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