fs/super.c

   1 /*
   2  *  linux/fs/super.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  *
   6  *  super.c contains code to handle: - mount structures
   7  *                                   - super-block tables
   8  *                                   - filesystem drivers list
   9  *                                   - mount system call
  10  *                                   - umount system call
  11  *                                   - ustat system call
  12  *
  13  * GK 2/5/95  -  Changed to support mounting the root fs via NFS
  14  *
  15  *  Added kerneld support: Jacques Gelinas and Bjorn Ekwall
  16  *  Added change_root: Werner Almesberger & Hans Lermen, Feb '96
  17  *  Added options to /proc/mounts:
  18  *    Torbjörn Lindh (torbjorn.lindh@gopta.se), April 14, 1996.
  19  *  Added devfs support: Richard Gooch <rgooch@atnf.csiro.au>, 13-JAN-1998
  20  *  Heavily rewritten for 'one fs - one tree' dcache architecture. AV, Mar 2000
  21  */
  22
  23 #include <linux/config.h>
  24 #include <linux/module.h>
  25 #include <linux/slab.h>
  26 #include <linux/init.h>
  27 #include <linux/smp_lock.h>
  28 #include <linux/acct.h>
  29 #include <linux/blkdev.h>
  30 #include <linux/quotaops.h>
  31 #include <linux/namei.h>
  32 #include <linux/buffer_head.h>          /* for fsync_super() */
  33 #include <linux/mount.h>
  34 #include <linux/security.h>
  35 #include <linux/vfs.h>
  36 #include <linux/writeback.h>            /* for the emergency remount stuff */
  37 #include <linux/idr.h>
  38 #include <asm/uaccess.h>
  39
  40
  41 void get_filesystem(struct file_system_type *fs);
  42 void put_filesystem(struct file_system_type *fs);
  43 struct file_system_type *get_fs_type(const char *name);
  44
  45 LIST_HEAD(super_blocks);
  46 spinlock_t sb_lock = SPIN_LOCK_UNLOCKED;
  47
  48 /**
  49  *      alloc_super     -       create new superblock
  50  *
  51  *      Allocates and initializes a new &struct super_block.  alloc_super()
  52  *      returns a pointer new superblock or %NULL if allocation had failed.
  53  */
  54 static struct super_block *alloc_super(void)
  55 {
  56         struct super_block *s = kmalloc(sizeof(struct super_block),  GFP_USER);
  57         static struct super_operations default_op;
  58
  59         if (s) {
  60                 memset(s, 0, sizeof(struct super_block));
  61                 if (security_sb_alloc(s)) {
  62                         kfree(s);
  63                         s = NULL;
  64                         goto out;
  65                 }
  66                 INIT_LIST_HEAD(&s->s_dirty);
  67                 INIT_LIST_HEAD(&s->s_io);
  68                 INIT_LIST_HEAD(&s->s_files);
  69                 INIT_LIST_HEAD(&s->s_instances);
  70                 INIT_HLIST_HEAD(&s->s_anon);
  71                 init_rwsem(&s->s_umount);
  72                 sema_init(&s->s_lock, 1);
  73                 down_write(&s->s_umount);
  74                 s->s_count = S_BIAS;
  75                 atomic_set(&s->s_active, 1);
  76                 sema_init(&s->s_vfs_rename_sem,1);
  77                 sema_init(&s->s_dquot.dqio_sem, 1);
  78                 sema_init(&s->s_dquot.dqonoff_sem, 1);
  79                 init_rwsem(&s->s_dquot.dqptr_sem);
  80                 s->s_maxbytes = MAX_NON_LFS;
  81                 s->dq_op = sb_dquot_ops;
  82                 s->s_qcop = sb_quotactl_ops;
  83                 s->s_op = &default_op;
  84         }
  85 out:
  86         return s;
  87 }
  88
  89 /**
  90  *      destroy_super   -       frees a superblock
  91  *      @s: superblock to free
  92  *
  93  *      Frees a superblock.
  94  */
  95 static inline void destroy_super(struct super_block *s)
  96 {
  97         security_sb_free(s);
  98         kfree(s);
  99 }
 100
 101 /* Superblock refcounting  */
 102
 103 /**
 104  *      put_super       -       drop a temporary reference to superblock
 105  *      @s: superblock in question
 106  *
 107  *      Drops a temporary reference, frees superblock if there's no
 108  *      references left.
 109  */
 110 static inline void put_super(struct super_block *s)
 111 {
 112         spin_lock(&sb_lock);
 113         if (!--s->s_count)
 114                 destroy_super(s);
 115         spin_unlock(&sb_lock);
 116 }
 117
 118 /**
 119  *      deactivate_super        -       drop an active reference to superblock
 120  *      @s: superblock to deactivate
 121  *
 122  *      Drops an active reference to superblock, acquiring a temprory one if
 123  *      there is no active references left.  In that case we lock superblock,
 124  *      tell fs driver to shut it down and drop the temporary reference we
 125  *      had just acquired.
 126  */
 127 void deactivate_super(struct super_block *s)
 128 {
 129         struct file_system_type *fs = s->s_type;
 130         if (atomic_dec_and_lock(&s->s_active, &sb_lock)) {
 131                 s->s_count -= S_BIAS-1;
 132                 spin_unlock(&sb_lock);
 133                 down_write(&s->s_umount);
 134                 fs->kill_sb(s);
 135                 put_filesystem(fs);
 136                 put_super(s);
 137         }
 138 }
 139
 140 EXPORT_SYMBOL(deactivate_super);
 141
 142 /**
 143  *      grab_super - acquire an active reference
 144  *      @s: reference we are trying to make active
 145  *
 146  *      Tries to acquire an active reference.  grab_super() is used when we
 147  *      had just found a superblock in super_blocks or fs_type->fs_supers
 148  *      and want to turn it into a full-blown active reference.  grab_super()
 149  *      is called with sb_lock held and drops it.  Returns 1 in case of
 150  *      success, 0 if we had failed (superblock contents was already dead or
 151  *      dying when grab_super() had been called).
 152  */
 153 static int grab_super(struct super_block *s)
 154 {
 155         s->s_count++;
 156         spin_unlock(&sb_lock);
 157         down_write(&s->s_umount);
 158         if (s->s_root) {
 159                 spin_lock(&sb_lock);
 160                 if (s->s_count > S_BIAS) {
 161                         atomic_inc(&s->s_active);
 162                         s->s_count--;
 163                         spin_unlock(&sb_lock);
 164                         return 1;
 165                 }
 166                 spin_unlock(&sb_lock);
 167         }
 168         up_write(&s->s_umount);
 169         put_super(s);
 170         yield();
 171         return 0;
 172 }
 173
 174 /**
 175  *      generic_shutdown_super  -       common helper for ->kill_sb()
 176  *      @sb: superblock to kill
 177  *
 178  *      generic_shutdown_super() does all fs-independent work on superblock
 179  *      shutdown.  Typical ->kill_sb() should pick all fs-specific objects
 180  *      that need destruction out of superblock, call generic_shutdown_super()
 181  *      and release aforementioned objects.  Note: dentries and inodes _are_
 182  *      taken care of and do not need specific handling.
 183  */
 184 void generic_shutdown_super(struct super_block *sb)
 185 {
 186         struct dentry *root = sb->s_root;
 187         struct super_operations *sop = sb->s_op;
 188
 189         if (root) {
 190                 sb->s_root = NULL;
 191                 shrink_dcache_parent(root);
 192                 shrink_dcache_anon(&sb->s_anon);
 193                 dput(root);
 194                 fsync_super(sb);
 195                 lock_super(sb);
 196                 lock_kernel();
 197                 sb->s_flags &= ~MS_ACTIVE;
 198                 /* bad name - it should be evict_inodes() */
 199                 invalidate_inodes(sb);
 200
 201                 if (sop->write_super && sb->s_dirt)
 202                         sop->write_super(sb);
 203                 if (sop->put_super)
 204                         sop->put_super(sb);
 205
 206                 /* Forget any remaining inodes */
 207                 if (invalidate_inodes(sb)) {
 208                         printk("VFS: Busy inodes after unmount. "
 209                            "Self-destruct in 5 seconds.  Have a nice day...\n");
 210                 }
 211
 212                 unlock_kernel();
 213                 unlock_super(sb);
 214         }
 215         spin_lock(&sb_lock);
 216         list_del(&sb->s_list);
 217         list_del(&sb->s_instances);
 218         spin_unlock(&sb_lock);
 219         up_write(&sb->s_umount);
 220 }
 221
 222 EXPORT_SYMBOL(generic_shutdown_super);
 223
 224 /**
 225  *      sget    -       find or create a superblock
 226  *      @type:  filesystem type superblock should belong to
 227  *      @test:  comparison callback
 228  *      @set:   setup callback
 229  *      @data:  argument to each of them
 230  */
 231 struct super_block *sget(struct file_system_type *type,
 232                         int (*test)(struct super_block *,void *),
 233                         int (*set)(struct super_block *,void *),
 234                         void *data)
 235 {
 236         struct super_block *s = NULL;
 237         struct list_head *p;
 238         int err;
 239
 240 retry:
 241         spin_lock(&sb_lock);
 242         if (test) list_for_each(p, &type->fs_supers) {
 243                 struct super_block *old;
 244                 old = list_entry(p, struct super_block, s_instances);
 245                 if (!test(old, data))
 246                         continue;
 247                 if (!grab_super(old))
 248                         goto retry;
 249                 if (s)
 250                         destroy_super(s);
 251                 return old;
 252         }
 253         if (!s) {
 254                 spin_unlock(&sb_lock);
 255                 s = alloc_super();
 256                 if (!s)
 257                         return ERR_PTR(-ENOMEM);
 258                 goto retry;
 259         }
 260
 261         err = set(s, data);
 262         if (err) {
 263                 spin_unlock(&sb_lock);
 264                 destroy_super(s);
 265                 return ERR_PTR(err);
 266         }
 267         s->s_type = type;
 268         list_add(&s->s_list, super_blocks.prev);
 269         list_add(&s->s_instances, &type->fs_supers);
 270         spin_unlock(&sb_lock);
 271         get_filesystem(type);
 272         return s;
 273 }
 274
 275 EXPORT_SYMBOL(sget);
 276
 277 void drop_super(struct super_block *sb)
 278 {
 279         up_read(&sb->s_umount);
 280         put_super(sb);
 281 }
 282
 283 EXPORT_SYMBOL(drop_super);
 284
 285 static inline void write_super(struct super_block *sb)
 286 {
 287         lock_super(sb);
 288         if (sb->s_root && sb->s_dirt)
 289                 if (sb->s_op->write_super)
 290                         sb->s_op->write_super(sb);
 291         unlock_super(sb);
 292 }
 293
 294 /*
 295  * Note: check the dirty flag before waiting, so we don't
 296  * hold up the sync while mounting a device. (The newly
 297  * mounted device won't need syncing.)
 298  */
 299 void sync_supers(void)
 300 {
 301         struct super_block * sb;
 302 restart:
 303         spin_lock(&sb_lock);
 304         sb = sb_entry(super_blocks.next);
 305         while (sb != sb_entry(&super_blocks))
 306                 if (sb->s_dirt) {
 307                         sb->s_count++;
 308                         spin_unlock(&sb_lock);
 309                         down_read(&sb->s_umount);
 310                         write_super(sb);
 311                         drop_super(sb);
 312                         goto restart;
 313                 } else
 314                         sb = sb_entry(sb->s_list.next);
 315         spin_unlock(&sb_lock);
 316 }
 317
 318 /*
 319  * Call the ->sync_fs super_op against all filesytems which are r/w and
 320  * which implement it.
 321  *
 322  * This operation is careful to avoid the livelock which could easily happen
 323  * if two or more filesystems are being continuously dirtied.  s_need_sync_fs
 324  * is used only here.  We set it against all filesystems and then clear it as
 325  * we sync them.  So redirtied filesystems are skipped.
 326  *
 327  * But if process A is currently running sync_filesytems and then process B
 328  * calls sync_filesystems as well, process B will set all the s_need_sync_fs
 329  * flags again, which will cause process A to resync everything.  Fix that with
 330  * a local mutex.
 331  *
 332  * (Fabian) Avoid sync_fs with clean fs & wait mode 0
 333  */
 334 void sync_filesystems(int wait)
 335 {
 336         struct super_block *sb;
 337         static DECLARE_MUTEX(mutex);
 338
 339         down(&mutex);           /* Could be down_interruptible */
 340         spin_lock(&sb_lock);
 341         for (sb = sb_entry(super_blocks.next); sb != sb_entry(&super_blocks);
 342                         sb = sb_entry(sb->s_list.next)) {
 343                 if (!sb->s_op->sync_fs)
 344                         continue;
 345                 if (sb->s_flags & MS_RDONLY)
 346                         continue;
 347                 sb->s_need_sync_fs = 1;
 348         }
 349         spin_unlock(&sb_lock);
 350
 351 restart:
 352         spin_lock(&sb_lock);
 353         for (sb = sb_entry(super_blocks.next); sb != sb_entry(&super_blocks);
 354                         sb = sb_entry(sb->s_list.next)) {
 355                 if (!sb->s_need_sync_fs)
 356                         continue;
 357                 sb->s_need_sync_fs = 0;
 358                 if (sb->s_flags & MS_RDONLY)
 359                         continue;       /* hm.  Was remounted r/o meanwhile */
 360                 sb->s_count++;
 361                 spin_unlock(&sb_lock);
 362                 down_read(&sb->s_umount);
 363                 if (sb->s_root && (wait || sb->s_dirt))
 364                         sb->s_op->sync_fs(sb, wait);
 365                 drop_super(sb);
 366                 goto restart;
 367         }
 368         spin_unlock(&sb_lock);
 369         up(&mutex);
 370 }
 371
 372 /**
 373  *      get_super - get the superblock of a device
 374  *      @bdev: device to get the superblock for
 375  *
 376  *      Scans the superblock list and finds the superblock of the file system
 377  *      mounted on the device given. %NULL is returned if no match is found.
 378  */
 379
 380 struct super_block * get_super(struct block_device *bdev)
 381 {
 382         struct list_head *p;
 383         if (!bdev)
 384                 return NULL;
 385 rescan:
 386         spin_lock(&sb_lock);
 387         list_for_each(p, &super_blocks) {
 388                 struct super_block *s = sb_entry(p);
 389                 if (s->s_bdev == bdev) {
 390                         s->s_count++;
 391                         spin_unlock(&sb_lock);
 392                         down_read(&s->s_umount);
 393                         if (s->s_root)
 394                                 return s;
 395                         drop_super(s);
 396                         goto rescan;
 397                 }
 398         }
 399         spin_unlock(&sb_lock);
 400         return NULL;
 401 }
 402
 403 EXPORT_SYMBOL(get_super);
 404
 405 struct super_block * user_get_super(dev_t dev)
 406 {
 407         struct list_head *p;
 408
 409 rescan:
 410         spin_lock(&sb_lock);
 411         list_for_each(p, &super_blocks) {
 412                 struct super_block *s = sb_entry(p);
 413                 if (s->s_dev ==  dev) {
 414                         s->s_count++;
 415                         spin_unlock(&sb_lock);
 416                         down_read(&s->s_umount);
 417                         if (s->s_root)
 418                                 return s;
 419                         drop_super(s);
 420                         goto rescan;
 421                 }
 422         }
 423         spin_unlock(&sb_lock);
 424         return NULL;
 425 }
 426
 427 EXPORT_SYMBOL(user_get_super);
 428
 429 asmlinkage long sys_ustat(unsigned dev, struct ustat __user * ubuf)
 430 {
 431         struct super_block *s;
 432         struct ustat tmp;
 433         struct kstatfs sbuf;
 434         int err = -EINVAL;
 435
 436         s = user_get_super(new_decode_dev(dev));
 437         if (s == NULL)
 438                 goto out;
 439         err = vfs_statfs(s, &sbuf);
 440         drop_super(s);
 441         if (err)
 442                 goto out;
 443
 444         memset(&tmp,0,sizeof(struct ustat));
 445         tmp.f_tfree = sbuf.f_bfree;
 446         tmp.f_tinode = sbuf.f_ffree;
 447
 448         err = copy_to_user(ubuf,&tmp,sizeof(struct ustat)) ? -EFAULT : 0;
 449 out:
 450         return err;
 451 }
 452
 453 /**
 454  *      mark_files_ro
 455  *      @sb: superblock in question
 456  *
 457  *      All files are marked read/only.  We don't care about pending
 458  *      delete files so this should be used in 'force' mode only
 459  */
 460
 461 static void mark_files_ro(struct super_block *sb)
 462 {
 463         struct file *f;
 464
 465         file_list_lock();
 466         list_for_each_entry(f, &sb->s_files, f_list) {
 467                 if (S_ISREG(f->f_dentry->d_inode->i_mode) && file_count(f))
 468                         f->f_mode &= ~FMODE_WRITE;
 469         }
 470         file_list_unlock();
 471 }
 472
 473 /**
 474  *      do_remount_sb - asks filesystem to change mount options.
 475  *      @sb:    superblock in question
 476  *      @flags: numeric part of options
 477  *      @data:  the rest of options
 478  *      @force: whether or not to force the change
 479  *
 480  *      Alters the mount options of a mounted file system.
 481  */
 482 int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
 483 {
 484         int retval;
 485
 486         if (!(flags & MS_RDONLY) && bdev_read_only(sb->s_bdev))
 487                 return -EACCES;
 488         if (flags & MS_RDONLY)
 489                 acct_auto_close(sb);
 490         shrink_dcache_sb(sb);
 491         fsync_super(sb);
 492
 493         /* If we are remounting RDONLY and current sb is read/write,
 494            make sure there are no rw files opened */
 495         if ((flags & MS_RDONLY) && !(sb->s_flags & MS_RDONLY)) {
 496                 if (force)
 497                         mark_files_ro(sb);
 498                 else if (!fs_may_remount_ro(sb))
 499                         return -EBUSY;
 500         }
 501
 502         if (sb->s_op->remount_fs) {
 503                 lock_super(sb);
 504                 retval = sb->s_op->remount_fs(sb, &flags, data);
 505                 unlock_super(sb);
 506                 if (retval)
 507                         return retval;
 508         }
 509         sb->s_flags = (sb->s_flags & ~MS_RMT_MASK) | (flags & MS_RMT_MASK);
 510         return 0;
 511 }
 512
 513 static void do_emergency_remount(unsigned long foo)
 514 {
 515         struct super_block *sb;
 516
 517         spin_lock(&sb_lock);
 518         list_for_each_entry(sb, &super_blocks, s_list) {
 519                 sb->s_count++;
 520                 spin_unlock(&sb_lock);
 521                 down_read(&sb->s_umount);
 522                 if (sb->s_root && sb->s_bdev && !(sb->s_flags & MS_RDONLY)) {
 523                         /*
 524                          * ->remount_fs needs lock_kernel().
 525                          *
 526                          * What lock protects sb->s_flags??
 527                          */
 528                         lock_kernel();
 529                         do_remount_sb(sb, MS_RDONLY, NULL, 1);
 530                         unlock_kernel();
 531                 }
 532                 drop_super(sb);
 533                 spin_lock(&sb_lock);
 534         }
 535         spin_unlock(&sb_lock);
 536         printk("Emergency Remount complete\n");
 537 }
 538
 539 void emergency_remount(void)
 540 {
 541         pdflush_operation(do_emergency_remount, 0);
 542 }
 543
 544 /*
 545  * Unnamed block devices are dummy devices used by virtual
 546  * filesystems which don't use real block-devices.  -- jrs
 547  */
 548
 549 static struct idr unnamed_dev_idr;
 550 static spinlock_t unnamed_dev_lock = SPIN_LOCK_UNLOCKED;/* protects the above */
 551
 552 int set_anon_super(struct super_block *s, void *data)
 553 {
 554         int dev;
 555
 556         spin_lock(&unnamed_dev_lock);
 557         if (idr_pre_get(&unnamed_dev_idr, GFP_ATOMIC) == 0) {
 558                 spin_unlock(&unnamed_dev_lock);
 559                 return -ENOMEM;
 560         }
 561         dev = idr_get_new(&unnamed_dev_idr, NULL);
 562         spin_unlock(&unnamed_dev_lock);
 563
 564         if ((dev & MAX_ID_MASK) == (1 << MINORBITS)) {
 565                 idr_remove(&unnamed_dev_idr, dev);
 566                 return -EMFILE;
 567         }
 568         s->s_dev = MKDEV(0, dev & MINORMASK);
 569         return 0;
 570 }
 571
 572 EXPORT_SYMBOL(set_anon_super);
 573
 574 void kill_anon_super(struct super_block *sb)
 575 {
 576         int slot = MINOR(sb->s_dev);
 577
 578         generic_shutdown_super(sb);
 579         spin_lock(&unnamed_dev_lock);
 580         idr_remove(&unnamed_dev_idr, slot);
 581         spin_unlock(&unnamed_dev_lock);
 582 }
 583
 584 EXPORT_SYMBOL(kill_anon_super);
 585
 586 void __init unnamed_dev_init(void)
 587 {
 588         idr_init(&unnamed_dev_idr);
 589 }
 590
 591 void kill_litter_super(struct super_block *sb)
 592 {
 593         if (sb->s_root)
 594                 d_genocide(sb->s_root);
 595         kill_anon_super(sb);
 596 }
 597
 598 EXPORT_SYMBOL(kill_litter_super);
 599
 600 static int set_bdev_super(struct super_block *s, void *data)
 601 {
 602         s->s_bdev = data;
 603         s->s_dev = s->s_bdev->bd_dev;
 604         return 0;
 605 }
 606
 607 static int test_bdev_super(struct super_block *s, void *data)
 608 {
 609         return (void *)s->s_bdev == data;
 610 }
 611
 612 struct super_block *get_sb_bdev(struct file_system_type *fs_type,
 613         int flags, const char *dev_name, void *data,
 614         int (*fill_super)(struct super_block *, void *, int))
 615 {
 616         struct block_device *bdev;
 617         struct super_block *s;
 618         int error = 0;
 619
 620         bdev = open_bdev_excl(dev_name, flags, fs_type);
 621         if (IS_ERR(bdev))
 622                 return (struct super_block *)bdev;
 623
 624         s = sget(fs_type, test_bdev_super, set_bdev_super, bdev);
 625         if (IS_ERR(s))
 626                 goto out;
 627
 628         if (s->s_root) {
 629                 if ((flags ^ s->s_flags) & MS_RDONLY) {
 630                         up_write(&s->s_umount);
 631                         deactivate_super(s);
 632                         s = ERR_PTR(-EBUSY);
 633                 }
 634                 goto out;
 635         } else {
 636                 char b[BDEVNAME_SIZE];
 637
 638                 s->s_flags = flags;
 639                 strlcpy(s->s_id, bdevname(bdev, b), sizeof(s->s_id));
 640                 s->s_old_blocksize = block_size(bdev);
 641                 sb_set_blocksize(s, s->s_old_blocksize);
 642                 error = fill_super(s, data, flags & MS_VERBOSE ? 1 : 0);
 643                 if (error) {
 644                         up_write(&s->s_umount);
 645                         deactivate_super(s);
 646                         s = ERR_PTR(error);
 647                 } else
 648                         s->s_flags |= MS_ACTIVE;
 649         }
 650
 651         return s;
 652
 653 out:
 654         close_bdev_excl(bdev);
 655         return s;
 656 }
 657
 658 EXPORT_SYMBOL(get_sb_bdev);
 659
 660 void kill_block_super(struct super_block *sb)
 661 {
 662         struct block_device *bdev = sb->s_bdev;
 663         generic_shutdown_super(sb);
 664         set_blocksize(bdev, sb->s_old_blocksize);
 665         close_bdev_excl(bdev);
 666 }
 667
 668 EXPORT_SYMBOL(kill_block_super);
 669
 670 struct super_block *get_sb_nodev(struct file_system_type *fs_type,
 671         int flags, void *data,
 672         int (*fill_super)(struct super_block *, void *, int))
 673 {
 674         int error;
 675         struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL);
 676
 677         if (IS_ERR(s))
 678                 return s;
 679
 680         s->s_flags = flags;
 681
 682         error = fill_super(s, data, flags & MS_VERBOSE ? 1 : 0);
 683         if (error) {
 684                 up_write(&s->s_umount);
 685                 deactivate_super(s);
 686                 return ERR_PTR(error);
 687         }
 688         s->s_flags |= MS_ACTIVE;
 689         return s;
 690 }
 691
 692 EXPORT_SYMBOL(get_sb_nodev);
 693
 694 static int compare_single(struct super_block *s, void *p)
 695 {
 696         return 1;
 697 }
 698
 699 struct super_block *get_sb_single(struct file_system_type *fs_type,
 700         int flags, void *data,
 701         int (*fill_super)(struct super_block *, void *, int))
 702 {
 703         struct super_block *s;
 704         int error;
 705
 706         s = sget(fs_type, compare_single, set_anon_super, NULL);
 707         if (IS_ERR(s))
 708                 return s;
 709         if (!s->s_root) {
 710                 s->s_flags = flags;
 711                 error = fill_super(s, data, flags & MS_VERBOSE ? 1 : 0);
 712                 if (error) {
 713                         up_write(&s->s_umount);
 714                         deactivate_super(s);
 715                         return ERR_PTR(error);
 716                 }
 717                 s->s_flags |= MS_ACTIVE;
 718         }
 719         do_remount_sb(s, flags, data, 0);
 720         return s;
 721 }
 722
 723 EXPORT_SYMBOL(get_sb_single);
 724
 725 struct vfsmount *
 726 do_kern_mount(const char *fstype, int flags, const char *name, void *data)
 727 {
 728         struct file_system_type *type = get_fs_type(fstype);
 729         struct super_block *sb = ERR_PTR(-ENOMEM);
 730         struct vfsmount *mnt;
 731         int error;
 732         char *secdata = NULL;
 733
 734         if (!type)
 735                 return ERR_PTR(-ENODEV);
 736
 737         mnt = alloc_vfsmnt(name);
 738         if (!mnt)
 739                 goto out;
 740
 741         if (data) {
 742                 secdata = alloc_secdata();
 743                 if (!secdata) {
 744                         sb = ERR_PTR(-ENOMEM);
 745                         goto out_mnt;
 746                 }
 747
 748                 error = security_sb_copy_data(type, data, secdata);
 749                 if (error) {
 750                         sb = ERR_PTR(error);
 751                         goto out_free_secdata;
 752                 }
 753         }
 754
 755         sb = type->get_sb(type, flags, name, data);
 756         if (IS_ERR(sb))
 757                 goto out_free_secdata;
 758         error = security_sb_kern_mount(sb, secdata);
 759         if (error)
 760                 goto out_sb;
 761         mnt->mnt_sb = sb;
 762         mnt->mnt_root = dget(sb->s_root);
 763         mnt->mnt_mountpoint = sb->s_root;
 764         mnt->mnt_parent = mnt;
 765         up_write(&sb->s_umount);
 766         put_filesystem(type);
 767         return mnt;
 768 out_sb:
 769         up_write(&sb->s_umount);
 770         deactivate_super(sb);
 771         sb = ERR_PTR(error);
 772 out_free_secdata:
 773         free_secdata(secdata);
 774 out_mnt:
 775         free_vfsmnt(mnt);
 776 out:
 777         put_filesystem(type);
 778         return (struct vfsmount *)sb;
 779 }
 780
 781 struct vfsmount *kern_mount(struct file_system_type *type)
 782 {
 783         return do_kern_mount(type->name, 0, type->name, NULL);
 784 }
 785
 786 EXPORT_SYMBOL(kern_mount);