fs/cachefiles/io.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* kiocb-using read/write
   3  *
   4  * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
   5  * Written by David Howells (dhowells@redhat.com)
   6  */
   7
   8 #include <linux/mount.h>
   9 #include <linux/slab.h>
  10 #include <linux/file.h>
  11 #include <linux/uio.h>
  12 #include <linux/falloc.h>
  13 #include <linux/sched/mm.h>
  14 #include <trace/events/fscache.h>
  15 #include "internal.h"
  16
  17 struct cachefiles_kiocb {
  18         struct kiocb            iocb;
  19         refcount_t              ki_refcnt;
  20         loff_t                  start;
  21         union {
  22                 size_t          skipped;
  23                 size_t          len;
  24         };
  25         struct cachefiles_object *object;
  26         netfs_io_terminated_t   term_func;
  27         void                    *term_func_priv;
  28         bool                    was_async;
  29         unsigned int            inval_counter;  /* Copy of cookie->inval_counter */
  30         u64                     b_writing;
  31 };
  32
  33 static inline void cachefiles_put_kiocb(struct cachefiles_kiocb *ki)
  34 {
  35         if (refcount_dec_and_test(&ki->ki_refcnt)) {
  36                 cachefiles_put_object(ki->object, cachefiles_obj_put_ioreq);
  37                 fput(ki->iocb.ki_filp);
  38                 kfree(ki);
  39         }
  40 }
  41
  42 /*
  43  * Handle completion of a read from the cache.
  44  */
  45 static void cachefiles_read_complete(struct kiocb *iocb, long ret)
  46 {
  47         struct cachefiles_kiocb *ki = container_of(iocb, struct cachefiles_kiocb, iocb);
  48         struct inode *inode = file_inode(ki->iocb.ki_filp);
  49
  50         _enter("%ld", ret);
  51
  52         if (ret < 0)
  53                 trace_cachefiles_io_error(ki->object, inode, ret,
  54                                           cachefiles_trace_read_error);
  55
  56         if (ki->term_func) {
  57                 if (ret >= 0) {
  58                         if (ki->object->cookie->inval_counter == ki->inval_counter)
  59                                 ki->skipped += ret;
  60                         else
  61                                 ret = -ESTALE;
  62                 }
  63
  64                 ki->term_func(ki->term_func_priv, ret, ki->was_async);
  65         }
  66
  67         cachefiles_put_kiocb(ki);
  68 }
  69
  70 /*
  71  * Initiate a read from the cache.
  72  */
  73 static int cachefiles_read(struct netfs_cache_resources *cres,
  74                            loff_t start_pos,
  75                            struct iov_iter *iter,
  76                            enum netfs_read_from_hole read_hole,
  77                            netfs_io_terminated_t term_func,
  78                            void *term_func_priv)
  79 {
  80         struct cachefiles_object *object;
  81         struct cachefiles_kiocb *ki;
  82         struct file *file;
  83         unsigned int old_nofs;
  84         ssize_t ret = -ENOBUFS;
  85         size_t len = iov_iter_count(iter), skipped = 0;
  86
  87         if (!fscache_wait_for_operation(cres, FSCACHE_WANT_READ))
  88                 goto presubmission_error;
  89
  90         fscache_count_read();
  91         object = cachefiles_cres_object(cres);
  92         file = cachefiles_cres_file(cres);
  93
  94         _enter("%pD,%li,%llx,%zx/%llx",
  95                file, file_inode(file)->i_ino, start_pos, len,
  96                i_size_read(file_inode(file)));
  97
  98         /* If the caller asked us to seek for data before doing the read, then
  99          * we should do that now.  If we find a gap, we fill it with zeros.
 100          */
 101         if (read_hole != NETFS_READ_HOLE_IGNORE) {
 102                 loff_t off = start_pos, off2;
 103
 104                 off2 = cachefiles_inject_read_error();
 105                 if (off2 == 0)
 106                         off2 = vfs_llseek(file, off, SEEK_DATA);
 107                 if (off2 < 0 && off2 >= (loff_t)-MAX_ERRNO && off2 != -ENXIO) {
 108                         skipped = 0;
 109                         ret = off2;
 110                         goto presubmission_error;
 111                 }
 112
 113                 if (off2 == -ENXIO || off2 >= start_pos + len) {
 114                         /* The region is beyond the EOF or there's no more data
 115                          * in the region, so clear the rest of the buffer and
 116                          * return success.
 117                          */
 118                         ret = -ENODATA;
 119                         if (read_hole == NETFS_READ_HOLE_FAIL)
 120                                 goto presubmission_error;
 121
 122                         iov_iter_zero(len, iter);
 123                         skipped = len;
 124                         ret = 0;
 125                         goto presubmission_error;
 126                 }
 127
 128                 skipped = off2 - off;
 129                 iov_iter_zero(skipped, iter);
 130         }
 131
 132         ret = -ENOMEM;
 133         ki = kzalloc(sizeof(struct cachefiles_kiocb), GFP_KERNEL);
 134         if (!ki)
 135                 goto presubmission_error;
 136
 137         refcount_set(&ki->ki_refcnt, 2);
 138         ki->iocb.ki_filp        = file;
 139         ki->iocb.ki_pos         = start_pos + skipped;
 140         ki->iocb.ki_flags       = IOCB_DIRECT;
 141         ki->iocb.ki_ioprio      = get_current_ioprio();
 142         ki->skipped             = skipped;
 143         ki->object              = object;
 144         ki->inval_counter       = cres->inval_counter;
 145         ki->term_func           = term_func;
 146         ki->term_func_priv      = term_func_priv;
 147         ki->was_async           = true;
 148
 149         if (ki->term_func)
 150                 ki->iocb.ki_complete = cachefiles_read_complete;
 151
 152         get_file(ki->iocb.ki_filp);
 153         cachefiles_grab_object(object, cachefiles_obj_get_ioreq);
 154
 155         trace_cachefiles_read(object, file_inode(file), ki->iocb.ki_pos, len - skipped);
 156         old_nofs = memalloc_nofs_save();
 157         ret = cachefiles_inject_read_error();
 158         if (ret == 0)
 159                 ret = vfs_iocb_iter_read(file, &ki->iocb, iter);
 160         memalloc_nofs_restore(old_nofs);
 161         switch (ret) {
 162         case -EIOCBQUEUED:
 163                 goto in_progress;
 164
 165         case -ERESTARTSYS:
 166         case -ERESTARTNOINTR:
 167         case -ERESTARTNOHAND:
 168         case -ERESTART_RESTARTBLOCK:
 169                 /* There's no easy way to restart the syscall since other AIO's
 170                  * may be already running. Just fail this IO with EINTR.
 171                  */
 172                 ret = -EINTR;
 173                 fallthrough;
 174         default:
 175                 ki->was_async = false;
 176                 cachefiles_read_complete(&ki->iocb, ret);
 177                 if (ret > 0)
 178                         ret = 0;
 179                 break;
 180         }
 181
 182 in_progress:
 183         cachefiles_put_kiocb(ki);
 184         _leave(" = %zd", ret);
 185         return ret;
 186
 187 presubmission_error:
 188         if (term_func)
 189                 term_func(term_func_priv, ret < 0 ? ret : skipped, false);
 190         return ret;
 191 }
 192
 193 /*
 194  * Query the occupancy of the cache in a region, returning where the next chunk
 195  * of data starts and how long it is.
 196  */
 197 static int cachefiles_query_occupancy(struct netfs_cache_resources *cres,
 198                                       loff_t start, size_t len, size_t granularity,
 199                                       loff_t *_data_start, size_t *_data_len)
 200 {
 201         struct cachefiles_object *object;
 202         struct file *file;
 203         loff_t off, off2;
 204
 205         *_data_start = -1;
 206         *_data_len = 0;
 207
 208         if (!fscache_wait_for_operation(cres, FSCACHE_WANT_READ))
 209                 return -ENOBUFS;
 210
 211         object = cachefiles_cres_object(cres);
 212         file = cachefiles_cres_file(cres);
 213         granularity = max_t(size_t, object->volume->cache->bsize, granularity);
 214
 215         _enter("%pD,%li,%llx,%zx/%llx",
 216                file, file_inode(file)->i_ino, start, len,
 217                i_size_read(file_inode(file)));
 218
 219         off = cachefiles_inject_read_error();
 220         if (off == 0)
 221                 off = vfs_llseek(file, start, SEEK_DATA);
 222         if (off == -ENXIO)
 223                 return -ENODATA; /* Beyond EOF */
 224         if (off < 0 && off >= (loff_t)-MAX_ERRNO)
 225                 return -ENOBUFS; /* Error. */
 226         if (round_up(off, granularity) >= start + len)
 227                 return -ENODATA; /* No data in range */
 228
 229         off2 = cachefiles_inject_read_error();
 230         if (off2 == 0)
 231                 off2 = vfs_llseek(file, off, SEEK_HOLE);
 232         if (off2 == -ENXIO)
 233                 return -ENODATA; /* Beyond EOF */
 234         if (off2 < 0 && off2 >= (loff_t)-MAX_ERRNO)
 235                 return -ENOBUFS; /* Error. */
 236
 237         /* Round away partial blocks */
 238         off = round_up(off, granularity);
 239         off2 = round_down(off2, granularity);
 240         if (off2 <= off)
 241                 return -ENODATA;
 242
 243         *_data_start = off;
 244         if (off2 > start + len)
 245                 *_data_len = len;
 246         else
 247                 *_data_len = off2 - off;
 248         return 0;
 249 }
 250
 251 /*
 252  * Handle completion of a write to the cache.
 253  */
 254 static void cachefiles_write_complete(struct kiocb *iocb, long ret)
 255 {
 256         struct cachefiles_kiocb *ki = container_of(iocb, struct cachefiles_kiocb, iocb);
 257         struct cachefiles_object *object = ki->object;
 258         struct inode *inode = file_inode(ki->iocb.ki_filp);
 259
 260         _enter("%ld", ret);
 261
 262         kiocb_end_write(iocb);
 263
 264         if (ret < 0)
 265                 trace_cachefiles_io_error(object, inode, ret,
 266                                           cachefiles_trace_write_error);
 267
 268         atomic_long_sub(ki->b_writing, &object->volume->cache->b_writing);
 269         set_bit(FSCACHE_COOKIE_HAVE_DATA, &object->cookie->flags);
 270         if (ki->term_func)
 271                 ki->term_func(ki->term_func_priv, ret, ki->was_async);
 272         cachefiles_put_kiocb(ki);
 273 }
 274
 275 /*
 276  * Initiate a write to the cache.
 277  */
 278 int __cachefiles_write(struct cachefiles_object *object,
 279                        struct file *file,
 280                        loff_t start_pos,
 281                        struct iov_iter *iter,
 282                        netfs_io_terminated_t term_func,
 283                        void *term_func_priv)
 284 {
 285         struct cachefiles_cache *cache;
 286         struct cachefiles_kiocb *ki;
 287         unsigned int old_nofs;
 288         ssize_t ret;
 289         size_t len = iov_iter_count(iter);
 290
 291         fscache_count_write();
 292         cache = object->volume->cache;
 293
 294         _enter("%pD,%li,%llx,%zx/%llx",
 295                file, file_inode(file)->i_ino, start_pos, len,
 296                i_size_read(file_inode(file)));
 297
 298         ki = kzalloc(sizeof(struct cachefiles_kiocb), GFP_KERNEL);
 299         if (!ki) {
 300                 if (term_func)
 301                         term_func(term_func_priv, -ENOMEM, false);
 302                 return -ENOMEM;
 303         }
 304
 305         refcount_set(&ki->ki_refcnt, 2);
 306         ki->iocb.ki_filp        = file;
 307         ki->iocb.ki_pos         = start_pos;
 308         ki->iocb.ki_flags       = IOCB_DIRECT | IOCB_WRITE;
 309         ki->iocb.ki_ioprio      = get_current_ioprio();
 310         ki->object              = object;
 311         ki->start               = start_pos;
 312         ki->len                 = len;
 313         ki->term_func           = term_func;
 314         ki->term_func_priv      = term_func_priv;
 315         ki->was_async           = true;
 316         ki->b_writing           = (len + (1 << cache->bshift) - 1) >> cache->bshift;
 317
 318         if (ki->term_func)
 319                 ki->iocb.ki_complete = cachefiles_write_complete;
 320         atomic_long_add(ki->b_writing, &cache->b_writing);
 321
 322         kiocb_start_write(&ki->iocb);
 323
 324         get_file(ki->iocb.ki_filp);
 325         cachefiles_grab_object(object, cachefiles_obj_get_ioreq);
 326
 327         trace_cachefiles_write(object, file_inode(file), ki->iocb.ki_pos, len);
 328         old_nofs = memalloc_nofs_save();
 329         ret = cachefiles_inject_write_error();
 330         if (ret == 0)
 331                 ret = vfs_iocb_iter_write(file, &ki->iocb, iter);
 332         memalloc_nofs_restore(old_nofs);
 333         switch (ret) {
 334         case -EIOCBQUEUED:
 335                 goto in_progress;
 336
 337         case -ERESTARTSYS:
 338         case -ERESTARTNOINTR:
 339         case -ERESTARTNOHAND:
 340         case -ERESTART_RESTARTBLOCK:
 341                 /* There's no easy way to restart the syscall since other AIO's
 342                  * may be already running. Just fail this IO with EINTR.
 343                  */
 344                 ret = -EINTR;
 345                 fallthrough;
 346         default:
 347                 ki->was_async = false;
 348                 cachefiles_write_complete(&ki->iocb, ret);
 349                 if (ret > 0)
 350                         ret = 0;
 351                 break;
 352         }
 353
 354 in_progress:
 355         cachefiles_put_kiocb(ki);
 356         _leave(" = %zd", ret);
 357         return ret;
 358 }
 359
 360 static int cachefiles_write(struct netfs_cache_resources *cres,
 361                             loff_t start_pos,
 362                             struct iov_iter *iter,
 363                             netfs_io_terminated_t term_func,
 364                             void *term_func_priv)
 365 {
 366         if (!fscache_wait_for_operation(cres, FSCACHE_WANT_WRITE)) {
 367                 if (term_func)
 368                         term_func(term_func_priv, -ENOBUFS, false);
 369                 return -ENOBUFS;
 370         }
 371
 372         return __cachefiles_write(cachefiles_cres_object(cres),
 373                                   cachefiles_cres_file(cres),
 374                                   start_pos, iter,
 375                                   term_func, term_func_priv);
 376 }
 377
 378 static inline enum netfs_io_source
 379 cachefiles_do_prepare_read(struct netfs_cache_resources *cres,
 380                            loff_t start, size_t *_len, loff_t i_size,
 381                            unsigned long *_flags, ino_t netfs_ino)
 382 {
 383         enum cachefiles_prepare_read_trace why;
 384         struct cachefiles_object *object = NULL;
 385         struct cachefiles_cache *cache;
 386         struct fscache_cookie *cookie = fscache_cres_cookie(cres);
 387         const struct cred *saved_cred;
 388         struct file *file = cachefiles_cres_file(cres);
 389         enum netfs_io_source ret = NETFS_DOWNLOAD_FROM_SERVER;
 390         size_t len = *_len;
 391         loff_t off, to;
 392         ino_t ino = file ? file_inode(file)->i_ino : 0;
 393         int rc;
 394
 395         _enter("%zx @%llx/%llx", len, start, i_size);
 396
 397         if (start >= i_size) {
 398                 ret = NETFS_FILL_WITH_ZEROES;
 399                 why = cachefiles_trace_read_after_eof;
 400                 goto out_no_object;
 401         }
 402
 403         if (test_bit(FSCACHE_COOKIE_NO_DATA_TO_READ, &cookie->flags)) {
 404                 __set_bit(NETFS_SREQ_COPY_TO_CACHE, _flags);
 405                 why = cachefiles_trace_read_no_data;
 406                 if (!test_bit(NETFS_SREQ_ONDEMAND, _flags))
 407                         goto out_no_object;
 408         }
 409
 410         /* The object and the file may be being created in the background. */
 411         if (!file) {
 412                 why = cachefiles_trace_read_no_file;
 413                 if (!fscache_wait_for_operation(cres, FSCACHE_WANT_READ))
 414                         goto out_no_object;
 415                 file = cachefiles_cres_file(cres);
 416                 if (!file)
 417                         goto out_no_object;
 418                 ino = file_inode(file)->i_ino;
 419         }
 420
 421         object = cachefiles_cres_object(cres);
 422         cache = object->volume->cache;
 423         cachefiles_begin_secure(cache, &saved_cred);
 424 retry:
 425         off = cachefiles_inject_read_error();
 426         if (off == 0)
 427                 off = vfs_llseek(file, start, SEEK_DATA);
 428         if (off < 0 && off >= (loff_t)-MAX_ERRNO) {
 429                 if (off == (loff_t)-ENXIO) {
 430                         why = cachefiles_trace_read_seek_nxio;
 431                         goto download_and_store;
 432                 }
 433                 trace_cachefiles_io_error(object, file_inode(file), off,
 434                                           cachefiles_trace_seek_error);
 435                 why = cachefiles_trace_read_seek_error;
 436                 goto out;
 437         }
 438
 439         if (off >= start + len) {
 440                 why = cachefiles_trace_read_found_hole;
 441                 goto download_and_store;
 442         }
 443
 444         if (off > start) {
 445                 off = round_up(off, cache->bsize);
 446                 len = off - start;
 447                 *_len = len;
 448                 why = cachefiles_trace_read_found_part;
 449                 goto download_and_store;
 450         }
 451
 452         to = cachefiles_inject_read_error();
 453         if (to == 0)
 454                 to = vfs_llseek(file, start, SEEK_HOLE);
 455         if (to < 0 && to >= (loff_t)-MAX_ERRNO) {
 456                 trace_cachefiles_io_error(object, file_inode(file), to,
 457                                           cachefiles_trace_seek_error);
 458                 why = cachefiles_trace_read_seek_error;
 459                 goto out;
 460         }
 461
 462         if (to < start + len) {
 463                 if (start + len >= i_size)
 464                         to = round_up(to, cache->bsize);
 465                 else
 466                         to = round_down(to, cache->bsize);
 467                 len = to - start;
 468                 *_len = len;
 469         }
 470
 471         why = cachefiles_trace_read_have_data;
 472         ret = NETFS_READ_FROM_CACHE;
 473         goto out;
 474
 475 download_and_store:
 476         __set_bit(NETFS_SREQ_COPY_TO_CACHE, _flags);
 477         if (test_bit(NETFS_SREQ_ONDEMAND, _flags)) {
 478                 rc = cachefiles_ondemand_read(object, start, len);
 479                 if (!rc) {
 480                         __clear_bit(NETFS_SREQ_ONDEMAND, _flags);
 481                         goto retry;
 482                 }
 483                 ret = NETFS_INVALID_READ;
 484         }
 485 out:
 486         cachefiles_end_secure(cache, saved_cred);
 487 out_no_object:
 488         trace_cachefiles_prep_read(object, start, len, *_flags, ret, why, ino, netfs_ino);
 489         return ret;
 490 }
 491
 492 /*
 493  * Prepare a read operation, shortening it to a cached/uncached
 494  * boundary as appropriate.
 495  */
 496 static enum netfs_io_source cachefiles_prepare_read(struct netfs_io_subrequest *subreq,
 497                                                     loff_t i_size)
 498 {
 499         return cachefiles_do_prepare_read(&subreq->rreq->cache_resources,
 500                                           subreq->start, &subreq->len, i_size,
 501                                           &subreq->flags, subreq->rreq->inode->i_ino);
 502 }
 503
 504 /*
 505  * Prepare an on-demand read operation, shortening it to a cached/uncached
 506  * boundary as appropriate.
 507  */
 508 static enum netfs_io_source
 509 cachefiles_prepare_ondemand_read(struct netfs_cache_resources *cres,
 510                                  loff_t start, size_t *_len, loff_t i_size,
 511                                  unsigned long *_flags, ino_t ino)
 512 {
 513         return cachefiles_do_prepare_read(cres, start, _len, i_size, _flags, ino);
 514 }
 515
 516 /*
 517  * Prepare for a write to occur.
 518  */
 519 int __cachefiles_prepare_write(struct cachefiles_object *object,
 520                                struct file *file,
 521                                loff_t *_start, size_t *_len,
 522                                bool no_space_allocated_yet)
 523 {
 524         struct cachefiles_cache *cache = object->volume->cache;
 525         loff_t start = *_start, pos;
 526         size_t len = *_len, down;
 527         int ret;
 528
 529         /* Round to DIO size */
 530         down = start - round_down(start, PAGE_SIZE);
 531         *_start = start - down;
 532         *_len = round_up(down + len, PAGE_SIZE);
 533
 534         /* We need to work out whether there's sufficient disk space to perform
 535          * the write - but we can skip that check if we have space already
 536          * allocated.
 537          */
 538         if (no_space_allocated_yet)
 539                 goto check_space;
 540
 541         pos = cachefiles_inject_read_error();
 542         if (pos == 0)
 543                 pos = vfs_llseek(file, *_start, SEEK_DATA);
 544         if (pos < 0 && pos >= (loff_t)-MAX_ERRNO) {
 545                 if (pos == -ENXIO)
 546                         goto check_space; /* Unallocated tail */
 547                 trace_cachefiles_io_error(object, file_inode(file), pos,
 548                                           cachefiles_trace_seek_error);
 549                 return pos;
 550         }
 551         if ((u64)pos >= (u64)*_start + *_len)
 552                 goto check_space; /* Unallocated region */
 553
 554         /* We have a block that's at least partially filled - if we're low on
 555          * space, we need to see if it's fully allocated.  If it's not, we may
 556          * want to cull it.
 557          */
 558         if (cachefiles_has_space(cache, 0, *_len / PAGE_SIZE,
 559                                  cachefiles_has_space_check) == 0)
 560                 return 0; /* Enough space to simply overwrite the whole block */
 561
 562         pos = cachefiles_inject_read_error();
 563         if (pos == 0)
 564                 pos = vfs_llseek(file, *_start, SEEK_HOLE);
 565         if (pos < 0 && pos >= (loff_t)-MAX_ERRNO) {
 566                 trace_cachefiles_io_error(object, file_inode(file), pos,
 567                                           cachefiles_trace_seek_error);
 568                 return pos;
 569         }
 570         if ((u64)pos >= (u64)*_start + *_len)
 571                 return 0; /* Fully allocated */
 572
 573         /* Partially allocated, but insufficient space: cull. */
 574         fscache_count_no_write_space();
 575         ret = cachefiles_inject_remove_error();
 576         if (ret == 0)
 577                 ret = vfs_fallocate(file, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
 578                                     *_start, *_len);
 579         if (ret < 0) {
 580                 trace_cachefiles_io_error(object, file_inode(file), ret,
 581                                           cachefiles_trace_fallocate_error);
 582                 cachefiles_io_error_obj(object,
 583                                         "CacheFiles: fallocate failed (%d)\n", ret);
 584                 ret = -EIO;
 585         }
 586
 587         return ret;
 588
 589 check_space:
 590         return cachefiles_has_space(cache, 0, *_len / PAGE_SIZE,
 591                                     cachefiles_has_space_for_write);
 592 }
 593
 594 static int cachefiles_prepare_write(struct netfs_cache_resources *cres,
 595                                     loff_t *_start, size_t *_len, loff_t i_size,
 596                                     bool no_space_allocated_yet)
 597 {
 598         struct cachefiles_object *object = cachefiles_cres_object(cres);
 599         struct cachefiles_cache *cache = object->volume->cache;
 600         const struct cred *saved_cred;
 601         int ret;
 602
 603         if (!cachefiles_cres_file(cres)) {
 604                 if (!fscache_wait_for_operation(cres, FSCACHE_WANT_WRITE))
 605                         return -ENOBUFS;
 606                 if (!cachefiles_cres_file(cres))
 607                         return -ENOBUFS;
 608         }
 609
 610         cachefiles_begin_secure(cache, &saved_cred);
 611         ret = __cachefiles_prepare_write(object, cachefiles_cres_file(cres),
 612                                          _start, _len,
 613                                          no_space_allocated_yet);
 614         cachefiles_end_secure(cache, saved_cred);
 615         return ret;
 616 }
 617
 618 /*
 619  * Clean up an operation.
 620  */
 621 static void cachefiles_end_operation(struct netfs_cache_resources *cres)
 622 {
 623         struct file *file = cachefiles_cres_file(cres);
 624
 625         if (file)
 626                 fput(file);
 627         fscache_end_cookie_access(fscache_cres_cookie(cres), fscache_access_io_end);
 628 }
 629
 630 static const struct netfs_cache_ops cachefiles_netfs_cache_ops = {
 631         .end_operation          = cachefiles_end_operation,
 632         .read                   = cachefiles_read,
 633         .write                  = cachefiles_write,
 634         .prepare_read           = cachefiles_prepare_read,
 635         .prepare_write          = cachefiles_prepare_write,
 636         .prepare_ondemand_read  = cachefiles_prepare_ondemand_read,
 637         .query_occupancy        = cachefiles_query_occupancy,
 638 };
 639
 640 /*
 641  * Open the cache file when beginning a cache operation.
 642  */
 643 bool cachefiles_begin_operation(struct netfs_cache_resources *cres,
 644                                 enum fscache_want_state want_state)
 645 {
 646         struct cachefiles_object *object = cachefiles_cres_object(cres);
 647
 648         if (!cachefiles_cres_file(cres)) {
 649                 cres->ops = &cachefiles_netfs_cache_ops;
 650                 if (object->file) {
 651                         spin_lock(&object->lock);
 652                         if (!cres->cache_priv2 && object->file)
 653                                 cres->cache_priv2 = get_file(object->file);
 654                         spin_unlock(&object->lock);
 655                 }
 656         }
 657
 658         if (!cachefiles_cres_file(cres) && want_state != FSCACHE_WANT_PARAMS) {
 659                 pr_err("failed to get cres->file\n");
 660                 return false;
 661         }
 662
 663         return true;
 664 }