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/mount.h>
  32 #include <linux/security.h>
  33 #include <linux/syscalls.h>
  34 #include <linux/vfs.h>
  35 #include <linux/writeback.h>            /* for the emergency remount stuff */
  36 #include <linux/idr.h>
  37 #include <linux/kobject.h>
  38 #include <linux/mutex.h>
  39 #include <linux/file.h>
  40 #include <linux/backing-dev.h>
  41 #include <asm/uaccess.h>
  42 #include "internal.h"
  43
  44
  45 LIST_HEAD(super_blocks);
  46 DEFINE_SPINLOCK(sb_lock);
  47
  48 /**
  49  *      alloc_super     -       create new superblock
  50  *      @type:  filesystem type superblock should belong to
  51  *
  52  *      Allocates and initializes a new &struct super_block.  alloc_super()
  53  *      returns a pointer new superblock or %NULL if allocation had failed.
  54  */
  55 static struct super_block *alloc_super(struct file_system_type *type)
  56 {
  57         struct super_block *s = kzalloc(sizeof(struct super_block),  GFP_USER);
  58         static const struct super_operations default_op;
  59
  60         if (s) {
  61                 if (security_sb_alloc(s)) {
  62                         kfree(s);
  63                         s = NULL;
  64                         goto out;
  65                 }
  66                 INIT_LIST_HEAD(&s->s_files);
  67                 INIT_LIST_HEAD(&s->s_instances);
  68                 INIT_HLIST_HEAD(&s->s_anon);
  69                 INIT_LIST_HEAD(&s->s_inodes);
  70                 INIT_LIST_HEAD(&s->s_dentry_lru);
  71                 init_rwsem(&s->s_umount);
  72                 mutex_init(&s->s_lock);
  73                 lockdep_set_class(&s->s_umount, &type->s_umount_key);
  74                 /*
  75                  * The locking rules for s_lock are up to the
  76                  * filesystem. For example ext3fs has different
  77                  * lock ordering than usbfs:
  78                  */
  79                 lockdep_set_class(&s->s_lock, &type->s_lock_key);
  80                 /*
  81                  * sget() can have s_umount recursion.
  82                  *
  83                  * When it cannot find a suitable sb, it allocates a new
  84                  * one (this one), and tries again to find a suitable old
  85                  * one.
  86                  *
  87                  * In case that succeeds, it will acquire the s_umount
  88                  * lock of the old one. Since these are clearly distrinct
  89                  * locks, and this object isn't exposed yet, there's no
  90                  * risk of deadlocks.
  91                  *
  92                  * Annotate this by putting this lock in a different
  93                  * subclass.
  94                  */
  95                 down_write_nested(&s->s_umount, SINGLE_DEPTH_NESTING);
  96                 s->s_count = 1;
  97                 atomic_set(&s->s_active, 1);
  98                 mutex_init(&s->s_vfs_rename_mutex);
  99                 mutex_init(&s->s_dquot.dqio_mutex);
 100                 mutex_init(&s->s_dquot.dqonoff_mutex);
 101                 init_rwsem(&s->s_dquot.dqptr_sem);
 102                 init_waitqueue_head(&s->s_wait_unfrozen);
 103                 s->s_maxbytes = MAX_NON_LFS;
 104                 s->dq_op = sb_dquot_ops;
 105                 s->s_qcop = sb_quotactl_ops;
 106                 s->s_op = &default_op;
 107                 s->s_time_gran = 1000000000;
 108         }
 109 out:
 110         return s;
 111 }
 112
 113 /**
 114  *      destroy_super   -       frees a superblock
 115  *      @s: superblock to free
 116  *
 117  *      Frees a superblock.
 118  */
 119 static inline void destroy_super(struct super_block *s)
 120 {
 121         security_sb_free(s);
 122         kfree(s->s_subtype);
 123         kfree(s->s_options);
 124         kfree(s);
 125 }
 126
 127 /* Superblock refcounting  */
 128
 129 /*
 130  * Drop a superblock's refcount.  Returns non-zero if the superblock was
 131  * destroyed.  The caller must hold sb_lock.
 132  */
 133 int __put_super(struct super_block *sb)
 134 {
 135         int ret = 0;
 136
 137         if (!--sb->s_count) {
 138                 list_del_init(&sb->s_list);
 139                 destroy_super(sb);
 140                 ret = 1;
 141         }
 142         return ret;
 143 }
 144
 145 /*
 146  * Drop a superblock's refcount.
 147  * Returns non-zero if the superblock is about to be destroyed and
 148  * at least is already removed from super_blocks list, so if we are
 149  * making a loop through super blocks then we need to restart.
 150  * The caller must hold sb_lock.
 151  */
 152 int __put_super_and_need_restart(struct super_block *sb)
 153 {
 154         /* check for race with generic_shutdown_super() */
 155         if (list_empty(&sb->s_instances)) {
 156                 /* super block is removed, need to restart... */
 157                 __put_super(sb);
 158                 return 1;
 159         }
 160         /* can't be the last, since s_list is still in use */
 161         sb->s_count--;
 162         BUG_ON(sb->s_count == 0);
 163         return 0;
 164 }
 165
 166 /**
 167  *      put_super       -       drop a temporary reference to superblock
 168  *      @sb: superblock in question
 169  *
 170  *      Drops a temporary reference, frees superblock if there's no
 171  *      references left.
 172  */
 173 void put_super(struct super_block *sb)
 174 {
 175         spin_lock(&sb_lock);
 176         __put_super(sb);
 177         spin_unlock(&sb_lock);
 178 }
 179
 180
 181 /**
 182  *      deactivate_locked_super -       drop an active reference to superblock
 183  *      @s: superblock to deactivate
 184  *
 185  *      Drops an active reference to superblock, converting it into a temprory
 186  *      one if there is no other active references left.  In that case we
 187  *      tell fs driver to shut it down and drop the temporary reference we
 188  *      had just acquired.
 189  *
 190  *      Caller holds exclusive lock on superblock; that lock is released.
 191  */
 192 void deactivate_locked_super(struct super_block *s)
 193 {
 194         struct file_system_type *fs = s->s_type;
 195         if (atomic_dec_and_test(&s->s_active)) {
 196                 vfs_dq_off(s, 0);
 197                 fs->kill_sb(s);
 198                 put_filesystem(fs);
 199                 put_super(s);
 200         } else {
 201                 up_write(&s->s_umount);
 202         }
 203 }
 204
 205 EXPORT_SYMBOL(deactivate_locked_super);
 206
 207 /**
 208  *      deactivate_super        -       drop an active reference to superblock
 209  *      @s: superblock to deactivate
 210  *
 211  *      Variant of deactivate_locked_super(), except that superblock is *not*
 212  *      locked by caller.  If we are going to drop the final active reference,
 213  *      lock will be acquired prior to that.
 214  */
 215 void deactivate_super(struct super_block *s)
 216 {
 217         if (!atomic_add_unless(&s->s_active, -1, 1)) {
 218                 down_write(&s->s_umount);
 219                 deactivate_locked_super(s);
 220         }
 221 }
 222
 223 EXPORT_SYMBOL(deactivate_super);
 224
 225 /**
 226  *      grab_super - acquire an active reference
 227  *      @s: reference we are trying to make active
 228  *
 229  *      Tries to acquire an active reference.  grab_super() is used when we
 230  *      had just found a superblock in super_blocks or fs_type->fs_supers
 231  *      and want to turn it into a full-blown active reference.  grab_super()
 232  *      is called with sb_lock held and drops it.  Returns 1 in case of
 233  *      success, 0 if we had failed (superblock contents was already dead or
 234  *      dying when grab_super() had been called).
 235  */
 236 static int grab_super(struct super_block *s) __releases(sb_lock)
 237 {
 238         if (atomic_inc_not_zero(&s->s_active)) {
 239                 spin_unlock(&sb_lock);
 240                 down_write(&s->s_umount);
 241                 return 1;
 242         }
 243         /* it's going away */
 244         s->s_count++;
 245         spin_unlock(&sb_lock);
 246         /* wait for it to die */
 247         down_write(&s->s_umount);
 248         up_write(&s->s_umount);
 249         put_super(s);
 250         return 0;
 251 }
 252
 253 /*
 254  * Superblock locking.  We really ought to get rid of these two.
 255  */
 256 void lock_super(struct super_block * sb)
 257 {
 258         get_fs_excl();
 259         mutex_lock(&sb->s_lock);
 260 }
 261
 262 void unlock_super(struct super_block * sb)
 263 {
 264         put_fs_excl();
 265         mutex_unlock(&sb->s_lock);
 266 }
 267
 268 EXPORT_SYMBOL(lock_super);
 269 EXPORT_SYMBOL(unlock_super);
 270
 271 /**
 272  *      generic_shutdown_super  -       common helper for ->kill_sb()
 273  *      @sb: superblock to kill
 274  *
 275  *      generic_shutdown_super() does all fs-independent work on superblock
 276  *      shutdown.  Typical ->kill_sb() should pick all fs-specific objects
 277  *      that need destruction out of superblock, call generic_shutdown_super()
 278  *      and release aforementioned objects.  Note: dentries and inodes _are_
 279  *      taken care of and do not need specific handling.
 280  *
 281  *      Upon calling this function, the filesystem may no longer alter or
 282  *      rearrange the set of dentries belonging to this super_block, nor may it
 283  *      change the attachments of dentries to inodes.
 284  */
 285 void generic_shutdown_super(struct super_block *sb)
 286 {
 287         const struct super_operations *sop = sb->s_op;
 288
 289
 290         if (sb->s_root) {
 291                 shrink_dcache_for_umount(sb);
 292                 sync_filesystem(sb);
 293                 get_fs_excl();
 294                 sb->s_flags &= ~MS_ACTIVE;
 295
 296                 /* bad name - it should be evict_inodes() */
 297                 invalidate_inodes(sb);
 298
 299                 if (sop->put_super)
 300                         sop->put_super(sb);
 301
 302                 /* Forget any remaining inodes */
 303                 if (invalidate_inodes(sb)) {
 304                         printk("VFS: Busy inodes after unmount of %s. "
 305                            "Self-destruct in 5 seconds.  Have a nice day...\n",
 306                            sb->s_id);
 307                 }
 308                 put_fs_excl();
 309         }
 310         spin_lock(&sb_lock);
 311         /* should be initialized for __put_super_and_need_restart() */
 312         list_del_init(&sb->s_instances);
 313         spin_unlock(&sb_lock);
 314         up_write(&sb->s_umount);
 315 }
 316
 317 EXPORT_SYMBOL(generic_shutdown_super);
 318
 319 /**
 320  *      sget    -       find or create a superblock
 321  *      @type:  filesystem type superblock should belong to
 322  *      @test:  comparison callback
 323  *      @set:   setup callback
 324  *      @data:  argument to each of them
 325  */
 326 struct super_block *sget(struct file_system_type *type,
 327                         int (*test)(struct super_block *,void *),
 328                         int (*set)(struct super_block *,void *),
 329                         void *data)
 330 {
 331         struct super_block *s = NULL;
 332         struct super_block *old;
 333         int err;
 334
 335 retry:
 336         spin_lock(&sb_lock);
 337         if (test) {
 338                 list_for_each_entry(old, &type->fs_supers, s_instances) {
 339                         if (!test(old, data))
 340                                 continue;
 341                         if (!grab_super(old))
 342                                 goto retry;
 343                         if (s) {
 344                                 up_write(&s->s_umount);
 345                                 destroy_super(s);
 346                         }
 347                         return old;
 348                 }
 349         }
 350         if (!s) {
 351                 spin_unlock(&sb_lock);
 352                 s = alloc_super(type);
 353                 if (!s)
 354                         return ERR_PTR(-ENOMEM);
 355                 goto retry;
 356         }
 357
 358         err = set(s, data);
 359         if (err) {
 360                 spin_unlock(&sb_lock);
 361                 up_write(&s->s_umount);
 362                 destroy_super(s);
 363                 return ERR_PTR(err);
 364         }
 365         s->s_type = type;
 366         strlcpy(s->s_id, type->name, sizeof(s->s_id));
 367         list_add_tail(&s->s_list, &super_blocks);
 368         list_add(&s->s_instances, &type->fs_supers);
 369         spin_unlock(&sb_lock);
 370         get_filesystem(type);
 371         return s;
 372 }
 373
 374 EXPORT_SYMBOL(sget);
 375
 376 void drop_super(struct super_block *sb)
 377 {
 378         up_read(&sb->s_umount);
 379         put_super(sb);
 380 }
 381
 382 EXPORT_SYMBOL(drop_super);
 383
 384 /**
 385  * sync_supers - helper for periodic superblock writeback
 386  *
 387  * Call the write_super method if present on all dirty superblocks in
 388  * the system.  This is for the periodic writeback used by most older
 389  * filesystems.  For data integrity superblock writeback use
 390  * sync_filesystems() instead.
 391  *
 392  * Note: check the dirty flag before waiting, so we don't
 393  * hold up the sync while mounting a device. (The newly
 394  * mounted device won't need syncing.)
 395  */
 396 void sync_supers(void)
 397 {
 398         struct super_block *sb;
 399
 400         spin_lock(&sb_lock);
 401 restart:
 402         list_for_each_entry(sb, &super_blocks, s_list) {
 403                 if (list_empty(&sb->s_instances))
 404                         continue;
 405                 if (sb->s_op->write_super && sb->s_dirt) {
 406                         sb->s_count++;
 407                         spin_unlock(&sb_lock);
 408
 409                         down_read(&sb->s_umount);
 410                         if (sb->s_root && sb->s_dirt)
 411                                 sb->s_op->write_super(sb);
 412                         up_read(&sb->s_umount);
 413
 414                         spin_lock(&sb_lock);
 415                         if (__put_super_and_need_restart(sb))
 416                                 goto restart;
 417                 }
 418         }
 419         spin_unlock(&sb_lock);
 420 }
 421
 422 /**
 423  *      get_super - get the superblock of a device
 424  *      @bdev: device to get the superblock for
 425  *
 426  *      Scans the superblock list and finds the superblock of the file system
 427  *      mounted on the device given. %NULL is returned if no match is found.
 428  */
 429
 430 struct super_block * get_super(struct block_device *bdev)
 431 {
 432         struct super_block *sb;
 433
 434         if (!bdev)
 435                 return NULL;
 436
 437         spin_lock(&sb_lock);
 438 rescan:
 439         list_for_each_entry(sb, &super_blocks, s_list) {
 440                 if (list_empty(&sb->s_instances))
 441                         continue;
 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 /**
 462  * get_active_super - get an active reference to the superblock of a device
 463  * @bdev: device to get the superblock for
 464  *
 465  * Scans the superblock list and finds the superblock of the file system
 466  * mounted on the device given.  Returns the superblock with an active
 467  * reference and s_umount held exclusively or %NULL if none was found.
 468  */
 469 struct super_block *get_active_super(struct block_device *bdev)
 470 {
 471         struct super_block *sb;
 472
 473         if (!bdev)
 474                 return NULL;
 475
 476         spin_lock(&sb_lock);
 477         list_for_each_entry(sb, &super_blocks, s_list) {
 478                 if (list_empty(&sb->s_instances))
 479                         continue;
 480                 if (sb->s_bdev != bdev)
 481                         continue;
 482
 483                 if (grab_super(sb)) /* drops sb_lock */
 484                         return sb;
 485
 486                 spin_lock(&sb_lock);
 487         }
 488         spin_unlock(&sb_lock);
 489         return NULL;
 490 }
 491
 492 struct super_block * user_get_super(dev_t dev)
 493 {
 494         struct super_block *sb;
 495
 496         spin_lock(&sb_lock);
 497 rescan:
 498         list_for_each_entry(sb, &super_blocks, s_list) {
 499                 if (list_empty(&sb->s_instances))
 500                         continue;
 501                 if (sb->s_dev ==  dev) {
 502                         sb->s_count++;
 503                         spin_unlock(&sb_lock);
 504                         down_read(&sb->s_umount);
 505                         if (sb->s_root)
 506                                 return sb;
 507                         up_read(&sb->s_umount);
 508                         /* restart only when sb is no longer on the list */
 509                         spin_lock(&sb_lock);
 510                         if (__put_super_and_need_restart(sb))
 511                                 goto rescan;
 512                 }
 513         }
 514         spin_unlock(&sb_lock);
 515         return NULL;
 516 }
 517
 518 SYSCALL_DEFINE2(ustat, unsigned, dev, struct ustat __user *, ubuf)
 519 {
 520         struct super_block *s;
 521         struct ustat tmp;
 522         struct kstatfs sbuf;
 523         int err = -EINVAL;
 524
 525         s = user_get_super(new_decode_dev(dev));
 526         if (s == NULL)
 527                 goto out;
 528         err = vfs_statfs(s->s_root, &sbuf);
 529         drop_super(s);
 530         if (err)
 531                 goto out;
 532
 533         memset(&tmp,0,sizeof(struct ustat));
 534         tmp.f_tfree = sbuf.f_bfree;
 535         tmp.f_tinode = sbuf.f_ffree;
 536
 537         err = copy_to_user(ubuf,&tmp,sizeof(struct ustat)) ? -EFAULT : 0;
 538 out:
 539         return err;
 540 }
 541
 542 /**
 543  *      do_remount_sb - asks filesystem to change mount options.
 544  *      @sb:    superblock in question
 545  *      @flags: numeric part of options
 546  *      @data:  the rest of options
 547  *      @force: whether or not to force the change
 548  *
 549  *      Alters the mount options of a mounted file system.
 550  */
 551 int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
 552 {
 553         int retval;
 554         int remount_rw, remount_ro;
 555
 556         if (sb->s_frozen != SB_UNFROZEN)
 557                 return -EBUSY;
 558
 559 #ifdef CONFIG_BLOCK
 560         if (!(flags & MS_RDONLY) && bdev_read_only(sb->s_bdev))
 561                 return -EACCES;
 562 #endif
 563
 564         if (flags & MS_RDONLY)
 565                 acct_auto_close(sb);
 566         shrink_dcache_sb(sb);
 567         sync_filesystem(sb);
 568
 569         remount_ro = (flags & MS_RDONLY) && !(sb->s_flags & MS_RDONLY);
 570         remount_rw = !(flags & MS_RDONLY) && (sb->s_flags & MS_RDONLY);
 571
 572         /* If we are remounting RDONLY and current sb is read/write,
 573            make sure there are no rw files opened */
 574         if (remount_ro) {
 575                 if (force)
 576                         mark_files_ro(sb);
 577                 else if (!fs_may_remount_ro(sb))
 578                         return -EBUSY;
 579                 retval = vfs_dq_off(sb, 1);
 580                 if (retval < 0 && retval != -ENOSYS)
 581                         return -EBUSY;
 582         }
 583
 584         if (sb->s_op->remount_fs) {
 585                 retval = sb->s_op->remount_fs(sb, &flags, data);
 586                 if (retval)
 587                         return retval;
 588         }
 589         sb->s_flags = (sb->s_flags & ~MS_RMT_MASK) | (flags & MS_RMT_MASK);
 590         if (remount_rw)
 591                 vfs_dq_quota_on_remount(sb);
 592         /*
 593          * Some filesystems modify their metadata via some other path than the
 594          * bdev buffer cache (eg. use a private mapping, or directories in
 595          * pagecache, etc). Also file data modifications go via their own
 596          * mappings. So If we try to mount readonly then copy the filesystem
 597          * from bdev, we could get stale data, so invalidate it to give a best
 598          * effort at coherency.
 599          */
 600         if (remount_ro && sb->s_bdev)
 601                 invalidate_bdev(sb->s_bdev);
 602         return 0;
 603 }
 604
 605 static void do_emergency_remount(struct work_struct *work)
 606 {
 607         struct super_block *sb;
 608
 609         spin_lock(&sb_lock);
 610         list_for_each_entry(sb, &super_blocks, s_list) {
 611                 if (list_empty(&sb->s_instances))
 612                         continue;
 613                 sb->s_count++;
 614                 spin_unlock(&sb_lock);
 615                 down_write(&sb->s_umount);
 616                 if (sb->s_root && sb->s_bdev && !(sb->s_flags & MS_RDONLY)) {
 617                         /*
 618                          * What lock protects sb->s_flags??
 619                          */
 620                         do_remount_sb(sb, MS_RDONLY, NULL, 1);
 621                 }
 622                 up_write(&sb->s_umount);
 623                 put_super(sb);
 624                 spin_lock(&sb_lock);
 625         }
 626         spin_unlock(&sb_lock);
 627         kfree(work);
 628         printk("Emergency Remount complete\n");
 629 }
 630
 631 void emergency_remount(void)
 632 {
 633         struct work_struct *work;
 634
 635         work = kmalloc(sizeof(*work), GFP_ATOMIC);
 636         if (work) {
 637                 INIT_WORK(work, do_emergency_remount);
 638                 schedule_work(work);
 639         }
 640 }
 641
 642 /*
 643  * Unnamed block devices are dummy devices used by virtual
 644  * filesystems which don't use real block-devices.  -- jrs
 645  */
 646
 647 static DEFINE_IDA(unnamed_dev_ida);
 648 static DEFINE_SPINLOCK(unnamed_dev_lock);/* protects the above */
 649 static int unnamed_dev_start = 0; /* don't bother trying below it */
 650
 651 int set_anon_super(struct super_block *s, void *data)
 652 {
 653         int dev;
 654         int error;
 655
 656  retry:
 657         if (ida_pre_get(&unnamed_dev_ida, GFP_ATOMIC) == 0)
 658                 return -ENOMEM;
 659         spin_lock(&unnamed_dev_lock);
 660         error = ida_get_new_above(&unnamed_dev_ida, unnamed_dev_start, &dev);
 661         if (!error)
 662                 unnamed_dev_start = dev + 1;
 663         spin_unlock(&unnamed_dev_lock);
 664         if (error == -EAGAIN)
 665                 /* We raced and lost with another CPU. */
 666                 goto retry;
 667         else if (error)
 668                 return -EAGAIN;
 669
 670         if ((dev & MAX_ID_MASK) == (1 << MINORBITS)) {
 671                 spin_lock(&unnamed_dev_lock);
 672                 ida_remove(&unnamed_dev_ida, dev);
 673                 if (unnamed_dev_start > dev)
 674                         unnamed_dev_start = dev;
 675                 spin_unlock(&unnamed_dev_lock);
 676                 return -EMFILE;
 677         }
 678         s->s_dev = MKDEV(0, dev & MINORMASK);
 679         s->s_bdi = &noop_backing_dev_info;
 680         return 0;
 681 }
 682
 683 EXPORT_SYMBOL(set_anon_super);
 684
 685 void kill_anon_super(struct super_block *sb)
 686 {
 687         int slot = MINOR(sb->s_dev);
 688
 689         generic_shutdown_super(sb);
 690         spin_lock(&unnamed_dev_lock);
 691         ida_remove(&unnamed_dev_ida, slot);
 692         if (slot < unnamed_dev_start)
 693                 unnamed_dev_start = slot;
 694         spin_unlock(&unnamed_dev_lock);
 695 }
 696
 697 EXPORT_SYMBOL(kill_anon_super);
 698
 699 void kill_litter_super(struct super_block *sb)
 700 {
 701         if (sb->s_root)
 702                 d_genocide(sb->s_root);
 703         kill_anon_super(sb);
 704 }
 705
 706 EXPORT_SYMBOL(kill_litter_super);
 707
 708 static int ns_test_super(struct super_block *sb, void *data)
 709 {
 710         return sb->s_fs_info == data;
 711 }
 712
 713 static int ns_set_super(struct super_block *sb, void *data)
 714 {
 715         sb->s_fs_info = data;
 716         return set_anon_super(sb, NULL);
 717 }
 718
 719 int get_sb_ns(struct file_system_type *fs_type, int flags, void *data,
 720         int (*fill_super)(struct super_block *, void *, int),
 721         struct vfsmount *mnt)
 722 {
 723         struct super_block *sb;
 724
 725         sb = sget(fs_type, ns_test_super, ns_set_super, data);
 726         if (IS_ERR(sb))
 727                 return PTR_ERR(sb);
 728
 729         if (!sb->s_root) {
 730                 int err;
 731                 sb->s_flags = flags;
 732                 err = fill_super(sb, data, flags & MS_SILENT ? 1 : 0);
 733                 if (err) {
 734                         deactivate_locked_super(sb);
 735                         return err;
 736                 }
 737
 738                 sb->s_flags |= MS_ACTIVE;
 739         }
 740
 741         simple_set_mnt(mnt, sb);
 742         return 0;
 743 }
 744
 745 EXPORT_SYMBOL(get_sb_ns);
 746
 747 #ifdef CONFIG_BLOCK
 748 static int set_bdev_super(struct super_block *s, void *data)
 749 {
 750         s->s_bdev = data;
 751         s->s_dev = s->s_bdev->bd_dev;
 752
 753         /*
 754          * We set the bdi here to the queue backing, file systems can
 755          * overwrite this in ->fill_super()
 756          */
 757         s->s_bdi = &bdev_get_queue(s->s_bdev)->backing_dev_info;
 758         return 0;
 759 }
 760
 761 static int test_bdev_super(struct super_block *s, void *data)
 762 {
 763         return (void *)s->s_bdev == data;
 764 }
 765
 766 int get_sb_bdev(struct file_system_type *fs_type,
 767         int flags, const char *dev_name, void *data,
 768         int (*fill_super)(struct super_block *, void *, int),
 769         struct vfsmount *mnt)
 770 {
 771         struct block_device *bdev;
 772         struct super_block *s;
 773         fmode_t mode = FMODE_READ;
 774         int error = 0;
 775
 776         if (!(flags & MS_RDONLY))
 777                 mode |= FMODE_WRITE;
 778
 779         bdev = open_bdev_exclusive(dev_name, mode, fs_type);
 780         if (IS_ERR(bdev))
 781                 return PTR_ERR(bdev);
 782
 783         /*
 784          * once the super is inserted into the list by sget, s_umount
 785          * will protect the lockfs code from trying to start a snapshot
 786          * while we are mounting
 787          */
 788         mutex_lock(&bdev->bd_fsfreeze_mutex);
 789         if (bdev->bd_fsfreeze_count > 0) {
 790                 mutex_unlock(&bdev->bd_fsfreeze_mutex);
 791                 error = -EBUSY;
 792                 goto error_bdev;
 793         }
 794         s = sget(fs_type, test_bdev_super, set_bdev_super, bdev);
 795         mutex_unlock(&bdev->bd_fsfreeze_mutex);
 796         if (IS_ERR(s))
 797                 goto error_s;
 798
 799         if (s->s_root) {
 800                 if ((flags ^ s->s_flags) & MS_RDONLY) {
 801                         deactivate_locked_super(s);
 802                         error = -EBUSY;
 803                         goto error_bdev;
 804                 }
 805
 806                 close_bdev_exclusive(bdev, mode);
 807         } else {
 808                 char b[BDEVNAME_SIZE];
 809
 810                 s->s_flags = flags;
 811                 s->s_mode = mode;
 812                 strlcpy(s->s_id, bdevname(bdev, b), sizeof(s->s_id));
 813                 sb_set_blocksize(s, block_size(bdev));
 814                 error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
 815                 if (error) {
 816                         deactivate_locked_super(s);
 817                         goto error;
 818                 }
 819
 820                 s->s_flags |= MS_ACTIVE;
 821                 bdev->bd_super = s;
 822         }
 823
 824         simple_set_mnt(mnt, s);
 825         return 0;
 826
 827 error_s:
 828         error = PTR_ERR(s);
 829 error_bdev:
 830         close_bdev_exclusive(bdev, mode);
 831 error:
 832         return error;
 833 }
 834
 835 EXPORT_SYMBOL(get_sb_bdev);
 836
 837 void kill_block_super(struct super_block *sb)
 838 {
 839         struct block_device *bdev = sb->s_bdev;
 840         fmode_t mode = sb->s_mode;
 841
 842         bdev->bd_super = NULL;
 843         generic_shutdown_super(sb);
 844         sync_blockdev(bdev);
 845         close_bdev_exclusive(bdev, mode);
 846 }
 847
 848 EXPORT_SYMBOL(kill_block_super);
 849 #endif
 850
 851 int get_sb_nodev(struct file_system_type *fs_type,
 852         int flags, void *data,
 853         int (*fill_super)(struct super_block *, void *, int),
 854         struct vfsmount *mnt)
 855 {
 856         int error;
 857         struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL);
 858
 859         if (IS_ERR(s))
 860                 return PTR_ERR(s);
 861
 862         s->s_flags = flags;
 863
 864         error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
 865         if (error) {
 866                 deactivate_locked_super(s);
 867                 return error;
 868         }
 869         s->s_flags |= MS_ACTIVE;
 870         simple_set_mnt(mnt, s);
 871         return 0;
 872 }
 873
 874 EXPORT_SYMBOL(get_sb_nodev);
 875
 876 static int compare_single(struct super_block *s, void *p)
 877 {
 878         return 1;
 879 }
 880
 881 int get_sb_single(struct file_system_type *fs_type,
 882         int flags, void *data,
 883         int (*fill_super)(struct super_block *, void *, int),
 884         struct vfsmount *mnt)
 885 {
 886         struct super_block *s;
 887         int error;
 888
 889         s = sget(fs_type, compare_single, set_anon_super, NULL);
 890         if (IS_ERR(s))
 891                 return PTR_ERR(s);
 892         if (!s->s_root) {
 893                 s->s_flags = flags;
 894                 error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
 895                 if (error) {
 896                         deactivate_locked_super(s);
 897                         return error;
 898                 }
 899                 s->s_flags |= MS_ACTIVE;
 900         } else {
 901                 do_remount_sb(s, flags, data, 0);
 902         }
 903         simple_set_mnt(mnt, s);
 904         return 0;
 905 }
 906
 907 EXPORT_SYMBOL(get_sb_single);
 908
 909 struct vfsmount *
 910 vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void *data)
 911 {
 912         struct vfsmount *mnt;
 913         char *secdata = NULL;
 914         int error;
 915
 916         if (!type)
 917                 return ERR_PTR(-ENODEV);
 918
 919         error = -ENOMEM;
 920         mnt = alloc_vfsmnt(name);
 921         if (!mnt)
 922                 goto out;
 923
 924         if (flags & MS_KERNMOUNT)
 925                 mnt->mnt_flags = MNT_INTERNAL;
 926
 927         if (data && !(type->fs_flags & FS_BINARY_MOUNTDATA)) {
 928                 secdata = alloc_secdata();
 929                 if (!secdata)
 930                         goto out_mnt;
 931
 932                 error = security_sb_copy_data(data, secdata);
 933                 if (error)
 934                         goto out_free_secdata;
 935         }
 936
 937         error = type->get_sb(type, flags, name, data, mnt);
 938         if (error < 0)
 939                 goto out_free_secdata;
 940         BUG_ON(!mnt->mnt_sb);
 941         WARN_ON(!mnt->mnt_sb->s_bdi);
 942
 943         error = security_sb_kern_mount(mnt->mnt_sb, flags, secdata);
 944         if (error)
 945                 goto out_sb;
 946
 947         /*
 948          * filesystems should never set s_maxbytes larger than MAX_LFS_FILESIZE
 949          * but s_maxbytes was an unsigned long long for many releases. Throw
 950          * this warning for a little while to try and catch filesystems that
 951          * violate this rule. This warning should be either removed or
 952          * converted to a BUG() in 2.6.34.
 953          */
 954         WARN((mnt->mnt_sb->s_maxbytes < 0), "%s set sb->s_maxbytes to "
 955                 "negative value (%lld)\n", type->name, mnt->mnt_sb->s_maxbytes);
 956
 957         mnt->mnt_mountpoint = mnt->mnt_root;
 958         mnt->mnt_parent = mnt;
 959         up_write(&mnt->mnt_sb->s_umount);
 960         free_secdata(secdata);
 961         return mnt;
 962 out_sb:
 963         dput(mnt->mnt_root);
 964         deactivate_locked_super(mnt->mnt_sb);
 965 out_free_secdata:
 966         free_secdata(secdata);
 967 out_mnt:
 968         free_vfsmnt(mnt);
 969 out:
 970         return ERR_PTR(error);
 971 }
 972
 973 EXPORT_SYMBOL_GPL(vfs_kern_mount);
 974
 975 static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype)
 976 {
 977         int err;
 978         const char *subtype = strchr(fstype, '.');
 979         if (subtype) {
 980                 subtype++;
 981                 err = -EINVAL;
 982                 if (!subtype[0])
 983                         goto err;
 984         } else
 985                 subtype = "";
 986
 987         mnt->mnt_sb->s_subtype = kstrdup(subtype, GFP_KERNEL);
 988         err = -ENOMEM;
 989         if (!mnt->mnt_sb->s_subtype)
 990                 goto err;
 991         return mnt;
 992
 993  err:
 994         mntput(mnt);
 995         return ERR_PTR(err);
 996 }
 997
 998 struct vfsmount *
 999 do_kern_mount(const char *fstype, int flags, const char *name, void *data)
1000 {
1001         struct file_system_type *type = get_fs_type(fstype);
1002         struct vfsmount *mnt;
1003         if (!type)
1004                 return ERR_PTR(-ENODEV);
1005         mnt = vfs_kern_mount(type, flags, name, data);
1006         if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) &&
1007             !mnt->mnt_sb->s_subtype)
1008                 mnt = fs_set_subtype(mnt, fstype);
1009         put_filesystem(type);
1010         return mnt;
1011 }
1012 EXPORT_SYMBOL_GPL(do_kern_mount);
1013
1014 struct vfsmount *kern_mount_data(struct file_system_type *type, void *data)
1015 {
1016         return vfs_kern_mount(type, MS_KERNMOUNT, type->name, data);
1017 }
1018
1019 EXPORT_SYMBOL_GPL(kern_mount_data);