linux/fs/super.c
<<
>>
Prefs
   1/*
   2 *  linux/fs/super.c
   3 *
   4 *  Copyright (C) 1991, 1992  Linus Torvalds
   5 *
   6 *  super.c contains code to handle: - mount structures
   7 *                                   - super-block tables
   8 *                                   - filesystem drivers list
   9 *                                   - mount system call
  10 *                                   - umount system call
  11 *                                   - ustat system call
  12 *
  13 * GK 2/5/95  -  Changed to support mounting the root fs via NFS
  14 *
  15 *  Added kerneld support: Jacques Gelinas and Bjorn Ekwall
  16 *  Added change_root: Werner Almesberger & Hans Lermen, Feb '96
  17 *  Added options to /proc/mounts:
  18 *    Torbjörn Lindh (torbjorn.lindh@gopta.se), April 14, 1996.
  19 *  Added devfs support: Richard Gooch <rgooch@atnf.csiro.au>, 13-JAN-1998
  20 *  Heavily rewritten for 'one fs - one tree' dcache architecture. AV, Mar 2000
  21 */
  22
  23#include <linux/module.h>
  24#include <linux/slab.h>
  25#include <linux/init.h>
  26#include <linux/smp_lock.h>
  27#include <linux/acct.h>
  28#include <linux/blkdev.h>
  29#include <linux/quotaops.h>
  30#include <linux/namei.h>
  31#include <linux/buffer_head.h>          /* for fsync_super() */
  32#include <linux/mount.h>
  33#include <linux/security.h>
  34#include <linux/syscalls.h>
  35#include <linux/vfs.h>
  36#include <linux/writeback.h>            /* for the emergency remount stuff */
  37#include <linux/idr.h>
  38#include <linux/kobject.h>
  39#include <linux/mutex.h>
  40#include <linux/file.h>
  41#include <asm/uaccess.h>
  42#include "internal.h"
  43
  44
  45LIST_HEAD(super_blocks);
  46DEFINE_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 */
  55static 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 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_dirty);
  67                INIT_LIST_HEAD(&s->s_io);
  68                INIT_LIST_HEAD(&s->s_more_io);
  69                INIT_LIST_HEAD(&s->s_files);
  70                INIT_LIST_HEAD(&s->s_instances);
  71                INIT_HLIST_HEAD(&s->s_anon);
  72                INIT_LIST_HEAD(&s->s_inodes);
  73                INIT_LIST_HEAD(&s->s_dentry_lru);
  74                init_rwsem(&s->s_umount);
  75                mutex_init(&s->s_lock);
  76                lockdep_set_class(&s->s_umount, &type->s_umount_key);
  77                /*
  78                 * The locking rules for s_lock are up to the
  79                 * filesystem. For example ext3fs has different
  80                 * lock ordering than usbfs:
  81                 */
  82                lockdep_set_class(&s->s_lock, &type->s_lock_key);
  83                down_write(&s->s_umount);
  84                s->s_count = S_BIAS;
  85                atomic_set(&s->s_active, 1);
  86                mutex_init(&s->s_vfs_rename_mutex);
  87                mutex_init(&s->s_dquot.dqio_mutex);
  88                mutex_init(&s->s_dquot.dqonoff_mutex);
  89                init_rwsem(&s->s_dquot.dqptr_sem);
  90                init_waitqueue_head(&s->s_wait_unfrozen);
  91                s->s_maxbytes = MAX_NON_LFS;
  92                s->dq_op = sb_dquot_ops;
  93                s->s_qcop = sb_quotactl_ops;
  94                s->s_op = &default_op;
  95                s->s_time_gran = 1000000000;
  96        }
  97out:
  98        return s;
  99}
 100
 101/**
 102 *      destroy_super   -       frees a superblock
 103 *      @s: superblock to free
 104 *
 105 *      Frees a superblock.
 106 */
 107static inline void destroy_super(struct super_block *s)
 108{
 109        security_sb_free(s);
 110        kfree(s->s_subtype);
 111        kfree(s->s_options);
 112        kfree(s);
 113}
 114
 115/* Superblock refcounting  */
 116
 117/*
 118 * Drop a superblock's refcount.  Returns non-zero if the superblock was
 119 * destroyed.  The caller must hold sb_lock.
 120 */
 121static int __put_super(struct super_block *sb)
 122{
 123        int ret = 0;
 124
 125        if (!--sb->s_count) {
 126                destroy_super(sb);
 127                ret = 1;
 128        }
 129        return ret;
 130}
 131
 132/*
 133 * Drop a superblock's refcount.
 134 * Returns non-zero if the superblock is about to be destroyed and
 135 * at least is already removed from super_blocks list, so if we are
 136 * making a loop through super blocks then we need to restart.
 137 * The caller must hold sb_lock.
 138 */
 139int __put_super_and_need_restart(struct super_block *sb)
 140{
 141        /* check for race with generic_shutdown_super() */
 142        if (list_empty(&sb->s_list)) {
 143                /* super block is removed, need to restart... */
 144                __put_super(sb);
 145                return 1;
 146        }
 147        /* can't be the last, since s_list is still in use */
 148        sb->s_count--;
 149        BUG_ON(sb->s_count == 0);
 150        return 0;
 151}
 152
 153/**
 154 *      put_super       -       drop a temporary reference to superblock
 155 *      @sb: superblock in question
 156 *
 157 *      Drops a temporary reference, frees superblock if there's no
 158 *      references left.
 159 */
 160static void put_super(struct super_block *sb)
 161{
 162        spin_lock(&sb_lock);
 163        __put_super(sb);
 164        spin_unlock(&sb_lock);
 165}
 166
 167
 168/**
 169 *      deactivate_super        -       drop an active reference to superblock
 170 *      @s: superblock to deactivate
 171 *
 172 *      Drops an active reference to superblock, acquiring a temprory one if
 173 *      there is no active references left.  In that case we lock superblock,
 174 *      tell fs driver to shut it down and drop the temporary reference we
 175 *      had just acquired.
 176 */
 177void deactivate_super(struct super_block *s)
 178{
 179        struct file_system_type *fs = s->s_type;
 180        if (atomic_dec_and_lock(&s->s_active, &sb_lock)) {
 181                s->s_count -= S_BIAS-1;
 182                spin_unlock(&sb_lock);
 183                DQUOT_OFF(s, 0);
 184                down_write(&s->s_umount);
 185                fs->kill_sb(s);
 186                put_filesystem(fs);
 187                put_super(s);
 188        }
 189}
 190
 191EXPORT_SYMBOL(deactivate_super);
 192
 193/**
 194 *      grab_super - acquire an active reference
 195 *      @s: reference we are trying to make active
 196 *
 197 *      Tries to acquire an active reference.  grab_super() is used when we
 198 *      had just found a superblock in super_blocks or fs_type->fs_supers
 199 *      and want to turn it into a full-blown active reference.  grab_super()
 200 *      is called with sb_lock held and drops it.  Returns 1 in case of
 201 *      success, 0 if we had failed (superblock contents was already dead or
 202 *      dying when grab_super() had been called).
 203 */
 204static int grab_super(struct super_block *s) __releases(sb_lock)
 205{
 206        s->s_count++;
 207        spin_unlock(&sb_lock);
 208        down_write(&s->s_umount);
 209        if (s->s_root) {
 210                spin_lock(&sb_lock);
 211                if (s->s_count > S_BIAS) {
 212                        atomic_inc(&s->s_active);
 213                        s->s_count--;
 214                        spin_unlock(&sb_lock);
 215                        return 1;
 216                }
 217                spin_unlock(&sb_lock);
 218        }
 219        up_write(&s->s_umount);
 220        put_super(s);
 221        yield();
 222        return 0;
 223}
 224
 225/*
 226 * Superblock locking.  We really ought to get rid of these two.
 227 */
 228void lock_super(struct super_block * sb)
 229{
 230        get_fs_excl();
 231        mutex_lock(&sb->s_lock);
 232}
 233
 234void unlock_super(struct super_block * sb)
 235{
 236        put_fs_excl();
 237        mutex_unlock(&sb->s_lock);
 238}
 239
 240EXPORT_SYMBOL(lock_super);
 241EXPORT_SYMBOL(unlock_super);
 242
 243/*
 244 * Write out and wait upon all dirty data associated with this
 245 * superblock.  Filesystem data as well as the underlying block
 246 * device.  Takes the superblock lock.  Requires a second blkdev
 247 * flush by the caller to complete the operation.
 248 */
 249void __fsync_super(struct super_block *sb)
 250{
 251        sync_inodes_sb(sb, 0);
 252        DQUOT_SYNC(sb);
 253        lock_super(sb);
 254        if (sb->s_dirt && sb->s_op->write_super)
 255                sb->s_op->write_super(sb);
 256        unlock_super(sb);
 257        if (sb->s_op->sync_fs)
 258                sb->s_op->sync_fs(sb, 1);
 259        sync_blockdev(sb->s_bdev);
 260        sync_inodes_sb(sb, 1);
 261}
 262
 263/*
 264 * Write out and wait upon all dirty data associated with this
 265 * superblock.  Filesystem data as well as the underlying block
 266 * device.  Takes the superblock lock.
 267 */
 268int fsync_super(struct super_block *sb)
 269{
 270        __fsync_super(sb);
 271        return sync_blockdev(sb->s_bdev);
 272}
 273
 274/**
 275 *      generic_shutdown_super  -       common helper for ->kill_sb()
 276 *      @sb: superblock to kill
 277 *
 278 *      generic_shutdown_super() does all fs-independent work on superblock
 279 *      shutdown.  Typical ->kill_sb() should pick all fs-specific objects
 280 *      that need destruction out of superblock, call generic_shutdown_super()
 281 *      and release aforementioned objects.  Note: dentries and inodes _are_
 282 *      taken care of and do not need specific handling.
 283 *
 284 *      Upon calling this function, the filesystem may no longer alter or
 285 *      rearrange the set of dentries belonging to this super_block, nor may it
 286 *      change the attachments of dentries to inodes.
 287 */
 288void generic_shutdown_super(struct super_block *sb)
 289{
 290        const struct super_operations *sop = sb->s_op;
 291
 292        if (sb->s_root) {
 293                shrink_dcache_for_umount(sb);
 294                fsync_super(sb);
 295                lock_super(sb);
 296                sb->s_flags &= ~MS_ACTIVE;
 297                /* bad name - it should be evict_inodes() */
 298                invalidate_inodes(sb);
 299                lock_kernel();
 300
 301                if (sop->write_super && sb->s_dirt)
 302                        sop->write_super(sb);
 303                if (sop->put_super)
 304                        sop->put_super(sb);
 305
 306                /* Forget any remaining inodes */
 307                if (invalidate_inodes(sb)) {
 308                        printk("VFS: Busy inodes after unmount of %s. "
 309                           "Self-destruct in 5 seconds.  Have a nice day...\n",
 310                           sb->s_id);
 311                }
 312
 313                unlock_kernel();
 314                unlock_super(sb);
 315        }
 316        spin_lock(&sb_lock);
 317        /* should be initialized for __put_super_and_need_restart() */
 318        list_del_init(&sb->s_list);
 319        list_del(&sb->s_instances);
 320        spin_unlock(&sb_lock);
 321        up_write(&sb->s_umount);
 322}
 323
 324EXPORT_SYMBOL(generic_shutdown_super);
 325
 326/**
 327 *      sget    -       find or create a superblock
 328 *      @type:  filesystem type superblock should belong to
 329 *      @test:  comparison callback
 330 *      @set:   setup callback
 331 *      @data:  argument to each of them
 332 */
 333struct super_block *sget(struct file_system_type *type,
 334                        int (*test)(struct super_block *,void *),
 335                        int (*set)(struct super_block *,void *),
 336                        void *data)
 337{
 338        struct super_block *s = NULL;
 339        struct super_block *old;
 340        int err;
 341
 342retry:
 343        spin_lock(&sb_lock);
 344        if (test) {
 345                list_for_each_entry(old, &type->fs_supers, s_instances) {
 346                        if (!test(old, data))
 347                                continue;
 348                        if (!grab_super(old))
 349                                goto retry;
 350                        if (s)
 351                                destroy_super(s);
 352                        return old;
 353                }
 354        }
 355        if (!s) {
 356                spin_unlock(&sb_lock);
 357                s = alloc_super(type);
 358                if (!s)
 359                        return ERR_PTR(-ENOMEM);
 360                goto retry;
 361        }
 362                
 363        err = set(s, data);
 364        if (err) {
 365                spin_unlock(&sb_lock);
 366                destroy_super(s);
 367                return ERR_PTR(err);
 368        }
 369        s->s_type = type;
 370        strlcpy(s->s_id, type->name, sizeof(s->s_id));
 371        list_add_tail(&s->s_list, &super_blocks);
 372        list_add(&s->s_instances, &type->fs_supers);
 373        spin_unlock(&sb_lock);
 374        get_filesystem(type);
 375        return s;
 376}
 377
 378EXPORT_SYMBOL(sget);
 379
 380void drop_super(struct super_block *sb)
 381{
 382        up_read(&sb->s_umount);
 383        put_super(sb);
 384}
 385
 386EXPORT_SYMBOL(drop_super);
 387
 388static inline void write_super(struct super_block *sb)
 389{
 390        lock_super(sb);
 391        if (sb->s_root && sb->s_dirt)
 392                if (sb->s_op->write_super)
 393                        sb->s_op->write_super(sb);
 394        unlock_super(sb);
 395}
 396
 397/*
 398 * Note: check the dirty flag before waiting, so we don't
 399 * hold up the sync while mounting a device. (The newly
 400 * mounted device won't need syncing.)
 401 */
 402void sync_supers(void)
 403{
 404        struct super_block *sb;
 405
 406        spin_lock(&sb_lock);
 407restart:
 408        list_for_each_entry(sb, &super_blocks, s_list) {
 409                if (sb->s_dirt) {
 410                        sb->s_count++;
 411                        spin_unlock(&sb_lock);
 412                        down_read(&sb->s_umount);
 413                        write_super(sb);
 414                        up_read(&sb->s_umount);
 415                        spin_lock(&sb_lock);
 416                        if (__put_super_and_need_restart(sb))
 417                                goto restart;
 418                }
 419        }
 420        spin_unlock(&sb_lock);
 421}
 422
 423/*
 424 * Call the ->sync_fs super_op against all filesystems which are r/w and
 425 * which implement it.
 426 *
 427 * This operation is careful to avoid the livelock which could easily happen
 428 * if two or more filesystems are being continuously dirtied.  s_need_sync_fs
 429 * is used only here.  We set it against all filesystems and then clear it as
 430 * we sync them.  So redirtied filesystems are skipped.
 431 *
 432 * But if process A is currently running sync_filesystems and then process B
 433 * calls sync_filesystems as well, process B will set all the s_need_sync_fs
 434 * flags again, which will cause process A to resync everything.  Fix that with
 435 * a local mutex.
 436 *
 437 * (Fabian) Avoid sync_fs with clean fs & wait mode 0
 438 */
 439void sync_filesystems(int wait)
 440{
 441        struct super_block *sb;
 442        static DEFINE_MUTEX(mutex);
 443
 444        mutex_lock(&mutex);             /* Could be down_interruptible */
 445        spin_lock(&sb_lock);
 446        list_for_each_entry(sb, &super_blocks, s_list) {
 447                if (!sb->s_op->sync_fs)
 448                        continue;
 449                if (sb->s_flags & MS_RDONLY)
 450                        continue;
 451                sb->s_need_sync_fs = 1;
 452        }
 453
 454restart:
 455        list_for_each_entry(sb, &super_blocks, s_list) {
 456                if (!sb->s_need_sync_fs)
 457                        continue;
 458                sb->s_need_sync_fs = 0;
 459                if (sb->s_flags & MS_RDONLY)
 460                        continue;       /* hm.  Was remounted r/o meanwhile */
 461                sb->s_count++;
 462                spin_unlock(&sb_lock);
 463                down_read(&sb->s_umount);
 464                if (sb->s_root && (wait || sb->s_dirt))
 465                        sb->s_op->sync_fs(sb, wait);
 466                up_read(&sb->s_umount);
 467                /* restart only when sb is no longer on the list */
 468                spin_lock(&sb_lock);
 469                if (__put_super_and_need_restart(sb))
 470                        goto restart;
 471        }
 472        spin_unlock(&sb_lock);
 473        mutex_unlock(&mutex);
 474}
 475
 476/**
 477 *      get_super - get the superblock of a device
 478 *      @bdev: device to get the superblock for
 479 *      
 480 *      Scans the superblock list and finds the superblock of the file system
 481 *      mounted on the device given. %NULL is returned if no match is found.
 482 */
 483
 484struct super_block * get_super(struct block_device *bdev)
 485{
 486        struct super_block *sb;
 487
 488        if (!bdev)
 489                return NULL;
 490
 491        spin_lock(&sb_lock);
 492rescan:
 493        list_for_each_entry(sb, &super_blocks, s_list) {
 494                if (sb->s_bdev == bdev) {
 495                        sb->s_count++;
 496                        spin_unlock(&sb_lock);
 497                        down_read(&sb->s_umount);
 498                        if (sb->s_root)
 499                                return sb;
 500                        up_read(&sb->s_umount);
 501                        /* restart only when sb is no longer on the list */
 502                        spin_lock(&sb_lock);
 503                        if (__put_super_and_need_restart(sb))
 504                                goto rescan;
 505                }
 506        }
 507        spin_unlock(&sb_lock);
 508        return NULL;
 509}
 510
 511EXPORT_SYMBOL(get_super);
 512 
 513struct super_block * user_get_super(dev_t dev)
 514{
 515        struct super_block *sb;
 516
 517        spin_lock(&sb_lock);
 518rescan:
 519        list_for_each_entry(sb, &super_blocks, s_list) {
 520                if (sb->s_dev ==  dev) {
 521                        sb->s_count++;
 522                        spin_unlock(&sb_lock);
 523                        down_read(&sb->s_umount);
 524                        if (sb->s_root)
 525                                return sb;
 526                        up_read(&sb->s_umount);
 527                        /* restart only when sb is no longer on the list */
 528                        spin_lock(&sb_lock);
 529                        if (__put_super_and_need_restart(sb))
 530                                goto rescan;
 531                }
 532        }
 533        spin_unlock(&sb_lock);
 534        return NULL;
 535}
 536
 537SYSCALL_DEFINE2(ustat, unsigned, dev, struct ustat __user *, ubuf)
 538{
 539        struct super_block *s;
 540        struct ustat tmp;
 541        struct kstatfs sbuf;
 542        int err = -EINVAL;
 543
 544        s = user_get_super(new_decode_dev(dev));
 545        if (s == NULL)
 546                goto out;
 547        err = vfs_statfs(s->s_root, &sbuf);
 548        drop_super(s);
 549        if (err)
 550                goto out;
 551
 552        memset(&tmp,0,sizeof(struct ustat));
 553        tmp.f_tfree = sbuf.f_bfree;
 554        tmp.f_tinode = sbuf.f_ffree;
 555
 556        err = copy_to_user(ubuf,&tmp,sizeof(struct ustat)) ? -EFAULT : 0;
 557out:
 558        return err;
 559}
 560
 561/**
 562 *      mark_files_ro - mark all files read-only
 563 *      @sb: superblock in question
 564 *
 565 *      All files are marked read-only.  We don't care about pending
 566 *      delete files so this should be used in 'force' mode only.
 567 */
 568
 569static void mark_files_ro(struct super_block *sb)
 570{
 571        struct file *f;
 572
 573retry:
 574        file_list_lock();
 575        list_for_each_entry(f, &sb->s_files, f_u.fu_list) {
 576                struct vfsmount *mnt;
 577                if (!S_ISREG(f->f_path.dentry->d_inode->i_mode))
 578                       continue;
 579                if (!file_count(f))
 580                        continue;
 581                if (!(f->f_mode & FMODE_WRITE))
 582                        continue;
 583                f->f_mode &= ~FMODE_WRITE;
 584                if (file_check_writeable(f) != 0)
 585                        continue;
 586                file_release_write(f);
 587                mnt = mntget(f->f_path.mnt);
 588                file_list_unlock();
 589                /*
 590                 * This can sleep, so we can't hold
 591                 * the file_list_lock() spinlock.
 592                 */
 593                mnt_drop_write(mnt);
 594                mntput(mnt);
 595                goto retry;
 596        }
 597        file_list_unlock();
 598}
 599
 600/**
 601 *      do_remount_sb - asks filesystem to change mount options.
 602 *      @sb:    superblock in question
 603 *      @flags: numeric part of options
 604 *      @data:  the rest of options
 605 *      @force: whether or not to force the change
 606 *
 607 *      Alters the mount options of a mounted file system.
 608 */
 609int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
 610{
 611        int retval;
 612        int remount_rw;
 613        
 614#ifdef CONFIG_BLOCK
 615        if (!(flags & MS_RDONLY) && bdev_read_only(sb->s_bdev))
 616                return -EACCES;
 617#endif
 618        if (flags & MS_RDONLY)
 619                acct_auto_close(sb);
 620        shrink_dcache_sb(sb);
 621        fsync_super(sb);
 622
 623        /* If we are remounting RDONLY and current sb is read/write,
 624           make sure there are no rw files opened */
 625        if ((flags & MS_RDONLY) && !(sb->s_flags & MS_RDONLY)) {
 626                if (force)
 627                        mark_files_ro(sb);
 628                else if (!fs_may_remount_ro(sb))
 629                        return -EBUSY;
 630                retval = DQUOT_OFF(sb, 1);
 631                if (retval < 0 && retval != -ENOSYS)
 632                        return -EBUSY;
 633        }
 634        remount_rw = !(flags & MS_RDONLY) && (sb->s_flags & MS_RDONLY);
 635
 636        if (sb->s_op->remount_fs) {
 637                lock_super(sb);
 638                retval = sb->s_op->remount_fs(sb, &flags, data);
 639                unlock_super(sb);
 640                if (retval)
 641                        return retval;
 642        }
 643        sb->s_flags = (sb->s_flags & ~MS_RMT_MASK) | (flags & MS_RMT_MASK);
 644        if (remount_rw)
 645                DQUOT_ON_REMOUNT(sb);
 646        return 0;
 647}
 648
 649static void do_emergency_remount(unsigned long foo)
 650{
 651        struct super_block *sb;
 652
 653        spin_lock(&sb_lock);
 654        list_for_each_entry(sb, &super_blocks, s_list) {
 655                sb->s_count++;
 656                spin_unlock(&sb_lock);
 657                down_read(&sb->s_umount);
 658                if (sb->s_root && sb->s_bdev && !(sb->s_flags & MS_RDONLY)) {
 659                        /*
 660                         * ->remount_fs needs lock_kernel().
 661                         *
 662                         * What lock protects sb->s_flags??
 663                         */
 664                        lock_kernel();
 665                        do_remount_sb(sb, MS_RDONLY, NULL, 1);
 666                        unlock_kernel();
 667                }
 668                drop_super(sb);
 669                spin_lock(&sb_lock);
 670        }
 671        spin_unlock(&sb_lock);
 672        printk("Emergency Remount complete\n");
 673}
 674
 675void emergency_remount(void)
 676{
 677        pdflush_operation(do_emergency_remount, 0);
 678}
 679
 680/*
 681 * Unnamed block devices are dummy devices used by virtual
 682 * filesystems which don't use real block-devices.  -- jrs
 683 */
 684
 685static DEFINE_IDA(unnamed_dev_ida);
 686static DEFINE_SPINLOCK(unnamed_dev_lock);/* protects the above */
 687
 688int set_anon_super(struct super_block *s, void *data)
 689{
 690        int dev;
 691        int error;
 692
 693 retry:
 694        if (ida_pre_get(&unnamed_dev_ida, GFP_ATOMIC) == 0)
 695                return -ENOMEM;
 696        spin_lock(&unnamed_dev_lock);
 697        error = ida_get_new(&unnamed_dev_ida, &dev);
 698        spin_unlock(&unnamed_dev_lock);
 699        if (error == -EAGAIN)
 700                /* We raced and lost with another CPU. */
 701                goto retry;
 702        else if (error)
 703                return -EAGAIN;
 704
 705        if ((dev & MAX_ID_MASK) == (1 << MINORBITS)) {
 706                spin_lock(&unnamed_dev_lock);
 707                ida_remove(&unnamed_dev_ida, dev);
 708                spin_unlock(&unnamed_dev_lock);
 709                return -EMFILE;
 710        }
 711        s->s_dev = MKDEV(0, dev & MINORMASK);
 712        return 0;
 713}
 714
 715EXPORT_SYMBOL(set_anon_super);
 716
 717void kill_anon_super(struct super_block *sb)
 718{
 719        int slot = MINOR(sb->s_dev);
 720
 721        generic_shutdown_super(sb);
 722        spin_lock(&unnamed_dev_lock);
 723        ida_remove(&unnamed_dev_ida, slot);
 724        spin_unlock(&unnamed_dev_lock);
 725}
 726
 727EXPORT_SYMBOL(kill_anon_super);
 728
 729void kill_litter_super(struct super_block *sb)
 730{
 731        if (sb->s_root)
 732                d_genocide(sb->s_root);
 733        kill_anon_super(sb);
 734}
 735
 736EXPORT_SYMBOL(kill_litter_super);
 737
 738#ifdef CONFIG_BLOCK
 739static int set_bdev_super(struct super_block *s, void *data)
 740{
 741        s->s_bdev = data;
 742        s->s_dev = s->s_bdev->bd_dev;
 743        return 0;
 744}
 745
 746static int test_bdev_super(struct super_block *s, void *data)
 747{
 748        return (void *)s->s_bdev == data;
 749}
 750
 751int get_sb_bdev(struct file_system_type *fs_type,
 752        int flags, const char *dev_name, void *data,
 753        int (*fill_super)(struct super_block *, void *, int),
 754        struct vfsmount *mnt)
 755{
 756        struct block_device *bdev;
 757        struct super_block *s;
 758        fmode_t mode = FMODE_READ;
 759        int error = 0;
 760
 761        if (!(flags & MS_RDONLY))
 762                mode |= FMODE_WRITE;
 763
 764        bdev = open_bdev_exclusive(dev_name, mode, fs_type);
 765        if (IS_ERR(bdev))
 766                return PTR_ERR(bdev);
 767
 768        /*
 769         * once the super is inserted into the list by sget, s_umount
 770         * will protect the lockfs code from trying to start a snapshot
 771         * while we are mounting
 772         */
 773        down(&bdev->bd_mount_sem);
 774        s = sget(fs_type, test_bdev_super, set_bdev_super, bdev);
 775        up(&bdev->bd_mount_sem);
 776        if (IS_ERR(s))
 777                goto error_s;
 778
 779        if (s->s_root) {
 780                if ((flags ^ s->s_flags) & MS_RDONLY) {
 781                        up_write(&s->s_umount);
 782                        deactivate_super(s);
 783                        error = -EBUSY;
 784                        goto error_bdev;
 785                }
 786
 787                close_bdev_exclusive(bdev, mode);
 788        } else {
 789                char b[BDEVNAME_SIZE];
 790
 791                s->s_flags = flags;
 792                s->s_mode = mode;
 793                strlcpy(s->s_id, bdevname(bdev, b), sizeof(s->s_id));
 794                sb_set_blocksize(s, block_size(bdev));
 795                error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
 796                if (error) {
 797                        up_write(&s->s_umount);
 798                        deactivate_super(s);
 799                        goto error;
 800                }
 801
 802                s->s_flags |= MS_ACTIVE;
 803        }
 804
 805        return simple_set_mnt(mnt, s);
 806
 807error_s:
 808        error = PTR_ERR(s);
 809error_bdev:
 810        close_bdev_exclusive(bdev, mode);
 811error:
 812        return error;
 813}
 814
 815EXPORT_SYMBOL(get_sb_bdev);
 816
 817void kill_block_super(struct super_block *sb)
 818{
 819        struct block_device *bdev = sb->s_bdev;
 820        fmode_t mode = sb->s_mode;
 821
 822        generic_shutdown_super(sb);
 823        sync_blockdev(bdev);
 824        close_bdev_exclusive(bdev, mode);
 825}
 826
 827EXPORT_SYMBOL(kill_block_super);
 828#endif
 829
 830int get_sb_nodev(struct file_system_type *fs_type,
 831        int flags, void *data,
 832        int (*fill_super)(struct super_block *, void *, int),
 833        struct vfsmount *mnt)
 834{
 835        int error;
 836        struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL);
 837
 838        if (IS_ERR(s))
 839                return PTR_ERR(s);
 840
 841        s->s_flags = flags;
 842
 843        error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
 844        if (error) {
 845                up_write(&s->s_umount);
 846                deactivate_super(s);
 847                return error;
 848        }
 849        s->s_flags |= MS_ACTIVE;
 850        return simple_set_mnt(mnt, s);
 851}
 852
 853EXPORT_SYMBOL(get_sb_nodev);
 854
 855static int compare_single(struct super_block *s, void *p)
 856{
 857        return 1;
 858}
 859
 860int get_sb_single(struct file_system_type *fs_type,
 861        int flags, void *data,
 862        int (*fill_super)(struct super_block *, void *, int),
 863        struct vfsmount *mnt)
 864{
 865        struct super_block *s;
 866        int error;
 867
 868        s = sget(fs_type, compare_single, set_anon_super, NULL);
 869        if (IS_ERR(s))
 870                return PTR_ERR(s);
 871        if (!s->s_root) {
 872                s->s_flags = flags;
 873                error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
 874                if (error) {
 875                        up_write(&s->s_umount);
 876                        deactivate_super(s);
 877                        return error;
 878                }
 879                s->s_flags |= MS_ACTIVE;
 880        }
 881        do_remount_sb(s, flags, data, 0);
 882        return simple_set_mnt(mnt, s);
 883}
 884
 885EXPORT_SYMBOL(get_sb_single);
 886
 887struct vfsmount *
 888vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void *data)
 889{
 890        struct vfsmount *mnt;
 891        char *secdata = NULL;
 892        int error;
 893
 894        if (!type)
 895                return ERR_PTR(-ENODEV);
 896
 897        error = -ENOMEM;
 898        mnt = alloc_vfsmnt(name);
 899        if (!mnt)
 900                goto out;
 901
 902        if (data && !(type->fs_flags & FS_BINARY_MOUNTDATA)) {
 903                secdata = alloc_secdata();
 904                if (!secdata)
 905                        goto out_mnt;
 906
 907                error = security_sb_copy_data(data, secdata);
 908                if (error)
 909                        goto out_free_secdata;
 910        }
 911
 912        error = type->get_sb(type, flags, name, data, mnt);
 913        if (error < 0)
 914                goto out_free_secdata;
 915        BUG_ON(!mnt->mnt_sb);
 916
 917        error = security_sb_kern_mount(mnt->mnt_sb, secdata);
 918        if (error)
 919                goto out_sb;
 920
 921        mnt->mnt_mountpoint = mnt->mnt_root;
 922        mnt->mnt_parent = mnt;
 923        up_write(&mnt->mnt_sb->s_umount);
 924        free_secdata(secdata);
 925        return mnt;
 926out_sb:
 927        dput(mnt->mnt_root);
 928        up_write(&mnt->mnt_sb->s_umount);
 929        deactivate_super(mnt->mnt_sb);
 930out_free_secdata:
 931        free_secdata(secdata);
 932out_mnt:
 933        free_vfsmnt(mnt);
 934out:
 935        return ERR_PTR(error);
 936}
 937
 938EXPORT_SYMBOL_GPL(vfs_kern_mount);
 939
 940static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype)
 941{
 942        int err;
 943        const char *subtype = strchr(fstype, '.');
 944        if (subtype) {
 945                subtype++;
 946                err = -EINVAL;
 947                if (!subtype[0])
 948                        goto err;
 949        } else
 950                subtype = "";
 951
 952        mnt->mnt_sb->s_subtype = kstrdup(subtype, GFP_KERNEL);
 953        err = -ENOMEM;
 954        if (!mnt->mnt_sb->s_subtype)
 955                goto err;
 956        return mnt;
 957
 958 err:
 959        mntput(mnt);
 960        return ERR_PTR(err);
 961}
 962
 963struct vfsmount *
 964do_kern_mount(const char *fstype, int flags, const char *name, void *data)
 965{
 966        struct file_system_type *type = get_fs_type(fstype);
 967        struct vfsmount *mnt;
 968        if (!type)
 969                return ERR_PTR(-ENODEV);
 970        mnt = vfs_kern_mount(type, flags, name, data);
 971        if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) &&
 972            !mnt->mnt_sb->s_subtype)
 973                mnt = fs_set_subtype(mnt, fstype);
 974        put_filesystem(type);
 975        return mnt;
 976}
 977EXPORT_SYMBOL_GPL(do_kern_mount);
 978
 979struct vfsmount *kern_mount_data(struct file_system_type *type, void *data)
 980{
 981        return vfs_kern_mount(type, MS_KERNMOUNT, type->name, data);
 982}
 983
 984EXPORT_SYMBOL_GPL(kern_mount_data);
 985
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.