fs/overlayfs/file.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2017 Red Hat, Inc.
   4  */
   5
   6 #include <linux/cred.h>
   7 #include <linux/file.h>
   8 #include <linux/mount.h>
   9 #include <linux/xattr.h>
  10 #include <linux/uio.h>
  11 #include <linux/uaccess.h>
  12 #include <linux/splice.h>
  13 #include <linux/security.h>
  14 #include <linux/mm.h>
  15 #include <linux/fs.h>
  16 #include "overlayfs.h"
  17
  18 struct ovl_aio_req {
  19         struct kiocb iocb;
  20         refcount_t ref;
  21         struct kiocb *orig_iocb;
  22         struct fd fd;
  23 };
  24
  25 static struct kmem_cache *ovl_aio_request_cachep;
  26
  27 static char ovl_whatisit(struct inode *inode, struct inode *realinode)
  28 {
  29         if (realinode != ovl_inode_upper(inode))
  30                 return 'l';
  31         if (ovl_has_upperdata(inode))
  32                 return 'u';
  33         else
  34                 return 'm';
  35 }
  36
  37 /* No atime modification on underlying */
  38 #define OVL_OPEN_FLAGS (O_NOATIME)
  39
  40 static struct file *ovl_open_realfile(const struct file *file,
  41                                       const struct path *realpath)
  42 {
  43         struct inode *realinode = d_inode(realpath->dentry);
  44         struct inode *inode = file_inode(file);
  45         struct mnt_idmap *real_idmap;
  46         struct file *realfile;
  47         const struct cred *old_cred;
  48         int flags = file->f_flags | OVL_OPEN_FLAGS;
  49         int acc_mode = ACC_MODE(flags);
  50         int err;
  51
  52         if (flags & O_APPEND)
  53                 acc_mode |= MAY_APPEND;
  54
  55         old_cred = ovl_override_creds(inode->i_sb);
  56         real_idmap = mnt_idmap(realpath->mnt);
  57         err = inode_permission(real_idmap, realinode, MAY_OPEN | acc_mode);
  58         if (err) {
  59                 realfile = ERR_PTR(err);
  60         } else {
  61                 if (!inode_owner_or_capable(real_idmap, realinode))
  62                         flags &= ~O_NOATIME;
  63
  64                 realfile = backing_file_open(&file->f_path, flags, realpath,
  65                                              current_cred());
  66         }
  67         revert_creds(old_cred);
  68
  69         pr_debug("open(%p[%pD2/%c], 0%o) -> (%p, 0%o)\n",
  70                  file, file, ovl_whatisit(inode, realinode), file->f_flags,
  71                  realfile, IS_ERR(realfile) ? 0 : realfile->f_flags);
  72
  73         return realfile;
  74 }
  75
  76 #define OVL_SETFL_MASK (O_APPEND | O_NONBLOCK | O_NDELAY | O_DIRECT)
  77
  78 static int ovl_change_flags(struct file *file, unsigned int flags)
  79 {
  80         struct inode *inode = file_inode(file);
  81         int err;
  82
  83         flags &= OVL_SETFL_MASK;
  84
  85         if (((flags ^ file->f_flags) & O_APPEND) && IS_APPEND(inode))
  86                 return -EPERM;
  87
  88         if ((flags & O_DIRECT) && !(file->f_mode & FMODE_CAN_ODIRECT))
  89                 return -EINVAL;
  90
  91         if (file->f_op->check_flags) {
  92                 err = file->f_op->check_flags(flags);
  93                 if (err)
  94                         return err;
  95         }
  96
  97         spin_lock(&file->f_lock);
  98         file->f_flags = (file->f_flags & ~OVL_SETFL_MASK) | flags;
  99         file->f_iocb_flags = iocb_flags(file);
 100         spin_unlock(&file->f_lock);
 101
 102         return 0;
 103 }
 104
 105 static int ovl_real_fdget_meta(const struct file *file, struct fd *real,
 106                                bool allow_meta)
 107 {
 108         struct dentry *dentry = file_dentry(file);
 109         struct path realpath;
 110         int err;
 111
 112         real->flags = 0;
 113         real->file = file->private_data;
 114
 115         if (allow_meta) {
 116                 ovl_path_real(dentry, &realpath);
 117         } else {
 118                 /* lazy lookup of lowerdata */
 119                 err = ovl_maybe_lookup_lowerdata(dentry);
 120                 if (err)
 121                         return err;
 122
 123                 ovl_path_realdata(dentry, &realpath);
 124         }
 125         if (!realpath.dentry)
 126                 return -EIO;
 127
 128         /* Has it been copied up since we'd opened it? */
 129         if (unlikely(file_inode(real->file) != d_inode(realpath.dentry))) {
 130                 real->flags = FDPUT_FPUT;
 131                 real->file = ovl_open_realfile(file, &realpath);
 132
 133                 return PTR_ERR_OR_ZERO(real->file);
 134         }
 135
 136         /* Did the flags change since open? */
 137         if (unlikely((file->f_flags ^ real->file->f_flags) & ~OVL_OPEN_FLAGS))
 138                 return ovl_change_flags(real->file, file->f_flags);
 139
 140         return 0;
 141 }
 142
 143 static int ovl_real_fdget(const struct file *file, struct fd *real)
 144 {
 145         if (d_is_dir(file_dentry(file))) {
 146                 real->flags = 0;
 147                 real->file = ovl_dir_real_file(file, false);
 148
 149                 return PTR_ERR_OR_ZERO(real->file);
 150         }
 151
 152         return ovl_real_fdget_meta(file, real, false);
 153 }
 154
 155 static int ovl_open(struct inode *inode, struct file *file)
 156 {
 157         struct dentry *dentry = file_dentry(file);
 158         struct file *realfile;
 159         struct path realpath;
 160         int err;
 161
 162         /* lazy lookup of lowerdata */
 163         err = ovl_maybe_lookup_lowerdata(dentry);
 164         if (err)
 165                 return err;
 166
 167         err = ovl_maybe_copy_up(dentry, file->f_flags);
 168         if (err)
 169                 return err;
 170
 171         /* No longer need these flags, so don't pass them on to underlying fs */
 172         file->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
 173
 174         ovl_path_realdata(dentry, &realpath);
 175         if (!realpath.dentry)
 176                 return -EIO;
 177
 178         realfile = ovl_open_realfile(file, &realpath);
 179         if (IS_ERR(realfile))
 180                 return PTR_ERR(realfile);
 181
 182         file->private_data = realfile;
 183
 184         return 0;
 185 }
 186
 187 static int ovl_release(struct inode *inode, struct file *file)
 188 {
 189         fput(file->private_data);
 190
 191         return 0;
 192 }
 193
 194 static loff_t ovl_llseek(struct file *file, loff_t offset, int whence)
 195 {
 196         struct inode *inode = file_inode(file);
 197         struct fd real;
 198         const struct cred *old_cred;
 199         loff_t ret;
 200
 201         /*
 202          * The two special cases below do not need to involve real fs,
 203          * so we can optimizing concurrent callers.
 204          */
 205         if (offset == 0) {
 206                 if (whence == SEEK_CUR)
 207                         return file->f_pos;
 208
 209                 if (whence == SEEK_SET)
 210                         return vfs_setpos(file, 0, 0);
 211         }
 212
 213         ret = ovl_real_fdget(file, &real);
 214         if (ret)
 215                 return ret;
 216
 217         /*
 218          * Overlay file f_pos is the master copy that is preserved
 219          * through copy up and modified on read/write, but only real
 220          * fs knows how to SEEK_HOLE/SEEK_DATA and real fs may impose
 221          * limitations that are more strict than ->s_maxbytes for specific
 222          * files, so we use the real file to perform seeks.
 223          */
 224         ovl_inode_lock(inode);
 225         real.file->f_pos = file->f_pos;
 226
 227         old_cred = ovl_override_creds(inode->i_sb);
 228         ret = vfs_llseek(real.file, offset, whence);
 229         revert_creds(old_cred);
 230
 231         file->f_pos = real.file->f_pos;
 232         ovl_inode_unlock(inode);
 233
 234         fdput(real);
 235
 236         return ret;
 237 }
 238
 239 static void ovl_file_accessed(struct file *file)
 240 {
 241         struct inode *inode, *upperinode;
 242
 243         if (file->f_flags & O_NOATIME)
 244                 return;
 245
 246         inode = file_inode(file);
 247         upperinode = ovl_inode_upper(inode);
 248
 249         if (!upperinode)
 250                 return;
 251
 252         if ((!timespec64_equal(&inode->i_mtime, &upperinode->i_mtime) ||
 253              !timespec64_equal(&inode->i_ctime, &upperinode->i_ctime))) {
 254                 inode->i_mtime = upperinode->i_mtime;
 255                 inode->i_ctime = upperinode->i_ctime;
 256         }
 257
 258         touch_atime(&file->f_path);
 259 }
 260
 261 static rwf_t ovl_iocb_to_rwf(int ifl)
 262 {
 263         rwf_t flags = 0;
 264
 265         if (ifl & IOCB_NOWAIT)
 266                 flags |= RWF_NOWAIT;
 267         if (ifl & IOCB_HIPRI)
 268                 flags |= RWF_HIPRI;
 269         if (ifl & IOCB_DSYNC)
 270                 flags |= RWF_DSYNC;
 271         if (ifl & IOCB_SYNC)
 272                 flags |= RWF_SYNC;
 273
 274         return flags;
 275 }
 276
 277 static inline void ovl_aio_put(struct ovl_aio_req *aio_req)
 278 {
 279         if (refcount_dec_and_test(&aio_req->ref)) {
 280                 fdput(aio_req->fd);
 281                 kmem_cache_free(ovl_aio_request_cachep, aio_req);
 282         }
 283 }
 284
 285 static void ovl_aio_cleanup_handler(struct ovl_aio_req *aio_req)
 286 {
 287         struct kiocb *iocb = &aio_req->iocb;
 288         struct kiocb *orig_iocb = aio_req->orig_iocb;
 289
 290         if (iocb->ki_flags & IOCB_WRITE) {
 291                 struct inode *inode = file_inode(orig_iocb->ki_filp);
 292
 293                 /* Actually acquired in ovl_write_iter() */
 294                 __sb_writers_acquired(file_inode(iocb->ki_filp)->i_sb,
 295                                       SB_FREEZE_WRITE);
 296                 file_end_write(iocb->ki_filp);
 297                 ovl_copyattr(inode);
 298         }
 299
 300         orig_iocb->ki_pos = iocb->ki_pos;
 301         ovl_aio_put(aio_req);
 302 }
 303
 304 static void ovl_aio_rw_complete(struct kiocb *iocb, long res)
 305 {
 306         struct ovl_aio_req *aio_req = container_of(iocb,
 307                                                    struct ovl_aio_req, iocb);
 308         struct kiocb *orig_iocb = aio_req->orig_iocb;
 309
 310         ovl_aio_cleanup_handler(aio_req);
 311         orig_iocb->ki_complete(orig_iocb, res);
 312 }
 313
 314 static ssize_t ovl_read_iter(struct kiocb *iocb, struct iov_iter *iter)
 315 {
 316         struct file *file = iocb->ki_filp;
 317         struct fd real;
 318         const struct cred *old_cred;
 319         ssize_t ret;
 320
 321         if (!iov_iter_count(iter))
 322                 return 0;
 323
 324         ret = ovl_real_fdget(file, &real);
 325         if (ret)
 326                 return ret;
 327
 328         ret = -EINVAL;
 329         if (iocb->ki_flags & IOCB_DIRECT &&
 330             !(real.file->f_mode & FMODE_CAN_ODIRECT))
 331                 goto out_fdput;
 332
 333         old_cred = ovl_override_creds(file_inode(file)->i_sb);
 334         if (is_sync_kiocb(iocb)) {
 335                 ret = vfs_iter_read(real.file, iter, &iocb->ki_pos,
 336                                     ovl_iocb_to_rwf(iocb->ki_flags));
 337         } else {
 338                 struct ovl_aio_req *aio_req;
 339
 340                 ret = -ENOMEM;
 341                 aio_req = kmem_cache_zalloc(ovl_aio_request_cachep, GFP_KERNEL);
 342                 if (!aio_req)
 343                         goto out;
 344
 345                 aio_req->fd = real;
 346                 real.flags = 0;
 347                 aio_req->orig_iocb = iocb;
 348                 kiocb_clone(&aio_req->iocb, iocb, real.file);
 349                 aio_req->iocb.ki_complete = ovl_aio_rw_complete;
 350                 refcount_set(&aio_req->ref, 2);
 351                 ret = vfs_iocb_iter_read(real.file, &aio_req->iocb, iter);
 352                 ovl_aio_put(aio_req);
 353                 if (ret != -EIOCBQUEUED)
 354                         ovl_aio_cleanup_handler(aio_req);
 355         }
 356 out:
 357         revert_creds(old_cred);
 358         ovl_file_accessed(file);
 359 out_fdput:
 360         fdput(real);
 361
 362         return ret;
 363 }
 364
 365 static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter)
 366 {
 367         struct file *file = iocb->ki_filp;
 368         struct inode *inode = file_inode(file);
 369         struct fd real;
 370         const struct cred *old_cred;
 371         ssize_t ret;
 372         int ifl = iocb->ki_flags;
 373
 374         if (!iov_iter_count(iter))
 375                 return 0;
 376
 377         inode_lock(inode);
 378         /* Update mode */
 379         ovl_copyattr(inode);
 380         ret = file_remove_privs(file);
 381         if (ret)
 382                 goto out_unlock;
 383
 384         ret = ovl_real_fdget(file, &real);
 385         if (ret)
 386                 goto out_unlock;
 387
 388         ret = -EINVAL;
 389         if (iocb->ki_flags & IOCB_DIRECT &&
 390             !(real.file->f_mode & FMODE_CAN_ODIRECT))
 391                 goto out_fdput;
 392
 393         if (!ovl_should_sync(OVL_FS(inode->i_sb)))
 394                 ifl &= ~(IOCB_DSYNC | IOCB_SYNC);
 395
 396         old_cred = ovl_override_creds(file_inode(file)->i_sb);
 397         if (is_sync_kiocb(iocb)) {
 398                 file_start_write(real.file);
 399                 ret = vfs_iter_write(real.file, iter, &iocb->ki_pos,
 400                                      ovl_iocb_to_rwf(ifl));
 401                 file_end_write(real.file);
 402                 /* Update size */
 403                 ovl_copyattr(inode);
 404         } else {
 405                 struct ovl_aio_req *aio_req;
 406
 407                 ret = -ENOMEM;
 408                 aio_req = kmem_cache_zalloc(ovl_aio_request_cachep, GFP_KERNEL);
 409                 if (!aio_req)
 410                         goto out;
 411
 412                 file_start_write(real.file);
 413                 /* Pacify lockdep, same trick as done in aio_write() */
 414                 __sb_writers_release(file_inode(real.file)->i_sb,
 415                                      SB_FREEZE_WRITE);
 416                 aio_req->fd = real;
 417                 real.flags = 0;
 418                 aio_req->orig_iocb = iocb;
 419                 kiocb_clone(&aio_req->iocb, iocb, real.file);
 420                 aio_req->iocb.ki_flags = ifl;
 421                 aio_req->iocb.ki_complete = ovl_aio_rw_complete;
 422                 refcount_set(&aio_req->ref, 2);
 423                 ret = vfs_iocb_iter_write(real.file, &aio_req->iocb, iter);
 424                 ovl_aio_put(aio_req);
 425                 if (ret != -EIOCBQUEUED)
 426                         ovl_aio_cleanup_handler(aio_req);
 427         }
 428 out:
 429         revert_creds(old_cred);
 430 out_fdput:
 431         fdput(real);
 432
 433 out_unlock:
 434         inode_unlock(inode);
 435
 436         return ret;
 437 }
 438
 439 static ssize_t ovl_splice_read(struct file *in, loff_t *ppos,
 440                                struct pipe_inode_info *pipe, size_t len,
 441                                unsigned int flags)
 442 {
 443         const struct cred *old_cred;
 444         struct fd real;
 445         ssize_t ret;
 446
 447         ret = ovl_real_fdget(in, &real);
 448         if (ret)
 449                 return ret;
 450
 451         old_cred = ovl_override_creds(file_inode(in)->i_sb);
 452         ret = vfs_splice_read(real.file, ppos, pipe, len, flags);
 453         revert_creds(old_cred);
 454         ovl_file_accessed(in);
 455
 456         fdput(real);
 457         return ret;
 458 }
 459
 460 /*
 461  * Calling iter_file_splice_write() directly from overlay's f_op may deadlock
 462  * due to lock order inversion between pipe->mutex in iter_file_splice_write()
 463  * and file_start_write(real.file) in ovl_write_iter().
 464  *
 465  * So do everything ovl_write_iter() does and call iter_file_splice_write() on
 466  * the real file.
 467  */
 468 static ssize_t ovl_splice_write(struct pipe_inode_info *pipe, struct file *out,
 469                                 loff_t *ppos, size_t len, unsigned int flags)
 470 {
 471         struct fd real;
 472         const struct cred *old_cred;
 473         struct inode *inode = file_inode(out);
 474         ssize_t ret;
 475
 476         inode_lock(inode);
 477         /* Update mode */
 478         ovl_copyattr(inode);
 479         ret = file_remove_privs(out);
 480         if (ret)
 481                 goto out_unlock;
 482
 483         ret = ovl_real_fdget(out, &real);
 484         if (ret)
 485                 goto out_unlock;
 486
 487         old_cred = ovl_override_creds(inode->i_sb);
 488         file_start_write(real.file);
 489
 490         ret = iter_file_splice_write(pipe, real.file, ppos, len, flags);
 491
 492         file_end_write(real.file);
 493         /* Update size */
 494         ovl_copyattr(inode);
 495         revert_creds(old_cred);
 496         fdput(real);
 497
 498 out_unlock:
 499         inode_unlock(inode);
 500
 501         return ret;
 502 }
 503
 504 static int ovl_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 505 {
 506         struct fd real;
 507         const struct cred *old_cred;
 508         int ret;
 509
 510         ret = ovl_sync_status(OVL_FS(file_inode(file)->i_sb));
 511         if (ret <= 0)
 512                 return ret;
 513
 514         ret = ovl_real_fdget_meta(file, &real, !datasync);
 515         if (ret)
 516                 return ret;
 517
 518         /* Don't sync lower file for fear of receiving EROFS error */
 519         if (file_inode(real.file) == ovl_inode_upper(file_inode(file))) {
 520                 old_cred = ovl_override_creds(file_inode(file)->i_sb);
 521                 ret = vfs_fsync_range(real.file, start, end, datasync);
 522                 revert_creds(old_cred);
 523         }
 524
 525         fdput(real);
 526
 527         return ret;
 528 }
 529
 530 static int ovl_mmap(struct file *file, struct vm_area_struct *vma)
 531 {
 532         struct file *realfile = file->private_data;
 533         const struct cred *old_cred;
 534         int ret;
 535
 536         if (!realfile->f_op->mmap)
 537                 return -ENODEV;
 538
 539         if (WARN_ON(file != vma->vm_file))
 540                 return -EIO;
 541
 542         vma_set_file(vma, realfile);
 543
 544         old_cred = ovl_override_creds(file_inode(file)->i_sb);
 545         ret = call_mmap(vma->vm_file, vma);
 546         revert_creds(old_cred);
 547         ovl_file_accessed(file);
 548
 549         return ret;
 550 }
 551
 552 static long ovl_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
 553 {
 554         struct inode *inode = file_inode(file);
 555         struct fd real;
 556         const struct cred *old_cred;
 557         int ret;
 558
 559         inode_lock(inode);
 560         /* Update mode */
 561         ovl_copyattr(inode);
 562         ret = file_remove_privs(file);
 563         if (ret)
 564                 goto out_unlock;
 565
 566         ret = ovl_real_fdget(file, &real);
 567         if (ret)
 568                 goto out_unlock;
 569
 570         old_cred = ovl_override_creds(file_inode(file)->i_sb);
 571         ret = vfs_fallocate(real.file, mode, offset, len);
 572         revert_creds(old_cred);
 573
 574         /* Update size */
 575         ovl_copyattr(inode);
 576
 577         fdput(real);
 578
 579 out_unlock:
 580         inode_unlock(inode);
 581
 582         return ret;
 583 }
 584
 585 static int ovl_fadvise(struct file *file, loff_t offset, loff_t len, int advice)
 586 {
 587         struct fd real;
 588         const struct cred *old_cred;
 589         int ret;
 590
 591         ret = ovl_real_fdget(file, &real);
 592         if (ret)
 593                 return ret;
 594
 595         old_cred = ovl_override_creds(file_inode(file)->i_sb);
 596         ret = vfs_fadvise(real.file, offset, len, advice);
 597         revert_creds(old_cred);
 598
 599         fdput(real);
 600
 601         return ret;
 602 }
 603
 604 enum ovl_copyop {
 605         OVL_COPY,
 606         OVL_CLONE,
 607         OVL_DEDUPE,
 608 };
 609
 610 static loff_t ovl_copyfile(struct file *file_in, loff_t pos_in,
 611                             struct file *file_out, loff_t pos_out,
 612                             loff_t len, unsigned int flags, enum ovl_copyop op)
 613 {
 614         struct inode *inode_out = file_inode(file_out);
 615         struct fd real_in, real_out;
 616         const struct cred *old_cred;
 617         loff_t ret;
 618
 619         inode_lock(inode_out);
 620         if (op != OVL_DEDUPE) {
 621                 /* Update mode */
 622                 ovl_copyattr(inode_out);
 623                 ret = file_remove_privs(file_out);
 624                 if (ret)
 625                         goto out_unlock;
 626         }
 627
 628         ret = ovl_real_fdget(file_out, &real_out);
 629         if (ret)
 630                 goto out_unlock;
 631
 632         ret = ovl_real_fdget(file_in, &real_in);
 633         if (ret) {
 634                 fdput(real_out);
 635                 goto out_unlock;
 636         }
 637
 638         old_cred = ovl_override_creds(file_inode(file_out)->i_sb);
 639         switch (op) {
 640         case OVL_COPY:
 641                 ret = vfs_copy_file_range(real_in.file, pos_in,
 642                                           real_out.file, pos_out, len, flags);
 643                 break;
 644
 645         case OVL_CLONE:
 646                 ret = vfs_clone_file_range(real_in.file, pos_in,
 647                                            real_out.file, pos_out, len, flags);
 648                 break;
 649
 650         case OVL_DEDUPE:
 651                 ret = vfs_dedupe_file_range_one(real_in.file, pos_in,
 652                                                 real_out.file, pos_out, len,
 653                                                 flags);
 654                 break;
 655         }
 656         revert_creds(old_cred);
 657
 658         /* Update size */
 659         ovl_copyattr(inode_out);
 660
 661         fdput(real_in);
 662         fdput(real_out);
 663
 664 out_unlock:
 665         inode_unlock(inode_out);
 666
 667         return ret;
 668 }
 669
 670 static ssize_t ovl_copy_file_range(struct file *file_in, loff_t pos_in,
 671                                    struct file *file_out, loff_t pos_out,
 672                                    size_t len, unsigned int flags)
 673 {
 674         return ovl_copyfile(file_in, pos_in, file_out, pos_out, len, flags,
 675                             OVL_COPY);
 676 }
 677
 678 static loff_t ovl_remap_file_range(struct file *file_in, loff_t pos_in,
 679                                    struct file *file_out, loff_t pos_out,
 680                                    loff_t len, unsigned int remap_flags)
 681 {
 682         enum ovl_copyop op;
 683
 684         if (remap_flags & ~(REMAP_FILE_DEDUP | REMAP_FILE_ADVISORY))
 685                 return -EINVAL;
 686
 687         if (remap_flags & REMAP_FILE_DEDUP)
 688                 op = OVL_DEDUPE;
 689         else
 690                 op = OVL_CLONE;
 691
 692         /*
 693          * Don't copy up because of a dedupe request, this wouldn't make sense
 694          * most of the time (data would be duplicated instead of deduplicated).
 695          */
 696         if (op == OVL_DEDUPE &&
 697             (!ovl_inode_upper(file_inode(file_in)) ||
 698              !ovl_inode_upper(file_inode(file_out))))
 699                 return -EPERM;
 700
 701         return ovl_copyfile(file_in, pos_in, file_out, pos_out, len,
 702                             remap_flags, op);
 703 }
 704
 705 static int ovl_flush(struct file *file, fl_owner_t id)
 706 {
 707         struct fd real;
 708         const struct cred *old_cred;
 709         int err;
 710
 711         err = ovl_real_fdget(file, &real);
 712         if (err)
 713                 return err;
 714
 715         if (real.file->f_op->flush) {
 716                 old_cred = ovl_override_creds(file_inode(file)->i_sb);
 717                 err = real.file->f_op->flush(real.file, id);
 718                 revert_creds(old_cred);
 719         }
 720         fdput(real);
 721
 722         return err;
 723 }
 724
 725 const struct file_operations ovl_file_operations = {
 726         .open           = ovl_open,
 727         .release        = ovl_release,
 728         .llseek         = ovl_llseek,
 729         .read_iter      = ovl_read_iter,
 730         .write_iter     = ovl_write_iter,
 731         .fsync          = ovl_fsync,
 732         .mmap           = ovl_mmap,
 733         .fallocate      = ovl_fallocate,
 734         .fadvise        = ovl_fadvise,
 735         .flush          = ovl_flush,
 736         .splice_read    = ovl_splice_read,
 737         .splice_write   = ovl_splice_write,
 738
 739         .copy_file_range        = ovl_copy_file_range,
 740         .remap_file_range       = ovl_remap_file_range,
 741 };
 742
 743 int __init ovl_aio_request_cache_init(void)
 744 {
 745         ovl_aio_request_cachep = kmem_cache_create("ovl_aio_req",
 746                                                    sizeof(struct ovl_aio_req),
 747                                                    0, SLAB_HWCACHE_ALIGN, NULL);
 748         if (!ovl_aio_request_cachep)
 749                 return -ENOMEM;
 750
 751         return 0;
 752 }
 753
 754 void ovl_aio_request_cache_destroy(void)
 755 {
 756         kmem_cache_destroy(ovl_aio_request_cachep);
 757 }