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