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/config.h>
  24 #include <linux/module.h>
  25 #include <linux/slab.h>
  26 #include <linux/init.h>
  27 #include <linux/smp_lock.h>
  28 #include <linux/acct.h>
  29 #include <linux/blkdev.h>
  30 #include <linux/quotaops.h>
  31 #include <linux/namei.h>
  32 #include <linux/buffer_head.h>          /* for fsync_super() */
  33 #include <linux/mount.h>
  34 #include <linux/security.h>
  35 #include <linux/syscalls.h>
  36 #include <linux/vfs.h>
  37 #include <linux/writeback.h>            /* for the emergency remount stuff */
  38 #include <linux/idr.h>
  39 #include <linux/kobject.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(void)
  57 {
  58         struct super_block *s = kmalloc(sizeof(struct super_block),  GFP_USER);
  59         static struct super_operations default_op;
  60
  61         if (s) {
  62                 memset(s, 0, sizeof(struct super_block));
  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                 sema_init(&s->s_lock, 1);
  76                 down_write(&s->s_umount);
  77                 s->s_count = S_BIAS;
  78                 atomic_set(&s->s_active, 1);
  79                 sema_init(&s->s_vfs_rename_sem,1);
  80                 sema_init(&s->s_dquot.dqio_sem, 1);
  81                 sema_init(&s->s_dquot.dqonoff_sem, 1);
  82                 init_rwsem(&s->s_dquot.dqptr_sem);
  83                 init_waitqueue_head(&s->s_wait_unfrozen);
  84                 s->s_maxbytes = MAX_NON_LFS;
  85                 s->dq_op = sb_dquot_ops;
  86                 s->s_qcop = sb_quotactl_ops;
  87                 s->s_op = &default_op;
  88                 s->s_time_gran = 1000000000;
  89         }
  90 out:
  91         return s;
  92 }
  93
  94 /**
  95  *      destroy_super   -       frees a superblock
  96  *      @s: superblock to free
  97  *
  98  *      Frees a superblock.
  99  */
 100 static inline void destroy_super(struct super_block *s)
 101 {
 102         security_sb_free(s);
 103         kfree(s);
 104 }
 105
 106 /* Superblock refcounting  */
 107
 108 /*
 109  * Drop a superblock's refcount.  Returns non-zero if the superblock was
 110  * destroyed.  The caller must hold sb_lock.
 111  */
 112 int __put_super(struct super_block *sb)
 113 {
 114         int ret = 0;
 115
 116         if (!--sb->s_count) {
 117                 destroy_super(sb);
 118                 ret = 1;
 119         }
 120         return ret;
 121 }
 122
 123 /*
 124  * Drop a superblock's refcount.
 125  * Returns non-zero if the superblock is about to be destroyed and
 126  * at least is already removed from super_blocks list, so if we are
 127  * making a loop through super blocks then we need to restart.
 128  * The caller must hold sb_lock.
 129  */
 130 int __put_super_and_need_restart(struct super_block *sb)
 131 {
 132         /* check for race with generic_shutdown_super() */
 133         if (list_empty(&sb->s_list)) {
 134                 /* super block is removed, need to restart... */
 135                 __put_super(sb);
 136                 return 1;
 137         }
 138         /* can't be the last, since s_list is still in use */
 139         sb->s_count--;
 140         BUG_ON(sb->s_count == 0);
 141         return 0;
 142 }
 143
 144 /**
 145  *      put_super       -       drop a temporary reference to superblock
 146  *      @sb: superblock in question
 147  *
 148  *      Drops a temporary reference, frees superblock if there's no
 149  *      references left.
 150  */
 151 static void put_super(struct super_block *sb)
 152 {
 153         spin_lock(&sb_lock);
 154         __put_super(sb);
 155         spin_unlock(&sb_lock);
 156 }
 157
 158
 159 /**
 160  *      deactivate_super        -       drop an active reference to superblock
 161  *      @s: superblock to deactivate
 162  *
 163  *      Drops an active reference to superblock, acquiring a temprory one if
 164  *      there is no active references left.  In that case we lock superblock,
 165  *      tell fs driver to shut it down and drop the temporary reference we
 166  *      had just acquired.
 167  */
 168 void deactivate_super(struct super_block *s)
 169 {
 170         struct file_system_type *fs = s->s_type;
 171         if (atomic_dec_and_lock(&s->s_active, &sb_lock)) {
 172                 s->s_count -= S_BIAS-1;
 173                 spin_unlock(&sb_lock);
 174                 DQUOT_OFF(s);
 175                 down_write(&s->s_umount);
 176                 fs->kill_sb(s);
 177                 put_filesystem(fs);
 178                 put_super(s);
 179         }
 180 }
 181
 182 EXPORT_SYMBOL(deactivate_super);
 183
 184 /**
 185  *      grab_super - acquire an active reference
 186  *      @s: reference we are trying to make active
 187  *
 188  *      Tries to acquire an active reference.  grab_super() is used when we
 189  *      had just found a superblock in super_blocks or fs_type->fs_supers
 190  *      and want to turn it into a full-blown active reference.  grab_super()
 191  *      is called with sb_lock held and drops it.  Returns 1 in case of
 192  *      success, 0 if we had failed (superblock contents was already dead or
 193  *      dying when grab_super() had been called).
 194  */
 195 static int grab_super(struct super_block *s)
 196 {
 197         s->s_count++;
 198         spin_unlock(&sb_lock);
 199         down_write(&s->s_umount);
 200         if (s->s_root) {
 201                 spin_lock(&sb_lock);
 202                 if (s->s_count > S_BIAS) {
 203                         atomic_inc(&s->s_active);
 204                         s->s_count--;
 205                         spin_unlock(&sb_lock);
 206                         return 1;
 207                 }
 208                 spin_unlock(&sb_lock);
 209         }
 210         up_write(&s->s_umount);
 211         put_super(s);
 212         yield();
 213         return 0;
 214 }
 215
 216 /**
 217  *      generic_shutdown_super  -       common helper for ->kill_sb()
 218  *      @sb: superblock to kill
 219  *
 220  *      generic_shutdown_super() does all fs-independent work on superblock
 221  *      shutdown.  Typical ->kill_sb() should pick all fs-specific objects
 222  *      that need destruction out of superblock, call generic_shutdown_super()
 223  *      and release aforementioned objects.  Note: dentries and inodes _are_
 224  *      taken care of and do not need specific handling.
 225  */
 226 void generic_shutdown_super(struct super_block *sb)
 227 {
 228         struct dentry *root = sb->s_root;
 229         struct super_operations *sop = sb->s_op;
 230
 231         if (root) {
 232                 sb->s_root = NULL;
 233                 shrink_dcache_parent(root);
 234                 shrink_dcache_anon(&sb->s_anon);
 235                 dput(root);
 236                 fsync_super(sb);
 237                 lock_super(sb);
 238                 sb->s_flags &= ~MS_ACTIVE;
 239                 /* bad name - it should be evict_inodes() */
 240                 invalidate_inodes(sb);
 241                 lock_kernel();
 242
 243                 if (sop->write_super && sb->s_dirt)
 244                         sop->write_super(sb);
 245                 if (sop->put_super)
 246                         sop->put_super(sb);
 247
 248                 /* Forget any remaining inodes */
 249                 if (invalidate_inodes(sb)) {
 250                         printk("VFS: Busy inodes after unmount. "
 251                            "Self-destruct in 5 seconds.  Have a nice day...\n");
 252                 }
 253
 254                 unlock_kernel();
 255                 unlock_super(sb);
 256         }
 257         spin_lock(&sb_lock);
 258         /* should be initialized for __put_super_and_need_restart() */
 259         list_del_init(&sb->s_list);
 260         list_del(&sb->s_instances);
 261         spin_unlock(&sb_lock);
 262         up_write(&sb->s_umount);
 263 }
 264
 265 EXPORT_SYMBOL(generic_shutdown_super);
 266
 267 /**
 268  *      sget    -       find or create a superblock
 269  *      @type:  filesystem type superblock should belong to
 270  *      @test:  comparison callback
 271  *      @set:   setup callback
 272  *      @data:  argument to each of them
 273  */
 274 struct super_block *sget(struct file_system_type *type,
 275                         int (*test)(struct super_block *,void *),
 276                         int (*set)(struct super_block *,void *),
 277                         void *data)
 278 {
 279         struct super_block *s = NULL;
 280         struct list_head *p;
 281         int err;
 282
 283 retry:
 284         spin_lock(&sb_lock);
 285         if (test) list_for_each(p, &type->fs_supers) {
 286                 struct super_block *old;
 287                 old = list_entry(p, struct super_block, s_instances);
 288                 if (!test(old, data))
 289                         continue;
 290                 if (!grab_super(old))
 291                         goto retry;
 292                 if (s)
 293                         destroy_super(s);
 294                 return old;
 295         }
 296         if (!s) {
 297                 spin_unlock(&sb_lock);
 298                 s = alloc_super();
 299                 if (!s)
 300                         return ERR_PTR(-ENOMEM);
 301                 goto retry;
 302         }
 303
 304         err = set(s, data);
 305         if (err) {
 306                 spin_unlock(&sb_lock);
 307                 destroy_super(s);
 308                 return ERR_PTR(err);
 309         }
 310         s->s_type = type;
 311         strlcpy(s->s_id, type->name, sizeof(s->s_id));
 312         list_add_tail(&s->s_list, &super_blocks);
 313         list_add(&s->s_instances, &type->fs_supers);
 314         spin_unlock(&sb_lock);
 315         get_filesystem(type);
 316         return s;
 317 }
 318
 319 EXPORT_SYMBOL(sget);
 320
 321 void drop_super(struct super_block *sb)
 322 {
 323         up_read(&sb->s_umount);
 324         put_super(sb);
 325 }
 326
 327 EXPORT_SYMBOL(drop_super);
 328
 329 static inline void write_super(struct super_block *sb)
 330 {
 331         lock_super(sb);
 332         if (sb->s_root && sb->s_dirt)
 333                 if (sb->s_op->write_super)
 334                         sb->s_op->write_super(sb);
 335         unlock_super(sb);
 336 }
 337
 338 /*
 339  * Note: check the dirty flag before waiting, so we don't
 340  * hold up the sync while mounting a device. (The newly
 341  * mounted device won't need syncing.)
 342  */
 343 void sync_supers(void)
 344 {
 345         struct super_block *sb;
 346
 347         spin_lock(&sb_lock);
 348 restart:
 349         list_for_each_entry(sb, &super_blocks, s_list) {
 350                 if (sb->s_dirt) {
 351                         sb->s_count++;
 352                         spin_unlock(&sb_lock);
 353                         down_read(&sb->s_umount);
 354                         write_super(sb);
 355                         up_read(&sb->s_umount);
 356                         spin_lock(&sb_lock);
 357                         if (__put_super_and_need_restart(sb))
 358                                 goto restart;
 359                 }
 360         }
 361         spin_unlock(&sb_lock);
 362 }
 363
 364 /*
 365  * Call the ->sync_fs super_op against all filesytems which are r/w and
 366  * which implement it.
 367  *
 368  * This operation is careful to avoid the livelock which could easily happen
 369  * if two or more filesystems are being continuously dirtied.  s_need_sync_fs
 370  * is used only here.  We set it against all filesystems and then clear it as
 371  * we sync them.  So redirtied filesystems are skipped.
 372  *
 373  * But if process A is currently running sync_filesytems and then process B
 374  * calls sync_filesystems as well, process B will set all the s_need_sync_fs
 375  * flags again, which will cause process A to resync everything.  Fix that with
 376  * a local mutex.
 377  *
 378  * (Fabian) Avoid sync_fs with clean fs & wait mode 0
 379  */
 380 void sync_filesystems(int wait)
 381 {
 382         struct super_block *sb;
 383         static DECLARE_MUTEX(mutex);
 384
 385         down(&mutex);           /* Could be down_interruptible */
 386         spin_lock(&sb_lock);
 387         list_for_each_entry(sb, &super_blocks, s_list) {
 388                 if (!sb->s_op->sync_fs)
 389                         continue;
 390                 if (sb->s_flags & MS_RDONLY)
 391                         continue;
 392                 sb->s_need_sync_fs = 1;
 393         }
 394
 395 restart:
 396         list_for_each_entry(sb, &super_blocks, s_list) {
 397                 if (!sb->s_need_sync_fs)
 398                         continue;
 399                 sb->s_need_sync_fs = 0;
 400                 if (sb->s_flags & MS_RDONLY)
 401                         continue;       /* hm.  Was remounted r/o meanwhile */
 402                 sb->s_count++;
 403                 spin_unlock(&sb_lock);
 404                 down_read(&sb->s_umount);
 405                 if (sb->s_root && (wait || sb->s_dirt))
 406                         sb->s_op->sync_fs(sb, wait);
 407                 up_read(&sb->s_umount);
 408                 /* restart only when sb is no longer on the list */
 409                 spin_lock(&sb_lock);
 410                 if (__put_super_and_need_restart(sb))
 411                         goto restart;
 412         }
 413         spin_unlock(&sb_lock);
 414         up(&mutex);
 415 }
 416
 417 /**
 418  *      get_super - get the superblock of a device
 419  *      @bdev: device to get the superblock for
 420  *
 421  *      Scans the superblock list and finds the superblock of the file system
 422  *      mounted on the device given. %NULL is returned if no match is found.
 423  */
 424
 425 struct super_block * get_super(struct block_device *bdev)
 426 {
 427         struct super_block *sb;
 428
 429         if (!bdev)
 430                 return NULL;
 431
 432         spin_lock(&sb_lock);
 433 rescan:
 434         list_for_each_entry(sb, &super_blocks, s_list) {
 435                 if (sb->s_bdev == bdev) {
 436                         sb->s_count++;
 437                         spin_unlock(&sb_lock);
 438                         down_read(&sb->s_umount);
 439                         if (sb->s_root)
 440                                 return sb;
 441                         up_read(&sb->s_umount);
 442                         /* restart only when sb is no longer on the list */
 443                         spin_lock(&sb_lock);
 444                         if (__put_super_and_need_restart(sb))
 445                                 goto rescan;
 446                 }
 447         }
 448         spin_unlock(&sb_lock);
 449         return NULL;
 450 }
 451
 452 EXPORT_SYMBOL(get_super);
 453
 454 struct super_block * user_get_super(dev_t dev)
 455 {
 456         struct super_block *sb;
 457
 458         spin_lock(&sb_lock);
 459 rescan:
 460         list_for_each_entry(sb, &super_blocks, s_list) {
 461                 if (sb->s_dev ==  dev) {
 462                         sb->s_count++;
 463                         spin_unlock(&sb_lock);
 464                         down_read(&sb->s_umount);
 465                         if (sb->s_root)
 466                                 return sb;
 467                         up_read(&sb->s_umount);
 468                         /* restart only when sb is no longer on the list */
 469                         spin_lock(&sb_lock);
 470                         if (__put_super_and_need_restart(sb))
 471                                 goto rescan;
 472                 }
 473         }
 474         spin_unlock(&sb_lock);
 475         return NULL;
 476 }
 477
 478 asmlinkage long sys_ustat(unsigned dev, struct ustat __user * ubuf)
 479 {
 480         struct super_block *s;
 481         struct ustat tmp;
 482         struct kstatfs sbuf;
 483         int err = -EINVAL;
 484
 485         s = user_get_super(new_decode_dev(dev));
 486         if (s == NULL)
 487                 goto out;
 488         err = vfs_statfs(s, &sbuf);
 489         drop_super(s);
 490         if (err)
 491                 goto out;
 492
 493         memset(&tmp,0,sizeof(struct ustat));
 494         tmp.f_tfree = sbuf.f_bfree;
 495         tmp.f_tinode = sbuf.f_ffree;
 496
 497         err = copy_to_user(ubuf,&tmp,sizeof(struct ustat)) ? -EFAULT : 0;
 498 out:
 499         return err;
 500 }
 501
 502 /**
 503  *      mark_files_ro
 504  *      @sb: superblock in question
 505  *
 506  *      All files are marked read/only.  We don't care about pending
 507  *      delete files so this should be used in 'force' mode only
 508  */
 509
 510 static void mark_files_ro(struct super_block *sb)
 511 {
 512         struct file *f;
 513
 514         file_list_lock();
 515         list_for_each_entry(f, &sb->s_files, f_u.fu_list) {
 516                 if (S_ISREG(f->f_dentry->d_inode->i_mode) && file_count(f))
 517                         f->f_mode &= ~FMODE_WRITE;
 518         }
 519         file_list_unlock();
 520 }
 521
 522 /**
 523  *      do_remount_sb - asks filesystem to change mount options.
 524  *      @sb:    superblock in question
 525  *      @flags: numeric part of options
 526  *      @data:  the rest of options
 527  *      @force: whether or not to force the change
 528  *
 529  *      Alters the mount options of a mounted file system.
 530  */
 531 int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
 532 {
 533         int retval;
 534
 535         if (!(flags & MS_RDONLY) && bdev_read_only(sb->s_bdev))
 536                 return -EACCES;
 537         if (flags & MS_RDONLY)
 538                 acct_auto_close(sb);
 539         shrink_dcache_sb(sb);
 540         fsync_super(sb);
 541
 542         /* If we are remounting RDONLY and current sb is read/write,
 543            make sure there are no rw files opened */
 544         if ((flags & MS_RDONLY) && !(sb->s_flags & MS_RDONLY)) {
 545                 if (force)
 546                         mark_files_ro(sb);
 547                 else if (!fs_may_remount_ro(sb))
 548                         return -EBUSY;
 549         }
 550
 551         if (sb->s_op->remount_fs) {
 552                 lock_super(sb);
 553                 retval = sb->s_op->remount_fs(sb, &flags, data);
 554                 unlock_super(sb);
 555                 if (retval)
 556                         return retval;
 557         }
 558         sb->s_flags = (sb->s_flags & ~MS_RMT_MASK) | (flags & MS_RMT_MASK);
 559         return 0;
 560 }
 561
 562 static void do_emergency_remount(unsigned long foo)
 563 {
 564         struct super_block *sb;
 565
 566         spin_lock(&sb_lock);
 567         list_for_each_entry(sb, &super_blocks, s_list) {
 568                 sb->s_count++;
 569                 spin_unlock(&sb_lock);
 570                 down_read(&sb->s_umount);
 571                 if (sb->s_root && sb->s_bdev && !(sb->s_flags & MS_RDONLY)) {
 572                         /*
 573                          * ->remount_fs needs lock_kernel().
 574                          *
 575                          * What lock protects sb->s_flags??
 576                          */
 577                         lock_kernel();
 578                         do_remount_sb(sb, MS_RDONLY, NULL, 1);
 579                         unlock_kernel();
 580                 }
 581                 drop_super(sb);
 582                 spin_lock(&sb_lock);
 583         }
 584         spin_unlock(&sb_lock);
 585         printk("Emergency Remount complete\n");
 586 }
 587
 588 void emergency_remount(void)
 589 {
 590         pdflush_operation(do_emergency_remount, 0);
 591 }
 592
 593 /*
 594  * Unnamed block devices are dummy devices used by virtual
 595  * filesystems which don't use real block-devices.  -- jrs
 596  */
 597
 598 static struct idr unnamed_dev_idr;
 599 static DEFINE_SPINLOCK(unnamed_dev_lock);/* protects the above */
 600
 601 int set_anon_super(struct super_block *s, void *data)
 602 {
 603         int dev;
 604         int error;
 605
 606  retry:
 607         if (idr_pre_get(&unnamed_dev_idr, GFP_ATOMIC) == 0)
 608                 return -ENOMEM;
 609         spin_lock(&unnamed_dev_lock);
 610         error = idr_get_new(&unnamed_dev_idr, NULL, &dev);
 611         spin_unlock(&unnamed_dev_lock);
 612         if (error == -EAGAIN)
 613                 /* We raced and lost with another CPU. */
 614                 goto retry;
 615         else if (error)
 616                 return -EAGAIN;
 617
 618         if ((dev & MAX_ID_MASK) == (1 << MINORBITS)) {
 619                 spin_lock(&unnamed_dev_lock);
 620                 idr_remove(&unnamed_dev_idr, dev);
 621                 spin_unlock(&unnamed_dev_lock);
 622                 return -EMFILE;
 623         }
 624         s->s_dev = MKDEV(0, dev & MINORMASK);
 625         return 0;
 626 }
 627
 628 EXPORT_SYMBOL(set_anon_super);
 629
 630 void kill_anon_super(struct super_block *sb)
 631 {
 632         int slot = MINOR(sb->s_dev);
 633
 634         generic_shutdown_super(sb);
 635         spin_lock(&unnamed_dev_lock);
 636         idr_remove(&unnamed_dev_idr, slot);
 637         spin_unlock(&unnamed_dev_lock);
 638 }
 639
 640 EXPORT_SYMBOL(kill_anon_super);
 641
 642 void __init unnamed_dev_init(void)
 643 {
 644         idr_init(&unnamed_dev_idr);
 645 }
 646
 647 void kill_litter_super(struct super_block *sb)
 648 {
 649         if (sb->s_root)
 650                 d_genocide(sb->s_root);
 651         kill_anon_super(sb);
 652 }
 653
 654 EXPORT_SYMBOL(kill_litter_super);
 655
 656 static int set_bdev_super(struct super_block *s, void *data)
 657 {
 658         s->s_bdev = data;
 659         s->s_dev = s->s_bdev->bd_dev;
 660         return 0;
 661 }
 662
 663 static int test_bdev_super(struct super_block *s, void *data)
 664 {
 665         return (void *)s->s_bdev == data;
 666 }
 667
 668 static void bdev_uevent(struct block_device *bdev, enum kobject_action action)
 669 {
 670         if (bdev->bd_disk) {
 671                 if (bdev->bd_part)
 672                         kobject_uevent(&bdev->bd_part->kobj, action, NULL);
 673                 else
 674                         kobject_uevent(&bdev->bd_disk->kobj, action, NULL);
 675         }
 676 }
 677
 678 struct super_block *get_sb_bdev(struct file_system_type *fs_type,
 679         int flags, const char *dev_name, void *data,
 680         int (*fill_super)(struct super_block *, void *, int))
 681 {
 682         struct block_device *bdev;
 683         struct super_block *s;
 684         int error = 0;
 685
 686         bdev = open_bdev_excl(dev_name, flags, fs_type);
 687         if (IS_ERR(bdev))
 688                 return (struct super_block *)bdev;
 689
 690         /*
 691          * once the super is inserted into the list by sget, s_umount
 692          * will protect the lockfs code from trying to start a snapshot
 693          * while we are mounting
 694          */
 695         down(&bdev->bd_mount_sem);
 696         s = sget(fs_type, test_bdev_super, set_bdev_super, bdev);
 697         up(&bdev->bd_mount_sem);
 698         if (IS_ERR(s))
 699                 goto out;
 700
 701         if (s->s_root) {
 702                 if ((flags ^ s->s_flags) & MS_RDONLY) {
 703                         up_write(&s->s_umount);
 704                         deactivate_super(s);
 705                         s = ERR_PTR(-EBUSY);
 706                 }
 707                 goto out;
 708         } else {
 709                 char b[BDEVNAME_SIZE];
 710
 711                 s->s_flags = flags;
 712                 strlcpy(s->s_id, bdevname(bdev, b), sizeof(s->s_id));
 713                 s->s_old_blocksize = block_size(bdev);
 714                 sb_set_blocksize(s, s->s_old_blocksize);
 715                 error = fill_super(s, data, flags & MS_VERBOSE ? 1 : 0);
 716                 if (error) {
 717                         up_write(&s->s_umount);
 718                         deactivate_super(s);
 719                         s = ERR_PTR(error);
 720                 } else {
 721                         s->s_flags |= MS_ACTIVE;
 722                         bdev_uevent(bdev, KOBJ_MOUNT);
 723                 }
 724         }
 725
 726         return s;
 727
 728 out:
 729         close_bdev_excl(bdev);
 730         return s;
 731 }
 732
 733 EXPORT_SYMBOL(get_sb_bdev);
 734
 735 void kill_block_super(struct super_block *sb)
 736 {
 737         struct block_device *bdev = sb->s_bdev;
 738
 739         bdev_uevent(bdev, KOBJ_UMOUNT);
 740         generic_shutdown_super(sb);
 741         sync_blockdev(bdev);
 742         close_bdev_excl(bdev);
 743 }
 744
 745 EXPORT_SYMBOL(kill_block_super);
 746
 747 struct super_block *get_sb_nodev(struct file_system_type *fs_type,
 748         int flags, void *data,
 749         int (*fill_super)(struct super_block *, void *, int))
 750 {
 751         int error;
 752         struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL);
 753
 754         if (IS_ERR(s))
 755                 return s;
 756
 757         s->s_flags = flags;
 758
 759         error = fill_super(s, data, flags & MS_VERBOSE ? 1 : 0);
 760         if (error) {
 761                 up_write(&s->s_umount);
 762                 deactivate_super(s);
 763                 return ERR_PTR(error);
 764         }
 765         s->s_flags |= MS_ACTIVE;
 766         return s;
 767 }
 768
 769 EXPORT_SYMBOL(get_sb_nodev);
 770
 771 static int compare_single(struct super_block *s, void *p)
 772 {
 773         return 1;
 774 }
 775
 776 struct super_block *get_sb_single(struct file_system_type *fs_type,
 777         int flags, void *data,
 778         int (*fill_super)(struct super_block *, void *, int))
 779 {
 780         struct super_block *s;
 781         int error;
 782
 783         s = sget(fs_type, compare_single, set_anon_super, NULL);
 784         if (IS_ERR(s))
 785                 return s;
 786         if (!s->s_root) {
 787                 s->s_flags = flags;
 788                 error = fill_super(s, data, flags & MS_VERBOSE ? 1 : 0);
 789                 if (error) {
 790                         up_write(&s->s_umount);
 791                         deactivate_super(s);
 792                         return ERR_PTR(error);
 793                 }
 794                 s->s_flags |= MS_ACTIVE;
 795         }
 796         do_remount_sb(s, flags, data, 0);
 797         return s;
 798 }
 799
 800 EXPORT_SYMBOL(get_sb_single);
 801
 802 struct vfsmount *
 803 do_kern_mount(const char *fstype, int flags, const char *name, void *data)
 804 {
 805         struct file_system_type *type = get_fs_type(fstype);
 806         struct super_block *sb = ERR_PTR(-ENOMEM);
 807         struct vfsmount *mnt;
 808         int error;
 809         char *secdata = NULL;
 810
 811         if (!type)
 812                 return ERR_PTR(-ENODEV);
 813
 814         mnt = alloc_vfsmnt(name);
 815         if (!mnt)
 816                 goto out;
 817
 818         if (data) {
 819                 secdata = alloc_secdata();
 820                 if (!secdata) {
 821                         sb = ERR_PTR(-ENOMEM);
 822                         goto out_mnt;
 823                 }
 824
 825                 error = security_sb_copy_data(type, data, secdata);
 826                 if (error) {
 827                         sb = ERR_PTR(error);
 828                         goto out_free_secdata;
 829                 }
 830         }
 831
 832         sb = type->get_sb(type, flags, name, data);
 833         if (IS_ERR(sb))
 834                 goto out_free_secdata;
 835         error = security_sb_kern_mount(sb, secdata);
 836         if (error)
 837                 goto out_sb;
 838         mnt->mnt_sb = sb;
 839         mnt->mnt_root = dget(sb->s_root);
 840         mnt->mnt_mountpoint = sb->s_root;
 841         mnt->mnt_parent = mnt;
 842         up_write(&sb->s_umount);
 843         free_secdata(secdata);
 844         put_filesystem(type);
 845         return mnt;
 846 out_sb:
 847         up_write(&sb->s_umount);
 848         deactivate_super(sb);
 849         sb = ERR_PTR(error);
 850 out_free_secdata:
 851         free_secdata(secdata);
 852 out_mnt:
 853         free_vfsmnt(mnt);
 854 out:
 855         put_filesystem(type);
 856         return (struct vfsmount *)sb;
 857 }
 858
 859 EXPORT_SYMBOL_GPL(do_kern_mount);
 860
 861 struct vfsmount *kern_mount(struct file_system_type *type)
 862 {
 863         return do_kern_mount(type->name, 0, type->name, NULL);
 864 }
 865
 866 EXPORT_SYMBOL(kern_mount);