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