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         if (ki->was_async)
 263                 kiocb_end_write(iocb);
 264
 265         if (ret < 0)
 266                 trace_cachefiles_io_error(object, inode, ret,
 267                                           cachefiles_trace_write_error);
 268
 269         atomic_long_sub(ki->b_writing, &object->volume->cache->b_writing);
 270         set_bit(FSCACHE_COOKIE_HAVE_DATA, &object->cookie->flags);
 271         if (ki->term_func)
 272                 ki->term_func(ki->term_func_priv, ret, ki->was_async);
 273         cachefiles_put_kiocb(ki);
 274 }
 275
 276 /*
 277  * Initiate a write to the cache.
 278  */
 279 int __cachefiles_write(struct cachefiles_object *object,
 280                        struct file *file,
 281                        loff_t start_pos,
 282                        struct iov_iter *iter,
 283                        netfs_io_terminated_t term_func,
 284                        void *term_func_priv)
 285 {
 286         struct cachefiles_cache *cache;
 287         struct cachefiles_kiocb *ki;
 288         unsigned int old_nofs;
 289         ssize_t ret;
 290         size_t len = iov_iter_count(iter);
 291
 292         fscache_count_write();
 293         cache = object->volume->cache;
 294
 295         _enter("%pD,%li,%llx,%zx/%llx",
 296                file, file_inode(file)->i_ino, start_pos, len,
 297                i_size_read(file_inode(file)));
 298
 299         ki = kzalloc(sizeof(struct cachefiles_kiocb), GFP_KERNEL);
 300         if (!ki) {
 301                 if (term_func)
 302                         term_func(term_func_priv, -ENOMEM, false);
 303                 return -ENOMEM;
 304         }
 305
 306         refcount_set(&ki->ki_refcnt, 2);
 307         ki->iocb.ki_filp        = file;
 308         ki->iocb.ki_pos         = start_pos;
 309         ki->iocb.ki_flags       = IOCB_DIRECT | IOCB_WRITE;
 310         ki->iocb.ki_ioprio      = get_current_ioprio();
 311         ki->object              = object;
 312         ki->start               = start_pos;
 313         ki->len                 = len;
 314         ki->term_func           = term_func;
 315         ki->term_func_priv      = term_func_priv;
 316         ki->was_async           = true;
 317         ki->b_writing           = (len + (1 << cache->bshift) - 1) >> cache->bshift;
 318
 319         if (ki->term_func)
 320                 ki->iocb.ki_complete = cachefiles_write_complete;
 321         atomic_long_add(ki->b_writing, &cache->b_writing);
 322
 323         get_file(ki->iocb.ki_filp);
 324         cachefiles_grab_object(object, cachefiles_obj_get_ioreq);
 325
 326         trace_cachefiles_write(object, file_inode(file), ki->iocb.ki_pos, len);
 327         old_nofs = memalloc_nofs_save();
 328         ret = cachefiles_inject_write_error();
 329         if (ret == 0)
 330                 ret = vfs_iocb_iter_write(file, &ki->iocb, iter);
 331         memalloc_nofs_restore(old_nofs);
 332         switch (ret) {
 333         case -EIOCBQUEUED:
 334                 goto in_progress;
 335
 336         case -ERESTARTSYS:
 337         case -ERESTARTNOINTR:
 338         case -ERESTARTNOHAND:
 339         case -ERESTART_RESTARTBLOCK:
 340                 /* There's no easy way to restart the syscall since other AIO's
 341                  * may be already running. Just fail this IO with EINTR.
 342                  */
 343                 ret = -EINTR;
 344                 fallthrough;
 345         default:
 346                 ki->was_async = false;
 347                 cachefiles_write_complete(&ki->iocb, ret);
 348                 if (ret > 0)
 349                         ret = 0;
 350                 break;
 351         }
 352
 353 in_progress:
 354         cachefiles_put_kiocb(ki);
 355         _leave(" = %zd", ret);
 356         return ret;
 357 }
 358
 359 static int cachefiles_write(struct netfs_cache_resources *cres,
 360                             loff_t start_pos,
 361                             struct iov_iter *iter,
 362                             netfs_io_terminated_t term_func,
 363                             void *term_func_priv)
 364 {
 365         if (!fscache_wait_for_operation(cres, FSCACHE_WANT_WRITE)) {
 366                 if (term_func)
 367                         term_func(term_func_priv, -ENOBUFS, false);
 368                 return -ENOBUFS;
 369         }
 370
 371         return __cachefiles_write(cachefiles_cres_object(cres),
 372                                   cachefiles_cres_file(cres),
 373                                   start_pos, iter,
 374                                   term_func, term_func_priv);
 375 }
 376
 377 static inline enum netfs_io_source
 378 cachefiles_do_prepare_read(struct netfs_cache_resources *cres,
 379                            loff_t start, size_t *_len, loff_t i_size,
 380                            unsigned long *_flags, ino_t netfs_ino)
 381 {
 382         enum cachefiles_prepare_read_trace why;
 383         struct cachefiles_object *object = NULL;
 384         struct cachefiles_cache *cache;
 385         struct fscache_cookie *cookie = fscache_cres_cookie(cres);
 386         const struct cred *saved_cred;
 387         struct file *file = cachefiles_cres_file(cres);
 388         enum netfs_io_source ret = NETFS_DOWNLOAD_FROM_SERVER;
 389         size_t len = *_len;
 390         loff_t off, to;
 391         ino_t ino = file ? file_inode(file)->i_ino : 0;
 392         int rc;
 393
 394         _enter("%zx @%llx/%llx", len, start, i_size);
 395
 396         if (start >= i_size) {
 397                 ret = NETFS_FILL_WITH_ZEROES;
 398                 why = cachefiles_trace_read_after_eof;
 399                 goto out_no_object;
 400         }
 401
 402         if (test_bit(FSCACHE_COOKIE_NO_DATA_TO_READ, &cookie->flags)) {
 403                 __set_bit(NETFS_SREQ_COPY_TO_CACHE, _flags);
 404                 why = cachefiles_trace_read_no_data;
 405                 if (!test_bit(NETFS_SREQ_ONDEMAND, _flags))
 406                         goto out_no_object;
 407         }
 408
 409         /* The object and the file may be being created in the background. */
 410         if (!file) {
 411                 why = cachefiles_trace_read_no_file;
 412                 if (!fscache_wait_for_operation(cres, FSCACHE_WANT_READ))
 413                         goto out_no_object;
 414                 file = cachefiles_cres_file(cres);
 415                 if (!file)
 416                         goto out_no_object;
 417                 ino = file_inode(file)->i_ino;
 418         }
 419
 420         object = cachefiles_cres_object(cres);
 421         cache = object->volume->cache;
 422         cachefiles_begin_secure(cache, &saved_cred);
 423 retry:
 424         off = cachefiles_inject_read_error();
 425         if (off == 0)
 426                 off = vfs_llseek(file, start, SEEK_DATA);
 427         if (off < 0 && off >= (loff_t)-MAX_ERRNO) {
 428                 if (off == (loff_t)-ENXIO) {
 429                         why = cachefiles_trace_read_seek_nxio;
 430                         goto download_and_store;
 431                 }
 432                 trace_cachefiles_io_error(object, file_inode(file), off,
 433                                           cachefiles_trace_seek_error);
 434                 why = cachefiles_trace_read_seek_error;
 435                 goto out;
 436         }
 437
 438         if (off >= start + len) {
 439                 why = cachefiles_trace_read_found_hole;
 440                 goto download_and_store;
 441         }
 442
 443         if (off > start) {
 444                 off = round_up(off, cache->bsize);
 445                 len = off - start;
 446                 *_len = len;
 447                 why = cachefiles_trace_read_found_part;
 448                 goto download_and_store;
 449         }
 450
 451         to = cachefiles_inject_read_error();
 452         if (to == 0)
 453                 to = vfs_llseek(file, start, SEEK_HOLE);
 454         if (to < 0 && to >= (loff_t)-MAX_ERRNO) {
 455                 trace_cachefiles_io_error(object, file_inode(file), to,
 456                                           cachefiles_trace_seek_error);
 457                 why = cachefiles_trace_read_seek_error;
 458                 goto out;
 459         }
 460
 461         if (to < start + len) {
 462                 if (start + len >= i_size)
 463                         to = round_up(to, cache->bsize);
 464                 else
 465                         to = round_down(to, cache->bsize);
 466                 len = to - start;
 467                 *_len = len;
 468         }
 469
 470         why = cachefiles_trace_read_have_data;
 471         ret = NETFS_READ_FROM_CACHE;
 472         goto out;
 473
 474 download_and_store:
 475         __set_bit(NETFS_SREQ_COPY_TO_CACHE, _flags);
 476         if (test_bit(NETFS_SREQ_ONDEMAND, _flags)) {
 477                 rc = cachefiles_ondemand_read(object, start, len);
 478                 if (!rc) {
 479                         __clear_bit(NETFS_SREQ_ONDEMAND, _flags);
 480                         goto retry;
 481                 }
 482                 ret = NETFS_INVALID_READ;
 483         }
 484 out:
 485         cachefiles_end_secure(cache, saved_cred);
 486 out_no_object:
 487         trace_cachefiles_prep_read(object, start, len, *_flags, ret, why, ino, netfs_ino);
 488         return ret;
 489 }
 490
 491 /*
 492  * Prepare a read operation, shortening it to a cached/uncached
 493  * boundary as appropriate.
 494  */
 495 static enum netfs_io_source cachefiles_prepare_read(struct netfs_io_subrequest *subreq,
 496                                                     loff_t i_size)
 497 {
 498         return cachefiles_do_prepare_read(&subreq->rreq->cache_resources,
 499                                           subreq->start, &subreq->len, i_size,
 500                                           &subreq->flags, subreq->rreq->inode->i_ino);
 501 }
 502
 503 /*
 504  * Prepare an on-demand read operation, shortening it to a cached/uncached
 505  * boundary as appropriate.
 506  */
 507 static enum netfs_io_source
 508 cachefiles_prepare_ondemand_read(struct netfs_cache_resources *cres,
 509                                  loff_t start, size_t *_len, loff_t i_size,
 510                                  unsigned long *_flags, ino_t ino)
 511 {
 512         return cachefiles_do_prepare_read(cres, start, _len, i_size, _flags, ino);
 513 }
 514
 515 /*
 516  * Prepare for a write to occur.
 517  */
 518 int __cachefiles_prepare_write(struct cachefiles_object *object,
 519                                struct file *file,
 520                                loff_t *_start, size_t *_len, size_t upper_len,
 521                                bool no_space_allocated_yet)
 522 {
 523         struct cachefiles_cache *cache = object->volume->cache;
 524         loff_t start = *_start, pos;
 525         size_t len = *_len;
 526         int ret;
 527
 528         /* Round to DIO size */
 529         start = round_down(*_start, PAGE_SIZE);
 530         if (start != *_start || *_len > upper_len) {
 531                 /* Probably asked to cache a streaming write written into the
 532                  * pagecache when the cookie was temporarily out of service to
 533                  * culling.
 534                  */
 535                 fscache_count_dio_misfit();
 536                 return -ENOBUFS;
 537         }
 538
 539         *_len = round_up(len, PAGE_SIZE);
 540
 541         /* We need to work out whether there's sufficient disk space to perform
 542          * the write - but we can skip that check if we have space already
 543          * allocated.
 544          */
 545         if (no_space_allocated_yet)
 546                 goto check_space;
 547
 548         pos = cachefiles_inject_read_error();
 549         if (pos == 0)
 550                 pos = vfs_llseek(file, start, SEEK_DATA);
 551         if (pos < 0 && pos >= (loff_t)-MAX_ERRNO) {
 552                 if (pos == -ENXIO)
 553                         goto check_space; /* Unallocated tail */
 554                 trace_cachefiles_io_error(object, file_inode(file), pos,
 555                                           cachefiles_trace_seek_error);
 556                 return pos;
 557         }
 558         if ((u64)pos >= (u64)start + *_len)
 559                 goto check_space; /* Unallocated region */
 560
 561         /* We have a block that's at least partially filled - if we're low on
 562          * space, we need to see if it's fully allocated.  If it's not, we may
 563          * want to cull it.
 564          */
 565         if (cachefiles_has_space(cache, 0, *_len / PAGE_SIZE,
 566                                  cachefiles_has_space_check) == 0)
 567                 return 0; /* Enough space to simply overwrite the whole block */
 568
 569         pos = cachefiles_inject_read_error();
 570         if (pos == 0)
 571                 pos = vfs_llseek(file, start, SEEK_HOLE);
 572         if (pos < 0 && pos >= (loff_t)-MAX_ERRNO) {
 573                 trace_cachefiles_io_error(object, file_inode(file), pos,
 574                                           cachefiles_trace_seek_error);
 575                 return pos;
 576         }
 577         if ((u64)pos >= (u64)start + *_len)
 578                 return 0; /* Fully allocated */
 579
 580         /* Partially allocated, but insufficient space: cull. */
 581         fscache_count_no_write_space();
 582         ret = cachefiles_inject_remove_error();
 583         if (ret == 0)
 584                 ret = vfs_fallocate(file, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
 585                                     start, *_len);
 586         if (ret < 0) {
 587                 trace_cachefiles_io_error(object, file_inode(file), ret,
 588                                           cachefiles_trace_fallocate_error);
 589                 cachefiles_io_error_obj(object,
 590                                         "CacheFiles: fallocate failed (%d)\n", ret);
 591                 ret = -EIO;
 592         }
 593
 594         return ret;
 595
 596 check_space:
 597         return cachefiles_has_space(cache, 0, *_len / PAGE_SIZE,
 598                                     cachefiles_has_space_for_write);
 599 }
 600
 601 static int cachefiles_prepare_write(struct netfs_cache_resources *cres,
 602                                     loff_t *_start, size_t *_len, size_t upper_len,
 603                                     loff_t i_size, bool no_space_allocated_yet)
 604 {
 605         struct cachefiles_object *object = cachefiles_cres_object(cres);
 606         struct cachefiles_cache *cache = object->volume->cache;
 607         const struct cred *saved_cred;
 608         int ret;
 609
 610         if (!cachefiles_cres_file(cres)) {
 611                 if (!fscache_wait_for_operation(cres, FSCACHE_WANT_WRITE))
 612                         return -ENOBUFS;
 613                 if (!cachefiles_cres_file(cres))
 614                         return -ENOBUFS;
 615         }
 616
 617         cachefiles_begin_secure(cache, &saved_cred);
 618         ret = __cachefiles_prepare_write(object, cachefiles_cres_file(cres),
 619                                          _start, _len, upper_len,
 620                                          no_space_allocated_yet);
 621         cachefiles_end_secure(cache, saved_cred);
 622         return ret;
 623 }
 624
 625 /*
 626  * Clean up an operation.
 627  */
 628 static void cachefiles_end_operation(struct netfs_cache_resources *cres)
 629 {
 630         struct file *file = cachefiles_cres_file(cres);
 631
 632         if (file)
 633                 fput(file);
 634         fscache_end_cookie_access(fscache_cres_cookie(cres), fscache_access_io_end);
 635 }
 636
 637 static const struct netfs_cache_ops cachefiles_netfs_cache_ops = {
 638         .end_operation          = cachefiles_end_operation,
 639         .read                   = cachefiles_read,
 640         .write                  = cachefiles_write,
 641         .prepare_read           = cachefiles_prepare_read,
 642         .prepare_write          = cachefiles_prepare_write,
 643         .prepare_ondemand_read  = cachefiles_prepare_ondemand_read,
 644         .query_occupancy        = cachefiles_query_occupancy,
 645 };
 646
 647 /*
 648  * Open the cache file when beginning a cache operation.
 649  */
 650 bool cachefiles_begin_operation(struct netfs_cache_resources *cres,
 651                                 enum fscache_want_state want_state)
 652 {
 653         struct cachefiles_object *object = cachefiles_cres_object(cres);
 654
 655         if (!cachefiles_cres_file(cres)) {
 656                 cres->ops = &cachefiles_netfs_cache_ops;
 657                 if (object->file) {
 658                         spin_lock(&object->lock);
 659                         if (!cres->cache_priv2 && object->file)
 660                                 cres->cache_priv2 = get_file(object->file);
 661                         spin_unlock(&object->lock);
 662                 }
 663         }
 664
 665         if (!cachefiles_cres_file(cres) && want_state != FSCACHE_WANT_PARAMS) {
 666                 pr_err("failed to get cres->file\n");
 667                 return false;
 668         }
 669
 670         return true;
 671 }