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/module.h>
  24 #include <linux/slab.h>
  25 #include <linux/init.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/syscalls.h>
  35 #include <linux/vfs.h>
  36 #include <linux/writeback.h>            /* for the emergency remount stuff */
  37 #include <linux/idr.h>
  38 #include <linux/kobject.h>
  39 #include <linux/mutex.h>
  40 #include <asm/uaccess.h>
  41
  42
  43 void get_filesystem(struct file_system_type *fs);
  44 void put_filesystem(struct file_system_type *fs);
  45 struct file_system_type *get_fs_type(const char *name);
  46
  47 LIST_HEAD(super_blocks);
  48 DEFINE_SPINLOCK(sb_lock);
  49
  50 /**
  51  *      alloc_super     -       create new superblock
  52  *      @type:  filesystem type superblock should belong to
  53  *
  54  *      Allocates and initializes a new &struct super_block.  alloc_super()
  55  *      returns a pointer new superblock or %NULL if allocation had failed.
  56  */
  57 static struct super_block *alloc_super(struct file_system_type *type)
  58 {
  59         struct super_block *s = kzalloc(sizeof(struct super_block),  GFP_USER);
  60         static struct super_operations default_op;
  61
  62         if (s) {
  63                 if (security_sb_alloc(s)) {
  64                         kfree(s);
  65                         s = NULL;
  66                         goto out;
  67                 }
  68                 INIT_LIST_HEAD(&s->s_dirty);
  69                 INIT_LIST_HEAD(&s->s_io);
  70                 INIT_LIST_HEAD(&s->s_files);
  71                 INIT_LIST_HEAD(&s->s_instances);
  72                 INIT_HLIST_HEAD(&s->s_anon);
  73                 INIT_LIST_HEAD(&s->s_inodes);
  74                 init_rwsem(&s->s_umount);
  75                 mutex_init(&s->s_lock);
  76                 lockdep_set_class(&s->s_umount, &type->s_umount_key);
  77                 /*
  78                  * The locking rules for s_lock are up to the
  79                  * filesystem. For example ext3fs has different
  80                  * lock ordering than usbfs:
  81                  */
  82                 lockdep_set_class(&s->s_lock, &type->s_lock_key);
  83                 down_write(&s->s_umount);
  84                 s->s_count = S_BIAS;
  85                 atomic_set(&s->s_active, 1);
  86                 mutex_init(&s->s_vfs_rename_mutex);
  87                 mutex_init(&s->s_dquot.dqio_mutex);
  88                 mutex_init(&s->s_dquot.dqonoff_mutex);
  89                 init_rwsem(&s->s_dquot.dqptr_sem);
  90                 init_waitqueue_head(&s->s_wait_unfrozen);
  91                 s->s_maxbytes = MAX_NON_LFS;
  92                 s->dq_op = sb_dquot_ops;
  93                 s->s_qcop = sb_quotactl_ops;
  94                 s->s_op = &default_op;
  95                 s->s_time_gran = 1000000000;
  96         }
  97 out:
  98         return s;
  99 }
 100
 101 /**
 102  *      destroy_super   -       frees a superblock
 103  *      @s: superblock to free
 104  *
 105  *      Frees a superblock.
 106  */
 107 static inline void destroy_super(struct super_block *s)
 108 {
 109         security_sb_free(s);
 110         kfree(s);
 111 }
 112
 113 /* Superblock refcounting  */
 114
 115 /*
 116  * Drop a superblock's refcount.  Returns non-zero if the superblock was
 117  * destroyed.  The caller must hold sb_lock.
 118  */
 119 int __put_super(struct super_block *sb)
 120 {
 121         int ret = 0;
 122
 123         if (!--sb->s_count) {
 124                 destroy_super(sb);
 125                 ret = 1;
 126         }
 127         return ret;
 128 }
 129
 130 /*
 131  * Drop a superblock's refcount.
 132  * Returns non-zero if the superblock is about to be destroyed and
 133  * at least is already removed from super_blocks list, so if we are
 134  * making a loop through super blocks then we need to restart.
 135  * The caller must hold sb_lock.
 136  */
 137 int __put_super_and_need_restart(struct super_block *sb)
 138 {
 139         /* check for race with generic_shutdown_super() */
 140         if (list_empty(&sb->s_list)) {
 141                 /* super block is removed, need to restart... */
 142                 __put_super(sb);
 143                 return 1;
 144         }
 145         /* can't be the last, since s_list is still in use */
 146         sb->s_count--;
 147         BUG_ON(sb->s_count == 0);
 148         return 0;
 149 }
 150
 151 /**
 152  *      put_super       -       drop a temporary reference to superblock
 153  *      @sb: superblock in question
 154  *
 155  *      Drops a temporary reference, frees superblock if there's no
 156  *      references left.
 157  */
 158 static void put_super(struct super_block *sb)
 159 {
 160         spin_lock(&sb_lock);
 161         __put_super(sb);
 162         spin_unlock(&sb_lock);
 163 }
 164
 165
 166 /**
 167  *      deactivate_super        -       drop an active reference to superblock
 168  *      @s: superblock to deactivate
 169  *
 170  *      Drops an active reference to superblock, acquiring a temprory one if
 171  *      there is no active references left.  In that case we lock superblock,
 172  *      tell fs driver to shut it down and drop the temporary reference we
 173  *      had just acquired.
 174  */
 175 void deactivate_super(struct super_block *s)
 176 {
 177         struct file_system_type *fs = s->s_type;
 178         if (atomic_dec_and_lock(&s->s_active, &sb_lock)) {
 179                 s->s_count -= S_BIAS-1;
 180                 spin_unlock(&sb_lock);
 181                 DQUOT_OFF(s);
 182                 down_write(&s->s_umount);
 183                 fs->kill_sb(s);
 184                 put_filesystem(fs);
 185                 put_super(s);
 186         }
 187 }
 188
 189 EXPORT_SYMBOL(deactivate_super);
 190
 191 /**
 192  *      grab_super - acquire an active reference
 193  *      @s: reference we are trying to make active
 194  *
 195  *      Tries to acquire an active reference.  grab_super() is used when we
 196  *      had just found a superblock in super_blocks or fs_type->fs_supers
 197  *      and want to turn it into a full-blown active reference.  grab_super()
 198  *      is called with sb_lock held and drops it.  Returns 1 in case of
 199  *      success, 0 if we had failed (superblock contents was already dead or
 200  *      dying when grab_super() had been called).
 201  */
 202 static int grab_super(struct super_block *s)
 203 {
 204         s->s_count++;
 205         spin_unlock(&sb_lock);
 206         down_write(&s->s_umount);
 207         if (s->s_root) {
 208                 spin_lock(&sb_lock);
 209                 if (s->s_count > S_BIAS) {
 210                         atomic_inc(&s->s_active);
 211                         s->s_count--;
 212                         spin_unlock(&sb_lock);
 213                         return 1;
 214                 }
 215                 spin_unlock(&sb_lock);
 216         }
 217         up_write(&s->s_umount);
 218         put_super(s);
 219         yield();
 220         return 0;
 221 }
 222
 223 /**
 224  *      generic_shutdown_super  -       common helper for ->kill_sb()
 225  *      @sb: superblock to kill
 226  *
 227  *      generic_shutdown_super() does all fs-independent work on superblock
 228  *      shutdown.  Typical ->kill_sb() should pick all fs-specific objects
 229  *      that need destruction out of superblock, call generic_shutdown_super()
 230  *      and release aforementioned objects.  Note: dentries and inodes _are_
 231  *      taken care of and do not need specific handling.
 232  */
 233 void generic_shutdown_super(struct super_block *sb)
 234 {
 235         struct dentry *root = sb->s_root;
 236         struct super_operations *sop = sb->s_op;
 237
 238         if (root) {
 239                 sb->s_root = NULL;
 240                 shrink_dcache_parent(root);
 241                 shrink_dcache_sb(sb);
 242                 dput(root);
 243                 fsync_super(sb);
 244                 lock_super(sb);
 245                 sb->s_flags &= ~MS_ACTIVE;
 246                 /* bad name - it should be evict_inodes() */
 247                 invalidate_inodes(sb);
 248                 lock_kernel();
 249
 250                 if (sop->write_super && sb->s_dirt)
 251                         sop->write_super(sb);
 252                 if (sop->put_super)
 253                         sop->put_super(sb);
 254
 255                 /* Forget any remaining inodes */
 256                 if (invalidate_inodes(sb)) {
 257                         printk("VFS: Busy inodes after unmount of %s. "
 258                            "Self-destruct in 5 seconds.  Have a nice day...\n",
 259                            sb->s_id);
 260                 }
 261
 262                 unlock_kernel();
 263                 unlock_super(sb);
 264         }
 265         spin_lock(&sb_lock);
 266         /* should be initialized for __put_super_and_need_restart() */
 267         list_del_init(&sb->s_list);
 268         list_del(&sb->s_instances);
 269         spin_unlock(&sb_lock);
 270         up_write(&sb->s_umount);
 271 }
 272
 273 EXPORT_SYMBOL(generic_shutdown_super);
 274
 275 /**
 276  *      sget    -       find or create a superblock
 277  *      @type:  filesystem type superblock should belong to
 278  *      @test:  comparison callback
 279  *      @set:   setup callback
 280  *      @data:  argument to each of them
 281  */
 282 struct super_block *sget(struct file_system_type *type,
 283                         int (*test)(struct super_block *,void *),
 284                         int (*set)(struct super_block *,void *),
 285                         void *data)
 286 {
 287         struct super_block *s = NULL;
 288         struct list_head *p;
 289         int err;
 290
 291 retry:
 292         spin_lock(&sb_lock);
 293         if (test) list_for_each(p, &type->fs_supers) {
 294                 struct super_block *old;
 295                 old = list_entry(p, struct super_block, s_instances);
 296                 if (!test(old, data))
 297                         continue;
 298                 if (!grab_super(old))
 299                         goto retry;
 300                 if (s)
 301                         destroy_super(s);
 302                 return old;
 303         }
 304         if (!s) {
 305                 spin_unlock(&sb_lock);
 306                 s = alloc_super(type);
 307                 if (!s)
 308                         return ERR_PTR(-ENOMEM);
 309                 goto retry;
 310         }
 311
 312         err = set(s, data);
 313         if (err) {
 314                 spin_unlock(&sb_lock);
 315                 destroy_super(s);
 316                 return ERR_PTR(err);
 317         }
 318         s->s_type = type;
 319         strlcpy(s->s_id, type->name, sizeof(s->s_id));
 320         list_add_tail(&s->s_list, &super_blocks);
 321         list_add(&s->s_instances, &type->fs_supers);
 322         spin_unlock(&sb_lock);
 323         get_filesystem(type);
 324         return s;
 325 }
 326
 327 EXPORT_SYMBOL(sget);
 328
 329 void drop_super(struct super_block *sb)
 330 {
 331         up_read(&sb->s_umount);
 332         put_super(sb);
 333 }
 334
 335 EXPORT_SYMBOL(drop_super);
 336
 337 static inline void write_super(struct super_block *sb)
 338 {
 339         lock_super(sb);
 340         if (sb->s_root && sb->s_dirt)
 341                 if (sb->s_op->write_super)
 342                         sb->s_op->write_super(sb);
 343         unlock_super(sb);
 344 }
 345
 346 /*
 347  * Note: check the dirty flag before waiting, so we don't
 348  * hold up the sync while mounting a device. (The newly
 349  * mounted device won't need syncing.)
 350  */
 351 void sync_supers(void)
 352 {
 353         struct super_block *sb;
 354
 355         spin_lock(&sb_lock);
 356 restart:
 357         list_for_each_entry(sb, &super_blocks, s_list) {
 358                 if (sb->s_dirt) {
 359                         sb->s_count++;
 360                         spin_unlock(&sb_lock);
 361                         down_read(&sb->s_umount);
 362                         write_super(sb);
 363                         up_read(&sb->s_umount);
 364                         spin_lock(&sb_lock);
 365                         if (__put_super_and_need_restart(sb))
 366                                 goto restart;
 367                 }
 368         }
 369         spin_unlock(&sb_lock);
 370 }
 371
 372 /*
 373  * Call the ->sync_fs super_op against all filesytems which are r/w and
 374  * which implement it.
 375  *
 376  * This operation is careful to avoid the livelock which could easily happen
 377  * if two or more filesystems are being continuously dirtied.  s_need_sync_fs
 378  * is used only here.  We set it against all filesystems and then clear it as
 379  * we sync them.  So redirtied filesystems are skipped.
 380  *
 381  * But if process A is currently running sync_filesytems and then process B
 382  * calls sync_filesystems as well, process B will set all the s_need_sync_fs
 383  * flags again, which will cause process A to resync everything.  Fix that with
 384  * a local mutex.
 385  *
 386  * (Fabian) Avoid sync_fs with clean fs & wait mode 0
 387  */
 388 void sync_filesystems(int wait)
 389 {
 390         struct super_block *sb;
 391         static DEFINE_MUTEX(mutex);
 392
 393         mutex_lock(&mutex);             /* Could be down_interruptible */
 394         spin_lock(&sb_lock);
 395         list_for_each_entry(sb, &super_blocks, s_list) {
 396                 if (!sb->s_op->sync_fs)
 397                         continue;
 398                 if (sb->s_flags & MS_RDONLY)
 399                         continue;
 400                 sb->s_need_sync_fs = 1;
 401         }
 402
 403 restart:
 404         list_for_each_entry(sb, &super_blocks, s_list) {
 405                 if (!sb->s_need_sync_fs)
 406                         continue;
 407                 sb->s_need_sync_fs = 0;
 408                 if (sb->s_flags & MS_RDONLY)
 409                         continue;       /* hm.  Was remounted r/o meanwhile */
 410                 sb->s_count++;
 411                 spin_unlock(&sb_lock);
 412                 down_read(&sb->s_umount);
 413                 if (sb->s_root && (wait || sb->s_dirt))
 414                         sb->s_op->sync_fs(sb, wait);
 415                 up_read(&sb->s_umount);
 416                 /* restart only when sb is no longer on the list */
 417                 spin_lock(&sb_lock);
 418                 if (__put_super_and_need_restart(sb))
 419                         goto restart;
 420         }
 421         spin_unlock(&sb_lock);
 422         mutex_unlock(&mutex);
 423 }
 424
 425 /**
 426  *      get_super - get the superblock of a device
 427  *      @bdev: device to get the superblock for
 428  *
 429  *      Scans the superblock list and finds the superblock of the file system
 430  *      mounted on the device given. %NULL is returned if no match is found.
 431  */
 432
 433 struct super_block * get_super(struct block_device *bdev)
 434 {
 435         struct super_block *sb;
 436
 437         if (!bdev)
 438                 return NULL;
 439
 440         spin_lock(&sb_lock);
 441 rescan:
 442         list_for_each_entry(sb, &super_blocks, s_list) {
 443                 if (sb->s_bdev == bdev) {
 444                         sb->s_count++;
 445                         spin_unlock(&sb_lock);
 446                         down_read(&sb->s_umount);
 447                         if (sb->s_root)
 448                                 return sb;
 449                         up_read(&sb->s_umount);
 450                         /* restart only when sb is no longer on the list */
 451                         spin_lock(&sb_lock);
 452                         if (__put_super_and_need_restart(sb))
 453                                 goto rescan;
 454                 }
 455         }
 456         spin_unlock(&sb_lock);
 457         return NULL;
 458 }
 459
 460 EXPORT_SYMBOL(get_super);
 461
 462 struct super_block * user_get_super(dev_t dev)
 463 {
 464         struct super_block *sb;
 465
 466         spin_lock(&sb_lock);
 467 rescan:
 468         list_for_each_entry(sb, &super_blocks, s_list) {
 469                 if (sb->s_dev ==  dev) {
 470                         sb->s_count++;
 471                         spin_unlock(&sb_lock);
 472                         down_read(&sb->s_umount);
 473                         if (sb->s_root)
 474                                 return sb;
 475                         up_read(&sb->s_umount);
 476                         /* restart only when sb is no longer on the list */
 477                         spin_lock(&sb_lock);
 478                         if (__put_super_and_need_restart(sb))
 479                                 goto rescan;
 480                 }
 481         }
 482         spin_unlock(&sb_lock);
 483         return NULL;
 484 }
 485
 486 asmlinkage long sys_ustat(unsigned dev, struct ustat __user * ubuf)
 487 {
 488         struct super_block *s;
 489         struct ustat tmp;
 490         struct kstatfs sbuf;
 491         int err = -EINVAL;
 492
 493         s = user_get_super(new_decode_dev(dev));
 494         if (s == NULL)
 495                 goto out;
 496         err = vfs_statfs(s->s_root, &sbuf);
 497         drop_super(s);
 498         if (err)
 499                 goto out;
 500
 501         memset(&tmp,0,sizeof(struct ustat));
 502         tmp.f_tfree = sbuf.f_bfree;
 503         tmp.f_tinode = sbuf.f_ffree;
 504
 505         err = copy_to_user(ubuf,&tmp,sizeof(struct ustat)) ? -EFAULT : 0;
 506 out:
 507         return err;
 508 }
 509
 510 /**
 511  *      mark_files_ro
 512  *      @sb: superblock in question
 513  *
 514  *      All files are marked read/only.  We don't care about pending
 515  *      delete files so this should be used in 'force' mode only
 516  */
 517
 518 static void mark_files_ro(struct super_block *sb)
 519 {
 520         struct file *f;
 521
 522         file_list_lock();
 523         list_for_each_entry(f, &sb->s_files, f_u.fu_list) {
 524                 if (S_ISREG(f->f_dentry->d_inode->i_mode) && file_count(f))
 525                         f->f_mode &= ~FMODE_WRITE;
 526         }
 527         file_list_unlock();
 528 }
 529
 530 /**
 531  *      do_remount_sb - asks filesystem to change mount options.
 532  *      @sb:    superblock in question
 533  *      @flags: numeric part of options
 534  *      @data:  the rest of options
 535  *      @force: whether or not to force the change
 536  *
 537  *      Alters the mount options of a mounted file system.
 538  */
 539 int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
 540 {
 541         int retval;
 542
 543         if (!(flags & MS_RDONLY) && bdev_read_only(sb->s_bdev))
 544                 return -EACCES;
 545         if (flags & MS_RDONLY)
 546                 acct_auto_close(sb);
 547         shrink_dcache_sb(sb);
 548         fsync_super(sb);
 549
 550         /* If we are remounting RDONLY and current sb is read/write,
 551            make sure there are no rw files opened */
 552         if ((flags & MS_RDONLY) && !(sb->s_flags & MS_RDONLY)) {
 553                 if (force)
 554                         mark_files_ro(sb);
 555                 else if (!fs_may_remount_ro(sb))
 556                         return -EBUSY;
 557         }
 558
 559         if (sb->s_op->remount_fs) {
 560                 lock_super(sb);
 561                 retval = sb->s_op->remount_fs(sb, &flags, data);
 562                 unlock_super(sb);
 563                 if (retval)
 564                         return retval;
 565         }
 566         sb->s_flags = (sb->s_flags & ~MS_RMT_MASK) | (flags & MS_RMT_MASK);
 567         return 0;
 568 }
 569
 570 static void do_emergency_remount(unsigned long foo)
 571 {
 572         struct super_block *sb;
 573
 574         spin_lock(&sb_lock);
 575         list_for_each_entry(sb, &super_blocks, s_list) {
 576                 sb->s_count++;
 577                 spin_unlock(&sb_lock);
 578                 down_read(&sb->s_umount);
 579                 if (sb->s_root && sb->s_bdev && !(sb->s_flags & MS_RDONLY)) {
 580                         /*
 581                          * ->remount_fs needs lock_kernel().
 582                          *
 583                          * What lock protects sb->s_flags??
 584                          */
 585                         lock_kernel();
 586                         do_remount_sb(sb, MS_RDONLY, NULL, 1);
 587                         unlock_kernel();
 588                 }
 589                 drop_super(sb);
 590                 spin_lock(&sb_lock);
 591         }
 592         spin_unlock(&sb_lock);
 593         printk("Emergency Remount complete\n");
 594 }
 595
 596 void emergency_remount(void)
 597 {
 598         pdflush_operation(do_emergency_remount, 0);
 599 }
 600
 601 /*
 602  * Unnamed block devices are dummy devices used by virtual
 603  * filesystems which don't use real block-devices.  -- jrs
 604  */
 605
 606 static struct idr unnamed_dev_idr;
 607 static DEFINE_SPINLOCK(unnamed_dev_lock);/* protects the above */
 608
 609 int set_anon_super(struct super_block *s, void *data)
 610 {
 611         int dev;
 612         int error;
 613
 614  retry:
 615         if (idr_pre_get(&unnamed_dev_idr, GFP_ATOMIC) == 0)
 616                 return -ENOMEM;
 617         spin_lock(&unnamed_dev_lock);
 618         error = idr_get_new(&unnamed_dev_idr, NULL, &dev);
 619         spin_unlock(&unnamed_dev_lock);
 620         if (error == -EAGAIN)
 621                 /* We raced and lost with another CPU. */
 622                 goto retry;
 623         else if (error)
 624                 return -EAGAIN;
 625
 626         if ((dev & MAX_ID_MASK) == (1 << MINORBITS)) {
 627                 spin_lock(&unnamed_dev_lock);
 628                 idr_remove(&unnamed_dev_idr, dev);
 629                 spin_unlock(&unnamed_dev_lock);
 630                 return -EMFILE;
 631         }
 632         s->s_dev = MKDEV(0, dev & MINORMASK);
 633         return 0;
 634 }
 635
 636 EXPORT_SYMBOL(set_anon_super);
 637
 638 void kill_anon_super(struct super_block *sb)
 639 {
 640         int slot = MINOR(sb->s_dev);
 641
 642         generic_shutdown_super(sb);
 643         spin_lock(&unnamed_dev_lock);
 644         idr_remove(&unnamed_dev_idr, slot);
 645         spin_unlock(&unnamed_dev_lock);
 646 }
 647
 648 EXPORT_SYMBOL(kill_anon_super);
 649
 650 void __init unnamed_dev_init(void)
 651 {
 652         idr_init(&unnamed_dev_idr);
 653 }
 654
 655 void kill_litter_super(struct super_block *sb)
 656 {
 657         if (sb->s_root)
 658                 d_genocide(sb->s_root);
 659         kill_anon_super(sb);
 660 }
 661
 662 EXPORT_SYMBOL(kill_litter_super);
 663
 664 static int set_bdev_super(struct super_block *s, void *data)
 665 {
 666         s->s_bdev = data;
 667         s->s_dev = s->s_bdev->bd_dev;
 668         return 0;
 669 }
 670
 671 static int test_bdev_super(struct super_block *s, void *data)
 672 {
 673         return (void *)s->s_bdev == data;
 674 }
 675
 676 static void bdev_uevent(struct block_device *bdev, enum kobject_action action)
 677 {
 678         if (bdev->bd_disk) {
 679                 if (bdev->bd_part)
 680                         kobject_uevent(&bdev->bd_part->kobj, action);
 681                 else
 682                         kobject_uevent(&bdev->bd_disk->kobj, action);
 683         }
 684 }
 685
 686 int get_sb_bdev(struct file_system_type *fs_type,
 687         int flags, const char *dev_name, void *data,
 688         int (*fill_super)(struct super_block *, void *, int),
 689         struct vfsmount *mnt)
 690 {
 691         struct block_device *bdev;
 692         struct super_block *s;
 693         int error = 0;
 694
 695         bdev = open_bdev_excl(dev_name, flags, fs_type);
 696         if (IS_ERR(bdev))
 697                 return PTR_ERR(bdev);
 698
 699         /*
 700          * once the super is inserted into the list by sget, s_umount
 701          * will protect the lockfs code from trying to start a snapshot
 702          * while we are mounting
 703          */
 704         mutex_lock(&bdev->bd_mount_mutex);
 705         s = sget(fs_type, test_bdev_super, set_bdev_super, bdev);
 706         mutex_unlock(&bdev->bd_mount_mutex);
 707         if (IS_ERR(s))
 708                 goto error_s;
 709
 710         if (s->s_root) {
 711                 if ((flags ^ s->s_flags) & MS_RDONLY) {
 712                         up_write(&s->s_umount);
 713                         deactivate_super(s);
 714                         error = -EBUSY;
 715                         goto error_bdev;
 716                 }
 717
 718                 close_bdev_excl(bdev);
 719         } else {
 720                 char b[BDEVNAME_SIZE];
 721
 722                 s->s_flags = flags;
 723                 strlcpy(s->s_id, bdevname(bdev, b), sizeof(s->s_id));
 724                 sb_set_blocksize(s, block_size(bdev));
 725                 error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
 726                 if (error) {
 727                         up_write(&s->s_umount);
 728                         deactivate_super(s);
 729                         goto error;
 730                 }
 731
 732                 s->s_flags |= MS_ACTIVE;
 733                 bdev_uevent(bdev, KOBJ_MOUNT);
 734         }
 735
 736         return simple_set_mnt(mnt, s);
 737
 738 error_s:
 739         error = PTR_ERR(s);
 740 error_bdev:
 741         close_bdev_excl(bdev);
 742 error:
 743         return error;
 744 }
 745
 746 EXPORT_SYMBOL(get_sb_bdev);
 747
 748 void kill_block_super(struct super_block *sb)
 749 {
 750         struct block_device *bdev = sb->s_bdev;
 751
 752         bdev_uevent(bdev, KOBJ_UMOUNT);
 753         generic_shutdown_super(sb);
 754         sync_blockdev(bdev);
 755         close_bdev_excl(bdev);
 756 }
 757
 758 EXPORT_SYMBOL(kill_block_super);
 759
 760 int get_sb_nodev(struct file_system_type *fs_type,
 761         int flags, void *data,
 762         int (*fill_super)(struct super_block *, void *, int),
 763         struct vfsmount *mnt)
 764 {
 765         int error;
 766         struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL);
 767
 768         if (IS_ERR(s))
 769                 return PTR_ERR(s);
 770
 771         s->s_flags = flags;
 772
 773         error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
 774         if (error) {
 775                 up_write(&s->s_umount);
 776                 deactivate_super(s);
 777                 return error;
 778         }
 779         s->s_flags |= MS_ACTIVE;
 780         return simple_set_mnt(mnt, s);
 781 }
 782
 783 EXPORT_SYMBOL(get_sb_nodev);
 784
 785 static int compare_single(struct super_block *s, void *p)
 786 {
 787         return 1;
 788 }
 789
 790 int get_sb_single(struct file_system_type *fs_type,
 791         int flags, void *data,
 792         int (*fill_super)(struct super_block *, void *, int),
 793         struct vfsmount *mnt)
 794 {
 795         struct super_block *s;
 796         int error;
 797
 798         s = sget(fs_type, compare_single, set_anon_super, NULL);
 799         if (IS_ERR(s))
 800                 return PTR_ERR(s);
 801         if (!s->s_root) {
 802                 s->s_flags = flags;
 803                 error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
 804                 if (error) {
 805                         up_write(&s->s_umount);
 806                         deactivate_super(s);
 807                         return error;
 808                 }
 809                 s->s_flags |= MS_ACTIVE;
 810         }
 811         do_remount_sb(s, flags, data, 0);
 812         return simple_set_mnt(mnt, s);
 813 }
 814
 815 EXPORT_SYMBOL(get_sb_single);
 816
 817 struct vfsmount *
 818 vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void *data)
 819 {
 820         struct vfsmount *mnt;
 821         char *secdata = NULL;
 822         int error;
 823
 824         if (!type)
 825                 return ERR_PTR(-ENODEV);
 826
 827         error = -ENOMEM;
 828         mnt = alloc_vfsmnt(name);
 829         if (!mnt)
 830                 goto out;
 831
 832         if (data) {
 833                 secdata = alloc_secdata();
 834                 if (!secdata)
 835                         goto out_mnt;
 836
 837                 error = security_sb_copy_data(type, data, secdata);
 838                 if (error)
 839                         goto out_free_secdata;
 840         }
 841
 842         error = type->get_sb(type, flags, name, data, mnt);
 843         if (error < 0)
 844                 goto out_free_secdata;
 845
 846         error = security_sb_kern_mount(mnt->mnt_sb, secdata);
 847         if (error)
 848                 goto out_sb;
 849
 850         mnt->mnt_mountpoint = mnt->mnt_root;
 851         mnt->mnt_parent = mnt;
 852         up_write(&mnt->mnt_sb->s_umount);
 853         free_secdata(secdata);
 854         return mnt;
 855 out_sb:
 856         dput(mnt->mnt_root);
 857         up_write(&mnt->mnt_sb->s_umount);
 858         deactivate_super(mnt->mnt_sb);
 859 out_free_secdata:
 860         free_secdata(secdata);
 861 out_mnt:
 862         free_vfsmnt(mnt);
 863 out:
 864         return ERR_PTR(error);
 865 }
 866
 867 EXPORT_SYMBOL_GPL(vfs_kern_mount);
 868
 869 struct vfsmount *
 870 do_kern_mount(const char *fstype, int flags, const char *name, void *data)
 871 {
 872         struct file_system_type *type = get_fs_type(fstype);
 873         struct vfsmount *mnt;
 874         if (!type)
 875                 return ERR_PTR(-ENODEV);
 876         mnt = vfs_kern_mount(type, flags, name, data);
 877         put_filesystem(type);
 878         return mnt;
 879 }
 880
 881 struct vfsmount *kern_mount(struct file_system_type *type)
 882 {
 883         return vfs_kern_mount(type, 0, type->name, NULL);
 884 }
 885
 886 EXPORT_SYMBOL(kern_mount);