drivers/staging/lustre/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, 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  * Client Lustre Page.
  37  *
  38  *   Author: Nikita Danilov <nikita.danilov@sun.com>
  39  */
  40
  41 #define DEBUG_SUBSYSTEM S_CLASS
  42
  43 #include "../../include/linux/libcfs/libcfs.h"
  44 #include "../include/obd_class.h"
  45 #include "../include/obd_support.h"
  46 #include <linux/list.h>
  47
  48 #include "../include/cl_object.h"
  49 #include "cl_internal.h"
  50
  51 static void cl_page_delete0(const struct lu_env *env, struct cl_page *pg,
  52                             int radix);
  53
  54 # define PASSERT(env, page, expr)                                          \
  55         do {                                                               \
  56                 if (unlikely(!(expr))) {                                   \
  57                         CL_PAGE_DEBUG(D_ERROR, (env), (page), #expr "\n"); \
  58                         LASSERT(0);                                        \
  59                 }                                                          \
  60         } while (0)
  61
  62 # define PINVRNT(env, page, exp) \
  63         ((void)sizeof(env), (void)sizeof(page), (void)sizeof !!(exp))
  64
  65 /**
  66  * Internal version of cl_page_top, it should be called if the page is
  67  * known to be not freed, says with page referenced, or radix tree lock held,
  68  * or page owned.
  69  */
  70 static struct cl_page *cl_page_top_trusted(struct cl_page *page)
  71 {
  72         while (page->cp_parent)
  73                 page = page->cp_parent;
  74         return page;
  75 }
  76
  77 /**
  78  * Internal version of cl_page_get().
  79  *
  80  * This function can be used to obtain initial reference to previously
  81  * unreferenced cached object. It can be called only if concurrent page
  82  * reclamation is somehow prevented, e.g., by locking page radix-tree
  83  * (cl_object_header::hdr->coh_page_guard), or by keeping a lock on a VM page,
  84  * associated with \a page.
  85  *
  86  * Use with care! Not exported.
  87  */
  88 static void cl_page_get_trust(struct cl_page *page)
  89 {
  90         LASSERT(atomic_read(&page->cp_ref) > 0);
  91         atomic_inc(&page->cp_ref);
  92 }
  93
  94 /**
  95  * Returns a slice within a page, corresponding to the given layer in the
  96  * device stack.
  97  *
  98  * \see cl_lock_at()
  99  */
 100 static const struct cl_page_slice *
 101 cl_page_at_trusted(const struct cl_page *page,
 102                    const struct lu_device_type *dtype)
 103 {
 104         const struct cl_page_slice *slice;
 105
 106         page = cl_page_top_trusted((struct cl_page *)page);
 107         do {
 108                 list_for_each_entry(slice, &page->cp_layers, cpl_linkage) {
 109                         if (slice->cpl_obj->co_lu.lo_dev->ld_type == dtype)
 110                                 return slice;
 111                 }
 112                 page = page->cp_child;
 113         } while (page);
 114         return NULL;
 115 }
 116
 117 /**
 118  * Returns a page with given index in the given object, or NULL if no page is
 119  * found. Acquires a reference on \a page.
 120  *
 121  * Locking: called under cl_object_header::coh_page_guard spin-lock.
 122  */
 123 struct cl_page *cl_page_lookup(struct cl_object_header *hdr, pgoff_t index)
 124 {
 125         struct cl_page *page;
 126
 127         assert_spin_locked(&hdr->coh_page_guard);
 128
 129         page = radix_tree_lookup(&hdr->coh_tree, index);
 130         if (page)
 131                 cl_page_get_trust(page);
 132         return page;
 133 }
 134 EXPORT_SYMBOL(cl_page_lookup);
 135
 136 /**
 137  * Returns a list of pages by a given [start, end] of \a obj.
 138  *
 139  * \param resched If not NULL, then we give up before hogging CPU for too
 140  * long and set *resched = 1, in that case caller should implement a retry
 141  * logic.
 142  *
 143  * Gang tree lookup (radix_tree_gang_lookup()) optimization is absolutely
 144  * crucial in the face of [offset, EOF] locks.
 145  *
 146  * Return at least one page in @queue unless there is no covered page.
 147  */
 148 int cl_page_gang_lookup(const struct lu_env *env, struct cl_object *obj,
 149                         struct cl_io *io, pgoff_t start, pgoff_t end,
 150                         cl_page_gang_cb_t cb, void *cbdata)
 151 {
 152         struct cl_object_header *hdr;
 153         struct cl_page    *page;
 154         struct cl_page   **pvec;
 155         const struct cl_page_slice  *slice;
 156         const struct lu_device_type *dtype;
 157         pgoff_t           idx;
 158         unsigned int         nr;
 159         unsigned int         i;
 160         unsigned int         j;
 161         int                   res = CLP_GANG_OKAY;
 162         int                   tree_lock = 1;
 163
 164         idx = start;
 165         hdr = cl_object_header(obj);
 166         pvec = cl_env_info(env)->clt_pvec;
 167         dtype = cl_object_top(obj)->co_lu.lo_dev->ld_type;
 168         spin_lock(&hdr->coh_page_guard);
 169         while ((nr = radix_tree_gang_lookup(&hdr->coh_tree, (void **)pvec,
 170                                             idx, CLT_PVEC_SIZE)) > 0) {
 171                 int end_of_region = 0;
 172
 173                 idx = pvec[nr - 1]->cp_index + 1;
 174                 for (i = 0, j = 0; i < nr; ++i) {
 175                         page = pvec[i];
 176                         pvec[i] = NULL;
 177
 178                         LASSERT(page->cp_type == CPT_CACHEABLE);
 179                         if (page->cp_index > end) {
 180                                 end_of_region = 1;
 181                                 break;
 182                         }
 183                         if (page->cp_state == CPS_FREEING)
 184                                 continue;
 185
 186                         slice = cl_page_at_trusted(page, dtype);
 187                         /*
 188                          * Pages for lsm-less file has no underneath sub-page
 189                          * for osc, in case of ...
 190                          */
 191                         PASSERT(env, page, slice);
 192
 193                         page = slice->cpl_page;
 194                         /*
 195                          * Can safely call cl_page_get_trust() under
 196                          * radix-tree spin-lock.
 197                          *
 198                          * XXX not true, because @page is from object another
 199                          * than @hdr and protected by different tree lock.
 200                          */
 201                         cl_page_get_trust(page);
 202                         lu_ref_add_atomic(&page->cp_reference,
 203                                           "gang_lookup", current);
 204                         pvec[j++] = page;
 205                 }
 206
 207                 /*
 208                  * Here a delicate locking dance is performed. Current thread
 209                  * holds a reference to a page, but has to own it before it
 210                  * can be placed into queue. Owning implies waiting, so
 211                  * radix-tree lock is to be released. After a wait one has to
 212                  * check that pages weren't truncated (cl_page_own() returns
 213                  * error in the latter case).
 214                  */
 215                 spin_unlock(&hdr->coh_page_guard);
 216                 tree_lock = 0;
 217
 218                 for (i = 0; i < j; ++i) {
 219                         page = pvec[i];
 220                         if (res == CLP_GANG_OKAY)
 221                                 res = (*cb)(env, io, page, cbdata);
 222                         lu_ref_del(&page->cp_reference,
 223                                    "gang_lookup", current);
 224                         cl_page_put(env, page);
 225                 }
 226                 if (nr < CLT_PVEC_SIZE || end_of_region)
 227                         break;
 228
 229                 if (res == CLP_GANG_OKAY && need_resched())
 230                         res = CLP_GANG_RESCHED;
 231                 if (res != CLP_GANG_OKAY)
 232                         break;
 233
 234                 spin_lock(&hdr->coh_page_guard);
 235                 tree_lock = 1;
 236         }
 237         if (tree_lock)
 238                 spin_unlock(&hdr->coh_page_guard);
 239         return res;
 240 }
 241 EXPORT_SYMBOL(cl_page_gang_lookup);
 242
 243 static void cl_page_free(const struct lu_env *env, struct cl_page *page)
 244 {
 245         struct cl_object *obj  = page->cp_obj;
 246
 247         PASSERT(env, page, list_empty(&page->cp_batch));
 248         PASSERT(env, page, !page->cp_owner);
 249         PASSERT(env, page, !page->cp_req);
 250         PASSERT(env, page, !page->cp_parent);
 251         PASSERT(env, page, page->cp_state == CPS_FREEING);
 252
 253         might_sleep();
 254         while (!list_empty(&page->cp_layers)) {
 255                 struct cl_page_slice *slice;
 256
 257                 slice = list_entry(page->cp_layers.next,
 258                                    struct cl_page_slice, cpl_linkage);
 259                 list_del_init(page->cp_layers.next);
 260                 slice->cpl_ops->cpo_fini(env, slice);
 261         }
 262         lu_object_ref_del_at(&obj->co_lu, &page->cp_obj_ref, "cl_page", page);
 263         cl_object_put(env, obj);
 264         lu_ref_fini(&page->cp_reference);
 265         kfree(page);
 266 }
 267
 268 /**
 269  * Helper function updating page state. This is the only place in the code
 270  * where cl_page::cp_state field is mutated.
 271  */
 272 static inline void cl_page_state_set_trust(struct cl_page *page,
 273                                            enum cl_page_state state)
 274 {
 275         /* bypass const. */
 276         *(enum cl_page_state *)&page->cp_state = state;
 277 }
 278
 279 static struct cl_page *cl_page_alloc(const struct lu_env *env,
 280                                      struct cl_object *o, pgoff_t ind,
 281                                      struct page *vmpage,
 282                                      enum cl_page_type type)
 283 {
 284         struct cl_page    *page;
 285         struct lu_object_header *head;
 286
 287         page = kzalloc(cl_object_header(o)->coh_page_bufsize, GFP_NOFS);
 288         if (page) {
 289                 int result = 0;
 290
 291                 atomic_set(&page->cp_ref, 1);
 292                 if (type == CPT_CACHEABLE) /* for radix tree */
 293                         atomic_inc(&page->cp_ref);
 294                 page->cp_obj = o;
 295                 cl_object_get(o);
 296                 lu_object_ref_add_at(&o->co_lu, &page->cp_obj_ref, "cl_page",
 297                                      page);
 298                 page->cp_index = ind;
 299                 cl_page_state_set_trust(page, CPS_CACHED);
 300                 page->cp_type = type;
 301                 INIT_LIST_HEAD(&page->cp_layers);
 302                 INIT_LIST_HEAD(&page->cp_batch);
 303                 INIT_LIST_HEAD(&page->cp_flight);
 304                 mutex_init(&page->cp_mutex);
 305                 lu_ref_init(&page->cp_reference);
 306                 head = o->co_lu.lo_header;
 307                 list_for_each_entry(o, &head->loh_layers, co_lu.lo_linkage) {
 308                         if (o->co_ops->coo_page_init) {
 309                                 result = o->co_ops->coo_page_init(env, o,
 310                                                                   page, vmpage);
 311                                 if (result != 0) {
 312                                         cl_page_delete0(env, page, 0);
 313                                         cl_page_free(env, page);
 314                                         page = ERR_PTR(result);
 315                                         break;
 316                                 }
 317                         }
 318                 }
 319         } else {
 320                 page = ERR_PTR(-ENOMEM);
 321         }
 322         return page;
 323 }
 324
 325 /**
 326  * Returns a cl_page with index \a idx at the object \a o, and associated with
 327  * the VM page \a vmpage.
 328  *
 329  * This is the main entry point into the cl_page caching interface. First, a
 330  * cache (implemented as a per-object radix tree) is consulted. If page is
 331  * found there, it is returned immediately. Otherwise new page is allocated
 332  * and returned. In any case, additional reference to page is acquired.
 333  *
 334  * \see cl_object_find(), cl_lock_find()
 335  */
 336 static struct cl_page *cl_page_find0(const struct lu_env *env,
 337                                      struct cl_object *o,
 338                                      pgoff_t idx, struct page *vmpage,
 339                                      enum cl_page_type type,
 340                                      struct cl_page *parent)
 341 {
 342         struct cl_page    *page = NULL;
 343         struct cl_page    *ghost = NULL;
 344         struct cl_object_header *hdr;
 345         int err;
 346
 347         LASSERT(type == CPT_CACHEABLE || type == CPT_TRANSIENT);
 348         might_sleep();
 349
 350         hdr = cl_object_header(o);
 351
 352         CDEBUG(D_PAGE, "%lu@"DFID" %p %lx %d\n",
 353                idx, PFID(&hdr->coh_lu.loh_fid), vmpage, vmpage->private, type);
 354         /* fast path. */
 355         if (type == CPT_CACHEABLE) {
 356                 /*
 357                  * vmpage lock is used to protect the child/parent
 358                  * relationship
 359                  */
 360                 KLASSERT(PageLocked(vmpage));
 361                 /*
 362                  * cl_vmpage_page() can be called here without any locks as
 363                  *
 364                  *     - "vmpage" is locked (which prevents ->private from
 365                  *       concurrent updates), and
 366                  *
 367                  *     - "o" cannot be destroyed while current thread holds a
 368                  *       reference on it.
 369                  */
 370                 page = cl_vmpage_page(vmpage, o);
 371                 PINVRNT(env, page,
 372                         ergo(page,
 373                              cl_page_vmpage(env, page) == vmpage &&
 374                              (void *)radix_tree_lookup(&hdr->coh_tree,
 375                                                        idx) == page));
 376         }
 377
 378         if (page)
 379                 return page;
 380
 381         /* allocate and initialize cl_page */
 382         page = cl_page_alloc(env, o, idx, vmpage, type);
 383         if (IS_ERR(page))
 384                 return page;
 385
 386         if (type == CPT_TRANSIENT) {
 387                 if (parent) {
 388                         LASSERT(!page->cp_parent);
 389                         page->cp_parent = parent;
 390                         parent->cp_child = page;
 391                 }
 392                 return page;
 393         }
 394
 395         /*
 396          * XXX optimization: use radix_tree_preload() here, and change tree
 397          * gfp mask to GFP_KERNEL in cl_object_header_init().
 398          */
 399         spin_lock(&hdr->coh_page_guard);
 400         err = radix_tree_insert(&hdr->coh_tree, idx, page);
 401         if (err != 0) {
 402                 ghost = page;
 403                 /*
 404                  * Noted by Jay: a lock on \a vmpage protects cl_page_find()
 405                  * from this race, but
 406                  *
 407                  *     0. it's better to have cl_page interface "locally
 408                  *     consistent" so that its correctness can be reasoned
 409                  *     about without appealing to the (obscure world of) VM
 410                  *     locking.
 411                  *
 412                  *     1. handling this race allows ->coh_tree to remain
 413                  *     consistent even when VM locking is somehow busted,
 414                  *     which is very useful during diagnosing and debugging.
 415                  */
 416                 page = ERR_PTR(err);
 417                 CL_PAGE_DEBUG(D_ERROR, env, ghost,
 418                               "fail to insert into radix tree: %d\n", err);
 419         } else {
 420                 if (parent) {
 421                         LASSERT(!page->cp_parent);
 422                         page->cp_parent = parent;
 423                         parent->cp_child = page;
 424                 }
 425                 hdr->coh_pages++;
 426         }
 427         spin_unlock(&hdr->coh_page_guard);
 428
 429         if (unlikely(ghost)) {
 430                 cl_page_delete0(env, ghost, 0);
 431                 cl_page_free(env, ghost);
 432         }
 433         return page;
 434 }
 435
 436 struct cl_page *cl_page_find(const struct lu_env *env, struct cl_object *o,
 437                              pgoff_t idx, struct page *vmpage,
 438                              enum cl_page_type type)
 439 {
 440         return cl_page_find0(env, o, idx, vmpage, type, NULL);
 441 }
 442 EXPORT_SYMBOL(cl_page_find);
 443
 444 struct cl_page *cl_page_find_sub(const struct lu_env *env, struct cl_object *o,
 445                                  pgoff_t idx, struct page *vmpage,
 446                                  struct cl_page *parent)
 447 {
 448         return cl_page_find0(env, o, idx, vmpage, parent->cp_type, parent);
 449 }
 450 EXPORT_SYMBOL(cl_page_find_sub);
 451
 452 static inline int cl_page_invariant(const struct cl_page *pg)
 453 {
 454         struct cl_object_header *header;
 455         struct cl_page    *parent;
 456         struct cl_page    *child;
 457         struct cl_io        *owner;
 458
 459         /*
 460          * Page invariant is protected by a VM lock.
 461          */
 462         LINVRNT(cl_page_is_vmlocked(NULL, pg));
 463
 464         header = cl_object_header(pg->cp_obj);
 465         parent = pg->cp_parent;
 466         child  = pg->cp_child;
 467         owner  = pg->cp_owner;
 468
 469         return cl_page_in_use(pg) &&
 470                 ergo(parent, parent->cp_child == pg) &&
 471                 ergo(child, child->cp_parent == pg) &&
 472                 ergo(child, pg->cp_obj != child->cp_obj) &&
 473                 ergo(parent, pg->cp_obj != parent->cp_obj) &&
 474                 ergo(owner && parent,
 475                      parent->cp_owner == pg->cp_owner->ci_parent) &&
 476                 ergo(owner && child, child->cp_owner->ci_parent == owner) &&
 477                 /*
 478                  * Either page is early in initialization (has neither child
 479                  * nor parent yet), or it is in the object radix tree.
 480                  */
 481                 ergo(pg->cp_state < CPS_FREEING && pg->cp_type == CPT_CACHEABLE,
 482                      (void *)radix_tree_lookup(&header->coh_tree,
 483                                                pg->cp_index) == pg ||
 484                      (!child && !parent));
 485 }
 486
 487 static void cl_page_state_set0(const struct lu_env *env,
 488                                struct cl_page *page, enum cl_page_state state)
 489 {
 490         enum cl_page_state old;
 491
 492         /*
 493          * Matrix of allowed state transitions [old][new], for sanity
 494          * checking.
 495          */
 496         static const int allowed_transitions[CPS_NR][CPS_NR] = {
 497                 [CPS_CACHED] = {
 498                         [CPS_CACHED]  = 0,
 499                         [CPS_OWNED]   = 1, /* io finds existing cached page */
 500                         [CPS_PAGEIN]  = 0,
 501                         [CPS_PAGEOUT] = 1, /* write-out from the cache */
 502                         [CPS_FREEING] = 1, /* eviction on the memory pressure */
 503                 },
 504                 [CPS_OWNED] = {
 505                         [CPS_CACHED]  = 1, /* release to the cache */
 506                         [CPS_OWNED]   = 0,
 507                         [CPS_PAGEIN]  = 1, /* start read immediately */
 508                         [CPS_PAGEOUT] = 1, /* start write immediately */
 509                         [CPS_FREEING] = 1, /* lock invalidation or truncate */
 510                 },
 511                 [CPS_PAGEIN] = {
 512                         [CPS_CACHED]  = 1, /* io completion */
 513                         [CPS_OWNED]   = 0,
 514                         [CPS_PAGEIN]  = 0,
 515                         [CPS_PAGEOUT] = 0,
 516                         [CPS_FREEING] = 0,
 517                 },
 518                 [CPS_PAGEOUT] = {
 519                         [CPS_CACHED]  = 1, /* io completion */
 520                         [CPS_OWNED]   = 0,
 521                         [CPS_PAGEIN]  = 0,
 522                         [CPS_PAGEOUT] = 0,
 523                         [CPS_FREEING] = 0,
 524                 },
 525                 [CPS_FREEING] = {
 526                         [CPS_CACHED]  = 0,
 527                         [CPS_OWNED]   = 0,
 528                         [CPS_PAGEIN]  = 0,
 529                         [CPS_PAGEOUT] = 0,
 530                         [CPS_FREEING] = 0,
 531                 }
 532         };
 533
 534         old = page->cp_state;
 535         PASSERT(env, page, allowed_transitions[old][state]);
 536         CL_PAGE_HEADER(D_TRACE, env, page, "%d -> %d\n", old, state);
 537         for (; page; page = page->cp_child) {
 538                 PASSERT(env, page, page->cp_state == old);
 539                 PASSERT(env, page,
 540                         equi(state == CPS_OWNED, page->cp_owner));
 541
 542                 cl_page_state_set_trust(page, state);
 543         }
 544 }
 545
 546 static void cl_page_state_set(const struct lu_env *env,
 547                               struct cl_page *page, enum cl_page_state state)
 548 {
 549         cl_page_state_set0(env, page, state);
 550 }
 551
 552 /**
 553  * Acquires an additional reference to a page.
 554  *
 555  * This can be called only by caller already possessing a reference to \a
 556  * page.
 557  *
 558  * \see cl_object_get(), cl_lock_get().
 559  */
 560 void cl_page_get(struct cl_page *page)
 561 {
 562         cl_page_get_trust(page);
 563 }
 564 EXPORT_SYMBOL(cl_page_get);
 565
 566 /**
 567  * Releases a reference to a page.
 568  *
 569  * When last reference is released, page is returned to the cache, unless it
 570  * is in cl_page_state::CPS_FREEING state, in which case it is immediately
 571  * destroyed.
 572  *
 573  * \see cl_object_put(), cl_lock_put().
 574  */
 575 void cl_page_put(const struct lu_env *env, struct cl_page *page)
 576 {
 577         PASSERT(env, page, atomic_read(&page->cp_ref) > !!page->cp_parent);
 578
 579         CL_PAGE_HEADER(D_TRACE, env, page, "%d\n",
 580                        atomic_read(&page->cp_ref));
 581
 582         if (atomic_dec_and_test(&page->cp_ref)) {
 583                 LASSERT(page->cp_state == CPS_FREEING);
 584
 585                 LASSERT(atomic_read(&page->cp_ref) == 0);
 586                 PASSERT(env, page, !page->cp_owner);
 587                 PASSERT(env, page, list_empty(&page->cp_batch));
 588                 /*
 589                  * Page is no longer reachable by other threads. Tear
 590                  * it down.
 591                  */
 592                 cl_page_free(env, page);
 593         }
 594 }
 595 EXPORT_SYMBOL(cl_page_put);
 596
 597 /**
 598  * Returns a VM page associated with a given cl_page.
 599  */
 600 struct page *cl_page_vmpage(const struct lu_env *env, struct cl_page *page)
 601 {
 602         const struct cl_page_slice *slice;
 603
 604         /*
 605          * Find uppermost layer with ->cpo_vmpage() method, and return its
 606          * result.
 607          */
 608         page = cl_page_top(page);
 609         do {
 610                 list_for_each_entry(slice, &page->cp_layers, cpl_linkage) {
 611                         if (slice->cpl_ops->cpo_vmpage)
 612                                 return slice->cpl_ops->cpo_vmpage(env, slice);
 613                 }
 614                 page = page->cp_child;
 615         } while (page);
 616         LBUG(); /* ->cpo_vmpage() has to be defined somewhere in the stack */
 617 }
 618 EXPORT_SYMBOL(cl_page_vmpage);
 619
 620 /**
 621  * Returns a cl_page associated with a VM page, and given cl_object.
 622  */
 623 struct cl_page *cl_vmpage_page(struct page *vmpage, struct cl_object *obj)
 624 {
 625         struct cl_page *top;
 626         struct cl_page *page;
 627
 628         KLASSERT(PageLocked(vmpage));
 629
 630         /*
 631          * NOTE: absence of races and liveness of data are guaranteed by page
 632          *       lock on a "vmpage". That works because object destruction has
 633          *       bottom-to-top pass.
 634          */
 635
 636         /*
 637          * This loop assumes that ->private points to the top-most page. This
 638          * can be rectified easily.
 639          */
 640         top = (struct cl_page *)vmpage->private;
 641         if (!top)
 642                 return NULL;
 643
 644         for (page = top; page; page = page->cp_child) {
 645                 if (cl_object_same(page->cp_obj, obj)) {
 646                         cl_page_get_trust(page);
 647                         break;
 648                 }
 649         }
 650         LASSERT(ergo(page, page->cp_type == CPT_CACHEABLE));
 651         return page;
 652 }
 653 EXPORT_SYMBOL(cl_vmpage_page);
 654
 655 /**
 656  * Returns the top-page for a given page.
 657  *
 658  * \see cl_object_top(), cl_io_top()
 659  */
 660 struct cl_page *cl_page_top(struct cl_page *page)
 661 {
 662         return cl_page_top_trusted(page);
 663 }
 664 EXPORT_SYMBOL(cl_page_top);
 665
 666 const struct cl_page_slice *cl_page_at(const struct cl_page *page,
 667                                        const struct lu_device_type *dtype)
 668 {
 669         return cl_page_at_trusted(page, dtype);
 670 }
 671 EXPORT_SYMBOL(cl_page_at);
 672
 673 #define CL_PAGE_OP(opname) offsetof(struct cl_page_operations, opname)
 674
 675 #define CL_PAGE_INVOKE(_env, _page, _op, _proto, ...)              \
 676 ({                                                                    \
 677         const struct lu_env     *__env  = (_env);                   \
 678         struct cl_page       *__page = (_page);            \
 679         const struct cl_page_slice *__scan;                          \
 680         int                      __result;                         \
 681         ptrdiff_t                  __op   = (_op);                   \
 682         int                    (*__method)_proto;                   \
 683                                                                         \
 684         __result = 0;                                              \
 685         __page = cl_page_top(__page);                              \
 686         do {                                                        \
 687                 list_for_each_entry(__scan, &__page->cp_layers,     \
 688                                         cpl_linkage) {            \
 689                         __method = *(void **)((char *)__scan->cpl_ops + \
 690                                               __op);                \
 691                         if (__method) {                                 \
 692                                 __result = (*__method)(__env, __scan,   \
 693                                                        ## __VA_ARGS__); \
 694                                 if (__result != 0)                    \
 695                                         break;                    \
 696                         }                                              \
 697                 }                                                      \
 698                 __page = __page->cp_child;                            \
 699         } while (__page && __result == 0);                            \
 700         if (__result > 0)                                              \
 701                 __result = 0;                                      \
 702         __result;                                                      \
 703 })
 704
 705 #define CL_PAGE_INVOID(_env, _page, _op, _proto, ...)              \
 706 do {                                                                \
 707         const struct lu_env     *__env  = (_env);                   \
 708         struct cl_page       *__page = (_page);            \
 709         const struct cl_page_slice *__scan;                          \
 710         ptrdiff_t                  __op   = (_op);                   \
 711         void                  (*__method)_proto;                    \
 712                                                                         \
 713         __page = cl_page_top(__page);                              \
 714         do {                                                        \
 715                 list_for_each_entry(__scan, &__page->cp_layers,     \
 716                                         cpl_linkage) {            \
 717                         __method = *(void **)((char *)__scan->cpl_ops + \
 718                                               __op);                \
 719                         if (__method)                              \
 720                                 (*__method)(__env, __scan,            \
 721                                             ## __VA_ARGS__);        \
 722                 }                                                      \
 723                 __page = __page->cp_child;                            \
 724         } while (__page);                                              \
 725 } while (0)
 726
 727 #define CL_PAGE_INVOID_REVERSE(_env, _page, _op, _proto, ...)          \
 728 do {                                                                    \
 729         const struct lu_env     *__env  = (_env);                       \
 730         struct cl_page       *__page = (_page);                \
 731         const struct cl_page_slice *__scan;                              \
 732         ptrdiff_t                  __op   = (_op);                       \
 733         void                  (*__method)_proto;                        \
 734                                                                             \
 735         /* get to the bottom page. */                                  \
 736         while (__page->cp_child)                                            \
 737                 __page = __page->cp_child;                                \
 738         do {                                                            \
 739                 list_for_each_entry_reverse(__scan, &__page->cp_layers, \
 740                                                 cpl_linkage) {        \
 741                         __method = *(void **)((char *)__scan->cpl_ops +     \
 742                                               __op);                    \
 743                         if (__method)                                  \
 744                                 (*__method)(__env, __scan,                \
 745                                             ## __VA_ARGS__);            \
 746                 }                                                          \
 747                 __page = __page->cp_parent;                              \
 748         } while (__page);                                                  \
 749 } while (0)
 750
 751 static int cl_page_invoke(const struct lu_env *env,
 752                           struct cl_io *io, struct cl_page *page, ptrdiff_t op)
 753
 754 {
 755         PINVRNT(env, page, cl_object_same(page->cp_obj, io->ci_obj));
 756         return CL_PAGE_INVOKE(env, page, op,
 757                               (const struct lu_env *,
 758                                const struct cl_page_slice *, struct cl_io *),
 759                               io);
 760 }
 761
 762 static void cl_page_invoid(const struct lu_env *env,
 763                            struct cl_io *io, struct cl_page *page, ptrdiff_t op)
 764
 765 {
 766         PINVRNT(env, page, cl_object_same(page->cp_obj, io->ci_obj));
 767         CL_PAGE_INVOID(env, page, op,
 768                        (const struct lu_env *,
 769                         const struct cl_page_slice *, struct cl_io *), io);
 770 }
 771
 772 static void cl_page_owner_clear(struct cl_page *page)
 773 {
 774         for (page = cl_page_top(page); page; page = page->cp_child) {
 775                 if (page->cp_owner) {
 776                         LASSERT(page->cp_owner->ci_owned_nr > 0);
 777                         page->cp_owner->ci_owned_nr--;
 778                         page->cp_owner = NULL;
 779                         page->cp_task = NULL;
 780                 }
 781         }
 782 }
 783
 784 static void cl_page_owner_set(struct cl_page *page)
 785 {
 786         for (page = cl_page_top(page); page; page = page->cp_child)
 787                 page->cp_owner->ci_owned_nr++;
 788 }
 789
 790 void cl_page_disown0(const struct lu_env *env,
 791                      struct cl_io *io, struct cl_page *pg)
 792 {
 793         enum cl_page_state state;
 794
 795         state = pg->cp_state;
 796         PINVRNT(env, pg, state == CPS_OWNED || state == CPS_FREEING);
 797         PINVRNT(env, pg, cl_page_invariant(pg));
 798         cl_page_owner_clear(pg);
 799
 800         if (state == CPS_OWNED)
 801                 cl_page_state_set(env, pg, CPS_CACHED);
 802         /*
 803          * Completion call-backs are executed in the bottom-up order, so that
 804          * uppermost layer (llite), responsible for VFS/VM interaction runs
 805          * last and can release locks safely.
 806          */
 807         CL_PAGE_INVOID_REVERSE(env, pg, CL_PAGE_OP(cpo_disown),
 808                                (const struct lu_env *,
 809                                 const struct cl_page_slice *, struct cl_io *),
 810                                io);
 811 }
 812
 813 /**
 814  * returns true, iff page is owned by the given io.
 815  */
 816 int cl_page_is_owned(const struct cl_page *pg, const struct cl_io *io)
 817 {
 818         LINVRNT(cl_object_same(pg->cp_obj, io->ci_obj));
 819         return pg->cp_state == CPS_OWNED && pg->cp_owner == io;
 820 }
 821 EXPORT_SYMBOL(cl_page_is_owned);
 822
 823 /**
 824  * Try to own a page by IO.
 825  *
 826  * Waits until page is in cl_page_state::CPS_CACHED state, and then switch it
 827  * into cl_page_state::CPS_OWNED state.
 828  *
 829  * \pre  !cl_page_is_owned(pg, io)
 830  * \post result == 0 iff cl_page_is_owned(pg, io)
 831  *
 832  * \retval 0   success
 833  *
 834  * \retval -ve failure, e.g., page was destroyed (and landed in
 835  *           cl_page_state::CPS_FREEING instead of cl_page_state::CPS_CACHED).
 836  *           or, page was owned by another thread, or in IO.
 837  *
 838  * \see cl_page_disown()
 839  * \see cl_page_operations::cpo_own()
 840  * \see cl_page_own_try()
 841  * \see cl_page_own
 842  */
 843 static int cl_page_own0(const struct lu_env *env, struct cl_io *io,
 844                         struct cl_page *pg, int nonblock)
 845 {
 846         int result;
 847
 848         PINVRNT(env, pg, !cl_page_is_owned(pg, io));
 849
 850         pg = cl_page_top(pg);
 851         io = cl_io_top(io);
 852
 853         if (pg->cp_state == CPS_FREEING) {
 854                 result = -ENOENT;
 855         } else {
 856                 result = CL_PAGE_INVOKE(env, pg, CL_PAGE_OP(cpo_own),
 857                                         (const struct lu_env *,
 858                                          const struct cl_page_slice *,
 859                                          struct cl_io *, int),
 860                                         io, nonblock);
 861                 if (result == 0) {
 862                         PASSERT(env, pg, !pg->cp_owner);
 863                         PASSERT(env, pg, !pg->cp_req);
 864                         pg->cp_owner = io;
 865                         pg->cp_task  = current;
 866                         cl_page_owner_set(pg);
 867                         if (pg->cp_state != CPS_FREEING) {
 868                                 cl_page_state_set(env, pg, CPS_OWNED);
 869                         } else {
 870                                 cl_page_disown0(env, io, pg);
 871                                 result = -ENOENT;
 872                         }
 873                 }
 874         }
 875         PINVRNT(env, pg, ergo(result == 0, cl_page_invariant(pg)));
 876         return result;
 877 }
 878
 879 /**
 880  * Own a page, might be blocked.
 881  *
 882  * \see cl_page_own0()
 883  */
 884 int cl_page_own(const struct lu_env *env, struct cl_io *io, struct cl_page *pg)
 885 {
 886         return cl_page_own0(env, io, pg, 0);
 887 }
 888 EXPORT_SYMBOL(cl_page_own);
 889
 890 /**
 891  * Nonblock version of cl_page_own().
 892  *
 893  * \see cl_page_own0()
 894  */
 895 int cl_page_own_try(const struct lu_env *env, struct cl_io *io,
 896                     struct cl_page *pg)
 897 {
 898         return cl_page_own0(env, io, pg, 1);
 899 }
 900 EXPORT_SYMBOL(cl_page_own_try);
 901
 902 /**
 903  * Assume page ownership.
 904  *
 905  * Called when page is already locked by the hosting VM.
 906  *
 907  * \pre !cl_page_is_owned(pg, io)
 908  * \post cl_page_is_owned(pg, io)
 909  *
 910  * \see cl_page_operations::cpo_assume()
 911  */
 912 void cl_page_assume(const struct lu_env *env,
 913                     struct cl_io *io, struct cl_page *pg)
 914 {
 915         PINVRNT(env, pg, cl_object_same(pg->cp_obj, io->ci_obj));
 916
 917         pg = cl_page_top(pg);
 918         io = cl_io_top(io);
 919
 920         cl_page_invoid(env, io, pg, CL_PAGE_OP(cpo_assume));
 921         PASSERT(env, pg, !pg->cp_owner);
 922         pg->cp_owner = io;
 923         pg->cp_task = current;
 924         cl_page_owner_set(pg);
 925         cl_page_state_set(env, pg, CPS_OWNED);
 926 }
 927 EXPORT_SYMBOL(cl_page_assume);
 928
 929 /**
 930  * Releases page ownership without unlocking the page.
 931  *
 932  * Moves page into cl_page_state::CPS_CACHED without releasing a lock on the
 933  * underlying VM page (as VM is supposed to do this itself).
 934  *
 935  * \pre   cl_page_is_owned(pg, io)
 936  * \post !cl_page_is_owned(pg, io)
 937  *
 938  * \see cl_page_assume()
 939  */
 940 void cl_page_unassume(const struct lu_env *env,
 941                       struct cl_io *io, struct cl_page *pg)
 942 {
 943         PINVRNT(env, pg, cl_page_is_owned(pg, io));
 944         PINVRNT(env, pg, cl_page_invariant(pg));
 945
 946         pg = cl_page_top(pg);
 947         io = cl_io_top(io);
 948         cl_page_owner_clear(pg);
 949         cl_page_state_set(env, pg, CPS_CACHED);
 950         CL_PAGE_INVOID_REVERSE(env, pg, CL_PAGE_OP(cpo_unassume),
 951                                (const struct lu_env *,
 952                                 const struct cl_page_slice *, struct cl_io *),
 953                                io);
 954 }
 955 EXPORT_SYMBOL(cl_page_unassume);
 956
 957 /**
 958  * Releases page ownership.
 959  *
 960  * Moves page into cl_page_state::CPS_CACHED.
 961  *
 962  * \pre   cl_page_is_owned(pg, io)
 963  * \post !cl_page_is_owned(pg, io)
 964  *
 965  * \see cl_page_own()
 966  * \see cl_page_operations::cpo_disown()
 967  */
 968 void cl_page_disown(const struct lu_env *env,
 969                     struct cl_io *io, struct cl_page *pg)
 970 {
 971         PINVRNT(env, pg, cl_page_is_owned(pg, io));
 972
 973         pg = cl_page_top(pg);
 974         io = cl_io_top(io);
 975         cl_page_disown0(env, io, pg);
 976 }
 977 EXPORT_SYMBOL(cl_page_disown);
 978
 979 /**
 980  * Called when page is to be removed from the object, e.g., as a result of
 981  * truncate.
 982  *
 983  * Calls cl_page_operations::cpo_discard() top-to-bottom.
 984  *
 985  * \pre cl_page_is_owned(pg, io)
 986  *
 987  * \see cl_page_operations::cpo_discard()
 988  */
 989 void cl_page_discard(const struct lu_env *env,
 990                      struct cl_io *io, struct cl_page *pg)
 991 {
 992         PINVRNT(env, pg, cl_page_is_owned(pg, io));
 993         PINVRNT(env, pg, cl_page_invariant(pg));
 994
 995         cl_page_invoid(env, io, pg, CL_PAGE_OP(cpo_discard));
 996 }
 997 EXPORT_SYMBOL(cl_page_discard);
 998
 999 /**
1000  * Version of cl_page_delete() that can be called for not fully constructed
1001  * pages, e.g,. in a error handling cl_page_find()->cl_page_delete0()
1002  * path. Doesn't check page invariant.
1003  */
1004 static void cl_page_delete0(const struct lu_env *env, struct cl_page *pg,
1005                             int radix)
1006 {
1007         struct cl_page *tmp = pg;
1008
1009         PASSERT(env, pg, pg == cl_page_top(pg));
1010         PASSERT(env, pg, pg->cp_state != CPS_FREEING);
1011
1012         /*
1013          * Severe all ways to obtain new pointers to @pg.
1014          */
1015         cl_page_owner_clear(pg);
1016
1017         /*
1018          * unexport the page firstly before freeing it so that
1019          * the page content is considered to be invalid.
1020          * We have to do this because a CPS_FREEING cl_page may
1021          * be NOT under the protection of a cl_lock.
1022          * Afterwards, if this page is found by other threads, then this
1023          * page will be forced to reread.
1024          */
1025         cl_page_export(env, pg, 0);
1026         cl_page_state_set0(env, pg, CPS_FREEING);
1027
1028         CL_PAGE_INVOID(env, pg, CL_PAGE_OP(cpo_delete),
1029                        (const struct lu_env *, const struct cl_page_slice *));
1030
1031         if (tmp->cp_type == CPT_CACHEABLE) {
1032                 if (!radix)
1033                         /* !radix means that @pg is not yet in the radix tree,
1034                          * skip removing it.
1035                          */
1036                         tmp = pg->cp_child;
1037                 for (; tmp; tmp = tmp->cp_child) {
1038                         void                *value;
1039                         struct cl_object_header *hdr;
1040
1041                         hdr = cl_object_header(tmp->cp_obj);
1042                         spin_lock(&hdr->coh_page_guard);
1043                         value = radix_tree_delete(&hdr->coh_tree,
1044                                                   tmp->cp_index);
1045                         PASSERT(env, tmp, value == tmp);
1046                         PASSERT(env, tmp, hdr->coh_pages > 0);
1047                         hdr->coh_pages--;
1048                         spin_unlock(&hdr->coh_page_guard);
1049                         cl_page_put(env, tmp);
1050                 }
1051         }
1052 }
1053
1054 /**
1055  * Called when a decision is made to throw page out of memory.
1056  *
1057  * Notifies all layers about page destruction by calling
1058  * cl_page_operations::cpo_delete() method top-to-bottom.
1059  *
1060  * Moves page into cl_page_state::CPS_FREEING state (this is the only place
1061  * where transition to this state happens).
1062  *
1063  * Eliminates all venues through which new references to the page can be
1064  * obtained:
1065  *
1066  *     - removes page from the radix trees,
1067  *
1068  *     - breaks linkage from VM page to cl_page.
1069  *
1070  * Once page reaches cl_page_state::CPS_FREEING, all remaining references will
1071  * drain after some time, at which point page will be recycled.
1072  *
1073  * \pre  pg == cl_page_top(pg)
1074  * \pre  VM page is locked
1075  * \post pg->cp_state == CPS_FREEING
1076  *
1077  * \see cl_page_operations::cpo_delete()
1078  */
1079 void cl_page_delete(const struct lu_env *env, struct cl_page *pg)
1080 {
1081         PINVRNT(env, pg, cl_page_invariant(pg));
1082         cl_page_delete0(env, pg, 1);
1083 }
1084 EXPORT_SYMBOL(cl_page_delete);
1085
1086 /**
1087  * Unmaps page from user virtual memory.
1088  *
1089  * Calls cl_page_operations::cpo_unmap() through all layers top-to-bottom. The
1090  * layer responsible for VM interaction has to unmap page from user space
1091  * virtual memory.
1092  *
1093  * \see cl_page_operations::cpo_unmap()
1094  */
1095 int cl_page_unmap(const struct lu_env *env,
1096                   struct cl_io *io, struct cl_page *pg)
1097 {
1098         PINVRNT(env, pg, cl_page_is_owned(pg, io));
1099         PINVRNT(env, pg, cl_page_invariant(pg));
1100
1101         return cl_page_invoke(env, io, pg, CL_PAGE_OP(cpo_unmap));
1102 }
1103 EXPORT_SYMBOL(cl_page_unmap);
1104
1105 /**
1106  * Marks page up-to-date.
1107  *
1108  * Call cl_page_operations::cpo_export() through all layers top-to-bottom. The
1109  * layer responsible for VM interaction has to mark/clear page as up-to-date
1110  * by the \a uptodate argument.
1111  *
1112  * \see cl_page_operations::cpo_export()
1113  */
1114 void cl_page_export(const struct lu_env *env, struct cl_page *pg, int uptodate)
1115 {
1116         PINVRNT(env, pg, cl_page_invariant(pg));
1117         CL_PAGE_INVOID(env, pg, CL_PAGE_OP(cpo_export),
1118                        (const struct lu_env *,
1119                         const struct cl_page_slice *, int), uptodate);
1120 }
1121 EXPORT_SYMBOL(cl_page_export);
1122
1123 /**
1124  * Returns true, iff \a pg is VM locked in a suitable sense by the calling
1125  * thread.
1126  */
1127 int cl_page_is_vmlocked(const struct lu_env *env, const struct cl_page *pg)
1128 {
1129         int result;
1130         const struct cl_page_slice *slice;
1131
1132         pg = cl_page_top_trusted((struct cl_page *)pg);
1133         slice = container_of(pg->cp_layers.next,
1134                              const struct cl_page_slice, cpl_linkage);
1135         PASSERT(env, pg, slice->cpl_ops->cpo_is_vmlocked);
1136         /*
1137          * Call ->cpo_is_vmlocked() directly instead of going through
1138          * CL_PAGE_INVOKE(), because cl_page_is_vmlocked() is used by
1139          * cl_page_invariant().
1140          */
1141         result = slice->cpl_ops->cpo_is_vmlocked(env, slice);
1142         PASSERT(env, pg, result == -EBUSY || result == -ENODATA);
1143         return result == -EBUSY;
1144 }
1145 EXPORT_SYMBOL(cl_page_is_vmlocked);
1146
1147 static enum cl_page_state cl_req_type_state(enum cl_req_type crt)
1148 {
1149         return crt == CRT_WRITE ? CPS_PAGEOUT : CPS_PAGEIN;
1150 }
1151
1152 static void cl_page_io_start(const struct lu_env *env,
1153                              struct cl_page *pg, enum cl_req_type crt)
1154 {
1155         /*
1156          * Page is queued for IO, change its state.
1157          */
1158         cl_page_owner_clear(pg);
1159         cl_page_state_set(env, pg, cl_req_type_state(crt));
1160 }
1161
1162 /**
1163  * Prepares page for immediate transfer. cl_page_operations::cpo_prep() is
1164  * called top-to-bottom. Every layer either agrees to submit this page (by
1165  * returning 0), or requests to omit this page (by returning -EALREADY). Layer
1166  * handling interactions with the VM also has to inform VM that page is under
1167  * transfer now.
1168  */
1169 int cl_page_prep(const struct lu_env *env, struct cl_io *io,
1170                  struct cl_page *pg, enum cl_req_type crt)
1171 {
1172         int result;
1173
1174         PINVRNT(env, pg, cl_page_is_owned(pg, io));
1175         PINVRNT(env, pg, cl_page_invariant(pg));
1176         PINVRNT(env, pg, crt < CRT_NR);
1177
1178         /*
1179          * XXX this has to be called bottom-to-top, so that llite can set up
1180          * PG_writeback without risking other layers deciding to skip this
1181          * page.
1182          */
1183         if (crt >= CRT_NR)
1184                 return -EINVAL;
1185         result = cl_page_invoke(env, io, pg, CL_PAGE_OP(io[crt].cpo_prep));
1186         if (result == 0)
1187                 cl_page_io_start(env, pg, crt);
1188
1189         CL_PAGE_HEADER(D_TRACE, env, pg, "%d %d\n", crt, result);
1190         return result;
1191 }
1192 EXPORT_SYMBOL(cl_page_prep);
1193
1194 /**
1195  * Notify layers about transfer completion.
1196  *
1197  * Invoked by transfer sub-system (which is a part of osc) to notify layers
1198  * that a transfer, of which this page is a part of has completed.
1199  *
1200  * Completion call-backs are executed in the bottom-up order, so that
1201  * uppermost layer (llite), responsible for the VFS/VM interaction runs last
1202  * and can release locks safely.
1203  *
1204  * \pre  pg->cp_state == CPS_PAGEIN || pg->cp_state == CPS_PAGEOUT
1205  * \post pg->cp_state == CPS_CACHED
1206  *
1207  * \see cl_page_operations::cpo_completion()
1208  */
1209 void cl_page_completion(const struct lu_env *env,
1210                         struct cl_page *pg, enum cl_req_type crt, int ioret)
1211 {
1212         struct cl_sync_io *anchor = pg->cp_sync_io;
1213
1214         PASSERT(env, pg, crt < CRT_NR);
1215         /* cl_page::cp_req already cleared by the caller (osc_completion()) */
1216         PASSERT(env, pg, !pg->cp_req);
1217         PASSERT(env, pg, pg->cp_state == cl_req_type_state(crt));
1218
1219         CL_PAGE_HEADER(D_TRACE, env, pg, "%d %d\n", crt, ioret);
1220         if (crt == CRT_READ && ioret == 0) {
1221                 PASSERT(env, pg, !(pg->cp_flags & CPF_READ_COMPLETED));
1222                 pg->cp_flags |= CPF_READ_COMPLETED;
1223         }
1224
1225         cl_page_state_set(env, pg, CPS_CACHED);
1226         if (crt >= CRT_NR)
1227                 return;
1228         CL_PAGE_INVOID_REVERSE(env, pg, CL_PAGE_OP(io[crt].cpo_completion),
1229                                (const struct lu_env *,
1230                                 const struct cl_page_slice *, int), ioret);
1231         if (anchor) {
1232                 LASSERT(cl_page_is_vmlocked(env, pg));
1233                 LASSERT(pg->cp_sync_io == anchor);
1234                 pg->cp_sync_io = NULL;
1235         }
1236         /*
1237          * As page->cp_obj is pinned by a reference from page->cp_req, it is
1238          * safe to call cl_page_put() without risking object destruction in a
1239          * non-blocking context.
1240          */
1241         cl_page_put(env, pg);
1242
1243         if (anchor)
1244                 cl_sync_io_note(anchor, ioret);
1245 }
1246 EXPORT_SYMBOL(cl_page_completion);
1247
1248 /**
1249  * Notify layers that transfer formation engine decided to yank this page from
1250  * the cache and to make it a part of a transfer.
1251  *
1252  * \pre  pg->cp_state == CPS_CACHED
1253  * \post pg->cp_state == CPS_PAGEIN || pg->cp_state == CPS_PAGEOUT
1254  *
1255  * \see cl_page_operations::cpo_make_ready()
1256  */
1257 int cl_page_make_ready(const struct lu_env *env, struct cl_page *pg,
1258                        enum cl_req_type crt)
1259 {
1260         int result;
1261
1262         PINVRNT(env, pg, crt < CRT_NR);
1263
1264         if (crt >= CRT_NR)
1265                 return -EINVAL;
1266         result = CL_PAGE_INVOKE(env, pg, CL_PAGE_OP(io[crt].cpo_make_ready),
1267                                 (const struct lu_env *,
1268                                  const struct cl_page_slice *));
1269         if (result == 0) {
1270                 PASSERT(env, pg, pg->cp_state == CPS_CACHED);
1271                 cl_page_io_start(env, pg, crt);
1272         }
1273         CL_PAGE_HEADER(D_TRACE, env, pg, "%d %d\n", crt, result);
1274         return result;
1275 }
1276 EXPORT_SYMBOL(cl_page_make_ready);
1277
1278 /**
1279  * Notify layers that high level io decided to place this page into a cache
1280  * for future transfer.
1281  *
1282  * The layer implementing transfer engine (osc) has to register this page in
1283  * its queues.
1284  *
1285  * \pre  cl_page_is_owned(pg, io)
1286  * \post cl_page_is_owned(pg, io)
1287  *
1288  * \see cl_page_operations::cpo_cache_add()
1289  */
1290 int cl_page_cache_add(const struct lu_env *env, struct cl_io *io,
1291                       struct cl_page *pg, enum cl_req_type crt)
1292 {
1293         const struct cl_page_slice *scan;
1294         int result = 0;
1295
1296         PINVRNT(env, pg, crt < CRT_NR);
1297         PINVRNT(env, pg, cl_page_is_owned(pg, io));
1298         PINVRNT(env, pg, cl_page_invariant(pg));
1299
1300         if (crt >= CRT_NR)
1301                 return -EINVAL;
1302
1303         list_for_each_entry(scan, &pg->cp_layers, cpl_linkage) {
1304                 if (!scan->cpl_ops->io[crt].cpo_cache_add)
1305                         continue;
1306
1307                 result = scan->cpl_ops->io[crt].cpo_cache_add(env, scan, io);
1308                 if (result != 0)
1309                         break;
1310         }
1311         CL_PAGE_HEADER(D_TRACE, env, pg, "%d %d\n", crt, result);
1312         return result;
1313 }
1314 EXPORT_SYMBOL(cl_page_cache_add);
1315
1316 /**
1317  * Called if a pge is being written back by kernel's intention.
1318  *
1319  * \pre  cl_page_is_owned(pg, io)
1320  * \post ergo(result == 0, pg->cp_state == CPS_PAGEOUT)
1321  *
1322  * \see cl_page_operations::cpo_flush()
1323  */
1324 int cl_page_flush(const struct lu_env *env, struct cl_io *io,
1325                   struct cl_page *pg)
1326 {
1327         int result;
1328
1329         PINVRNT(env, pg, cl_page_is_owned(pg, io));
1330         PINVRNT(env, pg, cl_page_invariant(pg));
1331
1332         result = cl_page_invoke(env, io, pg, CL_PAGE_OP(cpo_flush));
1333
1334         CL_PAGE_HEADER(D_TRACE, env, pg, "%d\n", result);
1335         return result;
1336 }
1337 EXPORT_SYMBOL(cl_page_flush);
1338
1339 /**
1340  * Checks whether page is protected by any extent lock is at least required
1341  * mode.
1342  *
1343  * \return the same as in cl_page_operations::cpo_is_under_lock() method.
1344  * \see cl_page_operations::cpo_is_under_lock()
1345  */
1346 int cl_page_is_under_lock(const struct lu_env *env, struct cl_io *io,
1347                           struct cl_page *page)
1348 {
1349         int rc;
1350
1351         PINVRNT(env, page, cl_page_invariant(page));
1352
1353         rc = CL_PAGE_INVOKE(env, page, CL_PAGE_OP(cpo_is_under_lock),
1354                             (const struct lu_env *,
1355                              const struct cl_page_slice *, struct cl_io *),
1356                             io);
1357         PASSERT(env, page, rc != 0);
1358         return rc;
1359 }
1360 EXPORT_SYMBOL(cl_page_is_under_lock);
1361
1362 static int page_prune_cb(const struct lu_env *env, struct cl_io *io,
1363                          struct cl_page *page, void *cbdata)
1364 {
1365         cl_page_own(env, io, page);
1366         cl_page_unmap(env, io, page);
1367         cl_page_discard(env, io, page);
1368         cl_page_disown(env, io, page);
1369         return CLP_GANG_OKAY;
1370 }
1371
1372 /**
1373  * Purges all cached pages belonging to the object \a obj.
1374  */
1375 int cl_pages_prune(const struct lu_env *env, struct cl_object *clobj)
1376 {
1377         struct cl_thread_info   *info;
1378         struct cl_object        *obj = cl_object_top(clobj);
1379         struct cl_io        *io;
1380         int                   result;
1381
1382         info  = cl_env_info(env);
1383         io    = &info->clt_io;
1384
1385         /*
1386          * initialize the io. This is ugly since we never do IO in this
1387          * function, we just make cl_page_list functions happy. -jay
1388          */
1389         io->ci_obj = obj;
1390         io->ci_ignore_layout = 1;
1391         result = cl_io_init(env, io, CIT_MISC, obj);
1392         if (result != 0) {
1393                 cl_io_fini(env, io);
1394                 return io->ci_result;
1395         }
1396
1397         do {
1398                 result = cl_page_gang_lookup(env, obj, io, 0, CL_PAGE_EOF,
1399                                              page_prune_cb, NULL);
1400                 if (result == CLP_GANG_RESCHED)
1401                         cond_resched();
1402         } while (result != CLP_GANG_OKAY);
1403
1404         cl_io_fini(env, io);
1405         return result;
1406 }
1407 EXPORT_SYMBOL(cl_pages_prune);
1408
1409 /**
1410  * Tells transfer engine that only part of a page is to be transmitted.
1411  *
1412  * \see cl_page_operations::cpo_clip()
1413  */
1414 void cl_page_clip(const struct lu_env *env, struct cl_page *pg,
1415                   int from, int to)
1416 {
1417         PINVRNT(env, pg, cl_page_invariant(pg));
1418
1419         CL_PAGE_HEADER(D_TRACE, env, pg, "%d %d\n", from, to);
1420         CL_PAGE_INVOID(env, pg, CL_PAGE_OP(cpo_clip),
1421                        (const struct lu_env *,
1422                         const struct cl_page_slice *, int, int),
1423                        from, to);
1424 }
1425 EXPORT_SYMBOL(cl_page_clip);
1426
1427 /**
1428  * Prints human readable representation of \a pg to the \a f.
1429  */
1430 void cl_page_header_print(const struct lu_env *env, void *cookie,
1431                           lu_printer_t printer, const struct cl_page *pg)
1432 {
1433         (*printer)(env, cookie,
1434                    "page@%p[%d %p:%lu ^%p_%p %d %d %d %p %p %#x]\n",
1435                    pg, atomic_read(&pg->cp_ref), pg->cp_obj,
1436                    pg->cp_index, pg->cp_parent, pg->cp_child,
1437                    pg->cp_state, pg->cp_error, pg->cp_type,
1438                    pg->cp_owner, pg->cp_req, pg->cp_flags);
1439 }
1440 EXPORT_SYMBOL(cl_page_header_print);
1441
1442 /**
1443  * Prints human readable representation of \a pg to the \a f.
1444  */
1445 void cl_page_print(const struct lu_env *env, void *cookie,
1446                    lu_printer_t printer, const struct cl_page *pg)
1447 {
1448         struct cl_page *scan;
1449
1450         for (scan = cl_page_top((struct cl_page *)pg); scan;
1451              scan = scan->cp_child)
1452                 cl_page_header_print(env, cookie, printer, scan);
1453         CL_PAGE_INVOKE(env, (struct cl_page *)pg, CL_PAGE_OP(cpo_print),
1454                        (const struct lu_env *env,
1455                         const struct cl_page_slice *slice,
1456                         void *cookie, lu_printer_t p), cookie, printer);
1457         (*printer)(env, cookie, "end page@%p\n", pg);
1458 }
1459 EXPORT_SYMBOL(cl_page_print);
1460
1461 /**
1462  * Cancel a page which is still in a transfer.
1463  */
1464 int cl_page_cancel(const struct lu_env *env, struct cl_page *page)
1465 {
1466         return CL_PAGE_INVOKE(env, page, CL_PAGE_OP(cpo_cancel),
1467                               (const struct lu_env *,
1468                                const struct cl_page_slice *));
1469 }
1470 EXPORT_SYMBOL(cl_page_cancel);
1471
1472 /**
1473  * Converts a byte offset within object \a obj into a page index.
1474  */
1475 loff_t cl_offset(const struct cl_object *obj, pgoff_t idx)
1476 {
1477         /*
1478          * XXX for now.
1479          */
1480         return (loff_t)idx << PAGE_CACHE_SHIFT;
1481 }
1482 EXPORT_SYMBOL(cl_offset);
1483
1484 /**
1485  * Converts a page index into a byte offset within object \a obj.
1486  */
1487 pgoff_t cl_index(const struct cl_object *obj, loff_t offset)
1488 {
1489         /*
1490          * XXX for now.
1491          */
1492         return offset >> PAGE_CACHE_SHIFT;
1493 }
1494 EXPORT_SYMBOL(cl_index);
1495
1496 int cl_page_size(const struct cl_object *obj)
1497 {
1498         return 1 << PAGE_CACHE_SHIFT;
1499 }
1500 EXPORT_SYMBOL(cl_page_size);
1501
1502 /**
1503  * Adds page slice to the compound page.
1504  *
1505  * This is called by cl_object_operations::coo_page_init() methods to add a
1506  * per-layer state to the page. New state is added at the end of
1507  * cl_page::cp_layers list, that is, it is at the bottom of the stack.
1508  *
1509  * \see cl_lock_slice_add(), cl_req_slice_add(), cl_io_slice_add()
1510  */
1511 void cl_page_slice_add(struct cl_page *page, struct cl_page_slice *slice,
1512                        struct cl_object *obj,
1513                        const struct cl_page_operations *ops)
1514 {
1515         list_add_tail(&slice->cpl_linkage, &page->cp_layers);
1516         slice->cpl_obj  = obj;
1517         slice->cpl_ops  = ops;
1518         slice->cpl_page = page;
1519 }
1520 EXPORT_SYMBOL(cl_page_slice_add);
1521
1522 int  cl_page_init(void)
1523 {
1524         return 0;
1525 }
1526
1527 void cl_page_fini(void)
1528 {
1529 }