1 files changed, 860 insertions, 0 deletions

diff --git a/fs/super.c b/fs/super.c
new file mode 100644
index 000000000000..3a1b8ca04ba6
--- /dev/null
+++ b/fs/super.c
@@ -0,0 +1,860 @@
+/*
+ *  linux/fs/super.c
+ *
+ *  Copyright (C) 1991, 1992  Linus Torvalds
+ *
+ *  super.c contains code to handle: - mount structures
+ *                                   - super-block tables
+ *                                   - filesystem drivers list
+ *                                   - mount system call
+ *                                   - umount system call
+ *                                   - ustat system call
+ *
+ * GK 2/5/95  -  Changed to support mounting the root fs via NFS
+ *
+ *  Added kerneld support: Jacques Gelinas and Bjorn Ekwall
+ *  Added change_root: Werner Almesberger & Hans Lermen, Feb '96
+ *  Added options to /proc/mounts:
+ *    Torbjörn Lindh (torbjorn.lindh@gopta.se), April 14, 1996.
+ *  Added devfs support: Richard Gooch <rgooch@atnf.csiro.au>, 13-JAN-1998
+ *  Heavily rewritten for 'one fs - one tree' dcache architecture. AV, Mar 2000
+ */
+
+#include <linux/config.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/init.h>
+#include <linux/smp_lock.h>
+#include <linux/acct.h>
+#include <linux/blkdev.h>
+#include <linux/quotaops.h>
+#include <linux/namei.h>
+#include <linux/buffer_head.h>          /* for fsync_super() */
+#include <linux/mount.h>
+#include <linux/security.h>
+#include <linux/syscalls.h>
+#include <linux/vfs.h>
+#include <linux/writeback.h>            /* for the emergency remount stuff */
+#include <linux/idr.h>
+#include <linux/kobject.h>
+#include <asm/uaccess.h>
+
+
+void get_filesystem(struct file_system_type *fs);
+void put_filesystem(struct file_system_type *fs);
+struct file_system_type *get_fs_type(const char *name);
+
+LIST_HEAD(super_blocks);
+DEFINE_SPINLOCK(sb_lock);
+
+/**
+ *      alloc_super     -       create new superblock
+ *
+ *      Allocates and initializes a new &struct super_block.  alloc_super()
+ *      returns a pointer new superblock or %NULL if allocation had failed.
+ */
+static struct super_block *alloc_super(void)
+{
+        struct super_block *s = kmalloc(sizeof(struct super_block),  GFP_USER);
+        static struct super_operations default_op;
+
+        if (s) {
+                memset(s, 0, sizeof(struct super_block));
+                if (security_sb_alloc(s)) {
+                        kfree(s);
+                        s = NULL;
+                        goto out;
+                }
+                INIT_LIST_HEAD(&s->s_dirty);
+                INIT_LIST_HEAD(&s->s_io);
+                INIT_LIST_HEAD(&s->s_files);
+                INIT_LIST_HEAD(&s->s_instances);
+                INIT_HLIST_HEAD(&s->s_anon);
+                INIT_LIST_HEAD(&s->s_inodes);
+                init_rwsem(&s->s_umount);
+                sema_init(&s->s_lock, 1);
+                down_write(&s->s_umount);
+                s->s_count = S_BIAS;
+                atomic_set(&s->s_active, 1);
+                sema_init(&s->s_vfs_rename_sem,1);
+                sema_init(&s->s_dquot.dqio_sem, 1);
+                sema_init(&s->s_dquot.dqonoff_sem, 1);
+                init_rwsem(&s->s_dquot.dqptr_sem);
+                init_waitqueue_head(&s->s_wait_unfrozen);
+                s->s_maxbytes = MAX_NON_LFS;
+                s->dq_op = sb_dquot_ops;
+                s->s_qcop = sb_quotactl_ops;
+                s->s_op = &default_op;
+                s->s_time_gran = 1000000000;
+        }
+out:
+        return s;
+}
+
+/**
+ *      destroy_super   -       frees a superblock
+ *      @s: superblock to free
+ *
+ *      Frees a superblock.
+ */
+static inline void destroy_super(struct super_block *s)
+{
+        security_sb_free(s);
+        kfree(s);
+}
+
+/* Superblock refcounting  */
+
+/*
+ * Drop a superblock's refcount.  Returns non-zero if the superblock was
+ * destroyed.  The caller must hold sb_lock.
+ */
+int __put_super(struct super_block *sb)
+{
+        int ret = 0;
+
+        if (!--sb->s_count) {
+                destroy_super(sb);
+                ret = 1;
+        }
+        return ret;
+}
+
+/*
+ * Drop a superblock's refcount.
+ * Returns non-zero if the superblock is about to be destroyed and
+ * at least is already removed from super_blocks list, so if we are
+ * making a loop through super blocks then we need to restart.
+ * The caller must hold sb_lock.
+ */
+int __put_super_and_need_restart(struct super_block *sb)
+{
+        /* check for race with generic_shutdown_super() */
+        if (list_empty(&sb->s_list)) {
+                /* super block is removed, need to restart... */
+                __put_super(sb);
+                return 1;
+        }
+        /* can't be the last, since s_list is still in use */
+        sb->s_count--;
+        BUG_ON(sb->s_count == 0);
+        return 0;
+}
+
+/**
+ *      put_super       -       drop a temporary reference to superblock
+ *      @sb: superblock in question
+ *
+ *      Drops a temporary reference, frees superblock if there's no
+ *      references left.
+ */
+static void put_super(struct super_block *sb)
+{
+        spin_lock(&sb_lock);
+        __put_super(sb);
+        spin_unlock(&sb_lock);
+}
+
+
+/**
+ *      deactivate_super        -       drop an active reference to superblock
+ *      @s: superblock to deactivate
+ *
+ *      Drops an active reference to superblock, acquiring a temprory one if
+ *      there is no active references left.  In that case we lock superblock,
+ *      tell fs driver to shut it down and drop the temporary reference we
+ *      had just acquired.
+ */
+void deactivate_super(struct super_block *s)
+{
+        struct file_system_type *fs = s->s_type;
+        if (atomic_dec_and_lock(&s->s_active, &sb_lock)) {
+                s->s_count -= S_BIAS-1;
+                spin_unlock(&sb_lock);
+                down_write(&s->s_umount);
+                fs->kill_sb(s);
+                put_filesystem(fs);
+                put_super(s);
+        }
+}
+
+EXPORT_SYMBOL(deactivate_super);
+
+/**
+ *      grab_super - acquire an active reference
+ *      @s: reference we are trying to make active
+ *
+ *      Tries to acquire an active reference.  grab_super() is used when we
+ *      had just found a superblock in super_blocks or fs_type->fs_supers
+ *      and want to turn it into a full-blown active reference.  grab_super()
+ *      is called with sb_lock held and drops it.  Returns 1 in case of
+ *      success, 0 if we had failed (superblock contents was already dead or
+ *      dying when grab_super() had been called).
+ */
+static int grab_super(struct super_block *s)
+{
+        s->s_count++;
+        spin_unlock(&sb_lock);
+        down_write(&s->s_umount);
+        if (s->s_root) {
+                spin_lock(&sb_lock);
+                if (s->s_count > S_BIAS) {
+                        atomic_inc(&s->s_active);
+                        s->s_count--;
+                        spin_unlock(&sb_lock);
+                        return 1;
+                }
+                spin_unlock(&sb_lock);
+        }
+        up_write(&s->s_umount);
+        put_super(s);
+        yield();
+        return 0;
+}
+
+/**
+ *      generic_shutdown_super  -       common helper for ->kill_sb()
+ *      @sb: superblock to kill
+ *
+ *      generic_shutdown_super() does all fs-independent work on superblock
+ *      shutdown.  Typical ->kill_sb() should pick all fs-specific objects
+ *      that need destruction out of superblock, call generic_shutdown_super()
+ *      and release aforementioned objects.  Note: dentries and inodes _are_
+ *      taken care of and do not need specific handling.
+ */
+void generic_shutdown_super(struct super_block *sb)
+{
+        struct dentry *root = sb->s_root;
+        struct super_operations *sop = sb->s_op;
+
+        if (root) {
+                sb->s_root = NULL;
+                shrink_dcache_parent(root);
+                shrink_dcache_anon(&sb->s_anon);
+                dput(root);
+                fsync_super(sb);
+                lock_super(sb);
+                sb->s_flags &= ~MS_ACTIVE;
+                /* bad name - it should be evict_inodes() */
+                invalidate_inodes(sb);
+                lock_kernel();
+
+                if (sop->write_super && sb->s_dirt)
+                        sop->write_super(sb);
+                if (sop->put_super)
+                        sop->put_super(sb);
+
+                /* Forget any remaining inodes */
+                if (invalidate_inodes(sb)) {
+                        printk("VFS: Busy inodes after unmount. "
+                           "Self-destruct in 5 seconds.  Have a nice day...\n");
+                }
+
+                unlock_kernel();
+                unlock_super(sb);
+        }
+        spin_lock(&sb_lock);
+        /* should be initialized for __put_super_and_need_restart() */
+        list_del_init(&sb->s_list);
+        list_del(&sb->s_instances);
+        spin_unlock(&sb_lock);
+        up_write(&sb->s_umount);
+}
+
+EXPORT_SYMBOL(generic_shutdown_super);
+
+/**
+ *      sget    -       find or create a superblock
+ *      @type:  filesystem type superblock should belong to
+ *      @test:  comparison callback
+ *      @set:   setup callback
+ *      @data:  argument to each of them
+ */
+struct super_block *sget(struct file_system_type *type,
+                        int (*test)(struct super_block *,void *),
+                        int (*set)(struct super_block *,void *),
+                        void *data)
+{
+        struct super_block *s = NULL;
+        struct list_head *p;
+        int err;
+
+retry:
+        spin_lock(&sb_lock);
+        if (test) list_for_each(p, &type->fs_supers) {
+                struct super_block *old;
+                old = list_entry(p, struct super_block, s_instances);
+                if (!test(old, data))
+                        continue;
+                if (!grab_super(old))
+                        goto retry;
+                if (s)
+                        destroy_super(s);
+                return old;
+        }
+        if (!s) {
+                spin_unlock(&sb_lock);
+                s = alloc_super();
+                if (!s)
+                        return ERR_PTR(-ENOMEM);
+                goto retry;
+        }
+                
+        err = set(s, data);
+        if (err) {
+                spin_unlock(&sb_lock);
+                destroy_super(s);
+                return ERR_PTR(err);
+        }
+        s->s_type = type;
+        strlcpy(s->s_id, type->name, sizeof(s->s_id));
+        list_add_tail(&s->s_list, &super_blocks);
+        list_add(&s->s_instances, &type->fs_supers);
+        spin_unlock(&sb_lock);
+        get_filesystem(type);
+        return s;
+}
+
+EXPORT_SYMBOL(sget);
+
+void drop_super(struct super_block *sb)
+{
+        up_read(&sb->s_umount);
+        put_super(sb);
+}
+
+EXPORT_SYMBOL(drop_super);
+
+static inline void write_super(struct super_block *sb)
+{
+        lock_super(sb);
+        if (sb->s_root && sb->s_dirt)
+                if (sb->s_op->write_super)
+                        sb->s_op->write_super(sb);
+        unlock_super(sb);
+}
+
+/*
+ * Note: check the dirty flag before waiting, so we don't
+ * hold up the sync while mounting a device. (The newly
+ * mounted device won't need syncing.)
+ */
+void sync_supers(void)
+{
+        struct super_block * sb;
+restart:
+        spin_lock(&sb_lock);
+        sb = sb_entry(super_blocks.next);
+        while (sb != sb_entry(&super_blocks))
+                if (sb->s_dirt) {
+                        sb->s_count++;
+                        spin_unlock(&sb_lock);
+                        down_read(&sb->s_umount);
+                        write_super(sb);
+                        drop_super(sb);
+                        goto restart;
+                } else
+                        sb = sb_entry(sb->s_list.next);
+        spin_unlock(&sb_lock);
+}
+
+/*
+ * Call the ->sync_fs super_op against all filesytems which are r/w and
+ * which implement it.
+ *
+ * This operation is careful to avoid the livelock which could easily happen
+ * if two or more filesystems are being continuously dirtied.  s_need_sync_fs
+ * is used only here.  We set it against all filesystems and then clear it as
+ * we sync them.  So redirtied filesystems are skipped.
+ *
+ * But if process A is currently running sync_filesytems and then process B
+ * calls sync_filesystems as well, process B will set all the s_need_sync_fs
+ * flags again, which will cause process A to resync everything.  Fix that with
+ * a local mutex.
+ *
+ * (Fabian) Avoid sync_fs with clean fs & wait mode 0
+ */
+void sync_filesystems(int wait)
+{
+        struct super_block *sb;
+        static DECLARE_MUTEX(mutex);
+
+        down(&mutex);           /* Could be down_interruptible */
+        spin_lock(&sb_lock);
+        for (sb = sb_entry(super_blocks.next); sb != sb_entry(&super_blocks);
+                        sb = sb_entry(sb->s_list.next)) {
+                if (!sb->s_op->sync_fs)
+                        continue;
+                if (sb->s_flags & MS_RDONLY)
+                        continue;
+                sb->s_need_sync_fs = 1;
+        }
+        spin_unlock(&sb_lock);
+
+restart:
+        spin_lock(&sb_lock);
+        for (sb = sb_entry(super_blocks.next); sb != sb_entry(&super_blocks);
+                        sb = sb_entry(sb->s_list.next)) {
+                if (!sb->s_need_sync_fs)
+                        continue;
+                sb->s_need_sync_fs = 0;
+                if (sb->s_flags & MS_RDONLY)
+                        continue;       /* hm.  Was remounted r/o meanwhile */
+                sb->s_count++;
+                spin_unlock(&sb_lock);
+                down_read(&sb->s_umount);
+                if (sb->s_root && (wait || sb->s_dirt))
+                        sb->s_op->sync_fs(sb, wait);
+                drop_super(sb);
+                goto restart;
+        }
+        spin_unlock(&sb_lock);
+        up(&mutex);
+}
+
+/**
+ *      get_super - get the superblock of a device
+ *      @bdev: device to get the superblock for
+ *      
+ *      Scans the superblock list and finds the superblock of the file system
+ *      mounted on the device given. %NULL is returned if no match is found.
+ */
+
+struct super_block * get_super(struct block_device *bdev)
+{
+        struct list_head *p;
+        if (!bdev)
+                return NULL;
+rescan:
+        spin_lock(&sb_lock);
+        list_for_each(p, &super_blocks) {
+                struct super_block *s = sb_entry(p);
+                if (s->s_bdev == bdev) {
+                        s->s_count++;
+                        spin_unlock(&sb_lock);
+                        down_read(&s->s_umount);
+                        if (s->s_root)
+                                return s;
+                        drop_super(s);
+                        goto rescan;
+                }
+        }
+        spin_unlock(&sb_lock);
+        return NULL;
+}
+
+EXPORT_SYMBOL(get_super);
+ 
+struct super_block * user_get_super(dev_t dev)
+{
+        struct list_head *p;
+
+rescan:
+        spin_lock(&sb_lock);
+        list_for_each(p, &super_blocks) {
+                struct super_block *s = sb_entry(p);
+                if (s->s_dev ==  dev) {
+                        s->s_count++;
+                        spin_unlock(&sb_lock);
+                        down_read(&s->s_umount);
+                        if (s->s_root)
+                                return s;
+                        drop_super(s);
+                        goto rescan;
+                }
+        }
+        spin_unlock(&sb_lock);
+        return NULL;
+}
+
+EXPORT_SYMBOL(user_get_super);
+
+asmlinkage long sys_ustat(unsigned dev, struct ustat __user * ubuf)
+{
+        struct super_block *s;
+        struct ustat tmp;
+        struct kstatfs sbuf;
+        int err = -EINVAL;
+
+        s = user_get_super(new_decode_dev(dev));
+        if (s == NULL)
+                goto out;
+        err = vfs_statfs(s, &sbuf);
+        drop_super(s);
+        if (err)
+                goto out;
+
+        memset(&tmp,0,sizeof(struct ustat));
+        tmp.f_tfree = sbuf.f_bfree;
+        tmp.f_tinode = sbuf.f_ffree;
+
+        err = copy_to_user(ubuf,&tmp,sizeof(struct ustat)) ? -EFAULT : 0;
+out:
+        return err;
+}
+
+/**
+ *      mark_files_ro
+ *      @sb: superblock in question
+ *
+ *      All files are marked read/only.  We don't care about pending
+ *      delete files so this should be used in 'force' mode only
+ */
+
+static void mark_files_ro(struct super_block *sb)
+{
+        struct file *f;
+
+        file_list_lock();
+        list_for_each_entry(f, &sb->s_files, f_list) {
+                if (S_ISREG(f->f_dentry->d_inode->i_mode) && file_count(f))
+                        f->f_mode &= ~FMODE_WRITE;
+        }
+        file_list_unlock();
+}
+
+/**
+ *      do_remount_sb - asks filesystem to change mount options.
+ *      @sb:    superblock in question
+ *      @flags: numeric part of options
+ *      @data:  the rest of options
+ *      @force: whether or not to force the change
+ *
+ *      Alters the mount options of a mounted file system.
+ */
+int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
+{
+        int retval;
+        
+        if (!(flags & MS_RDONLY) && bdev_read_only(sb->s_bdev))
+                return -EACCES;
+        if (flags & MS_RDONLY)
+                acct_auto_close(sb);
+        shrink_dcache_sb(sb);
+        fsync_super(sb);
+
+        /* If we are remounting RDONLY and current sb is read/write,
+           make sure there are no rw files opened */
+        if ((flags & MS_RDONLY) && !(sb->s_flags & MS_RDONLY)) {
+                if (force)
+                        mark_files_ro(sb);
+                else if (!fs_may_remount_ro(sb))
+                        return -EBUSY;
+        }
+
+        if (sb->s_op->remount_fs) {
+                lock_super(sb);
+                retval = sb->s_op->remount_fs(sb, &flags, data);
+                unlock_super(sb);
+                if (retval)
+                        return retval;
+        }
+        sb->s_flags = (sb->s_flags & ~MS_RMT_MASK) | (flags & MS_RMT_MASK);
+        return 0;
+}
+
+static void do_emergency_remount(unsigned long foo)
+{
+        struct super_block *sb;
+
+        spin_lock(&sb_lock);
+        list_for_each_entry(sb, &super_blocks, s_list) {
+                sb->s_count++;
+                spin_unlock(&sb_lock);
+                down_read(&sb->s_umount);
+                if (sb->s_root && sb->s_bdev && !(sb->s_flags & MS_RDONLY)) {
+                        /*
+                         * ->remount_fs needs lock_kernel().
+                         *
+                         * What lock protects sb->s_flags??
+                         */
+                        lock_kernel();
+                        do_remount_sb(sb, MS_RDONLY, NULL, 1);
+                        unlock_kernel();
+                }
+                drop_super(sb);
+                spin_lock(&sb_lock);
+        }
+        spin_unlock(&sb_lock);
+        printk("Emergency Remount complete\n");
+}
+
+void emergency_remount(void)
+{
+        pdflush_operation(do_emergency_remount, 0);
+}
+
+/*
+ * Unnamed block devices are dummy devices used by virtual
+ * filesystems which don't use real block-devices.  -- jrs
+ */
+
+static struct idr unnamed_dev_idr;
+static DEFINE_SPINLOCK(unnamed_dev_lock);/* protects the above */
+
+int set_anon_super(struct super_block *s, void *data)
+{
+        int dev;
+        int error;
+
+ retry:
+        if (idr_pre_get(&unnamed_dev_idr, GFP_ATOMIC) == 0)
+                return -ENOMEM;
+        spin_lock(&unnamed_dev_lock);
+        error = idr_get_new(&unnamed_dev_idr, NULL, &dev);
+        spin_unlock(&unnamed_dev_lock);
+        if (error == -EAGAIN)
+                /* We raced and lost with another CPU. */
+                goto retry;
+        else if (error)
+                return -EAGAIN;
+
+        if ((dev & MAX_ID_MASK) == (1 << MINORBITS)) {
+                spin_lock(&unnamed_dev_lock);
+                idr_remove(&unnamed_dev_idr, dev);
+                spin_unlock(&unnamed_dev_lock);
+                return -EMFILE;
+        }
+        s->s_dev = MKDEV(0, dev & MINORMASK);
+        return 0;
+}
+
+EXPORT_SYMBOL(set_anon_super);
+
+void kill_anon_super(struct super_block *sb)
+{
+        int slot = MINOR(sb->s_dev);
+
+        generic_shutdown_super(sb);
+        spin_lock(&unnamed_dev_lock);
+        idr_remove(&unnamed_dev_idr, slot);
+        spin_unlock(&unnamed_dev_lock);
+}
+
+EXPORT_SYMBOL(kill_anon_super);
+
+void __init unnamed_dev_init(void)
+{
+        idr_init(&unnamed_dev_idr);
+}
+
+void kill_litter_super(struct super_block *sb)
+{
+        if (sb->s_root)
+                d_genocide(sb->s_root);
+        kill_anon_super(sb);
+}
+
+EXPORT_SYMBOL(kill_litter_super);
+
+static int set_bdev_super(struct super_block *s, void *data)
+{
+        s->s_bdev = data;
+        s->s_dev = s->s_bdev->bd_dev;
+        return 0;
+}
+
+static int test_bdev_super(struct super_block *s, void *data)
+{
+        return (void *)s->s_bdev == data;
+}
+
+static void bdev_uevent(struct block_device *bdev, enum kobject_action action)
+{
+        if (bdev->bd_disk) {
+                if (bdev->bd_part)
+                        kobject_uevent(&bdev->bd_part->kobj, action, NULL);
+                else
+                        kobject_uevent(&bdev->bd_disk->kobj, action, NULL);
+        }
+}
+
+struct super_block *get_sb_bdev(struct file_system_type *fs_type,
+        int flags, const char *dev_name, void *data,
+        int (*fill_super)(struct super_block *, void *, int))
+{
+        struct block_device *bdev;
+        struct super_block *s;
+        int error = 0;
+
+        bdev = open_bdev_excl(dev_name, flags, fs_type);
+        if (IS_ERR(bdev))
+                return (struct super_block *)bdev;
+
+        /*
+         * once the super is inserted into the list by sget, s_umount
+         * will protect the lockfs code from trying to start a snapshot
+         * while we are mounting
+         */
+        down(&bdev->bd_mount_sem);
+        s = sget(fs_type, test_bdev_super, set_bdev_super, bdev);
+        up(&bdev->bd_mount_sem);
+        if (IS_ERR(s))
+                goto out;
+
+        if (s->s_root) {
+                if ((flags ^ s->s_flags) & MS_RDONLY) {
+                        up_write(&s->s_umount);
+                        deactivate_super(s);
+                        s = ERR_PTR(-EBUSY);
+                }
+                goto out;
+        } else {
+                char b[BDEVNAME_SIZE];
+
+                s->s_flags = flags;
+                strlcpy(s->s_id, bdevname(bdev, b), sizeof(s->s_id));
+                s->s_old_blocksize = block_size(bdev);
+                sb_set_blocksize(s, s->s_old_blocksize);
+                error = fill_super(s, data, flags & MS_VERBOSE ? 1 : 0);
+                if (error) {
+                        up_write(&s->s_umount);
+                        deactivate_super(s);
+                        s = ERR_PTR(error);
+                } else {
+                        s->s_flags |= MS_ACTIVE;
+                        bdev_uevent(bdev, KOBJ_MOUNT);
+                }
+        }
+
+        return s;
+
+out:
+        close_bdev_excl(bdev);
+        return s;
+}
+
+EXPORT_SYMBOL(get_sb_bdev);
+
+void kill_block_super(struct super_block *sb)
+{
+        struct block_device *bdev = sb->s_bdev;
+
+        bdev_uevent(bdev, KOBJ_UMOUNT);
+        generic_shutdown_super(sb);
+        sync_blockdev(bdev);
+        close_bdev_excl(bdev);
+}
+
+EXPORT_SYMBOL(kill_block_super);
+
+struct super_block *get_sb_nodev(struct file_system_type *fs_type,
+        int flags, void *data,
+        int (*fill_super)(struct super_block *, void *, int))
+{
+        int error;
+        struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL);
+
+        if (IS_ERR(s))
+                return s;
+
+        s->s_flags = flags;
+
+        error = fill_super(s, data, flags & MS_VERBOSE ? 1 : 0);
+        if (error) {
+                up_write(&s->s_umount);
+                deactivate_super(s);
+                return ERR_PTR(error);
+        }
+        s->s_flags |= MS_ACTIVE;
+        return s;
+}
+
+EXPORT_SYMBOL(get_sb_nodev);
+
+static int compare_single(struct super_block *s, void *p)
+{
+        return 1;
+}
+
+struct super_block *get_sb_single(struct file_system_type *fs_type,
+        int flags, void *data,
+        int (*fill_super)(struct super_block *, void *, int))
+{
+        struct super_block *s;
+        int error;
+
+        s = sget(fs_type, compare_single, set_anon_super, NULL);
+        if (IS_ERR(s))
+                return s;
+        if (!s->s_root) {
+                s->s_flags = flags;
+                error = fill_super(s, data, flags & MS_VERBOSE ? 1 : 0);
+                if (error) {
+                        up_write(&s->s_umount);
+                        deactivate_super(s);
+                        return ERR_PTR(error);
+                }
+                s->s_flags |= MS_ACTIVE;
+        }
+        do_remount_sb(s, flags, data, 0);
+        return s;
+}
+
+EXPORT_SYMBOL(get_sb_single);
+
+struct vfsmount *
+do_kern_mount(const char *fstype, int flags, const char *name, void *data)
+{
+        struct file_system_type *type = get_fs_type(fstype);
+        struct super_block *sb = ERR_PTR(-ENOMEM);
+        struct vfsmount *mnt;
+        int error;
+        char *secdata = NULL;
+
+        if (!type)
+                return ERR_PTR(-ENODEV);
+
+        mnt = alloc_vfsmnt(name);
+        if (!mnt)
+                goto out;
+
+        if (data) {
+                secdata = alloc_secdata();
+                if (!secdata) {
+                        sb = ERR_PTR(-ENOMEM);
+                        goto out_mnt;
+                }
+
+                error = security_sb_copy_data(type, data, secdata);
+                if (error) {
+                        sb = ERR_PTR(error);
+                        goto out_free_secdata;
+                }
+        }
+
+        sb = type->get_sb(type, flags, name, data);
+        if (IS_ERR(sb))
+                goto out_free_secdata;
+        error = security_sb_kern_mount(sb, secdata);
+        if (error)
+                goto out_sb;
+        mnt->mnt_sb = sb;
+        mnt->mnt_root = dget(sb->s_root);
+        mnt->mnt_mountpoint = sb->s_root;
+        mnt->mnt_parent = mnt;
+        mnt->mnt_namespace = current->namespace;
+        up_write(&sb->s_umount);
+        put_filesystem(type);
+        return mnt;
+out_sb:
+        up_write(&sb->s_umount);
+        deactivate_super(sb);
+        sb = ERR_PTR(error);
+out_free_secdata:
+        free_secdata(secdata);
+out_mnt:
+        free_vfsmnt(mnt);
+out:
+        put_filesystem(type);
+        return (struct vfsmount *)sb;
+}
+
+EXPORT_SYMBOL_GPL(do_kern_mount);
+
+struct vfsmount *kern_mount(struct file_system_type *type)
+{
+        return do_kern_mount(type->name, 0, type->name, NULL);
+}
+
+EXPORT_SYMBOL(kern_mount);