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 <asm/uaccess.h>
  41 #include "internal.h"
  42
  43
  44 LIST_HEAD(super_blocks);
  45 DEFINE_SPINLOCK(sb_lock);
  46
  47 /**
  48  *      alloc_super     -       create new superblock
  49  *      @type:  filesystem type superblock should belong to
  50  *
  51  *      Allocates and initializes a new &struct super_block.  alloc_super()
  52  *      returns a pointer new superblock or %NULL if allocation had failed.
  53  */
  54 static struct super_block *alloc_super(struct file_system_type *type)
  55 {
  56         struct super_block *s = kzalloc(sizeof(struct super_block),  GFP_USER);
  57         static struct super_operations default_op;
  58
  59         if (s) {
  60                 if (security_sb_alloc(s)) {
  61                         kfree(s);
  62                         s = NULL;
  63                         goto out;
  64                 }
  65                 INIT_LIST_HEAD(&s->s_files);
  66                 INIT_LIST_HEAD(&s->s_instances);
  67                 INIT_HLIST_HEAD(&s->s_anon);
  68                 INIT_LIST_HEAD(&s->s_inodes);
  69                 INIT_LIST_HEAD(&s->s_dentry_lru);
  70                 init_rwsem(&s->s_umount);
  71                 mutex_init(&s->s_lock);
  72                 lockdep_set_class(&s->s_umount, &type->s_umount_key);
  73                 /*
  74                  * The locking rules for s_lock are up to the
  75                  * filesystem. For example ext3fs has different
  76                  * lock ordering than usbfs:
  77                  */
  78                 lockdep_set_class(&s->s_lock, &type->s_lock_key);
  79                 /*
  80                  * sget() can have s_umount recursion.
  81                  *
  82                  * When it cannot find a suitable sb, it allocates a new
  83                  * one (this one), and tries again to find a suitable old
  84                  * one.
  85                  *
  86                  * In case that succeeds, it will acquire the s_umount
  87                  * lock of the old one. Since these are clearly distrinct
  88                  * locks, and this object isn't exposed yet, there's no
  89                  * risk of deadlocks.
  90                  *
  91                  * Annotate this by putting this lock in a different
  92                  * subclass.
  93                  */
  94                 down_write_nested(&s->s_umount, SINGLE_DEPTH_NESTING);
  95                 s->s_count = S_BIAS;
  96                 atomic_set(&s->s_active, 1);
  97                 mutex_init(&s->s_vfs_rename_mutex);
  98                 mutex_init(&s->s_dquot.dqio_mutex);
  99                 mutex_init(&s->s_dquot.dqonoff_mutex);
 100                 init_rwsem(&s->s_dquot.dqptr_sem);
 101                 init_waitqueue_head(&s->s_wait_unfrozen);
 102                 s->s_maxbytes = MAX_NON_LFS;
 103                 s->dq_op = sb_dquot_ops;
 104                 s->s_qcop = sb_quotactl_ops;
 105                 s->s_op = &default_op;
 106                 s->s_time_gran = 1000000000;
 107         }
 108 out:
 109         return s;
 110 }
 111
 112 /**
 113  *      destroy_super   -       frees a superblock
 114  *      @s: superblock to free
 115  *
 116  *      Frees a superblock.
 117  */
 118 static inline void destroy_super(struct super_block *s)
 119 {
 120         security_sb_free(s);
 121         kfree(s->s_subtype);
 122         kfree(s->s_options);
 123         kfree(s);
 124 }
 125
 126 /* Superblock refcounting  */
 127
 128 /*
 129  * Drop a superblock's refcount.  Returns non-zero if the superblock was
 130  * destroyed.  The caller must hold sb_lock.
 131  */
 132 static int __put_super(struct super_block *sb)
 133 {
 134         int ret = 0;
 135
 136         if (!--sb->s_count) {
 137                 destroy_super(sb);
 138                 ret = 1;
 139         }
 140         return ret;
 141 }
 142
 143 /*
 144  * Drop a superblock's refcount.
 145  * Returns non-zero if the superblock is about to be destroyed and
 146  * at least is already removed from super_blocks list, so if we are
 147  * making a loop through super blocks then we need to restart.
 148  * The caller must hold sb_lock.
 149  */
 150 int __put_super_and_need_restart(struct super_block *sb)
 151 {
 152         /* check for race with generic_shutdown_super() */
 153         if (list_empty(&sb->s_list)) {
 154                 /* super block is removed, need to restart... */
 155                 __put_super(sb);
 156                 return 1;
 157         }
 158         /* can't be the last, since s_list is still in use */
 159         sb->s_count--;
 160         BUG_ON(sb->s_count == 0);
 161         return 0;
 162 }
 163
 164 /**
 165  *      put_super       -       drop a temporary reference to superblock
 166  *      @sb: superblock in question
 167  *
 168  *      Drops a temporary reference, frees superblock if there's no
 169  *      references left.
 170  */
 171 void put_super(struct super_block *sb)
 172 {
 173         spin_lock(&sb_lock);
 174         __put_super(sb);
 175         spin_unlock(&sb_lock);
 176 }
 177
 178
 179 /**
 180  *      deactivate_super        -       drop an active reference to superblock
 181  *      @s: superblock to deactivate
 182  *
 183  *      Drops an active reference to superblock, acquiring a temprory one if
 184  *      there is no active references left.  In that case we lock superblock,
 185  *      tell fs driver to shut it down and drop the temporary reference we
 186  *      had just acquired.
 187  */
 188 void deactivate_super(struct super_block *s)
 189 {
 190         struct file_system_type *fs = s->s_type;
 191         if (atomic_dec_and_lock(&s->s_active, &sb_lock)) {
 192                 s->s_count -= S_BIAS-1;
 193                 spin_unlock(&sb_lock);
 194                 vfs_dq_off(s, 0);
 195                 down_write(&s->s_umount);
 196                 fs->kill_sb(s);
 197                 put_filesystem(fs);
 198                 put_super(s);
 199         }
 200 }
 201
 202 EXPORT_SYMBOL(deactivate_super);
 203
 204 /**
 205  *      deactivate_locked_super -       drop an active reference to superblock
 206  *      @s: superblock to deactivate
 207  *
 208  *      Equivalent of up_write(&s->s_umount); deactivate_super(s);, except that
 209  *      it does not unlock it until it's all over.  As the result, it's safe to
 210  *      use to dispose of new superblock on ->get_sb() failure exits - nobody
 211  *      will see the sucker until it's all over.  Equivalent using up_write +
 212  *      deactivate_super is safe for that purpose only if superblock is either
 213  *      safe to use or has NULL ->s_root when we unlock.
 214  */
 215 void deactivate_locked_super(struct super_block *s)
 216 {
 217         struct file_system_type *fs = s->s_type;
 218         if (atomic_dec_and_lock(&s->s_active, &sb_lock)) {
 219                 s->s_count -= S_BIAS-1;
 220                 spin_unlock(&sb_lock);
 221                 vfs_dq_off(s, 0);
 222                 fs->kill_sb(s);
 223                 put_filesystem(fs);
 224                 put_super(s);
 225         } else {
 226                 up_write(&s->s_umount);
 227         }
 228 }
 229
 230 EXPORT_SYMBOL(deactivate_locked_super);
 231
 232 /**
 233  *      grab_super - acquire an active reference
 234  *      @s: reference we are trying to make active
 235  *
 236  *      Tries to acquire an active reference.  grab_super() is used when we
 237  *      had just found a superblock in super_blocks or fs_type->fs_supers
 238  *      and want to turn it into a full-blown active reference.  grab_super()
 239  *      is called with sb_lock held and drops it.  Returns 1 in case of
 240  *      success, 0 if we had failed (superblock contents was already dead or
 241  *      dying when grab_super() had been called).
 242  */
 243 static int grab_super(struct super_block *s) __releases(sb_lock)
 244 {
 245         s->s_count++;
 246         spin_unlock(&sb_lock);
 247         down_write(&s->s_umount);
 248         if (s->s_root) {
 249                 spin_lock(&sb_lock);
 250                 if (s->s_count > S_BIAS) {
 251                         atomic_inc(&s->s_active);
 252                         s->s_count--;
 253                         spin_unlock(&sb_lock);
 254                         return 1;
 255                 }
 256                 spin_unlock(&sb_lock);
 257         }
 258         up_write(&s->s_umount);
 259         put_super(s);
 260         yield();
 261         return 0;
 262 }
 263
 264 /*
 265  * Superblock locking.  We really ought to get rid of these two.
 266  */
 267 void lock_super(struct super_block * sb)
 268 {
 269         get_fs_excl();
 270         mutex_lock(&sb->s_lock);
 271 }
 272
 273 void unlock_super(struct super_block * sb)
 274 {
 275         put_fs_excl();
 276         mutex_unlock(&sb->s_lock);
 277 }
 278
 279 EXPORT_SYMBOL(lock_super);
 280 EXPORT_SYMBOL(unlock_super);
 281
 282 /**
 283  *      generic_shutdown_super  -       common helper for ->kill_sb()
 284  *      @sb: superblock to kill
 285  *
 286  *      generic_shutdown_super() does all fs-independent work on superblock
 287  *      shutdown.  Typical ->kill_sb() should pick all fs-specific objects
 288  *      that need destruction out of superblock, call generic_shutdown_super()
 289  *      and release aforementioned objects.  Note: dentries and inodes _are_
 290  *      taken care of and do not need specific handling.
 291  *
 292  *      Upon calling this function, the filesystem may no longer alter or
 293  *      rearrange the set of dentries belonging to this super_block, nor may it
 294  *      change the attachments of dentries to inodes.
 295  */
 296 void generic_shutdown_super(struct super_block *sb)
 297 {
 298         const struct super_operations *sop = sb->s_op;
 299
 300
 301         if (sb->s_root) {
 302                 shrink_dcache_for_umount(sb);
 303                 sync_filesystem(sb);
 304                 get_fs_excl();
 305                 sb->s_flags &= ~MS_ACTIVE;
 306
 307                 /* bad name - it should be evict_inodes() */
 308                 invalidate_inodes(sb);
 309
 310                 if (sop->put_super)
 311                         sop->put_super(sb);
 312
 313                 /* Forget any remaining inodes */
 314                 if (invalidate_inodes(sb)) {
 315                         printk("VFS: Busy inodes after unmount of %s. "
 316                            "Self-destruct in 5 seconds.  Have a nice day...\n",
 317                            sb->s_id);
 318                 }
 319                 put_fs_excl();
 320         }
 321         spin_lock(&sb_lock);
 322         /* should be initialized for __put_super_and_need_restart() */
 323         list_del_init(&sb->s_list);
 324         list_del(&sb->s_instances);
 325         spin_unlock(&sb_lock);
 326         up_write(&sb->s_umount);
 327 }
 328
 329 EXPORT_SYMBOL(generic_shutdown_super);
 330
 331 /**
 332  *      sget    -       find or create a superblock
 333  *      @type:  filesystem type superblock should belong to
 334  *      @test:  comparison callback
 335  *      @set:   setup callback
 336  *      @data:  argument to each of them
 337  */
 338 struct super_block *sget(struct file_system_type *type,
 339                         int (*test)(struct super_block *,void *),
 340                         int (*set)(struct super_block *,void *),
 341                         void *data)
 342 {
 343         struct super_block *s = NULL;
 344         struct super_block *old;
 345         int err;
 346
 347 retry:
 348         spin_lock(&sb_lock);
 349         if (test) {
 350                 list_for_each_entry(old, &type->fs_supers, s_instances) {
 351                         if (!test(old, data))
 352                                 continue;
 353                         if (!grab_super(old))
 354                                 goto retry;
 355                         if (s) {
 356                                 up_write(&s->s_umount);
 357                                 destroy_super(s);
 358                         }
 359                         return old;
 360                 }
 361         }
 362         if (!s) {
 363                 spin_unlock(&sb_lock);
 364                 s = alloc_super(type);
 365                 if (!s)
 366                         return ERR_PTR(-ENOMEM);
 367                 goto retry;
 368         }
 369
 370         err = set(s, data);
 371         if (err) {
 372                 spin_unlock(&sb_lock);
 373                 up_write(&s->s_umount);
 374                 destroy_super(s);
 375                 return ERR_PTR(err);
 376         }
 377         s->s_type = type;
 378         strlcpy(s->s_id, type->name, sizeof(s->s_id));
 379         list_add_tail(&s->s_list, &super_blocks);
 380         list_add(&s->s_instances, &type->fs_supers);
 381         spin_unlock(&sb_lock);
 382         get_filesystem(type);
 383         return s;
 384 }
 385
 386 EXPORT_SYMBOL(sget);
 387
 388 void drop_super(struct super_block *sb)
 389 {
 390         up_read(&sb->s_umount);
 391         put_super(sb);
 392 }
 393
 394 EXPORT_SYMBOL(drop_super);
 395
 396 /**
 397  * sync_supers - helper for periodic superblock writeback
 398  *
 399  * Call the write_super method if present on all dirty superblocks in
 400  * the system.  This is for the periodic writeback used by most older
 401  * filesystems.  For data integrity superblock writeback use
 402  * sync_filesystems() instead.
 403  *
 404  * Note: check the dirty flag before waiting, so we don't
 405  * hold up the sync while mounting a device. (The newly
 406  * mounted device won't need syncing.)
 407  */
 408 void sync_supers(void)
 409 {
 410         struct super_block *sb;
 411
 412         spin_lock(&sb_lock);
 413 restart:
 414         list_for_each_entry(sb, &super_blocks, s_list) {
 415                 if (sb->s_op->write_super && sb->s_dirt) {
 416                         sb->s_count++;
 417                         spin_unlock(&sb_lock);
 418
 419                         down_read(&sb->s_umount);
 420                         if (sb->s_root && sb->s_dirt)
 421                                 sb->s_op->write_super(sb);
 422                         up_read(&sb->s_umount);
 423
 424                         spin_lock(&sb_lock);
 425                         if (__put_super_and_need_restart(sb))
 426                                 goto restart;
 427                 }
 428         }
 429         spin_unlock(&sb_lock);
 430 }
 431
 432 /**
 433  *      get_super - get the superblock of a device
 434  *      @bdev: device to get the superblock for
 435  *
 436  *      Scans the superblock list and finds the superblock of the file system
 437  *      mounted on the device given. %NULL is returned if no match is found.
 438  */
 439
 440 struct super_block * get_super(struct block_device *bdev)
 441 {
 442         struct super_block *sb;
 443
 444         if (!bdev)
 445                 return NULL;
 446
 447         spin_lock(&sb_lock);
 448 rescan:
 449         list_for_each_entry(sb, &super_blocks, s_list) {
 450                 if (sb->s_bdev == bdev) {
 451                         sb->s_count++;
 452                         spin_unlock(&sb_lock);
 453                         down_read(&sb->s_umount);
 454                         if (sb->s_root)
 455                                 return sb;
 456                         up_read(&sb->s_umount);
 457                         /* restart only when sb is no longer on the list */
 458                         spin_lock(&sb_lock);
 459                         if (__put_super_and_need_restart(sb))
 460                                 goto rescan;
 461                 }
 462         }
 463         spin_unlock(&sb_lock);
 464         return NULL;
 465 }
 466
 467 EXPORT_SYMBOL(get_super);
 468
 469 struct super_block * user_get_super(dev_t dev)
 470 {
 471         struct super_block *sb;
 472
 473         spin_lock(&sb_lock);
 474 rescan:
 475         list_for_each_entry(sb, &super_blocks, s_list) {
 476                 if (sb->s_dev ==  dev) {
 477                         sb->s_count++;
 478                         spin_unlock(&sb_lock);
 479                         down_read(&sb->s_umount);
 480                         if (sb->s_root)
 481                                 return sb;
 482                         up_read(&sb->s_umount);
 483                         /* restart only when sb is no longer on the list */
 484                         spin_lock(&sb_lock);
 485                         if (__put_super_and_need_restart(sb))
 486                                 goto rescan;
 487                 }
 488         }
 489         spin_unlock(&sb_lock);
 490         return NULL;
 491 }
 492
 493 SYSCALL_DEFINE2(ustat, unsigned, dev, struct ustat __user *, ubuf)
 494 {
 495         struct super_block *s;
 496         struct ustat tmp;
 497         struct kstatfs sbuf;
 498         int err = -EINVAL;
 499
 500         s = user_get_super(new_decode_dev(dev));
 501         if (s == NULL)
 502                 goto out;
 503         err = vfs_statfs(s->s_root, &sbuf);
 504         drop_super(s);
 505         if (err)
 506                 goto out;
 507
 508         memset(&tmp,0,sizeof(struct ustat));
 509         tmp.f_tfree = sbuf.f_bfree;
 510         tmp.f_tinode = sbuf.f_ffree;
 511
 512         err = copy_to_user(ubuf,&tmp,sizeof(struct ustat)) ? -EFAULT : 0;
 513 out:
 514         return err;
 515 }
 516
 517 /**
 518  *      do_remount_sb - asks filesystem to change mount options.
 519  *      @sb:    superblock in question
 520  *      @flags: numeric part of options
 521  *      @data:  the rest of options
 522  *      @force: whether or not to force the change
 523  *
 524  *      Alters the mount options of a mounted file system.
 525  */
 526 int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
 527 {
 528         int retval;
 529         int remount_rw;
 530
 531 #ifdef CONFIG_BLOCK
 532         if (!(flags & MS_RDONLY) && bdev_read_only(sb->s_bdev))
 533                 return -EACCES;
 534 #endif
 535         if (flags & MS_RDONLY)
 536                 acct_auto_close(sb);
 537         shrink_dcache_sb(sb);
 538         sync_filesystem(sb);
 539
 540         /* If we are remounting RDONLY and current sb is read/write,
 541            make sure there are no rw files opened */
 542         if ((flags & MS_RDONLY) && !(sb->s_flags & MS_RDONLY)) {
 543                 if (force)
 544                         mark_files_ro(sb);
 545                 else if (!fs_may_remount_ro(sb))
 546                         return -EBUSY;
 547                 retval = vfs_dq_off(sb, 1);
 548                 if (retval < 0 && retval != -ENOSYS)
 549                         return -EBUSY;
 550         }
 551         remount_rw = !(flags & MS_RDONLY) && (sb->s_flags & MS_RDONLY);
 552
 553         if (sb->s_op->remount_fs) {
 554                 retval = sb->s_op->remount_fs(sb, &flags, data);
 555                 if (retval)
 556                         return retval;
 557         }
 558         sb->s_flags = (sb->s_flags & ~MS_RMT_MASK) | (flags & MS_RMT_MASK);
 559         if (remount_rw)
 560                 vfs_dq_quota_on_remount(sb);
 561         return 0;
 562 }
 563
 564 static void do_emergency_remount(struct work_struct *work)
 565 {
 566         struct super_block *sb;
 567
 568         spin_lock(&sb_lock);
 569         list_for_each_entry(sb, &super_blocks, s_list) {
 570                 sb->s_count++;
 571                 spin_unlock(&sb_lock);
 572                 down_write(&sb->s_umount);
 573                 if (sb->s_root && sb->s_bdev && !(sb->s_flags & MS_RDONLY)) {
 574                         /*
 575                          * ->remount_fs needs lock_kernel().
 576                          *
 577                          * What lock protects sb->s_flags??
 578                          */
 579                         do_remount_sb(sb, MS_RDONLY, NULL, 1);
 580                 }
 581                 up_write(&sb->s_umount);
 582                 put_super(sb);
 583                 spin_lock(&sb_lock);
 584         }
 585         spin_unlock(&sb_lock);
 586         kfree(work);
 587         printk("Emergency Remount complete\n");
 588 }
 589
 590 void emergency_remount(void)
 591 {
 592         struct work_struct *work;
 593
 594         work = kmalloc(sizeof(*work), GFP_ATOMIC);
 595         if (work) {
 596                 INIT_WORK(work, do_emergency_remount);
 597                 schedule_work(work);
 598         }
 599 }
 600
 601 /*
 602  * Unnamed block devices are dummy devices used by virtual
 603  * filesystems which don't use real block-devices.  -- jrs
 604  */
 605
 606 static DEFINE_IDA(unnamed_dev_ida);
 607 static DEFINE_SPINLOCK(unnamed_dev_lock);/* protects the above */
 608 static int unnamed_dev_start = 0; /* don't bother trying below it */
 609
 610 int set_anon_super(struct super_block *s, void *data)
 611 {
 612         int dev;
 613         int error;
 614
 615  retry:
 616         if (ida_pre_get(&unnamed_dev_ida, GFP_ATOMIC) == 0)
 617                 return -ENOMEM;
 618         spin_lock(&unnamed_dev_lock);
 619         error = ida_get_new_above(&unnamed_dev_ida, unnamed_dev_start, &dev);
 620         if (!error)
 621                 unnamed_dev_start = dev + 1;
 622         spin_unlock(&unnamed_dev_lock);
 623         if (error == -EAGAIN)
 624                 /* We raced and lost with another CPU. */
 625                 goto retry;
 626         else if (error)
 627                 return -EAGAIN;
 628
 629         if ((dev & MAX_ID_MASK) == (1 << MINORBITS)) {
 630                 spin_lock(&unnamed_dev_lock);
 631                 ida_remove(&unnamed_dev_ida, dev);
 632                 if (unnamed_dev_start > dev)
 633                         unnamed_dev_start = dev;
 634                 spin_unlock(&unnamed_dev_lock);
 635                 return -EMFILE;
 636         }
 637         s->s_dev = MKDEV(0, dev & MINORMASK);
 638         return 0;
 639 }
 640
 641 EXPORT_SYMBOL(set_anon_super);
 642
 643 void kill_anon_super(struct super_block *sb)
 644 {
 645         int slot = MINOR(sb->s_dev);
 646
 647         generic_shutdown_super(sb);
 648         spin_lock(&unnamed_dev_lock);
 649         ida_remove(&unnamed_dev_ida, slot);
 650         if (slot < unnamed_dev_start)
 651                 unnamed_dev_start = slot;
 652         spin_unlock(&unnamed_dev_lock);
 653 }
 654
 655 EXPORT_SYMBOL(kill_anon_super);
 656
 657 void kill_litter_super(struct super_block *sb)
 658 {
 659         if (sb->s_root)
 660                 d_genocide(sb->s_root);
 661         kill_anon_super(sb);
 662 }
 663
 664 EXPORT_SYMBOL(kill_litter_super);
 665
 666 static int ns_test_super(struct super_block *sb, void *data)
 667 {
 668         return sb->s_fs_info == data;
 669 }
 670
 671 static int ns_set_super(struct super_block *sb, void *data)
 672 {
 673         sb->s_fs_info = data;
 674         return set_anon_super(sb, NULL);
 675 }
 676
 677 int get_sb_ns(struct file_system_type *fs_type, int flags, void *data,
 678         int (*fill_super)(struct super_block *, void *, int),
 679         struct vfsmount *mnt)
 680 {
 681         struct super_block *sb;
 682
 683         sb = sget(fs_type, ns_test_super, ns_set_super, data);
 684         if (IS_ERR(sb))
 685                 return PTR_ERR(sb);
 686
 687         if (!sb->s_root) {
 688                 int err;
 689                 sb->s_flags = flags;
 690                 err = fill_super(sb, data, flags & MS_SILENT ? 1 : 0);
 691                 if (err) {
 692                         deactivate_locked_super(sb);
 693                         return err;
 694                 }
 695
 696                 sb->s_flags |= MS_ACTIVE;
 697         }
 698
 699         simple_set_mnt(mnt, sb);
 700         return 0;
 701 }
 702
 703 EXPORT_SYMBOL(get_sb_ns);
 704
 705 #ifdef CONFIG_BLOCK
 706 static int set_bdev_super(struct super_block *s, void *data)
 707 {
 708         s->s_bdev = data;
 709         s->s_dev = s->s_bdev->bd_dev;
 710
 711         /*
 712          * We set the bdi here to the queue backing, file systems can
 713          * overwrite this in ->fill_super()
 714          */
 715         s->s_bdi = &bdev_get_queue(s->s_bdev)->backing_dev_info;
 716         return 0;
 717 }
 718
 719 static int test_bdev_super(struct super_block *s, void *data)
 720 {
 721         return (void *)s->s_bdev == data;
 722 }
 723
 724 int get_sb_bdev(struct file_system_type *fs_type,
 725         int flags, const char *dev_name, void *data,
 726         int (*fill_super)(struct super_block *, void *, int),
 727         struct vfsmount *mnt)
 728 {
 729         struct block_device *bdev;
 730         struct super_block *s;
 731         fmode_t mode = FMODE_READ;
 732         int error = 0;
 733
 734         if (!(flags & MS_RDONLY))
 735                 mode |= FMODE_WRITE;
 736
 737         bdev = open_bdev_exclusive(dev_name, mode, fs_type);
 738         if (IS_ERR(bdev))
 739                 return PTR_ERR(bdev);
 740
 741         /*
 742          * once the super is inserted into the list by sget, s_umount
 743          * will protect the lockfs code from trying to start a snapshot
 744          * while we are mounting
 745          */
 746         down(&bdev->bd_mount_sem);
 747         s = sget(fs_type, test_bdev_super, set_bdev_super, bdev);
 748         up(&bdev->bd_mount_sem);
 749         if (IS_ERR(s))
 750                 goto error_s;
 751
 752         if (s->s_root) {
 753                 if ((flags ^ s->s_flags) & MS_RDONLY) {
 754                         deactivate_locked_super(s);
 755                         error = -EBUSY;
 756                         goto error_bdev;
 757                 }
 758
 759                 close_bdev_exclusive(bdev, mode);
 760         } else {
 761                 char b[BDEVNAME_SIZE];
 762
 763                 s->s_flags = flags;
 764                 s->s_mode = mode;
 765                 strlcpy(s->s_id, bdevname(bdev, b), sizeof(s->s_id));
 766                 sb_set_blocksize(s, block_size(bdev));
 767                 error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
 768                 if (error) {
 769                         deactivate_locked_super(s);
 770                         goto error;
 771                 }
 772
 773                 s->s_flags |= MS_ACTIVE;
 774                 bdev->bd_super = s;
 775         }
 776
 777         simple_set_mnt(mnt, s);
 778         return 0;
 779
 780 error_s:
 781         error = PTR_ERR(s);
 782 error_bdev:
 783         close_bdev_exclusive(bdev, mode);
 784 error:
 785         return error;
 786 }
 787
 788 EXPORT_SYMBOL(get_sb_bdev);
 789
 790 void kill_block_super(struct super_block *sb)
 791 {
 792         struct block_device *bdev = sb->s_bdev;
 793         fmode_t mode = sb->s_mode;
 794
 795         bdev->bd_super = NULL;
 796         generic_shutdown_super(sb);
 797         sync_blockdev(bdev);
 798         close_bdev_exclusive(bdev, mode);
 799 }
 800
 801 EXPORT_SYMBOL(kill_block_super);
 802 #endif
 803
 804 int get_sb_nodev(struct file_system_type *fs_type,
 805         int flags, void *data,
 806         int (*fill_super)(struct super_block *, void *, int),
 807         struct vfsmount *mnt)
 808 {
 809         int error;
 810         struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL);
 811
 812         if (IS_ERR(s))
 813                 return PTR_ERR(s);
 814
 815         s->s_flags = flags;
 816
 817         error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
 818         if (error) {
 819                 deactivate_locked_super(s);
 820                 return error;
 821         }
 822         s->s_flags |= MS_ACTIVE;
 823         simple_set_mnt(mnt, s);
 824         return 0;
 825 }
 826
 827 EXPORT_SYMBOL(get_sb_nodev);
 828
 829 static int compare_single(struct super_block *s, void *p)
 830 {
 831         return 1;
 832 }
 833
 834 int get_sb_single(struct file_system_type *fs_type,
 835         int flags, void *data,
 836         int (*fill_super)(struct super_block *, void *, int),
 837         struct vfsmount *mnt)
 838 {
 839         struct super_block *s;
 840         int error;
 841
 842         s = sget(fs_type, compare_single, set_anon_super, NULL);
 843         if (IS_ERR(s))
 844                 return PTR_ERR(s);
 845         if (!s->s_root) {
 846                 s->s_flags = flags;
 847                 error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
 848                 if (error) {
 849                         deactivate_locked_super(s);
 850                         return error;
 851                 }
 852                 s->s_flags |= MS_ACTIVE;
 853         }
 854         do_remount_sb(s, flags, data, 0);
 855         simple_set_mnt(mnt, s);
 856         return 0;
 857 }
 858
 859 EXPORT_SYMBOL(get_sb_single);
 860
 861 struct vfsmount *
 862 vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void *data)
 863 {
 864         struct vfsmount *mnt;
 865         char *secdata = NULL;
 866         int error;
 867
 868         if (!type)
 869                 return ERR_PTR(-ENODEV);
 870
 871         error = -ENOMEM;
 872         mnt = alloc_vfsmnt(name);
 873         if (!mnt)
 874                 goto out;
 875
 876         if (data && !(type->fs_flags & FS_BINARY_MOUNTDATA)) {
 877                 secdata = alloc_secdata();
 878                 if (!secdata)
 879                         goto out_mnt;
 880
 881                 error = security_sb_copy_data(data, secdata);
 882                 if (error)
 883                         goto out_free_secdata;
 884         }
 885
 886         error = type->get_sb(type, flags, name, data, mnt);
 887         if (error < 0)
 888                 goto out_free_secdata;
 889         BUG_ON(!mnt->mnt_sb);
 890
 891         error = security_sb_kern_mount(mnt->mnt_sb, flags, secdata);
 892         if (error)
 893                 goto out_sb;
 894
 895         mnt->mnt_mountpoint = mnt->mnt_root;
 896         mnt->mnt_parent = mnt;
 897         up_write(&mnt->mnt_sb->s_umount);
 898         free_secdata(secdata);
 899         return mnt;
 900 out_sb:
 901         dput(mnt->mnt_root);
 902         deactivate_locked_super(mnt->mnt_sb);
 903 out_free_secdata:
 904         free_secdata(secdata);
 905 out_mnt:
 906         free_vfsmnt(mnt);
 907 out:
 908         return ERR_PTR(error);
 909 }
 910
 911 EXPORT_SYMBOL_GPL(vfs_kern_mount);
 912
 913 static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype)
 914 {
 915         int err;
 916         const char *subtype = strchr(fstype, '.');
 917         if (subtype) {
 918                 subtype++;
 919                 err = -EINVAL;
 920                 if (!subtype[0])
 921                         goto err;
 922         } else
 923                 subtype = "";
 924
 925         mnt->mnt_sb->s_subtype = kstrdup(subtype, GFP_KERNEL);
 926         err = -ENOMEM;
 927         if (!mnt->mnt_sb->s_subtype)
 928                 goto err;
 929         return mnt;
 930
 931  err:
 932         mntput(mnt);
 933         return ERR_PTR(err);
 934 }
 935
 936 struct vfsmount *
 937 do_kern_mount(const char *fstype, int flags, const char *name, void *data)
 938 {
 939         struct file_system_type *type = get_fs_type(fstype);
 940         struct vfsmount *mnt;
 941         if (!type)
 942                 return ERR_PTR(-ENODEV);
 943         mnt = vfs_kern_mount(type, flags, name, data);
 944         if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) &&
 945             !mnt->mnt_sb->s_subtype)
 946                 mnt = fs_set_subtype(mnt, fstype);
 947         put_filesystem(type);
 948         return mnt;
 949 }
 950 EXPORT_SYMBOL_GPL(do_kern_mount);
 951
 952 struct vfsmount *kern_mount_data(struct file_system_type *type, void *data)
 953 {
 954         return vfs_kern_mount(type, MS_KERNMOUNT, type->name, data);
 955 }
 956
 957 EXPORT_SYMBOL_GPL(kern_mount_data);