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 };
  23
  24 static struct kmem_cache *ovl_aio_request_cachep;
  25
  26 static char ovl_whatisit(struct inode *inode, struct inode *realinode)
  27 {
  28         if (realinode != ovl_inode_upper(inode))
  29                 return 'l';
  30         if (ovl_has_upperdata(inode))
  31                 return 'u';
  32         else
  33                 return 'm';
  34 }
  35
  36 /* No atime modification on underlying */
  37 #define OVL_OPEN_FLAGS (O_NOATIME)
  38
  39 static struct file *ovl_open_realfile(const struct file *file,
  40                                       const struct path *realpath)
  41 {
  42         struct inode *realinode = d_inode(realpath->dentry);
  43         struct inode *inode = file_inode(file);
  44         struct mnt_idmap *real_idmap;
  45         struct file *realfile;
  46         const struct cred *old_cred;
  47         int flags = file->f_flags | OVL_OPEN_FLAGS;
  48         int acc_mode = ACC_MODE(flags);
  49         int err;
  50
  51         if (flags & O_APPEND)
  52                 acc_mode |= MAY_APPEND;
  53
  54         old_cred = ovl_override_creds(inode->i_sb);
  55         real_idmap = mnt_idmap(realpath->mnt);
  56         err = inode_permission(real_idmap, realinode, MAY_OPEN | acc_mode);
  57         if (err) {
  58                 realfile = ERR_PTR(err);
  59         } else {
  60                 if (!inode_owner_or_capable(real_idmap, realinode))
  61                         flags &= ~O_NOATIME;
  62
  63                 realfile = backing_file_open(&file->f_path, flags, realpath,
  64                                              current_cred());
  65         }
  66         revert_creds(old_cred);
  67
  68         pr_debug("open(%p[%pD2/%c], 0%o) -> (%p, 0%o)\n",
  69                  file, file, ovl_whatisit(inode, realinode), file->f_flags,
  70                  realfile, IS_ERR(realfile) ? 0 : realfile->f_flags);
  71
  72         return realfile;
  73 }
  74
  75 #define OVL_SETFL_MASK (O_APPEND | O_NONBLOCK | O_NDELAY | O_DIRECT)
  76
  77 static int ovl_change_flags(struct file *file, unsigned int flags)
  78 {
  79         struct inode *inode = file_inode(file);
  80         int err;
  81
  82         flags &= OVL_SETFL_MASK;
  83
  84         if (((flags ^ file->f_flags) & O_APPEND) && IS_APPEND(inode))
  85                 return -EPERM;
  86
  87         if ((flags & O_DIRECT) && !(file->f_mode & FMODE_CAN_ODIRECT))
  88                 return -EINVAL;
  89
  90         if (file->f_op->check_flags) {
  91                 err = file->f_op->check_flags(flags);
  92                 if (err)
  93                         return err;
  94         }
  95
  96         spin_lock(&file->f_lock);
  97         file->f_flags = (file->f_flags & ~OVL_SETFL_MASK) | flags;
  98         file->f_iocb_flags = iocb_flags(file);
  99         spin_unlock(&file->f_lock);
 100
 101         return 0;
 102 }
 103
 104 static int ovl_real_fdget_meta(const struct file *file, struct fd *real,
 105                                bool allow_meta)
 106 {
 107         struct dentry *dentry = file_dentry(file);
 108         struct path realpath;
 109         int err;
 110
 111         real->flags = 0;
 112         real->file = file->private_data;
 113
 114         if (allow_meta) {
 115                 ovl_path_real(dentry, &realpath);
 116         } else {
 117                 /* lazy lookup and verify of lowerdata */
 118                 err = ovl_verify_lowerdata(dentry);
 119                 if (err)
 120                         return err;
 121
 122                 ovl_path_realdata(dentry, &realpath);
 123         }
 124         if (!realpath.dentry)
 125                 return -EIO;
 126
 127         /* Has it been copied up since we'd opened it? */
 128         if (unlikely(file_inode(real->file) != d_inode(realpath.dentry))) {
 129                 real->flags = FDPUT_FPUT;
 130                 real->file = ovl_open_realfile(file, &realpath);
 131
 132                 return PTR_ERR_OR_ZERO(real->file);
 133         }
 134
 135         /* Did the flags change since open? */
 136         if (unlikely((file->f_flags ^ real->file->f_flags) & ~OVL_OPEN_FLAGS))
 137                 return ovl_change_flags(real->file, file->f_flags);
 138
 139         return 0;
 140 }
 141
 142 static int ovl_real_fdget(const struct file *file, struct fd *real)
 143 {
 144         if (d_is_dir(file_dentry(file))) {
 145                 real->flags = 0;
 146                 real->file = ovl_dir_real_file(file, false);
 147
 148                 return PTR_ERR_OR_ZERO(real->file);
 149         }
 150
 151         return ovl_real_fdget_meta(file, real, false);
 152 }
 153
 154 static int ovl_open(struct inode *inode, struct file *file)
 155 {
 156         struct dentry *dentry = file_dentry(file);
 157         struct file *realfile;
 158         struct path realpath;
 159         int err;
 160
 161         /* lazy lookup and verify lowerdata */
 162         err = ovl_verify_lowerdata(dentry);
 163         if (err)
 164                 return err;
 165
 166         err = ovl_maybe_copy_up(dentry, file->f_flags);
 167         if (err)
 168                 return err;
 169
 170         /* No longer need these flags, so don't pass them on to underlying fs */
 171         file->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
 172
 173         ovl_path_realdata(dentry, &realpath);
 174         if (!realpath.dentry)
 175                 return -EIO;
 176
 177         realfile = ovl_open_realfile(file, &realpath);
 178         if (IS_ERR(realfile))
 179                 return PTR_ERR(realfile);
 180
 181         file->private_data = realfile;
 182
 183         return 0;
 184 }
 185
 186 static int ovl_release(struct inode *inode, struct file *file)
 187 {
 188         fput(file->private_data);
 189
 190         return 0;
 191 }
 192
 193 static loff_t ovl_llseek(struct file *file, loff_t offset, int whence)
 194 {
 195         struct inode *inode = file_inode(file);
 196         struct fd real;
 197         const struct cred *old_cred;
 198         loff_t ret;
 199
 200         /*
 201          * The two special cases below do not need to involve real fs,
 202          * so we can optimizing concurrent callers.
 203          */
 204         if (offset == 0) {
 205                 if (whence == SEEK_CUR)
 206                         return file->f_pos;
 207
 208                 if (whence == SEEK_SET)
 209                         return vfs_setpos(file, 0, 0);
 210         }
 211
 212         ret = ovl_real_fdget(file, &real);
 213         if (ret)
 214                 return ret;
 215
 216         /*
 217          * Overlay file f_pos is the master copy that is preserved
 218          * through copy up and modified on read/write, but only real
 219          * fs knows how to SEEK_HOLE/SEEK_DATA and real fs may impose
 220          * limitations that are more strict than ->s_maxbytes for specific
 221          * files, so we use the real file to perform seeks.
 222          */
 223         ovl_inode_lock(inode);
 224         real.file->f_pos = file->f_pos;
 225
 226         old_cred = ovl_override_creds(inode->i_sb);
 227         ret = vfs_llseek(real.file, offset, whence);
 228         revert_creds(old_cred);
 229
 230         file->f_pos = real.file->f_pos;
 231         ovl_inode_unlock(inode);
 232
 233         fdput(real);
 234
 235         return ret;
 236 }
 237
 238 static void ovl_file_accessed(struct file *file)
 239 {
 240         struct inode *inode, *upperinode;
 241         struct timespec64 ctime, uctime;
 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         ctime = inode_get_ctime(inode);
 253         uctime = inode_get_ctime(upperinode);
 254         if ((!timespec64_equal(&inode->i_mtime, &upperinode->i_mtime) ||
 255              !timespec64_equal(&ctime, &uctime))) {
 256                 inode->i_mtime = upperinode->i_mtime;
 257                 inode_set_ctime_to_ts(inode, uctime);
 258         }
 259
 260         touch_atime(&file->f_path);
 261 }
 262
 263 static rwf_t ovl_iocb_to_rwf(int ifl)
 264 {
 265         rwf_t flags = 0;
 266
 267         if (ifl & IOCB_NOWAIT)
 268                 flags |= RWF_NOWAIT;
 269         if (ifl & IOCB_HIPRI)
 270                 flags |= RWF_HIPRI;
 271         if (ifl & IOCB_DSYNC)
 272                 flags |= RWF_DSYNC;
 273         if (ifl & IOCB_SYNC)
 274                 flags |= RWF_SYNC;
 275
 276         return flags;
 277 }
 278
 279 static inline void ovl_aio_put(struct ovl_aio_req *aio_req)
 280 {
 281         if (refcount_dec_and_test(&aio_req->ref)) {
 282                 fput(aio_req->iocb.ki_filp);
 283                 kmem_cache_free(ovl_aio_request_cachep, aio_req);
 284         }
 285 }
 286
 287 static void ovl_aio_cleanup_handler(struct ovl_aio_req *aio_req)
 288 {
 289         struct kiocb *iocb = &aio_req->iocb;
 290         struct kiocb *orig_iocb = aio_req->orig_iocb;
 291
 292         if (iocb->ki_flags & IOCB_WRITE) {
 293                 struct inode *inode = file_inode(orig_iocb->ki_filp);
 294
 295                 kiocb_end_write(iocb);
 296                 ovl_copyattr(inode);
 297         }
 298
 299         orig_iocb->ki_pos = iocb->ki_pos;
 300         ovl_aio_put(aio_req);
 301 }
 302
 303 static void ovl_aio_rw_complete(struct kiocb *iocb, long res)
 304 {
 305         struct ovl_aio_req *aio_req = container_of(iocb,
 306                                                    struct ovl_aio_req, iocb);
 307         struct kiocb *orig_iocb = aio_req->orig_iocb;
 308
 309         ovl_aio_cleanup_handler(aio_req);
 310         orig_iocb->ki_complete(orig_iocb, res);
 311 }
 312
 313 static ssize_t ovl_read_iter(struct kiocb *iocb, struct iov_iter *iter)
 314 {
 315         struct file *file = iocb->ki_filp;
 316         struct fd real;
 317         const struct cred *old_cred;
 318         ssize_t ret;
 319
 320         if (!iov_iter_count(iter))
 321                 return 0;
 322
 323         ret = ovl_real_fdget(file, &real);
 324         if (ret)
 325                 return ret;
 326
 327         ret = -EINVAL;
 328         if (iocb->ki_flags & IOCB_DIRECT &&
 329             !(real.file->f_mode & FMODE_CAN_ODIRECT))
 330                 goto out_fdput;
 331
 332         old_cred = ovl_override_creds(file_inode(file)->i_sb);
 333         if (is_sync_kiocb(iocb)) {
 334                 ret = vfs_iter_read(real.file, iter, &iocb->ki_pos,
 335                                     ovl_iocb_to_rwf(iocb->ki_flags));
 336         } else {
 337                 struct ovl_aio_req *aio_req;
 338
 339                 ret = -ENOMEM;
 340                 aio_req = kmem_cache_zalloc(ovl_aio_request_cachep, GFP_KERNEL);
 341                 if (!aio_req)
 342                         goto out;
 343
 344                 aio_req->orig_iocb = iocb;
 345                 kiocb_clone(&aio_req->iocb, iocb, get_file(real.file));
 346                 aio_req->iocb.ki_complete = ovl_aio_rw_complete;
 347                 refcount_set(&aio_req->ref, 2);
 348                 ret = vfs_iocb_iter_read(real.file, &aio_req->iocb, iter);
 349                 ovl_aio_put(aio_req);
 350                 if (ret != -EIOCBQUEUED)
 351                         ovl_aio_cleanup_handler(aio_req);
 352         }
 353 out:
 354         revert_creds(old_cred);
 355         ovl_file_accessed(file);
 356 out_fdput:
 357         fdput(real);
 358
 359         return ret;
 360 }
 361
 362 static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter)
 363 {
 364         struct file *file = iocb->ki_filp;
 365         struct inode *inode = file_inode(file);
 366         struct fd real;
 367         const struct cred *old_cred;
 368         ssize_t ret;
 369         int ifl = iocb->ki_flags;
 370
 371         if (!iov_iter_count(iter))
 372                 return 0;
 373
 374         inode_lock(inode);
 375         /* Update mode */
 376         ovl_copyattr(inode);
 377         ret = file_remove_privs(file);
 378         if (ret)
 379                 goto out_unlock;
 380
 381         ret = ovl_real_fdget(file, &real);
 382         if (ret)
 383                 goto out_unlock;
 384
 385         ret = -EINVAL;
 386         if (iocb->ki_flags & IOCB_DIRECT &&
 387             !(real.file->f_mode & FMODE_CAN_ODIRECT))
 388                 goto out_fdput;
 389
 390         if (!ovl_should_sync(OVL_FS(inode->i_sb)))
 391                 ifl &= ~(IOCB_DSYNC | IOCB_SYNC);
 392
 393         /*
 394          * Overlayfs doesn't support deferred completions, don't copy
 395          * this property in case it is set by the issuer.
 396          */
 397         ifl &= ~IOCB_DIO_CALLER_COMP;
 398
 399         old_cred = ovl_override_creds(file_inode(file)->i_sb);
 400         if (is_sync_kiocb(iocb)) {
 401                 file_start_write(real.file);
 402                 ret = vfs_iter_write(real.file, iter, &iocb->ki_pos,
 403                                      ovl_iocb_to_rwf(ifl));
 404                 file_end_write(real.file);
 405                 /* Update size */
 406                 ovl_copyattr(inode);
 407         } else {
 408                 struct ovl_aio_req *aio_req;
 409
 410                 ret = -ENOMEM;
 411                 aio_req = kmem_cache_zalloc(ovl_aio_request_cachep, GFP_KERNEL);
 412                 if (!aio_req)
 413                         goto out;
 414
 415                 aio_req->orig_iocb = iocb;
 416                 kiocb_clone(&aio_req->iocb, iocb, get_file(real.file));
 417                 aio_req->iocb.ki_flags = ifl;
 418                 aio_req->iocb.ki_complete = ovl_aio_rw_complete;
 419                 refcount_set(&aio_req->ref, 2);
 420                 kiocb_start_write(&aio_req->iocb);
 421                 ret = vfs_iocb_iter_write(real.file, &aio_req->iocb, iter);
 422                 ovl_aio_put(aio_req);
 423                 if (ret != -EIOCBQUEUED)
 424                         ovl_aio_cleanup_handler(aio_req);
 425         }
 426 out:
 427         revert_creds(old_cred);
 428 out_fdput:
 429         fdput(real);
 430
 431 out_unlock:
 432         inode_unlock(inode);
 433
 434         return ret;
 435 }
 436
 437 static ssize_t ovl_splice_read(struct file *in, loff_t *ppos,
 438                                struct pipe_inode_info *pipe, size_t len,
 439                                unsigned int flags)
 440 {
 441         const struct cred *old_cred;
 442         struct fd real;
 443         ssize_t ret;
 444
 445         ret = ovl_real_fdget(in, &real);
 446         if (ret)
 447                 return ret;
 448
 449         old_cred = ovl_override_creds(file_inode(in)->i_sb);
 450         ret = vfs_splice_read(real.file, ppos, pipe, len, flags);
 451         revert_creds(old_cred);
 452         ovl_file_accessed(in);
 453
 454         fdput(real);
 455         return ret;
 456 }
 457
 458 /*
 459  * Calling iter_file_splice_write() directly from overlay's f_op may deadlock
 460  * due to lock order inversion between pipe->mutex in iter_file_splice_write()
 461  * and file_start_write(real.file) in ovl_write_iter().
 462  *
 463  * So do everything ovl_write_iter() does and call iter_file_splice_write() on
 464  * the real file.
 465  */
 466 static ssize_t ovl_splice_write(struct pipe_inode_info *pipe, struct file *out,
 467                                 loff_t *ppos, size_t len, unsigned int flags)
 468 {
 469         struct fd real;
 470         const struct cred *old_cred;
 471         struct inode *inode = file_inode(out);
 472         ssize_t ret;
 473
 474         inode_lock(inode);
 475         /* Update mode */
 476         ovl_copyattr(inode);
 477         ret = file_remove_privs(out);
 478         if (ret)
 479                 goto out_unlock;
 480
 481         ret = ovl_real_fdget(out, &real);
 482         if (ret)
 483                 goto out_unlock;
 484
 485         old_cred = ovl_override_creds(inode->i_sb);
 486         file_start_write(real.file);
 487
 488         ret = iter_file_splice_write(pipe, real.file, ppos, len, flags);
 489
 490         file_end_write(real.file);
 491         /* Update size */
 492         ovl_copyattr(inode);
 493         revert_creds(old_cred);
 494         fdput(real);
 495
 496 out_unlock:
 497         inode_unlock(inode);
 498
 499         return ret;
 500 }
 501
 502 static int ovl_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 503 {
 504         struct fd real;
 505         const struct cred *old_cred;
 506         int ret;
 507
 508         ret = ovl_sync_status(OVL_FS(file_inode(file)->i_sb));
 509         if (ret <= 0)
 510                 return ret;
 511
 512         ret = ovl_real_fdget_meta(file, &real, !datasync);
 513         if (ret)
 514                 return ret;
 515
 516         /* Don't sync lower file for fear of receiving EROFS error */
 517         if (file_inode(real.file) == ovl_inode_upper(file_inode(file))) {
 518                 old_cred = ovl_override_creds(file_inode(file)->i_sb);
 519                 ret = vfs_fsync_range(real.file, start, end, datasync);
 520                 revert_creds(old_cred);
 521         }
 522
 523         fdput(real);
 524
 525         return ret;
 526 }
 527
 528 static int ovl_mmap(struct file *file, struct vm_area_struct *vma)
 529 {
 530         struct file *realfile = file->private_data;
 531         const struct cred *old_cred;
 532         int ret;
 533
 534         if (!realfile->f_op->mmap)
 535                 return -ENODEV;
 536
 537         if (WARN_ON(file != vma->vm_file))
 538                 return -EIO;
 539
 540         vma_set_file(vma, realfile);
 541
 542         old_cred = ovl_override_creds(file_inode(file)->i_sb);
 543         ret = call_mmap(vma->vm_file, vma);
 544         revert_creds(old_cred);
 545         ovl_file_accessed(file);
 546
 547         return ret;
 548 }
 549
 550 static long ovl_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
 551 {
 552         struct inode *inode = file_inode(file);
 553         struct fd real;
 554         const struct cred *old_cred;
 555         int ret;
 556
 557         inode_lock(inode);
 558         /* Update mode */
 559         ovl_copyattr(inode);
 560         ret = file_remove_privs(file);
 561         if (ret)
 562                 goto out_unlock;
 563
 564         ret = ovl_real_fdget(file, &real);
 565         if (ret)
 566                 goto out_unlock;
 567
 568         old_cred = ovl_override_creds(file_inode(file)->i_sb);
 569         ret = vfs_fallocate(real.file, mode, offset, len);
 570         revert_creds(old_cred);
 571
 572         /* Update size */
 573         ovl_copyattr(inode);
 574
 575         fdput(real);
 576
 577 out_unlock:
 578         inode_unlock(inode);
 579
 580         return ret;
 581 }
 582
 583 static int ovl_fadvise(struct file *file, loff_t offset, loff_t len, int advice)
 584 {
 585         struct fd real;
 586         const struct cred *old_cred;
 587         int ret;
 588
 589         ret = ovl_real_fdget(file, &real);
 590         if (ret)
 591                 return ret;
 592
 593         old_cred = ovl_override_creds(file_inode(file)->i_sb);
 594         ret = vfs_fadvise(real.file, offset, len, advice);
 595         revert_creds(old_cred);
 596
 597         fdput(real);
 598
 599         return ret;
 600 }
 601
 602 enum ovl_copyop {
 603         OVL_COPY,
 604         OVL_CLONE,
 605         OVL_DEDUPE,
 606 };
 607
 608 static loff_t ovl_copyfile(struct file *file_in, loff_t pos_in,
 609                             struct file *file_out, loff_t pos_out,
 610                             loff_t len, unsigned int flags, enum ovl_copyop op)
 611 {
 612         struct inode *inode_out = file_inode(file_out);
 613         struct fd real_in, real_out;
 614         const struct cred *old_cred;
 615         loff_t ret;
 616
 617         inode_lock(inode_out);
 618         if (op != OVL_DEDUPE) {
 619                 /* Update mode */
 620                 ovl_copyattr(inode_out);
 621                 ret = file_remove_privs(file_out);
 622                 if (ret)
 623                         goto out_unlock;
 624         }
 625
 626         ret = ovl_real_fdget(file_out, &real_out);
 627         if (ret)
 628                 goto out_unlock;
 629
 630         ret = ovl_real_fdget(file_in, &real_in);
 631         if (ret) {
 632                 fdput(real_out);
 633                 goto out_unlock;
 634         }
 635
 636         old_cred = ovl_override_creds(file_inode(file_out)->i_sb);
 637         switch (op) {
 638         case OVL_COPY:
 639                 ret = vfs_copy_file_range(real_in.file, pos_in,
 640                                           real_out.file, pos_out, len, flags);
 641                 break;
 642
 643         case OVL_CLONE:
 644                 ret = vfs_clone_file_range(real_in.file, pos_in,
 645                                            real_out.file, pos_out, len, flags);
 646                 break;
 647
 648         case OVL_DEDUPE:
 649                 ret = vfs_dedupe_file_range_one(real_in.file, pos_in,
 650                                                 real_out.file, pos_out, len,
 651                                                 flags);
 652                 break;
 653         }
 654         revert_creds(old_cred);
 655
 656         /* Update size */
 657         ovl_copyattr(inode_out);
 658
 659         fdput(real_in);
 660         fdput(real_out);
 661
 662 out_unlock:
 663         inode_unlock(inode_out);
 664
 665         return ret;
 666 }
 667
 668 static ssize_t ovl_copy_file_range(struct file *file_in, loff_t pos_in,
 669                                    struct file *file_out, loff_t pos_out,
 670                                    size_t len, unsigned int flags)
 671 {
 672         return ovl_copyfile(file_in, pos_in, file_out, pos_out, len, flags,
 673                             OVL_COPY);
 674 }
 675
 676 static loff_t ovl_remap_file_range(struct file *file_in, loff_t pos_in,
 677                                    struct file *file_out, loff_t pos_out,
 678                                    loff_t len, unsigned int remap_flags)
 679 {
 680         enum ovl_copyop op;
 681
 682         if (remap_flags & ~(REMAP_FILE_DEDUP | REMAP_FILE_ADVISORY))
 683                 return -EINVAL;
 684
 685         if (remap_flags & REMAP_FILE_DEDUP)
 686                 op = OVL_DEDUPE;
 687         else
 688                 op = OVL_CLONE;
 689
 690         /*
 691          * Don't copy up because of a dedupe request, this wouldn't make sense
 692          * most of the time (data would be duplicated instead of deduplicated).
 693          */
 694         if (op == OVL_DEDUPE &&
 695             (!ovl_inode_upper(file_inode(file_in)) ||
 696              !ovl_inode_upper(file_inode(file_out))))
 697                 return -EPERM;
 698
 699         return ovl_copyfile(file_in, pos_in, file_out, pos_out, len,
 700                             remap_flags, op);
 701 }
 702
 703 static int ovl_flush(struct file *file, fl_owner_t id)
 704 {
 705         struct fd real;
 706         const struct cred *old_cred;
 707         int err;
 708
 709         err = ovl_real_fdget(file, &real);
 710         if (err)
 711                 return err;
 712
 713         if (real.file->f_op->flush) {
 714                 old_cred = ovl_override_creds(file_inode(file)->i_sb);
 715                 err = real.file->f_op->flush(real.file, id);
 716                 revert_creds(old_cred);
 717         }
 718         fdput(real);
 719
 720         return err;
 721 }
 722
 723 const struct file_operations ovl_file_operations = {
 724         .open           = ovl_open,
 725         .release        = ovl_release,
 726         .llseek         = ovl_llseek,
 727         .read_iter      = ovl_read_iter,
 728         .write_iter     = ovl_write_iter,
 729         .fsync          = ovl_fsync,
 730         .mmap           = ovl_mmap,
 731         .fallocate      = ovl_fallocate,
 732         .fadvise        = ovl_fadvise,
 733         .flush          = ovl_flush,
 734         .splice_read    = ovl_splice_read,
 735         .splice_write   = ovl_splice_write,
 736
 737         .copy_file_range        = ovl_copy_file_range,
 738         .remap_file_range       = ovl_remap_file_range,
 739 };
 740
 741 int __init ovl_aio_request_cache_init(void)
 742 {
 743         ovl_aio_request_cachep = kmem_cache_create("ovl_aio_req",
 744                                                    sizeof(struct ovl_aio_req),
 745                                                    0, SLAB_HWCACHE_ALIGN, NULL);
 746         if (!ovl_aio_request_cachep)
 747                 return -ENOMEM;
 748
 749         return 0;
 750 }
 751
 752 void ovl_aio_request_cache_destroy(void)
 753 {
 754         kmem_cache_destroy(ovl_aio_request_cachep);
 755 }