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) __releases(sb_lock)
 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  * Superblock locking.  We really ought to get rid of these two.
 225  */
 226 void lock_super(struct super_block * sb)
 227 {
 228         get_fs_excl();
 229         mutex_lock(&sb->s_lock);
 230 }
 231
 232 void unlock_super(struct super_block * sb)
 233 {
 234         put_fs_excl();
 235         mutex_unlock(&sb->s_lock);
 236 }
 237
 238 EXPORT_SYMBOL(lock_super);
 239 EXPORT_SYMBOL(unlock_super);
 240
 241 /*
 242  * Write out and wait upon all dirty data associated with this
 243  * superblock.  Filesystem data as well as the underlying block
 244  * device.  Takes the superblock lock.  Requires a second blkdev
 245  * flush by the caller to complete the operation.
 246  */
 247 void __fsync_super(struct super_block *sb)
 248 {
 249         sync_inodes_sb(sb, 0);
 250         DQUOT_SYNC(sb);
 251         lock_super(sb);
 252         if (sb->s_dirt && sb->s_op->write_super)
 253                 sb->s_op->write_super(sb);
 254         unlock_super(sb);
 255         if (sb->s_op->sync_fs)
 256                 sb->s_op->sync_fs(sb, 1);
 257         sync_blockdev(sb->s_bdev);
 258         sync_inodes_sb(sb, 1);
 259 }
 260
 261 /*
 262  * Write out and wait upon all dirty data associated with this
 263  * superblock.  Filesystem data as well as the underlying block
 264  * device.  Takes the superblock lock.
 265  */
 266 int fsync_super(struct super_block *sb)
 267 {
 268         __fsync_super(sb);
 269         return sync_blockdev(sb->s_bdev);
 270 }
 271
 272 /**
 273  *      generic_shutdown_super  -       common helper for ->kill_sb()
 274  *      @sb: superblock to kill
 275  *
 276  *      generic_shutdown_super() does all fs-independent work on superblock
 277  *      shutdown.  Typical ->kill_sb() should pick all fs-specific objects
 278  *      that need destruction out of superblock, call generic_shutdown_super()
 279  *      and release aforementioned objects.  Note: dentries and inodes _are_
 280  *      taken care of and do not need specific handling.
 281  *
 282  *      Upon calling this function, the filesystem may no longer alter or
 283  *      rearrange the set of dentries belonging to this super_block, nor may it
 284  *      change the attachments of dentries to inodes.
 285  */
 286 void generic_shutdown_super(struct super_block *sb)
 287 {
 288         struct super_operations *sop = sb->s_op;
 289
 290         if (sb->s_root) {
 291                 shrink_dcache_for_umount(sb);
 292                 fsync_super(sb);
 293                 lock_super(sb);
 294                 sb->s_flags &= ~MS_ACTIVE;
 295                 /* bad name - it should be evict_inodes() */
 296                 invalidate_inodes(sb);
 297                 lock_kernel();
 298
 299                 if (sop->write_super && sb->s_dirt)
 300                         sop->write_super(sb);
 301                 if (sop->put_super)
 302                         sop->put_super(sb);
 303
 304                 /* Forget any remaining inodes */
 305                 if (invalidate_inodes(sb)) {
 306                         printk("VFS: Busy inodes after unmount of %s. "
 307                            "Self-destruct in 5 seconds.  Have a nice day...\n",
 308                            sb->s_id);
 309                 }
 310
 311                 unlock_kernel();
 312                 unlock_super(sb);
 313         }
 314         spin_lock(&sb_lock);
 315         /* should be initialized for __put_super_and_need_restart() */
 316         list_del_init(&sb->s_list);
 317         list_del(&sb->s_instances);
 318         spin_unlock(&sb_lock);
 319         up_write(&sb->s_umount);
 320 }
 321
 322 EXPORT_SYMBOL(generic_shutdown_super);
 323
 324 /**
 325  *      sget    -       find or create a superblock
 326  *      @type:  filesystem type superblock should belong to
 327  *      @test:  comparison callback
 328  *      @set:   setup callback
 329  *      @data:  argument to each of them
 330  */
 331 struct super_block *sget(struct file_system_type *type,
 332                         int (*test)(struct super_block *,void *),
 333                         int (*set)(struct super_block *,void *),
 334                         void *data)
 335 {
 336         struct super_block *s = NULL;
 337         struct list_head *p;
 338         int err;
 339
 340 retry:
 341         spin_lock(&sb_lock);
 342         if (test) list_for_each(p, &type->fs_supers) {
 343                 struct super_block *old;
 344                 old = list_entry(p, struct super_block, s_instances);
 345                 if (!test(old, data))
 346                         continue;
 347                 if (!grab_super(old))
 348                         goto retry;
 349                 if (s)
 350                         destroy_super(s);
 351                 return old;
 352         }
 353         if (!s) {
 354                 spin_unlock(&sb_lock);
 355                 s = alloc_super(type);
 356                 if (!s)
 357                         return ERR_PTR(-ENOMEM);
 358                 goto retry;
 359         }
 360
 361         err = set(s, data);
 362         if (err) {
 363                 spin_unlock(&sb_lock);
 364                 destroy_super(s);
 365                 return ERR_PTR(err);
 366         }
 367         s->s_type = type;
 368         strlcpy(s->s_id, type->name, sizeof(s->s_id));
 369         list_add_tail(&s->s_list, &super_blocks);
 370         list_add(&s->s_instances, &type->fs_supers);
 371         spin_unlock(&sb_lock);
 372         get_filesystem(type);
 373         return s;
 374 }
 375
 376 EXPORT_SYMBOL(sget);
 377
 378 void drop_super(struct super_block *sb)
 379 {
 380         up_read(&sb->s_umount);
 381         put_super(sb);
 382 }
 383
 384 EXPORT_SYMBOL(drop_super);
 385
 386 static inline void write_super(struct super_block *sb)
 387 {
 388         lock_super(sb);
 389         if (sb->s_root && sb->s_dirt)
 390                 if (sb->s_op->write_super)
 391                         sb->s_op->write_super(sb);
 392         unlock_super(sb);
 393 }
 394
 395 /*
 396  * Note: check the dirty flag before waiting, so we don't
 397  * hold up the sync while mounting a device. (The newly
 398  * mounted device won't need syncing.)
 399  */
 400 void sync_supers(void)
 401 {
 402         struct super_block *sb;
 403
 404         spin_lock(&sb_lock);
 405 restart:
 406         list_for_each_entry(sb, &super_blocks, s_list) {
 407                 if (sb->s_dirt) {
 408                         sb->s_count++;
 409                         spin_unlock(&sb_lock);
 410                         down_read(&sb->s_umount);
 411                         write_super(sb);
 412                         up_read(&sb->s_umount);
 413                         spin_lock(&sb_lock);
 414                         if (__put_super_and_need_restart(sb))
 415                                 goto restart;
 416                 }
 417         }
 418         spin_unlock(&sb_lock);
 419 }
 420
 421 /*
 422  * Call the ->sync_fs super_op against all filesytems which are r/w and
 423  * which implement it.
 424  *
 425  * This operation is careful to avoid the livelock which could easily happen
 426  * if two or more filesystems are being continuously dirtied.  s_need_sync_fs
 427  * is used only here.  We set it against all filesystems and then clear it as
 428  * we sync them.  So redirtied filesystems are skipped.
 429  *
 430  * But if process A is currently running sync_filesytems and then process B
 431  * calls sync_filesystems as well, process B will set all the s_need_sync_fs
 432  * flags again, which will cause process A to resync everything.  Fix that with
 433  * a local mutex.
 434  *
 435  * (Fabian) Avoid sync_fs with clean fs & wait mode 0
 436  */
 437 void sync_filesystems(int wait)
 438 {
 439         struct super_block *sb;
 440         static DEFINE_MUTEX(mutex);
 441
 442         mutex_lock(&mutex);             /* Could be down_interruptible */
 443         spin_lock(&sb_lock);
 444         list_for_each_entry(sb, &super_blocks, s_list) {
 445                 if (!sb->s_op->sync_fs)
 446                         continue;
 447                 if (sb->s_flags & MS_RDONLY)
 448                         continue;
 449                 sb->s_need_sync_fs = 1;
 450         }
 451
 452 restart:
 453         list_for_each_entry(sb, &super_blocks, s_list) {
 454                 if (!sb->s_need_sync_fs)
 455                         continue;
 456                 sb->s_need_sync_fs = 0;
 457                 if (sb->s_flags & MS_RDONLY)
 458                         continue;       /* hm.  Was remounted r/o meanwhile */
 459                 sb->s_count++;
 460                 spin_unlock(&sb_lock);
 461                 down_read(&sb->s_umount);
 462                 if (sb->s_root && (wait || sb->s_dirt))
 463                         sb->s_op->sync_fs(sb, wait);
 464                 up_read(&sb->s_umount);
 465                 /* restart only when sb is no longer on the list */
 466                 spin_lock(&sb_lock);
 467                 if (__put_super_and_need_restart(sb))
 468                         goto restart;
 469         }
 470         spin_unlock(&sb_lock);
 471         mutex_unlock(&mutex);
 472 }
 473
 474 /**
 475  *      get_super - get the superblock of a device
 476  *      @bdev: device to get the superblock for
 477  *
 478  *      Scans the superblock list and finds the superblock of the file system
 479  *      mounted on the device given. %NULL is returned if no match is found.
 480  */
 481
 482 struct super_block * get_super(struct block_device *bdev)
 483 {
 484         struct super_block *sb;
 485
 486         if (!bdev)
 487                 return NULL;
 488
 489         spin_lock(&sb_lock);
 490 rescan:
 491         list_for_each_entry(sb, &super_blocks, s_list) {
 492                 if (sb->s_bdev == bdev) {
 493                         sb->s_count++;
 494                         spin_unlock(&sb_lock);
 495                         down_read(&sb->s_umount);
 496                         if (sb->s_root)
 497                                 return sb;
 498                         up_read(&sb->s_umount);
 499                         /* restart only when sb is no longer on the list */
 500                         spin_lock(&sb_lock);
 501                         if (__put_super_and_need_restart(sb))
 502                                 goto rescan;
 503                 }
 504         }
 505         spin_unlock(&sb_lock);
 506         return NULL;
 507 }
 508
 509 EXPORT_SYMBOL(get_super);
 510
 511 struct super_block * user_get_super(dev_t dev)
 512 {
 513         struct super_block *sb;
 514
 515         spin_lock(&sb_lock);
 516 rescan:
 517         list_for_each_entry(sb, &super_blocks, s_list) {
 518                 if (sb->s_dev ==  dev) {
 519                         sb->s_count++;
 520                         spin_unlock(&sb_lock);
 521                         down_read(&sb->s_umount);
 522                         if (sb->s_root)
 523                                 return sb;
 524                         up_read(&sb->s_umount);
 525                         /* restart only when sb is no longer on the list */
 526                         spin_lock(&sb_lock);
 527                         if (__put_super_and_need_restart(sb))
 528                                 goto rescan;
 529                 }
 530         }
 531         spin_unlock(&sb_lock);
 532         return NULL;
 533 }
 534
 535 asmlinkage long sys_ustat(unsigned dev, struct ustat __user * ubuf)
 536 {
 537         struct super_block *s;
 538         struct ustat tmp;
 539         struct kstatfs sbuf;
 540         int err = -EINVAL;
 541
 542         s = user_get_super(new_decode_dev(dev));
 543         if (s == NULL)
 544                 goto out;
 545         err = vfs_statfs(s->s_root, &sbuf);
 546         drop_super(s);
 547         if (err)
 548                 goto out;
 549
 550         memset(&tmp,0,sizeof(struct ustat));
 551         tmp.f_tfree = sbuf.f_bfree;
 552         tmp.f_tinode = sbuf.f_ffree;
 553
 554         err = copy_to_user(ubuf,&tmp,sizeof(struct ustat)) ? -EFAULT : 0;
 555 out:
 556         return err;
 557 }
 558
 559 /**
 560  *      mark_files_ro
 561  *      @sb: superblock in question
 562  *
 563  *      All files are marked read/only.  We don't care about pending
 564  *      delete files so this should be used in 'force' mode only
 565  */
 566
 567 static void mark_files_ro(struct super_block *sb)
 568 {
 569         struct file *f;
 570
 571         file_list_lock();
 572         list_for_each_entry(f, &sb->s_files, f_u.fu_list) {
 573                 if (S_ISREG(f->f_path.dentry->d_inode->i_mode) && file_count(f))
 574                         f->f_mode &= ~FMODE_WRITE;
 575         }
 576         file_list_unlock();
 577 }
 578
 579 /**
 580  *      do_remount_sb - asks filesystem to change mount options.
 581  *      @sb:    superblock in question
 582  *      @flags: numeric part of options
 583  *      @data:  the rest of options
 584  *      @force: whether or not to force the change
 585  *
 586  *      Alters the mount options of a mounted file system.
 587  */
 588 int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
 589 {
 590         int retval;
 591
 592 #ifdef CONFIG_BLOCK
 593         if (!(flags & MS_RDONLY) && bdev_read_only(sb->s_bdev))
 594                 return -EACCES;
 595 #endif
 596         if (flags & MS_RDONLY)
 597                 acct_auto_close(sb);
 598         shrink_dcache_sb(sb);
 599         fsync_super(sb);
 600
 601         /* If we are remounting RDONLY and current sb is read/write,
 602            make sure there are no rw files opened */
 603         if ((flags & MS_RDONLY) && !(sb->s_flags & MS_RDONLY)) {
 604                 if (force)
 605                         mark_files_ro(sb);
 606                 else if (!fs_may_remount_ro(sb))
 607                         return -EBUSY;
 608         }
 609
 610         if (sb->s_op->remount_fs) {
 611                 lock_super(sb);
 612                 retval = sb->s_op->remount_fs(sb, &flags, data);
 613                 unlock_super(sb);
 614                 if (retval)
 615                         return retval;
 616         }
 617         sb->s_flags = (sb->s_flags & ~MS_RMT_MASK) | (flags & MS_RMT_MASK);
 618         return 0;
 619 }
 620
 621 static void do_emergency_remount(unsigned long foo)
 622 {
 623         struct super_block *sb;
 624
 625         spin_lock(&sb_lock);
 626         list_for_each_entry(sb, &super_blocks, s_list) {
 627                 sb->s_count++;
 628                 spin_unlock(&sb_lock);
 629                 down_read(&sb->s_umount);
 630                 if (sb->s_root && sb->s_bdev && !(sb->s_flags & MS_RDONLY)) {
 631                         /*
 632                          * ->remount_fs needs lock_kernel().
 633                          *
 634                          * What lock protects sb->s_flags??
 635                          */
 636                         lock_kernel();
 637                         do_remount_sb(sb, MS_RDONLY, NULL, 1);
 638                         unlock_kernel();
 639                 }
 640                 drop_super(sb);
 641                 spin_lock(&sb_lock);
 642         }
 643         spin_unlock(&sb_lock);
 644         printk("Emergency Remount complete\n");
 645 }
 646
 647 void emergency_remount(void)
 648 {
 649         pdflush_operation(do_emergency_remount, 0);
 650 }
 651
 652 /*
 653  * Unnamed block devices are dummy devices used by virtual
 654  * filesystems which don't use real block-devices.  -- jrs
 655  */
 656
 657 static struct idr unnamed_dev_idr;
 658 static DEFINE_SPINLOCK(unnamed_dev_lock);/* protects the above */
 659
 660 int set_anon_super(struct super_block *s, void *data)
 661 {
 662         int dev;
 663         int error;
 664
 665  retry:
 666         if (idr_pre_get(&unnamed_dev_idr, GFP_ATOMIC) == 0)
 667                 return -ENOMEM;
 668         spin_lock(&unnamed_dev_lock);
 669         error = idr_get_new(&unnamed_dev_idr, NULL, &dev);
 670         spin_unlock(&unnamed_dev_lock);
 671         if (error == -EAGAIN)
 672                 /* We raced and lost with another CPU. */
 673                 goto retry;
 674         else if (error)
 675                 return -EAGAIN;
 676
 677         if ((dev & MAX_ID_MASK) == (1 << MINORBITS)) {
 678                 spin_lock(&unnamed_dev_lock);
 679                 idr_remove(&unnamed_dev_idr, dev);
 680                 spin_unlock(&unnamed_dev_lock);
 681                 return -EMFILE;
 682         }
 683         s->s_dev = MKDEV(0, dev & MINORMASK);
 684         return 0;
 685 }
 686
 687 EXPORT_SYMBOL(set_anon_super);
 688
 689 void kill_anon_super(struct super_block *sb)
 690 {
 691         int slot = MINOR(sb->s_dev);
 692
 693         generic_shutdown_super(sb);
 694         spin_lock(&unnamed_dev_lock);
 695         idr_remove(&unnamed_dev_idr, slot);
 696         spin_unlock(&unnamed_dev_lock);
 697 }
 698
 699 EXPORT_SYMBOL(kill_anon_super);
 700
 701 void __init unnamed_dev_init(void)
 702 {
 703         idr_init(&unnamed_dev_idr);
 704 }
 705
 706 void kill_litter_super(struct super_block *sb)
 707 {
 708         if (sb->s_root)
 709                 d_genocide(sb->s_root);
 710         kill_anon_super(sb);
 711 }
 712
 713 EXPORT_SYMBOL(kill_litter_super);
 714
 715 #ifdef CONFIG_BLOCK
 716 static int set_bdev_super(struct super_block *s, void *data)
 717 {
 718         s->s_bdev = data;
 719         s->s_dev = s->s_bdev->bd_dev;
 720         return 0;
 721 }
 722
 723 static int test_bdev_super(struct super_block *s, void *data)
 724 {
 725         return (void *)s->s_bdev == data;
 726 }
 727
 728 static void bdev_uevent(struct block_device *bdev, enum kobject_action action)
 729 {
 730         if (bdev->bd_disk) {
 731                 if (bdev->bd_part)
 732                         kobject_uevent(&bdev->bd_part->kobj, action);
 733                 else
 734                         kobject_uevent(&bdev->bd_disk->kobj, action);
 735         }
 736 }
 737
 738 int get_sb_bdev(struct file_system_type *fs_type,
 739         int flags, const char *dev_name, void *data,
 740         int (*fill_super)(struct super_block *, void *, int),
 741         struct vfsmount *mnt)
 742 {
 743         struct block_device *bdev;
 744         struct super_block *s;
 745         int error = 0;
 746
 747         bdev = open_bdev_excl(dev_name, flags, fs_type);
 748         if (IS_ERR(bdev))
 749                 return PTR_ERR(bdev);
 750
 751         /*
 752          * once the super is inserted into the list by sget, s_umount
 753          * will protect the lockfs code from trying to start a snapshot
 754          * while we are mounting
 755          */
 756         down(&bdev->bd_mount_sem);
 757         s = sget(fs_type, test_bdev_super, set_bdev_super, bdev);
 758         up(&bdev->bd_mount_sem);
 759         if (IS_ERR(s))
 760                 goto error_s;
 761
 762         if (s->s_root) {
 763                 if ((flags ^ s->s_flags) & MS_RDONLY) {
 764                         up_write(&s->s_umount);
 765                         deactivate_super(s);
 766                         error = -EBUSY;
 767                         goto error_bdev;
 768                 }
 769
 770                 close_bdev_excl(bdev);
 771         } else {
 772                 char b[BDEVNAME_SIZE];
 773
 774                 s->s_flags = flags;
 775                 strlcpy(s->s_id, bdevname(bdev, b), sizeof(s->s_id));
 776                 sb_set_blocksize(s, block_size(bdev));
 777                 error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
 778                 if (error) {
 779                         up_write(&s->s_umount);
 780                         deactivate_super(s);
 781                         goto error;
 782                 }
 783
 784                 s->s_flags |= MS_ACTIVE;
 785                 bdev_uevent(bdev, KOBJ_MOUNT);
 786         }
 787
 788         return simple_set_mnt(mnt, s);
 789
 790 error_s:
 791         error = PTR_ERR(s);
 792 error_bdev:
 793         close_bdev_excl(bdev);
 794 error:
 795         return error;
 796 }
 797
 798 EXPORT_SYMBOL(get_sb_bdev);
 799
 800 void kill_block_super(struct super_block *sb)
 801 {
 802         struct block_device *bdev = sb->s_bdev;
 803
 804         bdev_uevent(bdev, KOBJ_UMOUNT);
 805         generic_shutdown_super(sb);
 806         sync_blockdev(bdev);
 807         close_bdev_excl(bdev);
 808 }
 809
 810 EXPORT_SYMBOL(kill_block_super);
 811 #endif
 812
 813 int get_sb_nodev(struct file_system_type *fs_type,
 814         int flags, void *data,
 815         int (*fill_super)(struct super_block *, void *, int),
 816         struct vfsmount *mnt)
 817 {
 818         int error;
 819         struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL);
 820
 821         if (IS_ERR(s))
 822                 return PTR_ERR(s);
 823
 824         s->s_flags = flags;
 825
 826         error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
 827         if (error) {
 828                 up_write(&s->s_umount);
 829                 deactivate_super(s);
 830                 return error;
 831         }
 832         s->s_flags |= MS_ACTIVE;
 833         return simple_set_mnt(mnt, s);
 834 }
 835
 836 EXPORT_SYMBOL(get_sb_nodev);
 837
 838 static int compare_single(struct super_block *s, void *p)
 839 {
 840         return 1;
 841 }
 842
 843 int get_sb_single(struct file_system_type *fs_type,
 844         int flags, void *data,
 845         int (*fill_super)(struct super_block *, void *, int),
 846         struct vfsmount *mnt)
 847 {
 848         struct super_block *s;
 849         int error;
 850
 851         s = sget(fs_type, compare_single, set_anon_super, NULL);
 852         if (IS_ERR(s))
 853                 return PTR_ERR(s);
 854         if (!s->s_root) {
 855                 s->s_flags = flags;
 856                 error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
 857                 if (error) {
 858                         up_write(&s->s_umount);
 859                         deactivate_super(s);
 860                         return error;
 861                 }
 862                 s->s_flags |= MS_ACTIVE;
 863         }
 864         do_remount_sb(s, flags, data, 0);
 865         return simple_set_mnt(mnt, s);
 866 }
 867
 868 EXPORT_SYMBOL(get_sb_single);
 869
 870 struct vfsmount *
 871 vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void *data)
 872 {
 873         struct vfsmount *mnt;
 874         char *secdata = NULL;
 875         int error;
 876
 877         if (!type)
 878                 return ERR_PTR(-ENODEV);
 879
 880         error = -ENOMEM;
 881         mnt = alloc_vfsmnt(name);
 882         if (!mnt)
 883                 goto out;
 884
 885         if (data) {
 886                 secdata = alloc_secdata();
 887                 if (!secdata)
 888                         goto out_mnt;
 889
 890                 error = security_sb_copy_data(type, data, secdata);
 891                 if (error)
 892                         goto out_free_secdata;
 893         }
 894
 895         error = type->get_sb(type, flags, name, data, mnt);
 896         if (error < 0)
 897                 goto out_free_secdata;
 898
 899         error = security_sb_kern_mount(mnt->mnt_sb, secdata);
 900         if (error)
 901                 goto out_sb;
 902
 903         mnt->mnt_mountpoint = mnt->mnt_root;
 904         mnt->mnt_parent = mnt;
 905         up_write(&mnt->mnt_sb->s_umount);
 906         free_secdata(secdata);
 907         return mnt;
 908 out_sb:
 909         dput(mnt->mnt_root);
 910         up_write(&mnt->mnt_sb->s_umount);
 911         deactivate_super(mnt->mnt_sb);
 912 out_free_secdata:
 913         free_secdata(secdata);
 914 out_mnt:
 915         free_vfsmnt(mnt);
 916 out:
 917         return ERR_PTR(error);
 918 }
 919
 920 EXPORT_SYMBOL_GPL(vfs_kern_mount);
 921
 922 struct vfsmount *
 923 do_kern_mount(const char *fstype, int flags, const char *name, void *data)
 924 {
 925         struct file_system_type *type = get_fs_type(fstype);
 926         struct vfsmount *mnt;
 927         if (!type)
 928                 return ERR_PTR(-ENODEV);
 929         mnt = vfs_kern_mount(type, flags, name, data);
 930         put_filesystem(type);
 931         return mnt;
 932 }
 933
 934 struct vfsmount *kern_mount(struct file_system_type *type)
 935 {
 936         return vfs_kern_mount(type, 0, type->name, NULL);
 937 }
 938
 939 EXPORT_SYMBOL(kern_mount);