cl_vmpage_page);
 500
 501 /**
 502  * Returns the top-page for a given page.
 503  *
 504  * \see cl_object_top(), cl_io_top()
 505  */
 506 struct cl_page *cl_page_top(struct cl_page *page)
 507 {
 508         return cl_page_top_trusted(page);
 509 }
 510 EXPORT_SYMBOL(cl_page_top);
 511
 512 const struct cl_page_slice *cl_page_at(const struct cl_page *page,
 513                                        const struct lu_device_type *dtype)
 514 {
 515         return cl_page_at_trusted(page, dtype);
 516 }
 517 EXPORT_SYMBOL(cl_page_at);
 518
 519 #define CL_PAGE_OP(opname) offsetof(struct cl_page_operations, opname)
 520
 521 #define CL_PAGE_INVOKE(_env, _page, _op, _proto, ...)                   \
 522 ({                                                                      \
 523         const struct lu_env        *__env  = (_env);                    \
 524         struct cl_page             *__page = (_page);                   \
 525         const struct cl_page_slice *__scan;                             \
 526         int                         __result;                           \
 527         ptrdiff_t                   __op   = (_op);                     \
 528         int                       (*__method)_proto;                    \
 529                                                                         \
 530         __result = 0;                                                   \
 531         __page = cl_page_top(__page);                                   \
 532         do {                                                            \
 533                 cfs_list_for_each_entry(__scan, &__page->cp_layers,     \
 534                                         cpl_linkage) {                  \
 535                         __method = *(void **)((char *)__scan->cpl_ops + \
 536                                               __op);                    \
 537                         if (__method != NULL) {                         \
 538                                 __result = (*__method)(__env, __scan,   \
 539                                                        ## __VA_ARGS__); \
 540                                 if (__result != 0)                      \
 541                                         break;                          \
 542                         }                                               \
 543                 }                                                       \
 544                 __page = __page->cp_child;                              \
 545         } while (__page != NULL && __result == 0);                      \
 546         if (__result > 0)                                               \
 547                 __result = 0;                                           \
 548         __result;                                                       \
 549 })
 550
 551 #define CL_PAGE_INVOID(_env, _page, _op, _proto, ...)                   \
 552 do {                                                                    \
 553         const struct lu_env        *__env  = (_env);                    \
 554         struct cl_page             *__page = (_page);                   \
 555         const struct cl_page_slice *__scan;                             \
 556         ptrdiff_t                   __op   = (_op);                     \
 557         void                      (*__method)_proto;                    \
 558                                                                         \
 559         __page = cl_page_top(__page);                                   \
 560         do {                                                            \
 561                 cfs_list_for_each_entry(__scan, &__page->cp_layers,     \
 562                                         cpl_linkage) {                  \
 563                         __method = *(void **)((char *)__scan->cpl_ops + \
 564                                               __op);                    \
 565                         if (__method != NULL)                           \
 566                                 (*__method)(__env, __scan,              \
 567                                             ## __VA_ARGS__);            \
 568                 }                                                       \
 569                 __page = __page->cp_child;                              \
 570         } while (__page != NULL);                                       \
 571 } while (0)
 572
 573 #define CL_PAGE_INVOID_REVERSE(_env, _page, _op, _proto, ...)               \
 574 do {                                                                        \
 575         const struct lu_env        *__env  = (_env);                        \
 576         struct cl_page             *__page = (_page);                       \
 577         const struct cl_page_slice *__scan;                                 \
 578         ptrdiff_t                   __op   = (_op);                         \
 579         void                      (*__method)_proto;                        \
 580                                                                             \
 581         /* get to the bottom page. */                                       \
 582         while (__page->cp_child != NULL)                                    \
 583                 __page = __page->cp_child;                                  \
 584         do {                                                                \
 585                 cfs_list_for_each_entry_reverse(__scan, &__page->cp_layers, \
 586                                                 cpl_linkage) {              \
 587                         __method = *(void **)((char *)__scan->cpl_ops +     \
 588                                               __op);                        \
 589                         if (__method != NULL)                               \
 590                                 (*__method)(__env, __scan,                  \
 591                                             ## __VA_ARGS__);                \
 592                 }                                                           \
 593                 __page = __page->cp_parent;                                 \
 594         } while (__page != NULL);                                           \
 595 } while (0)
 596
 597 static int cl_page_invoke(const struct lu_env *env,
 598                           struct cl_io *io, struct cl_page *page, ptrdiff_t op)
 599
 600 {
 601         PINVRNT(env, page, cl_object_same(page->cp_obj, io->ci_obj));
 602         ENTRY;
 603         RETURN(CL_PAGE_INVOKE(env, page, op,
 604                               (const struct lu_env *,
 605                                const struct cl_page_slice *, struct cl_io *),
 606                               io));
 607 }
 608
 609 static void cl_page_invoid(const struct lu_env *env,
 610                            struct cl_io *io, struct cl_page *page, ptrdiff_t op)
 611
 612 {
 613         PINVRNT(env, page, cl_object_same(page->cp_obj, io->ci_obj));
 614         ENTRY;
 615         CL_PAGE_INVOID(env, page, op,
 616                        (const struct lu_env *,
 617                         const struct cl_page_slice *, struct cl_io *), io);
 618         EXIT;
 619 }
 620
 621 static void cl_page_owner_clear(struct cl_page *page)
 622 {
 623         ENTRY;
 624         for (page = cl_page_top(page); page != NULL; page = page->cp_child) {
 625                 if (page->cp_owner != NULL) {
 626                         LASSERT(page->cp_owner->ci_owned_nr > 0);
 627                         page->cp_owner->ci_owned_nr--;
 628                         page->cp_owner = NULL;
 629                         page->cp_task = NULL;
 630                 }
 631         }
 632         EXIT;
 633 }
 634
 635 static void cl_page_owner_set(struct cl_page *page)
 636 {
 637         ENTRY;
 638         for (page = cl_page_top(page); page != NULL; page = page->cp_child) {
 639                 LASSERT(page->cp_owner != NULL);
 640                 page->cp_owner->ci_owned_nr++;
 641         }
 642         EXIT;
 643 }
 644
 645 void cl_page_disown0(const struct lu_env *env,
 646                      struct cl_io *io, struct cl_page *pg)
 647 {
 648         enum cl_page_state state;
 649
 650         ENTRY;
 651         state = pg->cp_state;
 652         PINVRNT(env, pg, state == CPS_OWNED || state == CPS_FREEING);
 653         PINVRNT(env, pg, cl_page_invariant(pg) || state == CPS_FREEING);
 654         cl_page_owner_clear(pg);
 655
 656         if (state == CPS_OWNED)
 657                 cl_page_state_set(env, pg, CPS_CACHED);
 658         /*
 659          * Completion call-backs are executed in the bottom-up order, so that
 660          * uppermost layer (llite), responsible for VFS/VM interaction runs
 661          * last and can release locks safely.
 662          */
 663         CL_PAGE_INVOID_REVERSE(env, pg, CL_PAGE_OP(cpo_disown),
 664                                (const struct lu_env *,
 665                                 const struct cl_page_slice *, struct cl_io *),
 666                                io);
 667         EXIT;
 668 }
 669
 670 /**
 671  * returns true, iff page is owned by the given io.
 672  */
 673 int cl_page_is_owned(const struct cl_page *pg, const struct cl_io *io)
 674 {
 675         LINVRNT(cl_object_same(pg->cp_obj, io->ci_obj));
 676         ENTRY;
 677         RETURN(pg->cp_state == CPS_OWNED && pg->cp_owner == io);
 678 }
 679 EXPORT_SYMBOL(cl_page_is_owned);
 680
 681 /**
 682  * Try to own a page by IO.
 683  *
 684  * Waits until page is in cl_page_state::CPS_CACHED state, and then switch it
 685  * into cl_page_state::CPS_OWNED state.
 686  *
 687  * \pre  !cl_page_is_owned(pg, io)
 688  * \post result == 0 iff cl_page_is_owned(pg, io)
 689  *
 690  * \retval 0   success
 691  *
 692  * \retval -ve failure, e.g., page was destroyed (and landed in
 693  *             cl_page_state::CPS_FREEING instead of cl_page_state::CPS_CACHED).
 694  *             or, page was owned by another thread, or in IO.
 695  *
 696  * \see cl_page_disown()
 697  * \see cl_page_operations::cpo_own()
 698  * \see cl_page_own_try()
 699  * \see cl_page_own
 700  */
 701 static int cl_page_own0(const struct lu_env *env, struct cl_io *io,
 702                         struct cl_page *pg, int nonblock)
 703 {
 704         int result;
 705
 706         PINVRNT(env, pg, !cl_page_is_owned(pg, io));
 707
 708         ENTRY;
 709         pg = cl_page_top(pg);
 710         io = cl_io_top(io);
 711
 712         if (pg->cp_state == CPS_FREEING) {
 713                 result = -ENOENT;
 714         } else {
 715                 result = CL_PAGE_INVOKE(env, pg, CL_PAGE_OP(cpo_own),
 716                                         (const struct lu_env *,
 717                                          const struct cl_page_slice *,
 718                                          struct cl_io *, int),
 719                                         io, nonblock);
 720                 if (result == 0) {
 721                         PASSERT(env, pg, pg->cp_owner == NULL);
 722                         PASSERT(env, pg, pg->cp_req == NULL);
 723                         pg->cp_owner = io;
 724                         pg->cp_task  = current;
 725                         cl_page_owner_set(pg);
 726                         if (pg->cp_state != CPS_FREEING) {
 727                                 cl_page_state_set(env, pg, CPS_OWNED);
 728                         } else {
 729                                 cl_page_disown0(env, io, pg);
 730                                 result = -ENOENT;
 731                         }
 732                 }
 733         }
 734         PINVRNT(env, pg, ergo(result == 0, cl_page_invariant(pg)));
 735         RETURN(result);
 736 }
 737
 738 /**
 739  * Own a page, might be blocked.
 740  *
 741  * \see cl_page_own0()
 742  */
 743 int cl_page_own(const struct lu_env *env, struct cl_io *io, struct cl_page *pg)
 744 {
 745         return cl_page_own0(env, io, pg, 0);
 746 }
 747 EXPORT_SYMBOL(cl_page_own);
 748
 749 /**
 750  * Nonblock version of cl_page_own().
 751  *
 752  * \see cl_page_own0()
 753  */
 754 int cl_page_own_try(const struct lu_env *env, struct cl_io *io,
 755                     struct cl_page *pg)
 756 {
 757         return cl_page_own0(env, io, pg, 1);
 758 }
 759 EXPORT_SYMBOL(cl_page_own_try);
 760
 761
 762 /**
 763  * Assume page ownership.
 764  *
 765  * Called when page is already locked by the hosting VM.
 766  *
 767  * \pre !cl_page_is_owned(pg, io)
 768  * \post cl_page_is_owned(pg, io)
 769  *
 770  * \see cl_page_operations::cpo_assume()
 771  */
 772 void cl_page_assume(const struct lu_env *env,
 773                     struct cl_io *io, struct cl_page *pg)
 774 {
 775         PINVRNT(env, pg, cl_object_same(pg->cp_obj, io->ci_obj));
 776
 777         ENTRY;
 778         pg = cl_page_top(pg);
 779         io = cl_io_top(io);
 780
 781         cl_page_invoid(env, io, pg, CL_PAGE_OP(cpo_assume));
 782         PASSERT(env, pg, pg->cp_owner == NULL);
 783         pg->cp_owner = io;
 784         pg->cp_task = current;
 785         cl_page_owner_set(pg);
 786         cl_page_state_set(env, pg, CPS_OWNED);
 787         EXIT;
 788 }
 789 EXPORT_SYMBOL(cl_page_assume);
 790
 791 /**
 792  * Releases page ownership without unlocking the page.
 793  *
 794  * Moves page into cl_page_state::CPS_CACHED without releasing a lock on the
 795  * underlying VM page (as VM is supposed to do this itself).
 796  *
 797  * \pre   cl_page_is_owned(pg, io)
 798  * \post !cl_page_is_owned(pg, io)
 799  *
 800  * \see cl_page_assume()
 801  */
 802 void cl_page_unassume(const struct lu_env *env,
 803                       struct cl_io *io, struct cl_page *pg)
 804 {
 805         PINVRNT(env, pg, cl_page_is_owned(pg, io));
 806         PINVRNT(env, pg, cl_page_invariant(pg));
 807
 808         ENTRY;
 809         pg = cl_page_top(pg);
 810         io = cl_io_top(io);
 811         cl_page_owner_clear(pg);
 812         cl_page_state_set(env, pg, CPS_CACHED);
 813         CL_PAGE_INVOID_REVERSE(env, pg, CL_PAGE_OP(cpo_unassume),
 814                                (const struct lu_env *,
 815                                 const struct cl_page_slice *, struct cl_io *),
 816                                io);
 817         EXIT;
 818 }
 819 EXPORT_SYMBOL(cl_page_unassume);
 820
 821 /**
 822  * Releases page ownership.
 823  *
 824  * Moves page into cl_page_state::CPS_CACHED.
 825  *
 826  * \pre   cl_page_is_owned(pg, io)
 827  * \post !cl_page_is_owned(pg, io)
 828  *
 829  * \see cl_page_own()
 830  * \see cl_page_operations::cpo_disown()
 831  */
 832 void cl_page_disown(const struct lu_env *env,
 833                     struct cl_io *io, struct cl_page *pg)
 834 {
 835         PINVRNT(env, pg, cl_page_is_owned(pg, io) ||
 836                          pg->cp_state == CPS_FREEING);
 837
 838         ENTRY;
 839         pg = cl_page_top(pg);
 840         io = cl_io_top(io);
 841         cl_page_disown0(env, io, pg);
 842         EXIT;
 843 }
 844 EXPORT_SYMBOL(cl_page_disown);
 845
 846 /**
 847  * Called when page is to be removed from the object, e.g., as a result of
 848  * truncate.
 849  *
 850  * Calls cl_page_operations::cpo_discard() top-to-bottom.
 851  *
 852  * \pre cl_page_is_owned(pg, io)
 853  *
 854  * \see cl_page_operations::cpo_discard()
 855  */
 856 void cl_page_discard(const struct lu_env *env,
 857                      struct cl_io *io, struct cl_page *pg)
 858 {
 859         PINVRNT(env, pg, cl_page_is_owned(pg, io));
 860         PINVRNT(env, pg, cl_page_invariant(pg));
 861
 862         cl_page_invoid(env, io, pg, CL_PAGE_OP(cpo_discard));
 863 }
 864 EXPORT_SYMBOL(cl_page_discard);
 865
 866 /**
 867  * Version of cl_page_delete() that can be called for not fully constructed
 868  * pages, e.g,. in a error handling cl_page_find()->cl_page_delete0()
 869  * path. Doesn't check page invariant.
 870  */
 871 static void cl_page_delete0(const struct lu_env *env, struct cl_page *pg)
 872 {
 873         ENTRY;
 874
 875         PASSERT(env, pg, pg == cl_page_top(pg));
 876         PASSERT(env, pg, pg->cp_state != CPS_FREEING);
 877
 878         /*
 879          * Severe all ways to obtain new pointers to @pg.
 880          */
 881         cl_page_owner_clear(pg);
 882
 883         cl_page_state_set0(env, pg, CPS_FREEING);
 884
 885         CL_PAGE_INVOID_REVERSE(env, pg, CL_PAGE_OP(cpo_delete),
 886                        (const struct lu_env *, const struct cl_page_slice *));
 887
 888         EXIT;
 889 }
 890
 891 /**
 892  * Called when a decision is made to throw page out of memory.
 893  *
 894  * Notifies all layers about page destruction by calling
 895  * cl_page_operations::cpo_delete() method top-to-bottom.
 896  *
 897  * Moves page into cl_page_state::CPS_FREEING state (this is the only place
 898  * where transition to this state happens).
 899  *
 900  * Eliminates all venues through which new references to the page can be
 901  * obtained:
 902  *
 903  *     - removes page from the radix trees,
 904  *
 905  *     - breaks linkage from VM page to cl_page.
 906  *
 907  * Once page reaches cl_page_state::CPS_FREEING, all remaining references will
 908  * drain after some time, at which point page will be recycled.
 909  *
 910  * \pre  pg == cl_page_top(pg)
 911  * \pre  VM page is locked
 912  * \post pg->cp_state == CPS_FREEING
 913  *
 914  * \see cl_page_operations::cpo_delete()
 915  */
 916 void cl_page_delete(const struct lu_env *env, struct cl_page *pg)
 917 {
 918         PINVRNT(env, pg, cl_page_invariant(pg));
 919         ENTRY;
 920         cl_page_delete0(env, pg);
 921         EXIT;
 922 }
 923 EXPORT_SYMBOL(cl_page_delete);
 924
 925 /**
 926  * Marks page up-to-date.
 927  *
 928  * Call cl_page_operations::cpo_export() through all layers top-to-bottom. The
 929  * layer responsible for VM interaction has to mark/clear page as up-to-date
 930  * by the \a uptodate argument.
 931  *
 932  * \see cl_page_operations::cpo_export()
 933  */
 934 void cl_page_export(const struct lu_env *env, struct cl_page *pg, int uptodate)
 935 {
 936         PINVRNT(env, pg, cl_page_invariant(pg));
 937         CL_PAGE_INVOID(env, pg, CL_PAGE_OP(cpo_export),
 938                        (const struct lu_env *,
 939                         const struct cl_page_slice *, int), uptodate);
 940 }
 941 EXPORT_SYMBOL(cl_page_export);
 942
 943 /**
 944  * Returns true, iff \a pg is VM locked in a suitable sense by the calling
 945  * thread.
 946  */
 947 int cl_page_is_vmlocked(const struct lu_env *env, const struct cl_page *pg)
 948 {
 949         int result;
 950         const struct cl_page_slice *slice;
 951
 952         ENTRY;
 953         pg = cl_page_top_trusted((struct cl_page *)pg);
 954         slice = container_of(pg->cp_layers.next,
 955                              const struct cl_page_slice, cpl_linkage);
 956         PASSERT(env, pg, slice->cpl_ops->cpo_is_vmlocked != NULL);
 957         /*
 958          * Call ->cpo_is_vmlocked() directly instead of going through
 959          * CL_PAGE_INVOKE(), because cl_page_is_vmlocked() is used by
 960          * cl_page_invariant().
 961          */
 962         result = slice->cpl_ops->cpo_is_vmlocked(env, slice);
 963         PASSERT(env, pg, result == -EBUSY || result == -ENODATA);
 964         RETURN(result == -EBUSY);
 965 }
 966 EXPORT_SYMBOL(cl_page_is_vmlocked);
 967
 968 static enum cl_page_state cl_req_type_state(enum cl_req_type crt)
 969 {
 970         ENTRY;
 971         RETURN(crt == CRT_WRITE ? CPS_PAGEOUT : CPS_PAGEIN);
 972 }
 973
 974 static void cl_page_io_start(const struct lu_env *env,
 975                              struct cl_page *pg, enum cl_req_type crt)
 976 {
 977         /*
 978          * Page is queued for IO, change its state.
 979          */
 980         ENTRY;
 981         cl_page_owner_clear(pg);
 982         cl_page_state_set(env, pg, cl_req_type_state(crt));
 983         EXIT;
 984 }
 985
 986 /**
 987  * Prepares page for immediate transfer. cl_page_operations::cpo_prep() is
 988  * called top-to-bottom. Every layer either agrees to submit this page (by
 989  * returning 0), or requests to omit this page (by returning -EALREADY). Layer
 990  * handling interactions with the VM also has to inform VM that page is under
 991  * transfer now.
 992  */
 993 int cl_page_prep(const struct lu_env *env, struct cl_io *io,
 994                  struct cl_page *pg, enum cl_req_type crt)
 995 {
 996         int result;
 997
 998         PINVRNT(env, pg, cl_page_is_owned(pg, io));
 999         PINVRNT(env, pg, cl_page_invariant(pg));
1000         PINVRNT(env, pg, crt < CRT_NR);
1001
1002         /*
1003          * XXX this has to be called bottom-to-top, so that llite can set up
1004          * PG_writeback without risking other layers deciding to skip this
1005          * page.
1006          */
1007         if (crt >= CRT_NR)
1008                 return -EINVAL;
1009         result = cl_page_invoke(env, io, pg, CL_PAGE_OP(io[crt].cpo_prep));
1010         if (result == 0)
1011                 cl_page_io_start(env, pg, crt);
1012
1013         KLASSERT(ergo(crt == CRT_WRITE && pg->cp_type == CPT_CACHEABLE,
1014                       equi(result == 0,
1015                            PageWriteback(cl_page_vmpage(env, pg)))));
1016         CL_PAGE_HEADER(D_TRACE, env, pg, "%d %d\n", crt, result);
1017         return result;
1018 }
1019 EXPORT_SYMBOL(cl_page_prep);
1020
1021 /**
1022  * Notify layers about transfer completion.
1023  *
1024  * Invoked by transfer sub-system (which is a part of osc) to notify layers
1025  * that a transfer, of which this page is a part of has completed.
1026  *
1027  * Completion call-backs are executed in the bottom-up order, so that
1028  * uppermost layer (llite), responsible for the VFS/VM interaction runs last
1029  * and can release locks safely.
1030  *
1031  * \pre  pg->cp_state == CPS_PAGEIN || pg->cp_state == CPS_PAGEOUT
1032  * \post pg->cp_state == CPS_CACHED
1033  *
1034  * \see cl_page_operations::cpo_completion()
1035  */
1036 void cl_page_completion(const struct lu_env *env,
1037                         struct cl_page *pg, enum cl_req_type crt, int ioret)
1038 {
1039         struct cl_sync_io *anchor = pg->cp_sync_io;
1040
1041         PASSERT(env, pg, crt < CRT_NR);
1042         /* cl_page::cp_req already cleared by the caller (osc_completion()) */
1043         PASSERT(env, pg, pg->cp_req == NULL);
1044         PASSERT(env, pg, pg->cp_state == cl_req_type_state(crt));
1045
1046         ENTRY;
1047         CL_PAGE_HEADER(D_TRACE, env, pg, "%d %d\n", crt, ioret);
1048         if (crt == CRT_READ && ioret == 0) {
1049                 PASSERT(env, pg, !(pg->cp_flags & CPF_READ_COMPLETED));
1050                 pg->cp_flags |= CPF_READ_COMPLETED;
1051         }
1052
1053         cl_page_state_set(env, pg, CPS_CACHED);
1054         if (crt >= CRT_NR)
1055                 return;
1056         CL_PAGE_INVOID_REVERSE(env, pg, CL_PAGE_OP(io[crt].cpo_completion),
1057                                (const struct lu_env *,
1058                                 const struct cl_page_slice *, int), ioret);
1059         if (anchor) {
1060                 LASSERT(cl_page_is_vmlocked(env, pg));
1061                 LASSERT(pg->cp_sync_io == anchor);
1062                 pg->cp_sync_io = NULL;
1063         }
1064         /*
1065          * As page->cp_obj is pinned by a reference from page->cp_req, it is
1066          * safe to call cl_page_put() without risking object destruction in a
1067          * non-blocking context.
1068          */
1069         cl_page_put(env, pg);
1070
1071         if (anchor)
1072                 cl_sync_io_note(anchor, ioret);
1073
1074         EXIT;
1075 }
1076 EXPORT_SYMBOL(cl_page_completion);
1077
1078 /**
1079  * Notify layers that transfer formation engine decided to yank this page from
1080  * the cache and to make it a part of a transfer.
1081  *
1082  * \pre  pg->cp_state == CPS_CACHED
1083  * \post pg->cp_state == CPS_PAGEIN || pg->cp_state == CPS_PAGEOUT
1084  *
1085  * \see cl_page_operations::cpo_make_ready()
1086  */
1087 int cl_page_make_ready(const struct lu_env *env, struct cl_page *pg,
1088                        enum cl_req_type crt)
1089 {
1090         int result;
1091
1092         PINVRNT(env, pg, crt < CRT_NR);
1093
1094         ENTRY;
1095         if (crt >= CRT_NR)
1096                 RETURN(-EINVAL);
1097         result = CL_PAGE_INVOKE(env, pg, CL_PAGE_OP(io[crt].cpo_make_ready),
1098                                 (const struct lu_env *,
1099                                  const struct cl_page_slice *));
1100         if (result == 0) {
1101                 PASSERT(env, pg, pg->cp_state == CPS_CACHED);
1102                 cl_page_io_start(env, pg, crt);
1103         }
1104         CL_PAGE_HEADER(D_TRACE, env, pg, "%d %d\n", crt, result);
1105         RETURN(result);
1106 }
1107 EXPORT_SYMBOL(cl_page_make_ready);
1108
1109 /**
1110  * Notify layers that high level io decided to place this page into a cache
1111  * for future transfer.
1112  *
1113  * The layer implementing transfer engine (osc) has to register this page in
1114  * its queues.
1115  *
1116  * \pre  cl_page_is_owned(pg, io)
1117  * \post cl_page_is_owned(pg, io)
1118  *
1119  * \see cl_page_operations::cpo_cache_add()
1120  */
1121 int cl_page_cache_add(const struct lu_env *env, struct cl_io *io,
1122                       struct cl_page *pg, enum cl_req_type crt)
1123 {
1124         const struct cl_page_slice *scan;
1125         int result = 0;
1126
1127         PINVRNT(env, pg, crt < CRT_NR);
1128         PINVRNT(env, pg, cl_page_is_owned(pg, io));
1129         PINVRNT(env, pg, cl_page_invariant(pg));
1130
1131         ENTRY;
1132
1133         if (crt >= CRT_NR)
1134                 RETURN(-EINVAL);
1135
1136         cfs_list_for_each_entry(scan, &pg->cp_layers, cpl_linkage) {
1137                 if (scan->cpl_ops->io[crt].cpo_cache_add == NULL)
1138                         continue;
1139
1140                 result = scan->cpl_ops->io[crt].cpo_cache_add(env, scan, io);
1141                 if (result != 0)
1142                         break;
1143         }
1144         CL_PAGE_HEADER(D_TRACE, env, pg, "%d %d\n", crt, result);
1145         RETURN(result);
1146 }
1147 EXPORT_SYMBOL(cl_page_cache_add);
1148
1149 /**
1150  * Called if a pge is being written back by kernel's intention.
1151  *
1152  * \pre  cl_page_is_owned(pg, io)
1153  * \post ergo(result == 0, pg->cp_state == CPS_PAGEOUT)
1154  *
1155  * \see cl_page_operations::cpo_flush()
1156  */
1157 int cl_page_flush(const struct lu_env *env, struct cl_io *io,
1158                   struct cl_page *pg)
1159 {
1160         int result;
1161
1162         PINVRNT(env, pg, cl_page_is_owned(pg, io));
1163         PINVRNT(env, pg, cl_page_invariant(pg));
1164
1165         ENTRY;
1166
1167         result = cl_page_invoke(env, io, pg, CL_PAGE_OP(cpo_flush));
1168
1169         CL_PAGE_HEADER(D_TRACE, env, pg, "%d\n", result);
1170         RETURN(result);
1171 }
1172 EXPORT_SYMBOL(cl_page_flush);
1173
1174 /**
1175  * Checks whether page is protected by any extent lock is at least required
1176  * mode.
1177  *
1178  * \return the same as in cl_page_operations::cpo_is_under_lock() method.
1179  * \see cl_page_operations::cpo_is_under_lock()
1180  */
1181 int cl_page_is_under_lock(const struct lu_env *env, struct cl_io *io,
1182                           struct cl_page *page)
1183 {
1184         int rc;
1185
1186         PINVRNT(env, page, cl_page_invariant(page));
1187
1188         ENTRY;
1189         rc = CL_PAGE_INVOKE(env, page, CL_PAGE_OP(cpo_is_under_lock),
1190                             (const struct lu_env *,
1191                              const struct cl_page_slice *, struct cl_io *),
1192                             io);
1193         PASSERT(env, page, rc != 0);
1194         RETURN(rc);
1195 }
1196 EXPORT_SYMBOL(cl_page_is_under_lock);
1197
1198 /**
1199  * Tells transfer engine that only part of a page is to be transmitted.
1200  *
1201  * \see cl_page_operations::cpo_clip()
1202  */
1203 void cl_page_clip(const struct lu_env *env, struct cl_page *pg,
1204                   int from, int to)
1205 {
1206         PINVRNT(env, pg, cl_page_invariant(pg));
1207
1208         CL_PAGE_HEADER(D_TRACE, env, pg, "%d %d\n", from, to);
1209         CL_PAGE_INVOID(env, pg, CL_PAGE_OP(cpo_clip),
1210                        (const struct lu_env *,
1211                         const struct cl_page_slice *,int, int),
1212                        from, to);
1213 }
1214 EXPORT_SYMBOL(cl_page_clip);
1215
1216 /**
1217  * Prints human readable representation of \a pg to the \a f.
1218  */
1219 void cl_page_header_print(const struct lu_env *env, void *cookie,
1220                           lu_printer_t printer, const struct cl_page *pg)
1221 {
1222         (*printer)(env, cookie,
1223                    "page@%p[%d %p:%lu ^%p_%p %d %d %d %p %p %#x]\n",
1224                    pg, cfs_atomic_read(&pg->cp_ref), pg->cp_obj,
1225                    pg->cp_index, pg->cp_parent, pg->cp_child,
1226                    pg->cp_state, pg->cp_error, pg->cp_type,
1227                    pg->cp_owner, pg->cp_req, pg->cp_flags);
1228 }
1229 EXPORT_SYMBOL(cl_page_header_print);
1230
1231 /**
1232  * Prints human readable representation of \a pg to the \a f.
1233  */
1234 void cl_page_print(const struct lu_env *env, void *cookie,
1235                    lu_printer_t printer, const struct cl_page *pg)
1236 {
1237         struct cl_page *scan;
1238
1239         for (scan = cl_page_top((struct cl_page *)pg);
1240              scan != NULL; scan = scan->cp_child)
1241                 cl_page_header_print(env, cookie, printer, scan);
1242         CL_PAGE_INVOKE(env, (struct cl_page *)pg, CL_PAGE_OP(cpo_print),
1243                        (const struct lu_env *env,
1244                         const struct cl_page_slice *slice,
1245                         void *cookie, lu_printer_t p), cookie, printer);
1246         (*printer)(env, cookie, "end page@%p\n", pg);
1247 }
1248 EXPORT_SYMBOL(cl_page_print);
1249
1250 /**
1251  * Cancel a page which is still in a transfer.
1252  */
1253 int cl_page_cancel(const struct lu_env *env, struct cl_page *page)
1254 {
1255         return CL_PAGE_INVOKE(env, page, CL_PAGE_OP(cpo_cancel),
1256                               (const struct lu_env *,
1257                                const struct cl_page_slice *));
1258 }
1259 EXPORT_SYMBOL(cl_page_cancel);
1260
1261 /**
1262  * Converts a byte offset within object \a obj into a page index.
1263  */
1264 loff_t cl_offset(const struct cl_object *obj, pgoff_t idx)
1265 {
1266         return (loff_t)idx << PAGE_CACHE_SHIFT;
1267 }
1268 EXPORT_SYMBOL(cl_offset);
1269
1270 /**
1271  * Converts a page index into a byte offset within object \a obj.
1272  */
1273 pgoff_t cl_index(const struct cl_object *obj, loff_t offset)
1274 {
1275         return offset >> PAGE_CACHE_SHIFT;
1276 }
1277 EXPORT_SYMBOL(cl_index);
1278
1279 int cl_page_size(const struct cl_object *obj)
1280 {
1281         return 1 << PAGE_CACHE_SHIFT;
1282 }
1283 EXPORT_SYMBOL(cl_page_size);
1284
1285 /**
1286  * Adds page slice to the compound page.
1287  *
1288  * This is called by cl_object_operations::coo_page_init() methods to add a
1289  * per-layer state to the page. New state is added at the end of
1290  * cl_page::cp_layers list, that is, it is at the bottom of the stack.
1291  *
1292  * \see cl_lock_slice_add(), cl_req_slice_add(), cl_io_slice_add()
1293  */
1294 void cl_page_slice_add(struct cl_page *page, struct cl_page_slice *slice,
1295                        struct cl_object *obj,
1296                        const struct cl_page_operations *ops)
1297 {
1298         ENTRY;
1299         cfs_list_add_tail(&slice->cpl_linkage, &page->cp_layers);
1300         slice->cpl_obj  = obj;
1301         slice->cpl_ops  = ops;
1302         slice->cpl_page = page;
1303         EXIT;
1304 }
1305 EXPORT_SYMBOL(cl_page_slice_add);
1306
1307 int  cl_page_init(void)
1308 {
1309         return 0;
1310 }
1311
1312 void cl_page_fini(void)
1313 {
1314 }