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                 lockdep_set_class(&s->s_umount, &type->s_umount_key);
  76                 /*
  77                  * The locking rules for s_lock are up to the
  78                  * filesystem. For example ext3fs has different
  79                  * lock ordering than usbfs:
  80                  */
  81                 lockdep_set_class(&s->s_lock, &type->s_lock_key);
  82                 down_write(&s->s_umount);
  83                 s->s_count = S_BIAS;
  84                 atomic_set(&s->s_active, 1);
  85                 mutex_init(&s->s_vfs_rename_mutex);
  86                 mutex_init(&s->s_dquot.dqio_mutex);
  87                 mutex_init(&s->s_dquot.dqonoff_mutex);
  88                 init_rwsem(&s->s_dquot.dqptr_sem);
  89                 init_waitqueue_head(&s->s_wait_unfrozen);
  90                 s->s_maxbytes = MAX_NON_LFS;
  91                 s->dq_op = sb_dquot_ops;
  92                 s->s_qcop = sb_quotactl_ops;
  93                 s->s_op = &default_op;
  94                 s->s_time_gran = 1000000000;
  95         }
  96 out:
  97         return s;
  98 }
  99
 100 /**
 101  *      destroy_super   -       frees a superblock
 102  *      @s: superblock to free
 103  *
 104  *      Frees a superblock.
 105  */
 106 static inline void destroy_super(struct super_block *s)
 107 {
 108         security_sb_free(s);
 109         kfree(s);
 110 }
 111
 112 /* Superblock refcounting  */
 113
 114 /*
 115  * Drop a superblock's refcount.  Returns non-zero if the superblock was
 116  * destroyed.  The caller must hold sb_lock.
 117  */
 118 int __put_super(struct super_block *sb)
 119 {
 120         int ret = 0;
 121
 122         if (!--sb->s_count) {
 123                 destroy_super(sb);
 124                 ret = 1;
 125         }
 126         return ret;
 127 }
 128
 129 /*
 130  * Drop a superblock's refcount.
 131  * Returns non-zero if the superblock is about to be destroyed and
 132  * at least is already removed from super_blocks list, so if we are
 133  * making a loop through super blocks then we need to restart.
 134  * The caller must hold sb_lock.
 135  */
 136 int __put_super_and_need_restart(struct super_block *sb)
 137 {
 138         /* check for race with generic_shutdown_super() */
 139         if (list_empty(&sb->s_list)) {
 140                 /* super block is removed, need to restart... */
 141                 __put_super(sb);
 142                 return 1;
 143         }
 144         /* can't be the last, since s_list is still in use */
 145         sb->s_count--;
 146         BUG_ON(sb->s_count == 0);
 147         return 0;
 148 }
 149
 150 /**
 151  *      put_super       -       drop a temporary reference to superblock
 152  *      @sb: superblock in question
 153  *
 154  *      Drops a temporary reference, frees superblock if there's no
 155  *      references left.
 156  */
 157 static void put_super(struct super_block *sb)
 158 {
 159         spin_lock(&sb_lock);
 160         __put_super(sb);
 161         spin_unlock(&sb_lock);
 162 }
 163
 164
 165 /**
 166  *      deactivate_super        -       drop an active reference to superblock
 167  *      @s: superblock to deactivate
 168  *
 169  *      Drops an active reference to superblock, acquiring a temprory one if
 170  *      there is no active references left.  In that case we lock superblock,
 171  *      tell fs driver to shut it down and drop the temporary reference we
 172  *      had just acquired.
 173  */
 174 void deactivate_super(struct super_block *s)
 175 {
 176         struct file_system_type *fs = s->s_type;
 177         if (atomic_dec_and_lock(&s->s_active, &sb_lock)) {
 178                 s->s_count -= S_BIAS-1;
 179                 spin_unlock(&sb_lock);
 180                 DQUOT_OFF(s);
 181                 down_write(&s->s_umount);
 182                 fs->kill_sb(s);
 183                 put_filesystem(fs);
 184                 put_super(s);
 185         }
 186 }
 187
 188 EXPORT_SYMBOL(deactivate_super);
 189
 190 /**
 191  *      grab_super - acquire an active reference
 192  *      @s: reference we are trying to make active
 193  *
 194  *      Tries to acquire an active reference.  grab_super() is used when we
 195  *      had just found a superblock in super_blocks or fs_type->fs_supers
 196  *      and want to turn it into a full-blown active reference.  grab_super()
 197  *      is called with sb_lock held and drops it.  Returns 1 in case of
 198  *      success, 0 if we had failed (superblock contents was already dead or
 199  *      dying when grab_super() had been called).
 200  */
 201 static int grab_super(struct super_block *s)
 202 {
 203         s->s_count++;
 204         spin_unlock(&sb_lock);
 205         down_write(&s->s_umount);
 206         if (s->s_root) {
 207                 spin_lock(&sb_lock);
 208                 if (s->s_count > S_BIAS) {
 209                         atomic_inc(&s->s_active);
 210                         s->s_count--;
 211                         spin_unlock(&sb_lock);
 212                         return 1;
 213                 }
 214                 spin_unlock(&sb_lock);
 215         }
 216         up_write(&s->s_umount);
 217         put_super(s);
 218         yield();
 219         return 0;
 220 }
 221
 222 /**
 223  *      generic_shutdown_super  -       common helper for ->kill_sb()
 224  *      @sb: superblock to kill
 225  *
 226  *      generic_shutdown_super() does all fs-independent work on superblock
 227  *      shutdown.  Typical ->kill_sb() should pick all fs-specific objects
 228  *      that need destruction out of superblock, call generic_shutdown_super()
 229  *      and release aforementioned objects.  Note: dentries and inodes _are_
 230  *      taken care of and do not need specific handling.
 231  */
 232 void generic_shutdown_super(struct super_block *sb)
 233 {
 234         struct dentry *root = sb->s_root;
 235         struct super_operations *sop = sb->s_op;
 236
 237         if (root) {
 238                 sb->s_root = NULL;
 239                 shrink_dcache_parent(root);
 240                 shrink_dcache_sb(sb);
 241                 dput(root);
 242                 fsync_super(sb);
 243                 lock_super(sb);
 244                 sb->s_flags &= ~MS_ACTIVE;
 245                 /* bad name - it should be evict_inodes() */
 246                 invalidate_inodes(sb);
 247                 lock_kernel();
 248
 249                 if (sop->write_super && sb->s_dirt)
 250                         sop->write_super(sb);
 251                 if (sop->put_super)
 252                         sop->put_super(sb);
 253
 254                 /* Forget any remaining inodes */
 255                 if (invalidate_inodes(sb)) {
 256                         printk("VFS: Busy inodes after unmount of %s. "
 257                            "Self-destruct in 5 seconds.  Have a nice day...\n",
 258                            sb->s_id);
 259                 }
 260
 261                 unlock_kernel();
 262                 unlock_super(sb);
 263         }
 264         spin_lock(&sb_lock);
 265         /* should be initialized for __put_super_and_need_restart() */
 266         list_del_init(&sb->s_list);
 267         list_del(&sb->s_instances);
 268         spin_unlock(&sb_lock);
 269         up_write(&sb->s_umount);
 270 }
 271
 272 EXPORT_SYMBOL(generic_shutdown_super);
 273
 274 /**
 275  *      sget    -       find or create a superblock
 276  *      @type:  filesystem type superblock should belong to
 277  *      @test:  comparison callback
 278  *      @set:   setup callback
 279  *      @data:  argument to each of them
 280  */
 281 struct super_block *sget(struct file_system_type *type,
 282                         int (*test)(struct super_block *,void *),
 283                         int (*set)(struct super_block *,void *),
 284                         void *data)
 285 {
 286         struct super_block *s = NULL;
 287         struct list_head *p;
 288         int err;
 289
 290 retry:
 291         spin_lock(&sb_lock);
 292         if (test) list_for_each(p, &type->fs_supers) {
 293                 struct super_block *old;
 294                 old = list_entry(p, struct super_block, s_instances);
 295                 if (!test(old, data))
 296                         continue;
 297                 if (!grab_super(old))
 298                         goto retry;
 299                 if (s)
 300                         destroy_super(s);
 301                 return old;
 302         }
 303         if (!s) {
 304                 spin_unlock(&sb_lock);
 305                 s = alloc_super(type);
 306                 if (!s)
 307                         return ERR_PTR(-ENOMEM);
 308                 goto retry;
 309         }
 310
 311         err = set(s, data);
 312         if (err) {
 313                 spin_unlock(&sb_lock);
 314                 destroy_super(s);
 315                 return ERR_PTR(err);
 316         }
 317         s->s_type = type;
 318         strlcpy(s->s_id, type->name, sizeof(s->s_id));
 319         list_add_tail(&s->s_list, &super_blocks);
 320         list_add(&s->s_instances, &type->fs_supers);
 321         spin_unlock(&sb_lock);
 322         get_filesystem(type);
 323         return s;
 324 }
 325
 326 EXPORT_SYMBOL(sget);
 327
 328 void drop_super(struct super_block *sb)
 329 {
 330         up_read(&sb->s_umount);
 331         put_super(sb);
 332 }
 333
 334 EXPORT_SYMBOL(drop_super);
 335
 336 static inline void write_super(struct super_block *sb)
 337 {
 338         lock_super(sb);
 339         if (sb->s_root && sb->s_dirt)
 340                 if (sb->s_op->write_super)
 341                         sb->s_op->write_super(sb);
 342         unlock_super(sb);
 343 }
 344
 345 /*
 346  * Note: check the dirty flag before waiting, so we don't
 347  * hold up the sync while mounting a device. (The newly
 348  * mounted device won't need syncing.)
 349  */
 350 void sync_supers(void)
 351 {
 352         struct super_block *sb;
 353
 354         spin_lock(&sb_lock);
 355 restart:
 356         list_for_each_entry(sb, &super_blocks, s_list) {
 357                 if (sb->s_dirt) {
 358                         sb->s_count++;
 359                         spin_unlock(&sb_lock);
 360                         down_read(&sb->s_umount);
 361                         write_super(sb);
 362                         up_read(&sb->s_umount);
 363                         spin_lock(&sb_lock);
 364                         if (__put_super_and_need_restart(sb))
 365                                 goto restart;
 366                 }
 367         }
 368         spin_unlock(&sb_lock);
 369 }
 370
 371 /*
 372  * Call the ->sync_fs super_op against all filesytems which are r/w and
 373  * which implement it.
 374  *
 375  * This operation is careful to avoid the livelock which could easily happen
 376  * if two or more filesystems are being continuously dirtied.  s_need_sync_fs
 377  * is used only here.  We set it against all filesystems and then clear it as
 378  * we sync them.  So redirtied filesystems are skipped.
 379  *
 380  * But if process A is currently running sync_filesytems and then process B
 381  * calls sync_filesystems as well, process B will set all the s_need_sync_fs
 382  * flags again, which will cause process A to resync everything.  Fix that with
 383  * a local mutex.
 384  *
 385  * (Fabian) Avoid sync_fs with clean fs & wait mode 0
 386  */
 387 void sync_filesystems(int wait)
 388 {
 389         struct super_block *sb;
 390         static DEFINE_MUTEX(mutex);
 391
 392         mutex_lock(&mutex);             /* Could be down_interruptible */
 393         spin_lock(&sb_lock);
 394         list_for_each_entry(sb, &super_blocks, s_list) {
 395                 if (!sb->s_op->sync_fs)
 396                         continue;
 397                 if (sb->s_flags & MS_RDONLY)
 398                         continue;
 399                 sb->s_need_sync_fs = 1;
 400         }
 401
 402 restart:
 403         list_for_each_entry(sb, &super_blocks, s_list) {
 404                 if (!sb->s_need_sync_fs)
 405                         continue;
 406                 sb->s_need_sync_fs = 0;
 407                 if (sb->s_flags & MS_RDONLY)
 408                         continue;       /* hm.  Was remounted r/o meanwhile */
 409                 sb->s_count++;
 410                 spin_unlock(&sb_lock);
 411                 down_read(&sb->s_umount);
 412                 if (sb->s_root && (wait || sb->s_dirt))
 413                         sb->s_op->sync_fs(sb, wait);
 414                 up_read(&sb->s_umount);
 415                 /* restart only when sb is no longer on the list */
 416                 spin_lock(&sb_lock);
 417                 if (__put_super_and_need_restart(sb))
 418                         goto restart;
 419         }
 420         spin_unlock(&sb_lock);
 421         mutex_unlock(&mutex);
 422 }
 423
 424 /**
 425  *      get_super - get the superblock of a device
 426  *      @bdev: device to get the superblock for
 427  *
 428  *      Scans the superblock list and finds the superblock of the file system
 429  *      mounted on the device given. %NULL is returned if no match is found.
 430  */
 431
 432 struct super_block * get_super(struct block_device *bdev)
 433 {
 434         struct super_block *sb;
 435
 436         if (!bdev)
 437                 return NULL;
 438
 439         spin_lock(&sb_lock);
 440 rescan:
 441         list_for_each_entry(sb, &super_blocks, s_list) {
 442                 if (sb->s_bdev == bdev) {
 443                         sb->s_count++;
 444                         spin_unlock(&sb_lock);
 445                         down_read(&sb->s_umount);
 446                         if (sb->s_root)
 447                                 return sb;
 448                         up_read(&sb->s_umount);
 449                         /* restart only when sb is no longer on the list */
 450                         spin_lock(&sb_lock);
 451                         if (__put_super_and_need_restart(sb))
 452                                 goto rescan;
 453                 }
 454         }
 455         spin_unlock(&sb_lock);
 456         return NULL;
 457 }
 458
 459 EXPORT_SYMBOL(get_super);
 460
 461 struct super_block * user_get_super(dev_t dev)
 462 {
 463         struct super_block *sb;
 464
 465         spin_lock(&sb_lock);
 466 rescan:
 467         list_for_each_entry(sb, &super_blocks, s_list) {
 468                 if (sb->s_dev ==  dev) {
 469                         sb->s_count++;
 470                         spin_unlock(&sb_lock);
 471                         down_read(&sb->s_umount);
 472                         if (sb->s_root)
 473                                 return sb;
 474                         up_read(&sb->s_umount);
 475                         /* restart only when sb is no longer on the list */
 476                         spin_lock(&sb_lock);
 477                         if (__put_super_and_need_restart(sb))
 478                                 goto rescan;
 479                 }
 480         }
 481         spin_unlock(&sb_lock);
 482         return NULL;
 483 }
 484
 485 asmlinkage long sys_ustat(unsigned dev, struct ustat __user * ubuf)
 486 {
 487         struct super_block *s;
 488         struct ustat tmp;
 489         struct kstatfs sbuf;
 490         int err = -EINVAL;
 491
 492         s = user_get_super(new_decode_dev(dev));
 493         if (s == NULL)
 494                 goto out;
 495         err = vfs_statfs(s->s_root, &sbuf);
 496         drop_super(s);
 497         if (err)
 498                 goto out;
 499
 500         memset(&tmp,0,sizeof(struct ustat));
 501         tmp.f_tfree = sbuf.f_bfree;
 502         tmp.f_tinode = sbuf.f_ffree;
 503
 504         err = copy_to_user(ubuf,&tmp,sizeof(struct ustat)) ? -EFAULT : 0;
 505 out:
 506         return err;
 507 }
 508
 509 /**
 510  *      mark_files_ro
 511  *      @sb: superblock in question
 512  *
 513  *      All files are marked read/only.  We don't care about pending
 514  *      delete files so this should be used in 'force' mode only
 515  */
 516
 517 static void mark_files_ro(struct super_block *sb)
 518 {
 519         struct file *f;
 520
 521         file_list_lock();
 522         list_for_each_entry(f, &sb->s_files, f_u.fu_list) {
 523                 if (S_ISREG(f->f_dentry->d_inode->i_mode) && file_count(f))
 524                         f->f_mode &= ~FMODE_WRITE;
 525         }
 526         file_list_unlock();
 527 }
 528
 529 /**
 530  *      do_remount_sb - asks filesystem to change mount options.
 531  *      @sb:    superblock in question
 532  *      @flags: numeric part of options
 533  *      @data:  the rest of options
 534  *      @force: whether or not to force the change
 535  *
 536  *      Alters the mount options of a mounted file system.
 537  */
 538 int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
 539 {
 540         int retval;
 541
 542         if (!(flags & MS_RDONLY) && bdev_read_only(sb->s_bdev))
 543                 return -EACCES;
 544         if (flags & MS_RDONLY)
 545                 acct_auto_close(sb);
 546         shrink_dcache_sb(sb);
 547         fsync_super(sb);
 548
 549         /* If we are remounting RDONLY and current sb is read/write,
 550            make sure there are no rw files opened */
 551         if ((flags & MS_RDONLY) && !(sb->s_flags & MS_RDONLY)) {
 552                 if (force)
 553                         mark_files_ro(sb);
 554                 else if (!fs_may_remount_ro(sb))
 555                         return -EBUSY;
 556         }
 557
 558         if (sb->s_op->remount_fs) {
 559                 lock_super(sb);
 560                 retval = sb->s_op->remount_fs(sb, &flags, data);
 561                 unlock_super(sb);
 562                 if (retval)
 563                         return retval;
 564         }
 565         sb->s_flags = (sb->s_flags & ~MS_RMT_MASK) | (flags & MS_RMT_MASK);
 566         return 0;
 567 }
 568
 569 static void do_emergency_remount(unsigned long foo)
 570 {
 571         struct super_block *sb;
 572
 573         spin_lock(&sb_lock);
 574         list_for_each_entry(sb, &super_blocks, s_list) {
 575                 sb->s_count++;
 576                 spin_unlock(&sb_lock);
 577                 down_read(&sb->s_umount);
 578                 if (sb->s_root && sb->s_bdev && !(sb->s_flags & MS_RDONLY)) {
 579                         /*
 580                          * ->remount_fs needs lock_kernel().
 581                          *
 582                          * What lock protects sb->s_flags??
 583                          */
 584                         lock_kernel();
 585                         do_remount_sb(sb, MS_RDONLY, NULL, 1);
 586                         unlock_kernel();
 587                 }
 588                 drop_super(sb);
 589                 spin_lock(&sb_lock);
 590         }
 591         spin_unlock(&sb_lock);
 592         printk("Emergency Remount complete\n");
 593 }
 594
 595 void emergency_remount(void)
 596 {
 597         pdflush_operation(do_emergency_remount, 0);
 598 }
 599
 600 /*
 601  * Unnamed block devices are dummy devices used by virtual
 602  * filesystems which don't use real block-devices.  -- jrs
 603  */
 604
 605 static struct idr unnamed_dev_idr;
 606 static DEFINE_SPINLOCK(unnamed_dev_lock);/* protects the above */
 607
 608 int set_anon_super(struct super_block *s, void *data)
 609 {
 610         int dev;
 611         int error;
 612
 613  retry:
 614         if (idr_pre_get(&unnamed_dev_idr, GFP_ATOMIC) == 0)
 615                 return -ENOMEM;
 616         spin_lock(&unnamed_dev_lock);
 617         error = idr_get_new(&unnamed_dev_idr, NULL, &dev);
 618         spin_unlock(&unnamed_dev_lock);
 619         if (error == -EAGAIN)
 620                 /* We raced and lost with another CPU. */
 621                 goto retry;
 622         else if (error)
 623                 return -EAGAIN;
 624
 625         if ((dev & MAX_ID_MASK) == (1 << MINORBITS)) {
 626                 spin_lock(&unnamed_dev_lock);
 627                 idr_remove(&unnamed_dev_idr, dev);
 628                 spin_unlock(&unnamed_dev_lock);
 629                 return -EMFILE;
 630         }
 631         s->s_dev = MKDEV(0, dev & MINORMASK);
 632         return 0;
 633 }
 634
 635 EXPORT_SYMBOL(set_anon_super);
 636
 637 void kill_anon_super(struct super_block *sb)
 638 {
 639         int slot = MINOR(sb->s_dev);
 640
 641         generic_shutdown_super(sb);
 642         spin_lock(&unnamed_dev_lock);
 643         idr_remove(&unnamed_dev_idr, slot);
 644         spin_unlock(&unnamed_dev_lock);
 645 }
 646
 647 EXPORT_SYMBOL(kill_anon_super);
 648
 649 void __init unnamed_dev_init(void)
 650 {
 651         idr_init(&unnamed_dev_idr);
 652 }
 653
 654 void kill_litter_super(struct super_block *sb)
 655 {
 656         if (sb->s_root)
 657                 d_genocide(sb->s_root);
 658         kill_anon_super(sb);
 659 }
 660
 661 EXPORT_SYMBOL(kill_litter_super);
 662
 663 static int set_bdev_super(struct super_block *s, void *data)
 664 {
 665         s->s_bdev = data;
 666         s->s_dev = s->s_bdev->bd_dev;
 667         return 0;
 668 }
 669
 670 static int test_bdev_super(struct super_block *s, void *data)
 671 {
 672         return (void *)s->s_bdev == data;
 673 }
 674
 675 static void bdev_uevent(struct block_device *bdev, enum kobject_action action)
 676 {
 677         if (bdev->bd_disk) {
 678                 if (bdev->bd_part)
 679                         kobject_uevent(&bdev->bd_part->kobj, action);
 680                 else
 681                         kobject_uevent(&bdev->bd_disk->kobj, action);
 682         }
 683 }
 684
 685 int get_sb_bdev(struct file_system_type *fs_type,
 686         int flags, const char *dev_name, void *data,
 687         int (*fill_super)(struct super_block *, void *, int),
 688         struct vfsmount *mnt)
 689 {
 690         struct block_device *bdev;
 691         struct super_block *s;
 692         int error = 0;
 693
 694         bdev = open_bdev_excl(dev_name, flags, fs_type);
 695         if (IS_ERR(bdev))
 696                 return PTR_ERR(bdev);
 697
 698         /*
 699          * once the super is inserted into the list by sget, s_umount
 700          * will protect the lockfs code from trying to start a snapshot
 701          * while we are mounting
 702          */
 703         mutex_lock(&bdev->bd_mount_mutex);
 704         s = sget(fs_type, test_bdev_super, set_bdev_super, bdev);
 705         mutex_unlock(&bdev->bd_mount_mutex);
 706         if (IS_ERR(s))
 707                 goto error_s;
 708
 709         if (s->s_root) {
 710                 if ((flags ^ s->s_flags) & MS_RDONLY) {
 711                         up_write(&s->s_umount);
 712                         deactivate_super(s);
 713                         error = -EBUSY;
 714                         goto error_bdev;
 715                 }
 716
 717                 close_bdev_excl(bdev);
 718         } else {
 719                 char b[BDEVNAME_SIZE];
 720
 721                 s->s_flags = flags;
 722                 strlcpy(s->s_id, bdevname(bdev, b), sizeof(s->s_id));
 723                 sb_set_blocksize(s, block_size(bdev));
 724                 error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
 725                 if (error) {
 726                         up_write(&s->s_umount);
 727                         deactivate_super(s);
 728                         goto error;
 729                 }
 730
 731                 s->s_flags |= MS_ACTIVE;
 732                 bdev_uevent(bdev, KOBJ_MOUNT);
 733         }
 734
 735         return simple_set_mnt(mnt, s);
 736
 737 error_s:
 738         error = PTR_ERR(s);
 739 error_bdev:
 740         close_bdev_excl(bdev);
 741 error:
 742         return error;
 743 }
 744
 745 EXPORT_SYMBOL(get_sb_bdev);
 746
 747 void kill_block_super(struct super_block *sb)
 748 {
 749         struct block_device *bdev = sb->s_bdev;
 750
 751         bdev_uevent(bdev, KOBJ_UMOUNT);
 752         generic_shutdown_super(sb);
 753         sync_blockdev(bdev);
 754         close_bdev_excl(bdev);
 755 }
 756
 757 EXPORT_SYMBOL(kill_block_super);
 758
 759 int get_sb_nodev(struct file_system_type *fs_type,
 760         int flags, void *data,
 761         int (*fill_super)(struct super_block *, void *, int),
 762         struct vfsmount *mnt)
 763 {
 764         int error;
 765         struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL);
 766
 767         if (IS_ERR(s))
 768                 return PTR_ERR(s);
 769
 770         s->s_flags = flags;
 771
 772         error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
 773         if (error) {
 774                 up_write(&s->s_umount);
 775                 deactivate_super(s);
 776                 return error;
 777         }
 778         s->s_flags |= MS_ACTIVE;
 779         return simple_set_mnt(mnt, s);
 780 }
 781
 782 EXPORT_SYMBOL(get_sb_nodev);
 783
 784 static int compare_single(struct super_block *s, void *p)
 785 {
 786         return 1;
 787 }
 788
 789 int get_sb_single(struct file_system_type *fs_type,
 790         int flags, void *data,
 791         int (*fill_super)(struct super_block *, void *, int),
 792         struct vfsmount *mnt)
 793 {
 794         struct super_block *s;
 795         int error;
 796
 797         s = sget(fs_type, compare_single, set_anon_super, NULL);
 798         if (IS_ERR(s))
 799                 return PTR_ERR(s);
 800         if (!s->s_root) {
 801                 s->s_flags = flags;
 802                 error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
 803                 if (error) {
 804                         up_write(&s->s_umount);
 805                         deactivate_super(s);
 806                         return error;
 807                 }
 808                 s->s_flags |= MS_ACTIVE;
 809         }
 810         do_remount_sb(s, flags, data, 0);
 811         return simple_set_mnt(mnt, s);
 812 }
 813
 814 EXPORT_SYMBOL(get_sb_single);
 815
 816 struct vfsmount *
 817 vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void *data)
 818 {
 819         struct vfsmount *mnt;
 820         char *secdata = NULL;
 821         int error;
 822
 823         if (!type)
 824                 return ERR_PTR(-ENODEV);
 825
 826         error = -ENOMEM;
 827         mnt = alloc_vfsmnt(name);
 828         if (!mnt)
 829                 goto out;
 830
 831         if (data) {
 832                 secdata = alloc_secdata();
 833                 if (!secdata)
 834                         goto out_mnt;
 835
 836                 error = security_sb_copy_data(type, data, secdata);
 837                 if (error)
 838                         goto out_free_secdata;
 839         }
 840
 841         error = type->get_sb(type, flags, name, data, mnt);
 842         if (error < 0)
 843                 goto out_free_secdata;
 844
 845         error = security_sb_kern_mount(mnt->mnt_sb, secdata);
 846         if (error)
 847                 goto out_sb;
 848
 849         mnt->mnt_mountpoint = mnt->mnt_root;
 850         mnt->mnt_parent = mnt;
 851         up_write(&mnt->mnt_sb->s_umount);
 852         free_secdata(secdata);
 853         return mnt;
 854 out_sb:
 855         dput(mnt->mnt_root);
 856         up_write(&mnt->mnt_sb->s_umount);
 857         deactivate_super(mnt->mnt_sb);
 858 out_free_secdata:
 859         free_secdata(secdata);
 860 out_mnt:
 861         free_vfsmnt(mnt);
 862 out:
 863         return ERR_PTR(error);
 864 }
 865
 866 EXPORT_SYMBOL_GPL(vfs_kern_mount);
 867
 868 struct vfsmount *
 869 do_kern_mount(const char *fstype, int flags, const char *name, void *data)
 870 {
 871         struct file_system_type *type = get_fs_type(fstype);
 872         struct vfsmount *mnt;
 873         if (!type)
 874                 return ERR_PTR(-ENODEV);
 875         mnt = vfs_kern_mount(type, flags, name, data);
 876         put_filesystem(type);
 877         return mnt;
 878 }
 879
 880 struct vfsmount *kern_mount(struct file_system_type *type)
 881 {
 882         return vfs_kern_mount(type, 0, type->name, NULL);
 883 }
 884
 885 EXPORT_SYMBOL(kern_mount);