patch-2.4.10 linux/fs/super.c

• Lines: 770
• Date: Sat Sep 22 20:35:43 2001
• Orig file: v2.4.9/linux/fs/super.c
• Orig date: Sun Aug 12 13:28:00 2001

diff -u --recursive --new-file v2.4.9/linux/fs/super.c linux/fs/super.c
@@ -122,6 +122,7 @@
 		return -EINVAL;
 	if (fs->next)
 		return -EBUSY;
+	INIT_LIST_HEAD(&fs->fs_supers);
 	write_lock(&file_systems_lock);
 	p = find_filesystem(fs->name);
 	if (*p)
@@ -288,8 +289,8 @@
 {
 	unsigned long tmp = ((unsigned long) mnt / L1_CACHE_BYTES);
 	tmp += ((unsigned long) dentry / L1_CACHE_BYTES);
-	tmp = tmp + (tmp >> hash_mask);
-	return tmp & hash_bits;
+	tmp = tmp + (tmp >> hash_bits);
+	return tmp & hash_mask;
 }
 
 struct vfsmount *alloc_vfsmnt(void)
@@ -387,8 +388,6 @@
 	spin_lock(&dcache_lock);
 	list_add(&mnt->mnt_list, vfsmntlist.prev);
 	spin_unlock(&dcache_lock);
-	if (sb->s_type->fs_flags & FS_SINGLE)
-		get_filesystem(sb->s_type);
 out:
 	return mnt;
 }
@@ -411,6 +410,7 @@
 	mnt->mnt_root = dget(root);
 	mnt->mnt_mountpoint = mnt->mnt_root;
 	mnt->mnt_parent = mnt;
+	mnt->mnt_flags = old->mnt_flags;
 
 	atomic_inc(&sb->s_active);
 out:
@@ -419,6 +419,9 @@
 
 static int graft_tree(struct vfsmount *mnt, struct nameidata *nd)
 {
+	if (mnt->mnt_sb->s_flags & MS_NOUSER)
+		return -EINVAL;
+
 	if (S_ISDIR(nd->dentry->d_inode->i_mode) !=
 	      S_ISDIR(mnt->mnt_root->d_inode->i_mode))
 		return -ENOTDIR;
@@ -435,8 +438,6 @@
 	list_add(&mnt->mnt_list, vfsmntlist.prev);
 	spin_unlock(&dcache_lock);
 	up(&nd->dentry->d_inode->i_zombie);
-	if (mnt->mnt_sb->s_type->fs_flags & FS_SINGLE)
-		get_filesystem(mnt->mnt_sb->s_type);
 	mntget(mnt);
 	return 0;
 fail:
@@ -520,16 +521,17 @@
 	int flag;
 	char *str;
 } fs_info[] = {
-	{ MS_NOEXEC, ",noexec" },
-	{ MS_NOSUID, ",nosuid" },
-	{ MS_NODEV, ",nodev" },
 	{ MS_SYNCHRONOUS, ",sync" },
 	{ MS_MANDLOCK, ",mand" },
 	{ MS_NOATIME, ",noatime" },
 	{ MS_NODIRATIME, ",nodiratime" },
-#ifdef MS_NOSUB			/* Can't find this except in mount.c */
-	{ MS_NOSUB, ",nosub" },
-#endif
+	{ 0, NULL }
+};
+
+static struct proc_fs_info mnt_info[] = {
+	{ MNT_NOSUID, ",nosuid" },
+	{ MNT_NODEV, ",nodev" },
+	{ MNT_NOEXEC, ",noexec" },
 	{ 0, NULL }
 };
 
@@ -580,6 +582,10 @@
 			if (tmp->mnt_sb->s_flags & fs_infop->flag)
 				MANGLE(fs_infop->str);
 		}
+		for (fs_infop = mnt_info; fs_infop->flag; fs_infop++) {
+			if (tmp->mnt_flags & fs_infop->flag)
+				MANGLE(fs_infop->str);
+		}
 		if (!strcmp("nfs", tmp->mnt_sb->s_type->name)) {
 			nfss = &tmp->mnt_sb->u.nfs_sb.s_server;
 			len += sprintf(buf+len, ",v%d", nfss->rpc_ops->version);
@@ -669,6 +675,7 @@
 
 static void put_super(struct super_block *sb)
 {
+	atomic_dec(&sb->s_active);
 	up_write(&sb->s_umount);
 	__put_super(sb);
 }
@@ -735,10 +742,6 @@
 	s = find_super(dev);
 	if (s) {
 		spin_unlock(&sb_lock);
-		/* Yes, it sucks. As soon as we get refcounting... */
-		/* Almost there - next two lines will go away RSN */
-		lock_super(s);
-		unlock_super(s);
 		down_read(&s->s_umount);
 		if (s->s_root)
 			return s;
@@ -792,6 +795,7 @@
 		INIT_LIST_HEAD(&s->s_dirty);
 		INIT_LIST_HEAD(&s->s_locked_inodes);
 		INIT_LIST_HEAD(&s->s_files);
+		INIT_LIST_HEAD(&s->s_instances);
 		init_rwsem(&s->s_umount);
 		sema_init(&s->s_lock, 1);
 		s->s_count = 1;
@@ -819,7 +823,10 @@
 	s->s_type = type;
 	spin_lock(&sb_lock);
 	list_add (&s->s_list, super_blocks.prev);
+	list_add (&s->s_instances, &type->fs_supers);
+	s->s_count += S_BIAS;
 	spin_unlock(&sb_lock);
+	down_write(&s->s_umount);
 	lock_super(s);
 	if (!type->read_super(s, data, silent))
 		goto out_fail;
@@ -835,11 +842,12 @@
 	s->s_bdev = 0;
 	s->s_type = NULL;
 	unlock_super(s);
-	atomic_dec(&s->s_active);
 	spin_lock(&sb_lock);
 	list_del(&s->s_list);
+	list_del(&s->s_instances);
+	s->s_count -= S_BIAS;
 	spin_unlock(&sb_lock);
-	__put_super(s);
+	put_super(s);
 	return NULL;
 }
 
@@ -871,16 +879,38 @@
 			kdevname(dev));
 }
 
+static int grab_super(struct super_block *sb)
+{
+	sb->s_count++;
+	atomic_inc(&sb->s_active);
+	spin_unlock(&sb_lock);
+	down_write(&sb->s_umount);
+	if (sb->s_root) {
+		spin_lock(&sb_lock);
+		if (sb->s_count > S_BIAS) {
+			sb->s_count--;
+			spin_unlock(&sb_lock);
+			return 1;
+		}
+		spin_unlock(&sb_lock);
+	}
+	put_super(sb);
+	return 0;
+}
+
 static struct super_block *get_sb_bdev(struct file_system_type *fs_type,
 	char *dev_name, int flags, void * data)
 {
 	struct inode *inode;
 	struct block_device *bdev;
 	struct block_device_operations *bdops;
-	struct super_block * sb;
+	struct super_block * s;
 	struct nameidata nd;
+	struct list_head *p;
 	kdev_t dev;
 	int error = 0;
+	mode_t mode = FMODE_READ; /* we always need it ;-) */
+
 	/* What device it is? */
 	if (!dev_name || !*dev_name)
 		return ERR_PTR(-EINVAL);
@@ -893,61 +923,85 @@
 	if (!S_ISBLK(inode->i_mode))
 		goto out;
 	error = -EACCES;
-	if (IS_NODEV(inode))
+	if (nd.mnt->mnt_flags & MNT_NODEV)
 		goto out;
+	bd_acquire(inode);
 	bdev = inode->i_bdev;
 	bdops = devfs_get_ops ( devfs_get_handle_from_inode (inode) );
 	if (bdops) bdev->bd_op = bdops;
 	/* Done with lookups, semaphore down */
-	down(&mount_sem);
 	dev = to_kdev_t(bdev->bd_dev);
-	sb = get_super(dev);
-	if (sb) {
-		if (fs_type == sb->s_type &&
-		    ((flags ^ sb->s_flags) & MS_RDONLY) == 0) {
-/*
- * We are heavily relying on mount_sem here. We _will_ get rid of that
- * ugliness RSN (and then atomicity of ->s_active will play), but first
- * we need to get rid of "reuse" branch of get_empty_super() and that
- * requires reference counters. Chicken and egg problem, but fortunately
- * we can use the fact that right now all accesses to ->s_active are
- * under mount_sem.
- */
-			if (atomic_read(&sb->s_active)) {
-				spin_lock(&sb_lock);
-				sb->s_count--;
-				spin_unlock(&sb_lock);
-			}
-			atomic_inc(&sb->s_active);
-			up_read(&sb->s_umount);
-			path_release(&nd);
-			return sb;
-		}
-		drop_super(sb);
-	} else {
-		mode_t mode = FMODE_READ; /* we always need it ;-) */
-		if (!(flags & MS_RDONLY))
-			mode |= FMODE_WRITE;
-		error = blkdev_get(bdev, mode, 0, BDEV_FS);
-		if (error)
-			goto out;
-		check_disk_change(dev);
-		error = -EACCES;
-		if (!(flags & MS_RDONLY) && is_read_only(dev))
+	if (!(flags & MS_RDONLY))
+		mode |= FMODE_WRITE;
+	error = blkdev_get(bdev, mode, 0, BDEV_FS);
+	if (error)
+		goto out;
+	check_disk_change(dev);
+	error = -EACCES;
+	if (!(flags & MS_RDONLY) && is_read_only(dev))
+		goto out1;
+
+	error = -ENOMEM;
+	s = alloc_super();
+	if (!s)
+		goto out1;
+	down_write(&s->s_umount);
+
+	error = -EBUSY;
+restart:
+	spin_lock(&sb_lock);
+
+	list_for_each(p, &super_blocks) {
+		struct super_block *old = sb_entry(p);
+		if (old->s_dev != dev)
+			continue;
+		if (old->s_type != fs_type ||
+		    ((flags ^ old->s_flags) & MS_RDONLY)) {
+			spin_unlock(&sb_lock);
+			put_super(s);
 			goto out1;
-		error = -EINVAL;
-		sb = read_super(dev, bdev, fs_type, flags, data, 0);
-		if (sb) {
-			get_filesystem(fs_type);
-			path_release(&nd);
-			return sb;
 		}
-out1:
+		if (!grab_super(old))
+			goto restart;
+		put_super(s);
 		blkdev_put(bdev, BDEV_FS);
+		path_release(&nd);
+		return old;
 	}
+	s->s_dev = dev;
+	s->s_bdev = bdev;
+	s->s_flags = flags;
+	s->s_type = fs_type;
+	list_add (&s->s_list, super_blocks.prev);
+	list_add (&s->s_instances, &fs_type->fs_supers);
+	s->s_count += S_BIAS;
+
+	spin_unlock(&sb_lock);
+
+	error = -EINVAL;
+	lock_super(s);
+	if (!fs_type->read_super(s, data, 0))
+		goto out_fail;
+	unlock_super(s);
+	get_filesystem(fs_type);
+	path_release(&nd);
+	return s;
+
+out_fail:
+	s->s_dev = 0;
+	s->s_bdev = 0;
+	s->s_type = NULL;
+	unlock_super(s);
+	spin_lock(&sb_lock);
+	list_del(&s->s_list);
+	list_del(&s->s_instances);
+	s->s_count -= S_BIAS;
+	spin_unlock(&sb_lock);
+	put_super(s);
+out1:
+	blkdev_put(bdev, BDEV_FS);
 out:
 	path_release(&nd);
-	up(&mount_sem);
 	return ERR_PTR(error);
 }
 
@@ -956,7 +1010,6 @@
 {
 	kdev_t dev;
 	int error = -EMFILE;
-	down(&mount_sem);
 	dev = get_unnamed_dev();
 	if (dev) {
 		struct super_block * sb;
@@ -968,25 +1021,65 @@
 		}
 		put_unnamed_dev(dev);
 	}
-	up(&mount_sem);
 	return ERR_PTR(error);
 }
 
 static struct super_block *get_sb_single(struct file_system_type *fs_type,
 	int flags, void *data)
 {
-	struct super_block * sb;
+	struct super_block * s = alloc_super();
+	if (!s)
+		return ERR_PTR(-ENOMEM);
+	down_write(&s->s_umount);
 	/*
 	 * Get the superblock of kernel-wide instance, but
 	 * keep the reference to fs_type.
 	 */
-	down(&mount_sem);
-	sb = fs_type->kern_mnt->mnt_sb;
-	if (!sb)
-		BUG();
-	atomic_inc(&sb->s_active);
-	do_remount_sb(sb, flags, data);
-	return sb;
+retry:
+	spin_lock(&sb_lock);
+	if (!list_empty(&fs_type->fs_supers)) {
+		struct super_block *old;
+		old = list_entry(fs_type->fs_supers.next, struct super_block,
+				s_instances);
+		if (!grab_super(old))
+			goto retry;
+		put_super(s);
+		do_remount_sb(old, flags, data);
+		return old;
+	} else {
+		kdev_t dev = get_unnamed_dev();
+		if (!dev) {
+			put_super(s);
+			return ERR_PTR(-EMFILE);
+		}
+		s->s_dev = dev;
+		s->s_flags = flags;
+		s->s_type = fs_type;
+		list_add (&s->s_list, super_blocks.prev);
+		list_add (&s->s_instances, &fs_type->fs_supers);
+		s->s_count += S_BIAS;
+		spin_unlock(&sb_lock);
+		lock_super(s);
+		if (!fs_type->read_super(s, data, 0))
+			goto out_fail;
+		unlock_super(s);
+		get_filesystem(fs_type);
+		return s;
+
+	out_fail:
+		s->s_dev = 0;
+		s->s_bdev = 0;
+		s->s_type = NULL;
+		unlock_super(s);
+		spin_lock(&sb_lock);
+		list_del(&s->s_list);
+		list_del(&s->s_instances);
+		s->s_count -= S_BIAS;
+		spin_unlock(&sb_lock);
+		put_super(s);
+		put_unnamed_dev(dev);
+		return ERR_PTR(-EINVAL);
+	}
 }
 
 static void kill_super(struct super_block *sb)
@@ -997,8 +1090,12 @@
 	struct file_system_type *fs = sb->s_type;
 	struct super_operations *sop = sb->s_op;
 
-	if (!atomic_dec_and_test(&sb->s_active))
+	if (!atomic_dec_and_lock(&sb->s_active, &sb_lock))
 		return;
+
+	sb->s_count -= S_BIAS;
+	spin_unlock(&sb_lock);
+
 	down_write(&sb->s_umount);
 	lock_kernel();
 	sb->s_root = NULL;
@@ -1030,14 +1127,15 @@
 	sb->s_type = NULL;
 	unlock_super(sb);
 	unlock_kernel();
-	if (bdev) {
+	if (bdev)
 		blkdev_put(bdev, BDEV_FS);
-		bdput(bdev);
-	} else
+	else
 		put_unnamed_dev(dev);
 	spin_lock(&sb_lock);
 	list_del(&sb->s_list);
+	list_del(&sb->s_instances);
 	spin_unlock(&sb_lock);
+	atomic_inc(&sb->s_active);
 	put_super(sb);
 }
 
@@ -1056,7 +1154,7 @@
 	if (flags & MS_RDONLY)
 		acct_auto_close(sb->s_dev);
 	shrink_dcache_sb(sb);
-	fsync_dev(sb->s_dev);
+	fsync_super(sb);
 	/* If we are remounting RDONLY, make sure there are no rw files open */
 	if ((flags & MS_RDONLY) && !(sb->s_flags & MS_RDONLY))
 		if (!fs_may_remount_ro(sb))
@@ -1079,34 +1177,6 @@
 	return 0;
 }
 
-struct vfsmount *kern_mount(struct file_system_type *type)
-{
-	struct super_block *sb;
-	struct vfsmount *mnt = alloc_vfsmnt();
-	kdev_t dev;
-
-	if (!mnt)
-		return ERR_PTR(-ENOMEM);
-
-	dev = get_unnamed_dev();
-	if (!dev) {
-		kmem_cache_free(mnt_cache, mnt);
-		return ERR_PTR(-EMFILE);
-	}
-	sb = read_super(dev, NULL, type, 0, NULL, 0);
-	if (!sb) {
-		put_unnamed_dev(dev);
-		kmem_cache_free(mnt_cache, mnt);
-		return ERR_PTR(-EINVAL);
-	}
-	mnt->mnt_sb = sb;
-	mnt->mnt_root = dget(sb->s_root);
-	mnt->mnt_mountpoint = mnt->mnt_root;
-	mnt->mnt_parent = mnt;
-	type->kern_mnt = mnt;
-	return mnt;
-}
-
 /*
  * Doesn't take quota and stuff into account. IOW, in some cases it will
  * give false negatives. The main reason why it's here is that we need
@@ -1140,8 +1210,11 @@
 		 * Special case for "unmounting" root ...
 		 * we just try to remount it readonly.
 		 */
-		if (!(sb->s_flags & MS_RDONLY))
+		if (!(sb->s_flags & MS_RDONLY)) {
+			down_write(&sb->s_umount);
 			retval = do_remount_sb(sb, MS_RDONLY, 0);
+			up_write(&sb->s_umount);
+		}
 		return retval;
 	}
 
@@ -1152,8 +1225,6 @@
 			spin_unlock(&dcache_lock);
 			return -EBUSY;
 		}
-		if (sb->s_type->fs_flags & FS_SINGLE)
-			put_filesystem(sb->s_type);
 		detach_mnt(mnt, &parent_nd);
 		list_del(&mnt->mnt_list);
 		spin_unlock(&dcache_lock);
@@ -1315,84 +1386,112 @@
  * on it - tough luck.
  */
 
-static int do_remount(struct nameidata *nd, int flags, char *data)
+static int do_remount(struct nameidata *nd,int flags,int mnt_flags,char *data)
 {
+	int err;
+	struct super_block * sb = nd->mnt->mnt_sb;
+
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
 
 	if (nd->dentry != nd->mnt->mnt_root)
 		return -EINVAL;
 
-	return do_remount_sb(nd->mnt->mnt_sb, flags, data);
+	down_write(&sb->s_umount);
+	err = do_remount_sb(sb, flags, data);
+	if (!err)
+		nd->mnt->mnt_flags=mnt_flags;
+	up_write(&sb->s_umount);
+	return err;
 }
 
-static int do_add_mount(struct nameidata *nd, char *type, int flags,
-			char *name, void *data)
+struct vfsmount *do_kern_mount(char *type, int flags, char *name, void *data)
 {
 	struct file_system_type * fstype;
 	struct vfsmount *mnt = NULL;
 	struct super_block *sb;
-	int retval = 0;
 
 	if (!type || !memchr(type, 0, PAGE_SIZE))
-		return -EINVAL;
+		return ERR_PTR(-EINVAL);
 
 	/* we need capabilities... */
 	if (!capable(CAP_SYS_ADMIN))
-		return -EPERM;
+		return ERR_PTR(-EPERM);
 
 	/* ... filesystem driver... */
 	fstype = get_fs_type(type);
 	if (!fstype)		
-		return -ENODEV;
+		return ERR_PTR(-ENODEV);
 
 	/* ... allocated vfsmount... */
-	retval = -ENOMEM;
 	mnt = alloc_vfsmnt();
-	if (!mnt)
+	if (!mnt) {
+		mnt = ERR_PTR(-ENOMEM);
 		goto fs_out;
+	}
 	if (name) {
 		mnt->mnt_devname = kmalloc(strlen(name)+1, GFP_KERNEL);
 		if (mnt->mnt_devname)
 			strcpy(mnt->mnt_devname, name);
 	}
 
-	/* get superblock, locks mount_sem on success */
-	if (fstype->fs_flags & FS_NOMOUNT)
-		sb = ERR_PTR(-EINVAL);
-	else if (fstype->fs_flags & FS_REQUIRES_DEV)
+	/* get locked superblock */
+	if (fstype->fs_flags & FS_REQUIRES_DEV)
 		sb = get_sb_bdev(fstype, name, flags, data);
 	else if (fstype->fs_flags & FS_SINGLE)
 		sb = get_sb_single(fstype, flags, data);
 	else
 		sb = get_sb_nodev(fstype, flags, data);
 
-	retval = PTR_ERR(sb);
 	if (IS_ERR(sb)) {
 		if (mnt->mnt_devname)
 			kfree(mnt->mnt_devname);
 		kmem_cache_free(mnt_cache, mnt);
+		mnt = (struct vfsmount *)sb;
 		goto fs_out;
 	}
+	if (fstype->fs_flags & FS_NOMOUNT)
+		sb->s_flags |= MS_NOUSER;
 
 	mnt->mnt_sb = sb;
 	mnt->mnt_root = dget(sb->s_root);
 	mnt->mnt_mountpoint = mnt->mnt_root;
 	mnt->mnt_parent = mnt;
+	up_write(&sb->s_umount);
+fs_out:
+	put_filesystem(fstype);
+	return mnt;
+}
 
+struct vfsmount *kern_mount(struct file_system_type *type)
+{
+	return do_kern_mount((char *)type->name, 0, (char *)type->name, NULL);
+}
+
+static int do_add_mount(struct nameidata *nd, char *type, int flags,
+			int mnt_flags, char *name, void *data)
+{
+	struct vfsmount *mnt = do_kern_mount(type, flags, name, data);
+	int retval = PTR_ERR(mnt);
+
+	if (IS_ERR(mnt))
+		goto out;
+
+	mnt->mnt_flags = mnt_flags;
+
+	down(&mount_sem);
 	/* Something was mounted here while we slept */
 	while(d_mountpoint(nd->dentry) && follow_down(&nd->mnt, &nd->dentry))
 		;
 
 	/* Refuse the same filesystem on the same mount point */
-	if (nd->mnt->mnt_sb == sb && nd->mnt->mnt_root == nd->dentry)
+	if (nd->mnt->mnt_sb == mnt->mnt_sb && nd->mnt->mnt_root == nd->dentry)
 		retval = -EBUSY;
 	else
 		retval = graft_tree(mnt, nd);
-	mntput(mnt);
 	up(&mount_sem);
-fs_out:
-	put_filesystem(fstype);
+	mntput(mnt);
+out:
 	return retval;
 }
 
@@ -1448,6 +1547,7 @@
 {
 	struct nameidata nd;
 	int retval = 0;
+	int mnt_flags = 0;
 
 	/* Discard magic */
 	if ((flags & MS_MGC_MSK) == MS_MGC_VAL)
@@ -1460,6 +1560,15 @@
 	if (dev_name && !memchr(dev_name, 0, PAGE_SIZE))
 		return -EINVAL;
 
+	/* Separate the per-mountpoint flags */
+	if (flags & MS_NOSUID)
+		mnt_flags |= MNT_NOSUID;
+	if (flags & MS_NODEV)
+		mnt_flags |= MNT_NODEV;
+	if (flags & MS_NOEXEC)
+		mnt_flags |= MNT_NOEXEC;
+	flags &= ~(MS_NOSUID|MS_NOEXEC|MS_NODEV);
+
 	/* ... and get the mountpoint */
 	if (path_init(dir_name, LOOKUP_FOLLOW|LOOKUP_POSITIVE, &nd))
 		retval = path_walk(dir_name, &nd);
@@ -1467,12 +1576,12 @@
 		return retval;
 
 	if (flags & MS_REMOUNT)
-		retval = do_remount(&nd, flags&~MS_REMOUNT,
+		retval = do_remount(&nd, flags&~MS_REMOUNT, mnt_flags,
 				  (char *)data_page);
 	else if (flags & MS_BIND)
 		retval = do_loopback(&nd, dev_name);
 	else
-		retval = do_add_mount(&nd, type_page, flags,
+		retval = do_add_mount(&nd, type_page, flags, mnt_flags,
 				      dev_name, data_page);
 	path_release(&nd);
 	return retval;
@@ -1607,6 +1716,7 @@
 	if (!ROOT_DEV)
 		panic("I have no root and I want to scream");
 
+retry:
 	bdev = bdget(kdev_t_to_nr(ROOT_DEV));
 	if (!bdev)
 		panic(__FUNCTION__ ": unable to allocate root device");
@@ -1618,7 +1728,7 @@
 	retval = blkdev_get(bdev, mode, 0, BDEV_FS);
 	if (retval == -EROFS) {
 		root_mountflags |= MS_RDONLY;
-		retval = blkdev_get(bdev, FMODE_READ, 0, BDEV_FS);
+		goto retry;
 	}
 	if (retval) {
 	        /*
@@ -1639,6 +1749,7 @@
 		fs_type = sb->s_type;
 		atomic_inc(&sb->s_active);
 		up_read(&sb->s_umount);
+		down_write(&sb->s_umount);
 		goto mount_it;
 	}
 
@@ -1659,6 +1770,8 @@
 	panic("VFS: Unable to mount root fs on %s", kdevname(ROOT_DEV));
 
 mount_it:
+	/* FIXME */
+	up_write(&sb->s_umount);
 	printk ("VFS: Mounted root (%s filesystem)%s.\n",
 		fs_type->name,
 		(sb->s_flags & MS_RDONLY) ? " readonly" : "");
@@ -1863,13 +1976,18 @@
 		int blivet;
 		struct block_device *ramdisk = old_rootmnt->mnt_sb->s_bdev;
 
+		atomic_inc(&ramdisk->bd_count);
 		blivet = blkdev_get(ramdisk, FMODE_READ, 0, BDEV_FS);
 		printk(KERN_NOTICE "Trying to unmount old root ... ");
 		if (!blivet) {
 			blivet = do_umount(old_rootmnt, 0);
 			mntput(old_rootmnt);
 			if (!blivet) {
-				ioctl_by_bdev(ramdisk, BLKFLSBUF, 0);
+				int ioctl_err;
+
+				ioctl_err = ioctl_by_bdev(ramdisk, BLKFLSBUF, 0);
+				if (ioctl_err)
+					printk("failed to release ramdisk %d...", ioctl_err);
 				printk("okay\n");
 				error = 0;
 			}
@@ -1906,27 +2024,36 @@
 		;
 
 	do {
-		unsigned long tmp;
-
-		nr_hash = (1UL << order) * PAGE_SIZE /
-			sizeof(struct list_head);
-		hash_mask = (nr_hash - 1);
-
-		tmp = nr_hash;
-		hash_bits = 0;
-		while ((tmp >>= 1UL) != 0UL)
-			hash_bits++;
-
 		mount_hashtable = (struct list_head *)
 			__get_free_pages(GFP_ATOMIC, order);
 	} while (mount_hashtable == NULL && --order >= 0);
 
-	printk("Mount-cache hash table entries: %d (order: %ld, %ld bytes)\n",
-			nr_hash, order, (PAGE_SIZE << order));
-
 	if (!mount_hashtable)
 		panic("Failed to allocate mount hash table\n");
 
+	/*
+	 * Find the power-of-two list-heads that can fit into the allocation..
+	 * We don't guarantee that "sizeof(struct list_head)" is necessarily
+	 * a power-of-two.
+	 */
+	nr_hash = (1UL << order) * PAGE_SIZE / sizeof(struct list_head);
+	hash_bits = 0;
+	do {
+		hash_bits++;
+	} while ((nr_hash >> hash_bits) != 0);
+	hash_bits--;
+
+	/*
+	 * Re-calculate the actual number of entries and the mask
+	 * from the number of bits we can fit.
+	 */
+	nr_hash = 1UL << hash_bits;
+	hash_mask = nr_hash-1;
+
+	printk("Mount-cache hash table entries: %d (order: %ld, %ld bytes)\n",
+			nr_hash, order, (PAGE_SIZE << order));
+
+	/* And initialize the newly allocated array */
 	d = mount_hashtable;
 	i = nr_hash;
 	do {