lustre/osc/osc_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, Whamcloud, Inc.
  31  */
  32 /*
  33  * This file is part of Lustre, http://www.lustre.org/
  34  * Lustre is a trademark of Sun Microsystems, Inc.
  35  *
  36  * Implementation of cl_page for OSC layer.
  37  *
  38  *   Author: Nikita Danilov <nikita.danilov@sun.com>
  39  */
  40
  41 #define DEBUG_SUBSYSTEM S_OSC
  42
  43 #include "osc_cl_internal.h"
  44
  45 /** \addtogroup osc
  46  *  @{
  47  */
  48
  49 /*
  50  * Comment out osc_page_protected because it may sleep inside the
  51  * the client_obd_list_lock.
  52  * client_obd_list_lock -> osc_ap_completion -> osc_completion ->
  53  *   -> osc_page_protected -> osc_page_is_dlocked -> osc_match_base
  54  *   -> ldlm_lock_match -> sptlrpc_import_check_ctx -> sleep.
  55  */
  56 #if 0
  57 static int osc_page_is_dlocked(const struct lu_env *env,
  58                                const struct osc_page *opg,
  59                                enum cl_lock_mode mode, int pending, int unref)
  60 {
  61         struct cl_page         *page;
  62         struct osc_object      *obj;
  63         struct osc_thread_info *info;
  64         struct ldlm_res_id     *resname;
  65         struct lustre_handle   *lockh;
  66         ldlm_policy_data_t     *policy;
  67         ldlm_mode_t             dlmmode;
  68         int                     flags;
  69
  70         cfs_might_sleep();
  71
  72         info = osc_env_info(env);
  73         resname = &info->oti_resname;
  74         policy = &info->oti_policy;
  75         lockh = &info->oti_handle;
  76         page = opg->ops_cl.cpl_page;
  77         obj = cl2osc(opg->ops_cl.cpl_obj);
  78
  79         flags = LDLM_FL_TEST_LOCK | LDLM_FL_BLOCK_GRANTED;
  80         if (pending)
  81                 flags |= LDLM_FL_CBPENDING;
  82
  83         dlmmode = osc_cl_lock2ldlm(mode) | LCK_PW;
  84         osc_lock_build_res(env, obj, resname);
  85         osc_index2policy(policy, page->cp_obj, page->cp_index, page->cp_index);
  86         return osc_match_base(osc_export(obj), resname, LDLM_EXTENT, policy,
  87                               dlmmode, &flags, NULL, lockh, unref);
  88 }
  89
  90 /**
  91  * Checks an invariant that a page in the cache is covered by a lock, as
  92  * needed.
  93  */
  94 static int osc_page_protected(const struct lu_env *env,
  95                               const struct osc_page *opg,
  96                               enum cl_lock_mode mode, int unref)
  97 {
  98         struct cl_object_header *hdr;
  99         struct cl_lock          *scan;
 100         struct cl_page          *page;
 101         struct cl_lock_descr    *descr;
 102         int result;
 103
 104         LINVRNT(!opg->ops_temp);
 105
 106         page = opg->ops_cl.cpl_page;
 107         if (page->cp_owner != NULL &&
 108             cl_io_top(page->cp_owner)->ci_lockreq == CILR_NEVER)
 109                 /*
 110                  * If IO is done without locks (liblustre, or lloop), lock is
 111                  * not required.
 112                  */
 113                 result = 1;
 114         else
 115                 /* otherwise check for a DLM lock */
 116         result = osc_page_is_dlocked(env, opg, mode, 1, unref);
 117         if (result == 0) {
 118                 /* maybe this page is a part of a lockless io? */
 119                 hdr = cl_object_header(opg->ops_cl.cpl_obj);
 120                 descr = &osc_env_info(env)->oti_descr;
 121                 descr->cld_mode = mode;
 122                 descr->cld_start = page->cp_index;
 123                 descr->cld_end   = page->cp_index;
 124                 cfs_spin_lock(&hdr->coh_lock_guard);
 125                 cfs_list_for_each_entry(scan, &hdr->coh_locks, cll_linkage) {
 126                         /*
 127                          * Lock-less sub-lock has to be either in HELD state
 128                          * (when io is actively going on), or in CACHED state,
 129                          * when top-lock is being unlocked:
 130                          * cl_io_unlock()->cl_unuse()->...->lov_lock_unuse().
 131                          */
 132                         if ((scan->cll_state == CLS_HELD ||
 133                              scan->cll_state == CLS_CACHED) &&
 134                             cl_lock_ext_match(&scan->cll_descr, descr)) {
 135                                 struct osc_lock *olck;
 136
 137                                 olck = osc_lock_at(scan);
 138                                 result = osc_lock_is_lockless(olck);
 139                                 break;
 140                         }
 141                 }
 142                 cfs_spin_unlock(&hdr->coh_lock_guard);
 143         }
 144         return result;
 145 }
 146 #else
 147 static int osc_page_protected(const struct lu_env *env,
 148                               const struct osc_page *opg,
 149                               enum cl_lock_mode mode, int unref)
 150 {
 151         return 1;
 152 }
 153 #endif
 154
 155 /*****************************************************************************
 156  *
 157  * Page operations.
 158  *
 159  */
 160 static void osc_page_fini(const struct lu_env *env,
 161                           struct cl_page_slice *slice)
 162 {
 163         struct osc_page *opg = cl2osc_page(slice);
 164         CDEBUG(D_TRACE, "%p\n", opg);
 165         LASSERT(opg->ops_lock == NULL);
 166         OBD_SLAB_FREE_PTR(opg, osc_page_kmem);
 167 }
 168
 169 static void osc_page_transfer_get(struct osc_page *opg, const char *label)
 170 {
 171         struct cl_page *page = cl_page_top(opg->ops_cl.cpl_page);
 172
 173         LASSERT(!opg->ops_transfer_pinned);
 174         cl_page_get(page);
 175         lu_ref_add_atomic(&page->cp_reference, label, page);
 176         opg->ops_transfer_pinned = 1;
 177 }
 178
 179 static void osc_page_transfer_put(const struct lu_env *env,
 180                                   struct osc_page *opg)
 181 {
 182         struct cl_page *page = cl_page_top(opg->ops_cl.cpl_page);
 183
 184         if (opg->ops_transfer_pinned) {
 185                 lu_ref_del(&page->cp_reference, "transfer", page);
 186                 opg->ops_transfer_pinned = 0;
 187                 cl_page_put(env, page);
 188         }
 189 }
 190
 191 /**
 192  * This is called once for every page when it is submitted for a transfer
 193  * either opportunistic (osc_page_cache_add()), or immediate
 194  * (osc_page_submit()).
 195  */
 196 static void osc_page_transfer_add(const struct lu_env *env,
 197                                   struct osc_page *opg, enum cl_req_type crt)
 198 {
 199         struct osc_object *obj;
 200
 201         obj = cl2osc(opg->ops_cl.cpl_obj);
 202         cfs_spin_lock(&obj->oo_seatbelt);
 203         cfs_list_add(&opg->ops_inflight, &obj->oo_inflight[crt]);
 204         opg->ops_submitter = cfs_current();
 205         cfs_spin_unlock(&obj->oo_seatbelt);
 206 }
 207
 208 static int osc_page_cache_add(const struct lu_env *env,
 209                               const struct cl_page_slice *slice,
 210                               struct cl_io *unused)
 211 {
 212         struct osc_page   *opg = cl2osc_page(slice);
 213         struct osc_object *obj = cl2osc(opg->ops_cl.cpl_obj);
 214         int result;
 215         /* All cacheable IO is async-capable */
 216         int brw_flags = OBD_BRW_ASYNC;
 217         int noquota = 0;
 218
 219         LINVRNT(osc_page_protected(env, opg, CLM_WRITE, 0));
 220         ENTRY;
 221
 222         /* Set the OBD_BRW_SRVLOCK before the page is queued. */
 223         brw_flags |= opg->ops_srvlock ? OBD_BRW_SRVLOCK : 0;
 224         if (!client_is_remote(osc_export(obj)) &&
 225             cfs_capable(CFS_CAP_SYS_RESOURCE)) {
 226                 brw_flags |= OBD_BRW_NOQUOTA;
 227                 noquota = OBD_BRW_NOQUOTA;
 228         }
 229
 230         osc_page_transfer_get(opg, "transfer\0cache");
 231         result = osc_queue_async_io(env, osc_export(obj), NULL, obj->oo_oinfo,
 232                                     &opg->ops_oap, OBD_BRW_WRITE | noquota,
 233                                     opg->ops_from, opg->ops_to - opg->ops_from,
 234                                     brw_flags, 0);
 235         if (result != 0)
 236                 osc_page_transfer_put(env, opg);
 237         else
 238                 osc_page_transfer_add(env, opg, CRT_WRITE);
 239         RETURN(result);
 240 }
 241
 242 void osc_index2policy(ldlm_policy_data_t *policy, const struct cl_object *obj,
 243                       pgoff_t start, pgoff_t end)
 244 {
 245         memset(policy, 0, sizeof *policy);
 246         policy->l_extent.start = cl_offset(obj, start);
 247         policy->l_extent.end   = cl_offset(obj, end + 1) - 1;
 248 }
 249
 250 static int osc_page_addref_lock(const struct lu_env *env,
 251                                 struct osc_page *opg,
 252                                 struct cl_lock *lock)
 253 {
 254         struct osc_lock *olock;
 255         int              rc;
 256
 257         LASSERT(opg->ops_lock == NULL);
 258
 259         olock = osc_lock_at(lock);
 260         if (cfs_atomic_inc_return(&olock->ols_pageref) <= 0) {
 261                 cfs_atomic_dec(&olock->ols_pageref);
 262                 cl_lock_put(env, lock);
 263                 rc = 1;
 264         } else {
 265                 opg->ops_lock = lock;
 266                 rc = 0;
 267         }
 268         return rc;
 269 }
 270
 271 static void osc_page_putref_lock(const struct lu_env *env,
 272                                  struct osc_page *opg)
 273 {
 274         struct cl_lock  *lock = opg->ops_lock;
 275         struct osc_lock *olock;
 276
 277         LASSERT(lock != NULL);
 278         olock = osc_lock_at(lock);
 279
 280         cfs_atomic_dec(&olock->ols_pageref);
 281         opg->ops_lock = NULL;
 282
 283         cl_lock_put(env, lock);
 284 }
 285
 286 static int osc_page_is_under_lock(const struct lu_env *env,
 287                                   const struct cl_page_slice *slice,
 288                                   struct cl_io *unused)
 289 {
 290         struct cl_lock *lock;
 291         int             result;
 292
 293         ENTRY;
 294         lock = cl_lock_at_page(env, slice->cpl_obj, slice->cpl_page,
 295                                NULL, 1, 0);
 296         if (lock != NULL &&
 297             osc_page_addref_lock(env, cl2osc_page(slice), lock) == 0)
 298                 result = -EBUSY;
 299         else
 300                 result = -ENODATA;
 301         RETURN(result);
 302 }
 303
 304 static void osc_page_disown(const struct lu_env *env,
 305                             const struct cl_page_slice *slice,
 306                             struct cl_io *io)
 307 {
 308         struct osc_page *opg = cl2osc_page(slice);
 309
 310         if (unlikely(opg->ops_lock))
 311                 osc_page_putref_lock(env, opg);
 312 }
 313
 314 static void osc_page_completion_read(const struct lu_env *env,
 315                                      const struct cl_page_slice *slice,
 316                                      int ioret)
 317 {
 318         struct osc_page *opg = cl2osc_page(slice);
 319
 320         if (likely(opg->ops_lock))
 321                 osc_page_putref_lock(env, opg);
 322 }
 323
 324 static int osc_page_fail(const struct lu_env *env,
 325                          const struct cl_page_slice *slice,
 326                          struct cl_io *unused)
 327 {
 328         /*
 329          * Cached read?
 330          */
 331         LBUG();
 332         return 0;
 333 }
 334
 335
 336 static const char *osc_list(cfs_list_t *head)
 337 {
 338         return cfs_list_empty(head) ? "-" : "+";
 339 }
 340
 341 static inline cfs_time_t osc_submit_duration(struct osc_page *opg)
 342 {
 343         if (opg->ops_submit_time == 0)
 344                 return 0;
 345
 346         return (cfs_time_current() - opg->ops_submit_time);
 347 }
 348
 349 static int osc_page_print(const struct lu_env *env,
 350                           const struct cl_page_slice *slice,
 351                           void *cookie, lu_printer_t printer)
 352 {
 353         struct osc_page       *opg = cl2osc_page(slice);
 354         struct osc_async_page *oap = &opg->ops_oap;
 355         struct osc_object     *obj = cl2osc(slice->cpl_obj);
 356         struct client_obd     *cli = &osc_export(obj)->exp_obd->u.cli;
 357         struct lov_oinfo      *loi = obj->oo_oinfo;
 358
 359         return (*printer)(env, cookie, LUSTRE_OSC_NAME"-page@%p: "
 360                           "1< %#x %d %u %s %s %s > "
 361                           "2< "LPU64" %u %u %#x %#x | %p %p %p %p %p > "
 362                           "3< %s %p %d %lu %d > "
 363                           "4< %d %d %d %lu %s | %s %s %s %s > "
 364                           "5< %s %s %s %s | %d %s %s | %d %s %s>\n",
 365                           opg,
 366                           /* 1 */
 367                           oap->oap_magic, oap->oap_cmd,
 368                           oap->oap_interrupted,
 369                           osc_list(&oap->oap_pending_item),
 370                           osc_list(&oap->oap_urgent_item),
 371                           osc_list(&oap->oap_rpc_item),
 372                           /* 2 */
 373                           oap->oap_obj_off, oap->oap_page_off, oap->oap_count,
 374                           oap->oap_async_flags, oap->oap_brw_flags,
 375                           oap->oap_request,
 376                           oap->oap_cli, oap->oap_loi, oap->oap_caller_ops,
 377                           oap->oap_caller_data,
 378                           /* 3 */
 379                           osc_list(&opg->ops_inflight),
 380                           opg->ops_submitter, opg->ops_transfer_pinned,
 381                           osc_submit_duration(opg), opg->ops_srvlock,
 382                           /* 4 */
 383                           cli->cl_r_in_flight, cli->cl_w_in_flight,
 384                           cli->cl_max_rpcs_in_flight,
 385                           cli->cl_avail_grant,
 386                           osc_list(&cli->cl_cache_waiters),
 387                           osc_list(&cli->cl_loi_ready_list),
 388                           osc_list(&cli->cl_loi_hp_ready_list),
 389                           osc_list(&cli->cl_loi_write_list),
 390                           osc_list(&cli->cl_loi_read_list),
 391                           /* 5 */
 392                           osc_list(&loi->loi_ready_item),
 393                           osc_list(&loi->loi_hp_ready_item),
 394                           osc_list(&loi->loi_write_item),
 395                           osc_list(&loi->loi_read_item),
 396                           loi->loi_read_lop.lop_num_pending,
 397                           osc_list(&loi->loi_read_lop.lop_pending),
 398                           osc_list(&loi->loi_read_lop.lop_urgent),
 399                           loi->loi_write_lop.lop_num_pending,
 400                           osc_list(&loi->loi_write_lop.lop_pending),
 401                           osc_list(&loi->loi_write_lop.lop_urgent));
 402 }
 403
 404 static void osc_page_delete(const struct lu_env *env,
 405                             const struct cl_page_slice *slice)
 406 {
 407         struct osc_page       *opg = cl2osc_page(slice);
 408         struct osc_object     *obj = cl2osc(opg->ops_cl.cpl_obj);
 409         struct osc_async_page *oap = &opg->ops_oap;
 410         int rc;
 411
 412         LINVRNT(opg->ops_temp || osc_page_protected(env, opg, CLM_READ, 1));
 413
 414         ENTRY;
 415         CDEBUG(D_TRACE, "%p\n", opg);
 416         osc_page_transfer_put(env, opg);
 417         rc = osc_teardown_async_page(osc_export(obj), NULL, obj->oo_oinfo, oap);
 418         if (rc) {
 419                 CL_PAGE_DEBUG(D_ERROR, env, cl_page_top(slice->cpl_page),
 420                               "Trying to teardown failed: %d\n", rc);
 421                 LASSERT(0);
 422         }
 423         cfs_spin_lock(&obj->oo_seatbelt);
 424         cfs_list_del_init(&opg->ops_inflight);
 425         cfs_spin_unlock(&obj->oo_seatbelt);
 426         EXIT;
 427 }
 428
 429 void osc_page_clip(const struct lu_env *env, const struct cl_page_slice *slice,
 430                    int from, int to)
 431 {
 432         struct osc_page       *opg = cl2osc_page(slice);
 433         struct osc_async_page *oap = &opg->ops_oap;
 434
 435         LINVRNT(osc_page_protected(env, opg, CLM_READ, 0));
 436
 437         opg->ops_from = from;
 438         opg->ops_to   = to;
 439         cfs_spin_lock(&oap->oap_lock);
 440         oap->oap_async_flags |= ASYNC_COUNT_STABLE;
 441         cfs_spin_unlock(&oap->oap_lock);
 442 }
 443
 444 static int osc_page_cancel(const struct lu_env *env,
 445                            const struct cl_page_slice *slice)
 446 {
 447         struct osc_page *opg       = cl2osc_page(slice);
 448         struct osc_async_page *oap = &opg->ops_oap;
 449         int rc = 0;
 450
 451         LINVRNT(osc_page_protected(env, opg, CLM_READ, 0));
 452
 453         client_obd_list_lock(&oap->oap_cli->cl_loi_list_lock);
 454         /* Check if the transferring against this page
 455          * is completed, or not even queued. */
 456         if (opg->ops_transfer_pinned)
 457                 /* FIXME: may not be interrupted.. */
 458                 rc = osc_oap_interrupted(env, oap);
 459         LASSERT(ergo(rc == 0, opg->ops_transfer_pinned == 0));
 460         client_obd_list_unlock(&oap->oap_cli->cl_loi_list_lock);
 461         return rc;
 462 }
 463
 464 static const struct cl_page_operations osc_page_ops = {
 465         .cpo_fini          = osc_page_fini,
 466         .cpo_print         = osc_page_print,
 467         .cpo_delete        = osc_page_delete,
 468         .cpo_is_under_lock = osc_page_is_under_lock,
 469         .cpo_disown        = osc_page_disown,
 470         .io = {
 471                 [CRT_READ] = {
 472                         .cpo_cache_add  = osc_page_fail,
 473                         .cpo_completion = osc_page_completion_read
 474                 },
 475                 [CRT_WRITE] = {
 476                         .cpo_cache_add  = osc_page_cache_add
 477                 }
 478         },
 479         .cpo_clip           = osc_page_clip,
 480         .cpo_cancel         = osc_page_cancel
 481 };
 482
 483 static int osc_make_ready(const struct lu_env *env, void *data, int cmd)
 484 {
 485         struct osc_page *opg  = data;
 486         struct cl_page  *page = cl_page_top(opg->ops_cl.cpl_page);
 487         int result;
 488
 489         LASSERT(cmd == OBD_BRW_WRITE); /* no cached reads */
 490         LINVRNT(osc_page_protected(env, opg, CLM_WRITE, 1));
 491
 492         ENTRY;
 493         result = cl_page_make_ready(env, page, CRT_WRITE);
 494         if (result == 0)
 495                 opg->ops_submit_time = cfs_time_current();
 496         RETURN(result);
 497 }
 498
 499 static int osc_refresh_count(const struct lu_env *env, void *data, int cmd)
 500 {
 501         struct cl_page   *page;
 502         struct osc_page  *osc = data;
 503         struct cl_object *obj;
 504         struct cl_attr   *attr = &osc_env_info(env)->oti_attr;
 505
 506         int result;
 507         loff_t kms;
 508
 509         LINVRNT(osc_page_protected(env, osc, CLM_READ, 1));
 510
 511         /* readpage queues with _COUNT_STABLE, shouldn't get here. */
 512         LASSERT(!(cmd & OBD_BRW_READ));
 513         LASSERT(osc != NULL);
 514         page = osc->ops_cl.cpl_page;
 515         obj = osc->ops_cl.cpl_obj;
 516
 517         cl_object_attr_lock(obj);
 518         result = cl_object_attr_get(env, obj, attr);
 519         cl_object_attr_unlock(obj);
 520         if (result < 0)
 521                 return result;
 522         kms = attr->cat_kms;
 523         if (cl_offset(obj, page->cp_index) >= kms)
 524                 /* catch race with truncate */
 525                 return 0;
 526         else if (cl_offset(obj, page->cp_index + 1) > kms)
 527                 /* catch sub-page write at end of file */
 528                 return kms % CFS_PAGE_SIZE;
 529         else
 530                 return CFS_PAGE_SIZE;
 531 }
 532
 533 static int osc_completion(const struct lu_env *env,
 534                           void *data, int cmd, struct obdo *oa, int rc)
 535 {
 536         struct osc_page       *opg  = data;
 537         struct osc_async_page *oap  = &opg->ops_oap;
 538         struct cl_page        *page = cl_page_top(opg->ops_cl.cpl_page);
 539         struct osc_object     *obj  = cl2osc(opg->ops_cl.cpl_obj);
 540         enum cl_req_type crt;
 541         int srvlock;
 542
 543         LINVRNT(osc_page_protected(env, opg, CLM_READ, 1));
 544
 545         ENTRY;
 546
 547         cmd &= ~OBD_BRW_NOQUOTA;
 548         LASSERT(equi(page->cp_state == CPS_PAGEIN,  cmd == OBD_BRW_READ));
 549         LASSERT(equi(page->cp_state == CPS_PAGEOUT, cmd == OBD_BRW_WRITE));
 550         LASSERT(opg->ops_transfer_pinned);
 551
 552         /*
 553          * page->cp_req can be NULL if io submission failed before
 554          * cl_req was allocated.
 555          */
 556         if (page->cp_req != NULL)
 557                 cl_req_page_done(env, page);
 558         LASSERT(page->cp_req == NULL);
 559
 560         /* As the transfer for this page is being done, clear the flags */
 561         cfs_spin_lock(&oap->oap_lock);
 562         oap->oap_async_flags = 0;
 563         cfs_spin_unlock(&oap->oap_lock);
 564
 565         crt = cmd == OBD_BRW_READ ? CRT_READ : CRT_WRITE;
 566         /* Clear opg->ops_transfer_pinned before VM lock is released. */
 567         opg->ops_transfer_pinned = 0;
 568
 569         cfs_spin_lock(&obj->oo_seatbelt);
 570         LASSERT(opg->ops_submitter != NULL);
 571         LASSERT(!cfs_list_empty(&opg->ops_inflight));
 572         cfs_list_del_init(&opg->ops_inflight);
 573         cfs_spin_unlock(&obj->oo_seatbelt);
 574
 575         opg->ops_submit_time = 0;
 576         srvlock = oap->oap_brw_flags & OBD_BRW_SRVLOCK;
 577
 578         cl_page_completion(env, page, crt, rc);
 579
 580         /* statistic */
 581         if (rc == 0 && srvlock) {
 582                 struct lu_device *ld    = opg->ops_cl.cpl_obj->co_lu.lo_dev;
 583                 struct osc_stats *stats = &lu2osc_dev(ld)->od_stats;
 584                 int bytes = oap->oap_count;
 585
 586                 if (crt == CRT_READ)
 587                         stats->os_lockless_reads += bytes;
 588                 else
 589                         stats->os_lockless_writes += bytes;
 590         }
 591
 592         /*
 593          * This has to be the last operation with the page, as locks are
 594          * released in cl_page_completion() and nothing except for the
 595          * reference counter protects page from concurrent reclaim.
 596          */
 597         lu_ref_del(&page->cp_reference, "transfer", page);
 598         /*
 599          * As page->cp_obj is pinned by a reference from page->cp_req, it is
 600          * safe to call cl_page_put() without risking object destruction in a
 601          * non-blocking context.
 602          */
 603         cl_page_put(env, page);
 604         RETURN(0);
 605 }
 606
 607 const static struct obd_async_page_ops osc_async_page_ops = {
 608         .ap_make_ready    = osc_make_ready,
 609         .ap_refresh_count = osc_refresh_count,
 610         .ap_completion    = osc_completion
 611 };
 612
 613 struct cl_page *osc_page_init(const struct lu_env *env,
 614                               struct cl_object *obj,
 615                               struct cl_page *page, cfs_page_t *vmpage)
 616 {
 617         struct osc_object *osc = cl2osc(obj);
 618         struct osc_page   *opg;
 619         int result;
 620
 621         OBD_SLAB_ALLOC_PTR_GFP(opg, osc_page_kmem, CFS_ALLOC_IO);
 622         if (opg != NULL) {
 623                 void *oap = &opg->ops_oap;
 624
 625                 opg->ops_from = 0;
 626                 opg->ops_to   = CFS_PAGE_SIZE;
 627
 628                 result = osc_prep_async_page(osc_export(osc),
 629                                              NULL, osc->oo_oinfo, vmpage,
 630                                              cl_offset(obj, page->cp_index),
 631                                              &osc_async_page_ops,
 632                                              opg, (void **)&oap, 1, NULL);
 633                 if (result == 0) {
 634                         struct osc_io *oio = osc_env_io(env);
 635                         opg->ops_srvlock = osc_io_srvlock(oio);
 636                         cl_page_slice_add(page, &opg->ops_cl, obj,
 637                                           &osc_page_ops);
 638                 }
 639                 /*
 640                  * Cannot assert osc_page_protected() here as read-ahead
 641                  * creates temporary pages outside of a lock.
 642                  */
 643 #ifdef INVARIANT_CHECK
 644                 opg->ops_temp = !osc_page_protected(env, opg, CLM_READ, 1);
 645 #endif
 646                 CFS_INIT_LIST_HEAD(&opg->ops_inflight);
 647         } else
 648                 result = -ENOMEM;
 649         return ERR_PTR(result);
 650 }
 651
 652 /**
 653  * Helper function called by osc_io_submit() for every page in an immediate
 654  * transfer (i.e., transferred synchronously).
 655  */
 656 void osc_io_submit_page(const struct lu_env *env,
 657                         struct osc_io *oio, struct osc_page *opg,
 658                         enum cl_req_type crt)
 659 {
 660         struct osc_async_page *oap = &opg->ops_oap;
 661         struct client_obd     *cli = oap->oap_cli;
 662         int flags = 0;
 663
 664         LINVRNT(osc_page_protected(env, opg,
 665                                    crt == CRT_WRITE ? CLM_WRITE : CLM_READ, 1));
 666
 667         oap->oap_page_off   = opg->ops_from;
 668         oap->oap_count      = opg->ops_to - opg->ops_from;
 669         /* Give a hint to OST that requests are coming from kswapd - bug19529 */
 670         if (cfs_memory_pressure_get())
 671                 oap->oap_brw_flags |= OBD_BRW_MEMALLOC;
 672         oap->oap_brw_flags |= OBD_BRW_SYNC;
 673         if (osc_io_srvlock(oio))
 674                 oap->oap_brw_flags |= OBD_BRW_SRVLOCK;
 675
 676         oap->oap_cmd = crt == CRT_WRITE ? OBD_BRW_WRITE : OBD_BRW_READ;
 677         if (!client_is_remote(osc_export(cl2osc(opg->ops_cl.cpl_obj))) &&
 678             cfs_capable(CFS_CAP_SYS_RESOURCE)) {
 679                 oap->oap_brw_flags |= OBD_BRW_NOQUOTA;
 680                 oap->oap_cmd |= OBD_BRW_NOQUOTA;
 681         }
 682
 683         if (oap->oap_cmd & OBD_BRW_READ)
 684                 flags = ASYNC_COUNT_STABLE;
 685         else if (!(oap->oap_brw_page.flag & OBD_BRW_FROM_GRANT))
 686                 osc_enter_cache_try(env, cli, oap->oap_loi, oap, 1);
 687
 688         cfs_spin_lock(&oap->oap_lock);
 689         oap->oap_async_flags |= OSC_FLAGS | flags;
 690         cfs_spin_unlock(&oap->oap_lock);
 691
 692         osc_oap_to_pending(oap);
 693         osc_page_transfer_get(opg, "transfer\0imm");
 694         osc_page_transfer_add(env, opg, crt);
 695 }
 696
 697 /** @} osc */