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