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 <linux/file.h>
  41 #include <asm/uaccess.h>
  42
  43
  44 LIST_HEAD(super_blocks);
  45 DEFINE_SPINLOCK(sb_lock);
  46
  47 /**
  48  *      alloc_super     -       create new superblock
  49  *      @type:  filesystem type superblock should belong to
  50  *
  51  *      Allocates and initializes a new &struct super_block.  alloc_super()
  52  *      returns a pointer new superblock or %NULL if allocation had failed.
  53  */
  54 static struct super_block *alloc_super(struct file_system_type *type)
  55 {
  56         struct super_block *s = kzalloc(sizeof(struct super_block),  GFP_USER);
  57         static struct super_operations default_op;
  58
  59         if (s) {
  60                 if (security_sb_alloc(s)) {
  61                         kfree(s);
  62                         s = NULL;
  63                         goto out;
  64                 }
  65                 INIT_LIST_HEAD(&s->s_dirty);
  66                 INIT_LIST_HEAD(&s->s_io);
  67                 INIT_LIST_HEAD(&s->s_more_io);
  68                 INIT_LIST_HEAD(&s->s_files);
  69                 INIT_LIST_HEAD(&s->s_instances);
  70                 INIT_HLIST_HEAD(&s->s_anon);
  71                 INIT_LIST_HEAD(&s->s_inodes);
  72                 init_rwsem(&s->s_umount);
  73                 mutex_init(&s->s_lock);
  74                 lockdep_set_class(&s->s_umount, &type->s_umount_key);
  75                 /*
  76                  * The locking rules for s_lock are up to the
  77                  * filesystem. For example ext3fs has different
  78                  * lock ordering than usbfs:
  79                  */
  80                 lockdep_set_class(&s->s_lock, &type->s_lock_key);
  81                 down_write(&s->s_umount);
  82                 s->s_count = S_BIAS;
  83                 atomic_set(&s->s_active, 1);
  84                 mutex_init(&s->s_vfs_rename_mutex);
  85                 mutex_init(&s->s_dquot.dqio_mutex);
  86                 mutex_init(&s->s_dquot.dqonoff_mutex);
  87                 init_rwsem(&s->s_dquot.dqptr_sem);
  88                 init_waitqueue_head(&s->s_wait_unfrozen);
  89                 s->s_maxbytes = MAX_NON_LFS;
  90                 s->dq_op = sb_dquot_ops;
  91                 s->s_qcop = sb_quotactl_ops;
  92                 s->s_op = &default_op;
  93                 s->s_time_gran = 1000000000;
  94         }
  95 out:
  96         return s;
  97 }
  98
  99 /**
 100  *      destroy_super   -       frees a superblock
 101  *      @s: superblock to free
 102  *
 103  *      Frees a superblock.
 104  */
 105 static inline void destroy_super(struct super_block *s)
 106 {
 107         security_sb_free(s);
 108         kfree(s->s_subtype);
 109         kfree(s->s_options);
 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         const 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 super_block *old;
 338         int err;
 339
 340 retry:
 341         spin_lock(&sb_lock);
 342         if (test) {
 343                 list_for_each_entry(old, &type->fs_supers, s_instances) {
 344                         if (!test(old, data))
 345                                 continue;
 346                         if (!grab_super(old))
 347                                 goto retry;
 348                         if (s)
 349                                 destroy_super(s);
 350                         return old;
 351                 }
 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 filesystems 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_filesystems 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 - mark all files read-only
 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 retry:
 572         file_list_lock();
 573         list_for_each_entry(f, &sb->s_files, f_u.fu_list) {
 574                 struct vfsmount *mnt;
 575                 if (!S_ISREG(f->f_path.dentry->d_inode->i_mode))
 576                        continue;
 577                 if (!file_count(f))
 578                         continue;
 579                 if (!(f->f_mode & FMODE_WRITE))
 580                         continue;
 581                 f->f_mode &= ~FMODE_WRITE;
 582                 if (file_check_writeable(f) != 0)
 583                         continue;
 584                 file_release_write(f);
 585                 mnt = mntget(f->f_path.mnt);
 586                 file_list_unlock();
 587                 /*
 588                  * This can sleep, so we can't hold
 589                  * the file_list_lock() spinlock.
 590                  */
 591                 mnt_drop_write(mnt);
 592                 mntput(mnt);
 593                 goto retry;
 594         }
 595         file_list_unlock();
 596 }
 597
 598 /**
 599  *      do_remount_sb - asks filesystem to change mount options.
 600  *      @sb:    superblock in question
 601  *      @flags: numeric part of options
 602  *      @data:  the rest of options
 603  *      @force: whether or not to force the change
 604  *
 605  *      Alters the mount options of a mounted file system.
 606  */
 607 int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
 608 {
 609         int retval;
 610
 611 #ifdef CONFIG_BLOCK
 612         if (!(flags & MS_RDONLY) && bdev_read_only(sb->s_bdev))
 613                 return -EACCES;
 614 #endif
 615         if (flags & MS_RDONLY)
 616                 acct_auto_close(sb);
 617         shrink_dcache_sb(sb);
 618         fsync_super(sb);
 619
 620         /* If we are remounting RDONLY and current sb is read/write,
 621            make sure there are no rw files opened */
 622         if ((flags & MS_RDONLY) && !(sb->s_flags & MS_RDONLY)) {
 623                 if (force)
 624                         mark_files_ro(sb);
 625                 else if (!fs_may_remount_ro(sb))
 626                         return -EBUSY;
 627                 DQUOT_OFF(sb);
 628         }
 629
 630         if (sb->s_op->remount_fs) {
 631                 lock_super(sb);
 632                 retval = sb->s_op->remount_fs(sb, &flags, data);
 633                 unlock_super(sb);
 634                 if (retval)
 635                         return retval;
 636         }
 637         sb->s_flags = (sb->s_flags & ~MS_RMT_MASK) | (flags & MS_RMT_MASK);
 638         return 0;
 639 }
 640
 641 static void do_emergency_remount(unsigned long foo)
 642 {
 643         struct super_block *sb;
 644
 645         spin_lock(&sb_lock);
 646         list_for_each_entry(sb, &super_blocks, s_list) {
 647                 sb->s_count++;
 648                 spin_unlock(&sb_lock);
 649                 down_read(&sb->s_umount);
 650                 if (sb->s_root && sb->s_bdev && !(sb->s_flags & MS_RDONLY)) {
 651                         /*
 652                          * ->remount_fs needs lock_kernel().
 653                          *
 654                          * What lock protects sb->s_flags??
 655                          */
 656                         lock_kernel();
 657                         do_remount_sb(sb, MS_RDONLY, NULL, 1);
 658                         unlock_kernel();
 659                 }
 660                 drop_super(sb);
 661                 spin_lock(&sb_lock);
 662         }
 663         spin_unlock(&sb_lock);
 664         printk("Emergency Remount complete\n");
 665 }
 666
 667 void emergency_remount(void)
 668 {
 669         pdflush_operation(do_emergency_remount, 0);
 670 }
 671
 672 /*
 673  * Unnamed block devices are dummy devices used by virtual
 674  * filesystems which don't use real block-devices.  -- jrs
 675  */
 676
 677 static struct idr unnamed_dev_idr;
 678 static DEFINE_SPINLOCK(unnamed_dev_lock);/* protects the above */
 679
 680 int set_anon_super(struct super_block *s, void *data)
 681 {
 682         int dev;
 683         int error;
 684
 685  retry:
 686         if (idr_pre_get(&unnamed_dev_idr, GFP_ATOMIC) == 0)
 687                 return -ENOMEM;
 688         spin_lock(&unnamed_dev_lock);
 689         error = idr_get_new(&unnamed_dev_idr, NULL, &dev);
 690         spin_unlock(&unnamed_dev_lock);
 691         if (error == -EAGAIN)
 692                 /* We raced and lost with another CPU. */
 693                 goto retry;
 694         else if (error)
 695                 return -EAGAIN;
 696
 697         if ((dev & MAX_ID_MASK) == (1 << MINORBITS)) {
 698                 spin_lock(&unnamed_dev_lock);
 699                 idr_remove(&unnamed_dev_idr, dev);
 700                 spin_unlock(&unnamed_dev_lock);
 701                 return -EMFILE;
 702         }
 703         s->s_dev = MKDEV(0, dev & MINORMASK);
 704         return 0;
 705 }
 706
 707 EXPORT_SYMBOL(set_anon_super);
 708
 709 void kill_anon_super(struct super_block *sb)
 710 {
 711         int slot = MINOR(sb->s_dev);
 712
 713         generic_shutdown_super(sb);
 714         spin_lock(&unnamed_dev_lock);
 715         idr_remove(&unnamed_dev_idr, slot);
 716         spin_unlock(&unnamed_dev_lock);
 717 }
 718
 719 EXPORT_SYMBOL(kill_anon_super);
 720
 721 void __init unnamed_dev_init(void)
 722 {
 723         idr_init(&unnamed_dev_idr);
 724 }
 725
 726 void kill_litter_super(struct super_block *sb)
 727 {
 728         if (sb->s_root)
 729                 d_genocide(sb->s_root);
 730         kill_anon_super(sb);
 731 }
 732
 733 EXPORT_SYMBOL(kill_litter_super);
 734
 735 #ifdef CONFIG_BLOCK
 736 static int set_bdev_super(struct super_block *s, void *data)
 737 {
 738         s->s_bdev = data;
 739         s->s_dev = s->s_bdev->bd_dev;
 740         return 0;
 741 }
 742
 743 static int test_bdev_super(struct super_block *s, void *data)
 744 {
 745         return (void *)s->s_bdev == data;
 746 }
 747
 748 int get_sb_bdev(struct file_system_type *fs_type,
 749         int flags, const char *dev_name, void *data,
 750         int (*fill_super)(struct super_block *, void *, int),
 751         struct vfsmount *mnt)
 752 {
 753         struct block_device *bdev;
 754         struct super_block *s;
 755         int error = 0;
 756
 757         bdev = open_bdev_excl(dev_name, flags, fs_type);
 758         if (IS_ERR(bdev))
 759                 return PTR_ERR(bdev);
 760
 761         /*
 762          * once the super is inserted into the list by sget, s_umount
 763          * will protect the lockfs code from trying to start a snapshot
 764          * while we are mounting
 765          */
 766         down(&bdev->bd_mount_sem);
 767         s = sget(fs_type, test_bdev_super, set_bdev_super, bdev);
 768         up(&bdev->bd_mount_sem);
 769         if (IS_ERR(s))
 770                 goto error_s;
 771
 772         if (s->s_root) {
 773                 if ((flags ^ s->s_flags) & MS_RDONLY) {
 774                         up_write(&s->s_umount);
 775                         deactivate_super(s);
 776                         error = -EBUSY;
 777                         goto error_bdev;
 778                 }
 779
 780                 close_bdev_excl(bdev);
 781         } else {
 782                 char b[BDEVNAME_SIZE];
 783
 784                 s->s_flags = flags;
 785                 strlcpy(s->s_id, bdevname(bdev, b), sizeof(s->s_id));
 786                 sb_set_blocksize(s, block_size(bdev));
 787                 error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
 788                 if (error) {
 789                         up_write(&s->s_umount);
 790                         deactivate_super(s);
 791                         goto error;
 792                 }
 793
 794                 s->s_flags |= MS_ACTIVE;
 795         }
 796
 797         return simple_set_mnt(mnt, s);
 798
 799 error_s:
 800         error = PTR_ERR(s);
 801 error_bdev:
 802         close_bdev_excl(bdev);
 803 error:
 804         return error;
 805 }
 806
 807 EXPORT_SYMBOL(get_sb_bdev);
 808
 809 void kill_block_super(struct super_block *sb)
 810 {
 811         struct block_device *bdev = sb->s_bdev;
 812
 813         generic_shutdown_super(sb);
 814         sync_blockdev(bdev);
 815         close_bdev_excl(bdev);
 816 }
 817
 818 EXPORT_SYMBOL(kill_block_super);
 819 #endif
 820
 821 int get_sb_nodev(struct file_system_type *fs_type,
 822         int flags, void *data,
 823         int (*fill_super)(struct super_block *, void *, int),
 824         struct vfsmount *mnt)
 825 {
 826         int error;
 827         struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL);
 828
 829         if (IS_ERR(s))
 830                 return PTR_ERR(s);
 831
 832         s->s_flags = flags;
 833
 834         error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
 835         if (error) {
 836                 up_write(&s->s_umount);
 837                 deactivate_super(s);
 838                 return error;
 839         }
 840         s->s_flags |= MS_ACTIVE;
 841         return simple_set_mnt(mnt, s);
 842 }
 843
 844 EXPORT_SYMBOL(get_sb_nodev);
 845
 846 static int compare_single(struct super_block *s, void *p)
 847 {
 848         return 1;
 849 }
 850
 851 int get_sb_single(struct file_system_type *fs_type,
 852         int flags, void *data,
 853         int (*fill_super)(struct super_block *, void *, int),
 854         struct vfsmount *mnt)
 855 {
 856         struct super_block *s;
 857         int error;
 858
 859         s = sget(fs_type, compare_single, set_anon_super, NULL);
 860         if (IS_ERR(s))
 861                 return PTR_ERR(s);
 862         if (!s->s_root) {
 863                 s->s_flags = flags;
 864                 error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
 865                 if (error) {
 866                         up_write(&s->s_umount);
 867                         deactivate_super(s);
 868                         return error;
 869                 }
 870                 s->s_flags |= MS_ACTIVE;
 871         }
 872         do_remount_sb(s, flags, data, 0);
 873         return simple_set_mnt(mnt, s);
 874 }
 875
 876 EXPORT_SYMBOL(get_sb_single);
 877
 878 struct vfsmount *
 879 vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void *data)
 880 {
 881         struct vfsmount *mnt;
 882         char *secdata = NULL;
 883         int error;
 884
 885         if (!type)
 886                 return ERR_PTR(-ENODEV);
 887
 888         error = -ENOMEM;
 889         mnt = alloc_vfsmnt(name);
 890         if (!mnt)
 891                 goto out;
 892
 893         if (data && !(type->fs_flags & FS_BINARY_MOUNTDATA)) {
 894                 secdata = alloc_secdata();
 895                 if (!secdata)
 896                         goto out_mnt;
 897
 898                 error = security_sb_copy_data(data, secdata);
 899                 if (error)
 900                         goto out_free_secdata;
 901         }
 902
 903         error = type->get_sb(type, flags, name, data, mnt);
 904         if (error < 0)
 905                 goto out_free_secdata;
 906         BUG_ON(!mnt->mnt_sb);
 907
 908         error = security_sb_kern_mount(mnt->mnt_sb, secdata);
 909         if (error)
 910                 goto out_sb;
 911
 912         mnt->mnt_mountpoint = mnt->mnt_root;
 913         mnt->mnt_parent = mnt;
 914         up_write(&mnt->mnt_sb->s_umount);
 915         free_secdata(secdata);
 916         return mnt;
 917 out_sb:
 918         dput(mnt->mnt_root);
 919         up_write(&mnt->mnt_sb->s_umount);
 920         deactivate_super(mnt->mnt_sb);
 921 out_free_secdata:
 922         free_secdata(secdata);
 923 out_mnt:
 924         free_vfsmnt(mnt);
 925 out:
 926         return ERR_PTR(error);
 927 }
 928
 929 EXPORT_SYMBOL_GPL(vfs_kern_mount);
 930
 931 static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype)
 932 {
 933         int err;
 934         const char *subtype = strchr(fstype, '.');
 935         if (subtype) {
 936                 subtype++;
 937                 err = -EINVAL;
 938                 if (!subtype[0])
 939                         goto err;
 940         } else
 941                 subtype = "";
 942
 943         mnt->mnt_sb->s_subtype = kstrdup(subtype, GFP_KERNEL);
 944         err = -ENOMEM;
 945         if (!mnt->mnt_sb->s_subtype)
 946                 goto err;
 947         return mnt;
 948
 949  err:
 950         mntput(mnt);
 951         return ERR_PTR(err);
 952 }
 953
 954 struct vfsmount *
 955 do_kern_mount(const char *fstype, int flags, const char *name, void *data)
 956 {
 957         struct file_system_type *type = get_fs_type(fstype);
 958         struct vfsmount *mnt;
 959         if (!type)
 960                 return ERR_PTR(-ENODEV);
 961         mnt = vfs_kern_mount(type, flags, name, data);
 962         if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) &&
 963             !mnt->mnt_sb->s_subtype)
 964                 mnt = fs_set_subtype(mnt, fstype);
 965         put_filesystem(type);
 966         return mnt;
 967 }
 968 EXPORT_SYMBOL_GPL(do_kern_mount);
 969
 970 struct vfsmount *kern_mount_data(struct file_system_type *type, void *data)
 971 {
 972         return vfs_kern_mount(type, MS_KERNMOUNT, type->name, data);
 973 }
 974
 975 EXPORT_SYMBOL_GPL(kern_mount_data);