diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 3b6f852..33ab165 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -505,7 +505,7 @@
 	u64 alloc_start;
 	struct btrfs_transaction *running_transaction;
 	struct btrfs_super_block super_copy;
-	struct extent_buffer *sb_buffer;
+	struct btrfs_super_block super_for_commit;
 	struct block_device *__bdev;
 	struct super_block *sb;
 	struct inode *btree_inode;
@@ -1208,6 +1208,7 @@
 
 /* struct btrfs_super_block */
 BTRFS_SETGET_STACK_FUNCS(super_bytenr, struct btrfs_super_block, bytenr, 64);
+BTRFS_SETGET_STACK_FUNCS(super_flags, struct btrfs_super_block, flags, 64);
 BTRFS_SETGET_STACK_FUNCS(super_generation, struct btrfs_super_block,
 			 generation, 64);
 BTRFS_SETGET_STACK_FUNCS(super_root, struct btrfs_super_block, root, 64);
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index fabc31b..9d5424a 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -78,9 +78,13 @@
 
 	spin_lock(&em_tree->lock);
 	em = lookup_extent_mapping(em_tree, start, len);
-	spin_unlock(&em_tree->lock);
-	if (em)
+	if (em) {
+		em->bdev =
+			BTRFS_I(inode)->root->fs_info->fs_devices->latest_bdev;
+		spin_unlock(&em_tree->lock);
 		goto out;
+	}
+	spin_unlock(&em_tree->lock);
 
 	em = alloc_extent_map(GFP_NOFS);
 	if (!em) {
@@ -90,7 +94,7 @@
 	em->start = 0;
 	em->len = (u64)-1;
 	em->block_start = 0;
-	em->bdev = inode->i_sb->s_bdev;
+	em->bdev = BTRFS_I(inode)->root->fs_info->fs_devices->latest_bdev;
 
 	spin_lock(&em_tree->lock);
 	ret = add_extent_mapping(em_tree, em);
@@ -435,11 +439,6 @@
 	ret = btrfs_bio_wq_end_io(root->fs_info, bio, 1);
 	BUG_ON(ret);
 
-	if (offset == BTRFS_SUPER_INFO_OFFSET) {
-		bio->bi_bdev = root->fs_info->fs_devices->latest_bdev;
-		submit_bio(rw, bio);
-		return 0;
-	}
 	return btrfs_map_bio(BTRFS_I(inode)->root, rw, bio, mirror_num);
 }
 
@@ -587,8 +586,7 @@
 	list = &fs_info->fs_devices->devices;
 	list_for_each(next, list) {
 		device = list_entry(next, struct btrfs_device, dev_list);
-		if (device->bdev && device->bdev != fs_info->sb->s_bdev)
-			close_bdev_excl(device->bdev);
+		close_bdev_excl(device->bdev);
 		device->bdev = NULL;
 	}
 	return 0;
@@ -1118,6 +1116,7 @@
 	u32 leafsize;
 	u32 blocksize;
 	u32 stripesize;
+	struct buffer_head *bh;
 	struct btrfs_root *extent_root = kmalloc(sizeof(struct btrfs_root),
 						 GFP_NOFS);
 	struct btrfs_root *tree_root = kmalloc(sizeof(struct btrfs_root),
@@ -1153,7 +1152,6 @@
 	spin_lock_init(&fs_info->new_trans_lock);
 
 	init_completion(&fs_info->kobj_unregister);
-	sb_set_blocksize(sb, BTRFS_SUPER_INFO_SIZE);
 	fs_info->tree_root = tree_root;
 	fs_info->extent_root = extent_root;
 	fs_info->chunk_root = chunk_root;
@@ -1170,6 +1168,9 @@
 	fs_info->btree_inode->i_ino = 1;
 	fs_info->btree_inode->i_nlink = 1;
 
+	sb->s_blocksize = 4096;
+	sb->s_blocksize_bits = blksize_bits(4096);
+
 	/*
 	 * we set the i_size on the btree inode to the max possible int.
 	 * the real end of the address space is determined by all of
@@ -1229,19 +1230,16 @@
 	__setup_root(4096, 4096, 4096, 4096, tree_root,
 		     fs_info, BTRFS_ROOT_TREE_OBJECTID);
 
-	fs_info->sb_buffer = read_tree_block(tree_root,
-					     BTRFS_SUPER_INFO_OFFSET,
-					     4096);
 
-	if (!fs_info->sb_buffer)
+	bh = __bread(fs_devices->latest_bdev,
+		     BTRFS_SUPER_INFO_OFFSET / 4096, 4096);
+	if (!bh)
 		goto fail_iput;
 
-	read_extent_buffer(fs_info->sb_buffer, &fs_info->super_copy, 0,
-			   sizeof(fs_info->super_copy));
+	memcpy(&fs_info->super_copy, bh->b_data, sizeof(fs_info->super_copy));
+	brelse(bh);
 
-	read_extent_buffer(fs_info->sb_buffer, fs_info->fsid,
-			   (unsigned long)btrfs_super_fsid(fs_info->sb_buffer),
-			   BTRFS_FSID_SIZE);
+	memcpy(fs_info->fsid, fs_info->super_copy.fsid, BTRFS_FSID_SIZE);
 
 	disk_super = &fs_info->super_copy;
 	if (!btrfs_super_root(disk_super))
@@ -1263,7 +1261,9 @@
 	tree_root->leafsize = leafsize;
 	tree_root->sectorsize = sectorsize;
 	tree_root->stripesize = stripesize;
-	sb_set_blocksize(sb, sectorsize);
+
+	sb->s_blocksize = sectorsize;
+	sb->s_blocksize_bits = blksize_bits(sectorsize);
 
 	if (strncmp((char *)(&disk_super->magic), BTRFS_MAGIC,
 		    sizeof(disk_super->magic))) {
@@ -1339,7 +1339,6 @@
 fail_sys_array:
 	mutex_unlock(&fs_info->fs_mutex);
 fail_sb_buffer:
-	free_extent_buffer(fs_info->sb_buffer);
 	extent_io_tree_empty_lru(&BTRFS_I(fs_info->btree_inode)->io_tree);
 fail_iput:
 	iput(fs_info->btree_inode);
@@ -1380,41 +1379,44 @@
 	struct list_head *cur;
 	struct list_head *head = &root->fs_info->fs_devices->devices;
 	struct btrfs_device *dev;
-	struct extent_buffer *sb;
+	struct btrfs_super_block *sb;
 	struct btrfs_dev_item *dev_item;
 	struct buffer_head *bh;
 	int ret;
 	int do_barriers;
 	int max_errors;
 	int total_errors = 0;
+	u32 crc;
+	u64 flags;
 
 	max_errors = btrfs_super_num_devices(&root->fs_info->super_copy) - 1;
 	do_barriers = !btrfs_test_opt(root, NOBARRIER);
 
-	sb = root->fs_info->sb_buffer;
-	dev_item = (struct btrfs_dev_item *)offsetof(struct btrfs_super_block,
-						      dev_item);
+	sb = &root->fs_info->super_for_commit;
+	dev_item = &sb->dev_item;
 	list_for_each(cur, head) {
 		dev = list_entry(cur, struct btrfs_device, dev_list);
-		btrfs_set_device_type(sb, dev_item, dev->type);
-		btrfs_set_device_id(sb, dev_item, dev->devid);
-		btrfs_set_device_total_bytes(sb, dev_item, dev->total_bytes);
-		btrfs_set_device_bytes_used(sb, dev_item, dev->bytes_used);
-		btrfs_set_device_io_align(sb, dev_item, dev->io_align);
-		btrfs_set_device_io_width(sb, dev_item, dev->io_width);
-		btrfs_set_device_sector_size(sb, dev_item, dev->sector_size);
-		write_extent_buffer(sb, dev->uuid,
-				    (unsigned long)btrfs_device_uuid(dev_item),
-				    BTRFS_UUID_SIZE);
+		btrfs_set_stack_device_type(dev_item, dev->type);
+		btrfs_set_stack_device_id(dev_item, dev->devid);
+		btrfs_set_stack_device_total_bytes(dev_item, dev->total_bytes);
+		btrfs_set_stack_device_bytes_used(dev_item, dev->bytes_used);
+		btrfs_set_stack_device_io_align(dev_item, dev->io_align);
+		btrfs_set_stack_device_io_width(dev_item, dev->io_width);
+		btrfs_set_stack_device_sector_size(dev_item, dev->sector_size);
+		memcpy(dev_item->uuid, dev->uuid, BTRFS_UUID_SIZE);
+		flags = btrfs_super_flags(sb);
+		btrfs_set_super_flags(sb, flags | BTRFS_HEADER_FLAG_WRITTEN);
 
-		btrfs_set_header_flag(sb, BTRFS_HEADER_FLAG_WRITTEN);
-		csum_tree_block(root, sb, 0);
 
-		bh = __getblk(dev->bdev, BTRFS_SUPER_INFO_OFFSET /
-			      root->fs_info->sb->s_blocksize,
+		crc = ~(u32)0;
+		crc = btrfs_csum_data(root, (char *)sb + BTRFS_CSUM_SIZE, crc,
+				      BTRFS_SUPER_INFO_SIZE - BTRFS_CSUM_SIZE);
+		btrfs_csum_final(crc, sb->csum);
+
+		bh = __getblk(dev->bdev, BTRFS_SUPER_INFO_OFFSET / 4096,
 			      BTRFS_SUPER_INFO_SIZE);
 
-		read_extent_buffer(sb, bh->b_data, 0, BTRFS_SUPER_INFO_SIZE);
+		memcpy(bh->b_data, sb, BTRFS_SUPER_INFO_SIZE);
 		dev->pending_io = bh;
 
 		get_bh(bh);
@@ -1483,15 +1485,6 @@
 	int ret;
 
 	ret = write_all_supers(root);
-#if 0
-	if (!btrfs_test_opt(root, NOBARRIER))
-		blkdev_issue_flush(sb->s_bdev, NULL);
-	set_extent_buffer_dirty(&BTRFS_I(btree_inode)->io_tree, super);
-	ret = sync_page_range_nolock(btree_inode, btree_inode->i_mapping,
-				     super->start, super->len);
-	if (!btrfs_test_opt(root, NOBARRIER))
-		blkdev_issue_flush(sb->s_bdev, NULL);
-#endif
 	return ret;
 }
 
@@ -1570,8 +1563,6 @@
 	if (root->fs_info->dev_root->node);
 		free_extent_buffer(root->fs_info->dev_root->node);
 
-	free_extent_buffer(fs_info->sb_buffer);
-
 	btrfs_free_block_groups(root->fs_info);
 	del_fs_roots(fs_info);
 
@@ -1652,7 +1643,7 @@
 {
 	struct backing_dev_info *bdi;
 
-	bdi = root->fs_info->sb->s_bdev->bd_inode->i_mapping->backing_dev_info;
+	bdi = &root->fs_info->bdi;
 	if (root->fs_info->throttles && bdi_write_congested(bdi)) {
 #if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,18)
 		congestion_wait(WRITE, HZ/20);
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index f94794a..c0e67bd 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -147,6 +147,8 @@
 	u64 end;
 	int ret;
 
+	bytenr = max_t(u64, bytenr,
+		       BTRFS_SUPER_INFO_OFFSET + BTRFS_SUPER_INFO_SIZE);
 	block_group_cache = &info->block_group_cache;
 	ret = find_first_extent_bit(block_group_cache,
 				    bytenr, &start, &end,
@@ -1059,16 +1061,25 @@
 	}
 }
 
-static u64 reduce_alloc_profile(u64 flags)
+static u64 reduce_alloc_profile(struct btrfs_root *root, u64 flags)
 {
+	u64 num_devices = root->fs_info->fs_devices->num_devices;
+
+	if (num_devices == 1)
+		flags &= ~(BTRFS_BLOCK_GROUP_RAID1 | BTRFS_BLOCK_GROUP_RAID0);
+	if (num_devices < 4)
+		flags &= ~BTRFS_BLOCK_GROUP_RAID10;
+
 	if ((flags & BTRFS_BLOCK_GROUP_DUP) &&
 	    (flags & (BTRFS_BLOCK_GROUP_RAID1 |
-		      BTRFS_BLOCK_GROUP_RAID10)))
+		      BTRFS_BLOCK_GROUP_RAID10))) {
 		flags &= ~BTRFS_BLOCK_GROUP_DUP;
+	}
 
 	if ((flags & BTRFS_BLOCK_GROUP_RAID1) &&
-	    (flags & BTRFS_BLOCK_GROUP_RAID10))
+	    (flags & BTRFS_BLOCK_GROUP_RAID10)) {
 		flags &= ~BTRFS_BLOCK_GROUP_RAID1;
+	}
 
 	if ((flags & BTRFS_BLOCK_GROUP_RAID0) &&
 	    ((flags & BTRFS_BLOCK_GROUP_RAID1) |
@@ -1078,7 +1089,6 @@
 	return flags;
 }
 
-
 static int do_chunk_alloc(struct btrfs_trans_handle *trans,
 			  struct btrfs_root *extent_root, u64 alloc_bytes,
 			  u64 flags)
@@ -1089,7 +1099,7 @@
 	u64 num_bytes;
 	int ret;
 
-	flags = reduce_alloc_profile(flags);
+	flags = reduce_alloc_profile(extent_root, flags);
 
 	space_info = __find_space_info(extent_root->fs_info, flags);
 	if (!space_info) {
@@ -1169,6 +1179,21 @@
 	return 0;
 }
 
+static u64 first_logical_byte(struct btrfs_root *root, u64 search_start)
+{
+	u64 start;
+	u64 end;
+	int ret;
+	ret = find_first_extent_bit(&root->fs_info->block_group_cache,
+				    search_start, &start, &end,
+				    BLOCK_GROUP_DATA | BLOCK_GROUP_METADATA |
+				    BLOCK_GROUP_SYSTEM);
+	if (ret)
+		return 0;
+	return start;
+}
+
+
 static int update_pinned_extents(struct btrfs_root *root,
 				u64 bytenr, u64 num, int pin)
 {
@@ -1185,16 +1210,25 @@
 	}
 	while (num > 0) {
 		cache = btrfs_lookup_block_group(fs_info, bytenr);
-		WARN_ON(!cache);
-		len = min(num, cache->key.offset -
-			  (bytenr - cache->key.objectid));
+		if (!cache) {
+			u64 first = first_logical_byte(root, bytenr);
+			WARN_ON(first < bytenr);
+			len = min(first - bytenr, num);
+		} else {
+			len = min(num, cache->key.offset -
+				  (bytenr - cache->key.objectid));
+		}
 		if (pin) {
-			cache->pinned += len;
-			cache->space_info->bytes_pinned += len;
+			if (cache) {
+				cache->pinned += len;
+				cache->space_info->bytes_pinned += len;
+			}
 			fs_info->total_pinned += len;
 		} else {
-			cache->pinned -= len;
-			cache->space_info->bytes_pinned -= len;
+			if (cache) {
+				cache->pinned -= len;
+				cache->space_info->bytes_pinned -= len;
+			}
 			fs_info->total_pinned -= len;
 		}
 		bytenr += len;
@@ -1547,7 +1581,7 @@
 				     int data)
 {
 	int ret;
-	u64 orig_search_start = search_start;
+	u64 orig_search_start;
 	struct btrfs_root * root = orig_root->fs_info->extent_root;
 	struct btrfs_fs_info *info = root->fs_info;
 	u64 total_needed = num_bytes;
@@ -1577,6 +1611,9 @@
 		}
 	}
 
+	search_start = max(search_start, first_logical_byte(root, 0));
+	orig_search_start = search_start;
+
 	if (search_end == (u64)-1)
 		search_end = btrfs_super_total_bytes(&info->super_copy);
 
@@ -1751,7 +1788,7 @@
 		data = BTRFS_BLOCK_GROUP_METADATA | alloc_profile;
 	}
 again:
-	data = reduce_alloc_profile(data);
+	data = reduce_alloc_profile(root, data);
 	if (root->ref_cows) {
 		if (!(data & BTRFS_BLOCK_GROUP_METADATA)) {
 			ret = do_chunk_alloc(trans, root->fs_info->extent_root,
@@ -2309,6 +2346,7 @@
 	struct file_ra_state *ra;
 	unsigned long total_read = 0;
 	unsigned long ra_pages;
+	struct btrfs_trans_handle *trans;
 
 	ra = kzalloc(sizeof(*ra), GFP_NOFS);
 
@@ -2326,9 +2364,13 @@
 				       calc_ra(i, last_index, ra_pages));
 		}
 		total_read++;
+		if (((u64)i << PAGE_CACHE_SHIFT) > inode->i_size)
+			goto truncate_racing;
+
 		page = grab_cache_page(inode->i_mapping, i);
-		if (!page)
+		if (!page) {
 			goto out_unlock;
+		}
 		if (!PageUptodate(page)) {
 			btrfs_readpage(NULL, page);
 			lock_page(page);
@@ -2350,20 +2392,33 @@
 
 		lock_extent(io_tree, page_start, page_end, GFP_NOFS);
 
-		set_page_dirty(page);
 		set_extent_delalloc(io_tree, page_start,
 				    page_end, GFP_NOFS);
+		set_page_dirty(page);
 
 		unlock_extent(io_tree, page_start, page_end, GFP_NOFS);
 		unlock_page(page);
 		page_cache_release(page);
-		balance_dirty_pages_ratelimited_nr(inode->i_mapping, 1);
 	}
+	balance_dirty_pages_ratelimited_nr(inode->i_mapping,
+					   total_read);
 
 out_unlock:
 	kfree(ra);
+	trans = btrfs_start_transaction(BTRFS_I(inode)->root, 1);
+	if (trans) {
+		btrfs_add_ordered_inode(inode);
+		btrfs_end_transaction(trans, BTRFS_I(inode)->root);
+		mark_inode_dirty(inode);
+	}
 	mutex_unlock(&inode->i_mutex);
 	return 0;
+
+truncate_racing:
+	vmtruncate(inode, inode->i_size);
+	balance_dirty_pages_ratelimited_nr(inode->i_mapping,
+					   total_read);
+	goto out_unlock;
 }
 
 /*
@@ -2466,6 +2521,27 @@
 	return 0;
 }
 
+static int noinline del_extent_zero(struct btrfs_root *extent_root,
+				    struct btrfs_path *path,
+				    struct btrfs_key *extent_key)
+{
+	int ret;
+	struct btrfs_trans_handle *trans;
+
+	trans = btrfs_start_transaction(extent_root, 1);
+	ret = btrfs_search_slot(trans, extent_root, extent_key, path, -1, 1);
+	if (ret > 0) {
+		ret = -EIO;
+		goto out;
+	}
+	if (ret < 0)
+		goto out;
+	ret = btrfs_del_item(trans, extent_root, path);
+out:
+	btrfs_end_transaction(trans, extent_root);
+	return ret;
+}
+
 static int noinline relocate_one_extent(struct btrfs_root *extent_root,
 					struct btrfs_path *path,
 					struct btrfs_key *extent_key)
@@ -2477,6 +2553,10 @@
 	u32 item_size;
 	int ret = 0;
 
+	if (extent_key->objectid == 0) {
+		ret = del_extent_zero(extent_root, path, extent_key);
+		goto out;
+	}
 	key.objectid = extent_key->objectid;
 	key.type = BTRFS_EXTENT_REF_KEY;
 	key.offset = 0;
@@ -2490,15 +2570,24 @@
 		ret = 0;
 		leaf = path->nodes[0];
 		nritems = btrfs_header_nritems(leaf);
-		if (path->slots[0] == nritems)
-			goto out;
+		if (path->slots[0] == nritems) {
+			ret = btrfs_next_leaf(extent_root, path);
+			if (ret > 0) {
+				ret = 0;
+				goto out;
+			}
+			if (ret < 0)
+				goto out;
+		}
 
 		btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
-		if (found_key.objectid != extent_key->objectid)
+		if (found_key.objectid != extent_key->objectid) {
 			break;
+		}
 
-		if (found_key.type != BTRFS_EXTENT_REF_KEY)
+		if (found_key.type != BTRFS_EXTENT_REF_KEY) {
 			break;
+		}
 
 		key.offset = found_key.offset + 1;
 		item_size = btrfs_item_size_nr(leaf, path->slots[0]);
@@ -2519,7 +2608,7 @@
 	u64 stripped = BTRFS_BLOCK_GROUP_RAID0 |
 		BTRFS_BLOCK_GROUP_RAID1 | BTRFS_BLOCK_GROUP_RAID10;
 
-	num_devices = btrfs_super_num_devices(&root->fs_info->super_copy);
+	num_devices = root->fs_info->fs_devices->num_devices;
 	if (num_devices == 1) {
 		stripped |= BTRFS_BLOCK_GROUP_DUP;
 		stripped = flags & ~stripped;
@@ -2535,9 +2624,6 @@
 		return flags;
 	} else {
 		/* they already had raid on here, just return */
-		if ((flags & BTRFS_BLOCK_GROUP_DUP) &&
-		    (flags & BTRFS_BLOCK_GROUP_RAID1)) {
-		}
 		if (flags & stripped)
 			return flags;
 
@@ -2570,7 +2656,7 @@
 	struct extent_buffer *leaf;
 	u32 nritems;
 	int ret;
-	int progress = 0;
+	int progress;
 
 	shrink_block_group = btrfs_lookup_block_group(root->fs_info,
 						      shrink_start);
@@ -2597,6 +2683,7 @@
 	shrink_block_group->ro = 1;
 
 	total_found = 0;
+	progress = 0;
 	key.objectid = shrink_start;
 	key.offset = 0;
 	key.type = 0;
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index f7beb9b..b437d3b 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -2194,6 +2194,8 @@
 again:
 	spin_lock(&em_tree->lock);
 	em = lookup_extent_mapping(em_tree, start, len);
+	if (em)
+		em->bdev = root->fs_info->fs_devices->latest_bdev;
 	spin_unlock(&em_tree->lock);
 
 	if (em) {
@@ -2212,7 +2214,7 @@
 
 	em->start = EXTENT_MAP_HOLE;
 	em->len = (u64)-1;
-	em->bdev = inode->i_sb->s_bdev;
+	em->bdev = root->fs_info->fs_devices->latest_bdev;
 	ret = btrfs_lookup_file_extent(trans, root, path,
 				       objectid, start, trans != NULL);
 	if (ret < 0) {
@@ -3101,6 +3103,27 @@
 	return ret;
 }
 
+long btrfs_ioctl_rm_dev(struct btrfs_root *root, void __user *arg)
+{
+	struct btrfs_ioctl_vol_args *vol_args;
+	int ret;
+
+	vol_args = kmalloc(sizeof(*vol_args), GFP_NOFS);
+
+	if (!vol_args)
+		return -ENOMEM;
+
+	if (copy_from_user(vol_args, arg, sizeof(*vol_args))) {
+		ret = -EFAULT;
+		goto out;
+	}
+	ret = btrfs_rm_device(root, vol_args->name);
+
+out:
+	kfree(vol_args);
+	return ret;
+}
+
 int dup_item_to_inode(struct btrfs_trans_handle *trans,
 		       struct btrfs_root *root,
 		       struct btrfs_path *path,
@@ -3294,6 +3317,8 @@
 		return btrfs_ioctl_resize(root, (void __user *)arg);
 	case BTRFS_IOC_ADD_DEV:
 		return btrfs_ioctl_add_dev(root, (void __user *)arg);
+	case BTRFS_IOC_RM_DEV:
+		return btrfs_ioctl_rm_dev(root, (void __user *)arg);
 	case BTRFS_IOC_BALANCE:
 		return btrfs_balance(root->fs_info->dev_root);
 	case BTRFS_IOC_CLONE:
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 7153dfa..020e5a8 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -315,24 +315,12 @@
 	sb->s_dirt = 0;
 }
 
-/*
- * This is almost a copy of get_sb_bdev in fs/super.c.
- * We need the local copy to allow direct mounting of
- * subvolumes, but this could be easily integrated back
- * into the generic version.  --hch
- */
-
-/* start copy & paste */
-static int set_bdev_super(struct super_block *s, void *data)
+static int btrfs_test_super(struct super_block *s, void *data)
 {
-	s->s_bdev = data;
-	s->s_dev = s->s_bdev->bd_dev;
-	return 0;
-}
+	struct btrfs_fs_devices *test_fs_devices = data;
+	struct btrfs_root *root = btrfs_sb(s);
 
-static int test_bdev_super(struct super_block *s, void *data)
-{
-	return (void *)s->s_bdev == data;
+	return root->fs_info->fs_devices == test_fs_devices;
 }
 
 int btrfs_get_sb_bdev(struct file_system_type *fs_type,
@@ -354,14 +342,9 @@
 		return error;
 
 	bdev = fs_devices->lowest_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);
+	btrfs_lock_volumes();
+	s = sget(fs_type, btrfs_test_super, set_anon_super, fs_devices);
+	btrfs_unlock_volumes();
 	if (IS_ERR(s))
 		goto error_s;
 
@@ -373,13 +356,11 @@
 			goto error_bdev;
 		}
 
-		close_bdev_excl(bdev);
 	} else {
 		char b[BDEVNAME_SIZE];
 
 		s->s_flags = flags;
 		strlcpy(s->s_id, bdevname(bdev, b), sizeof(s->s_id));
-		sb_set_blocksize(s, block_size(bdev));
 		error = btrfs_fill_super(s, fs_devices, data,
 					 flags & MS_SILENT ? 1 : 0);
 		if (error) {
@@ -458,7 +439,7 @@
 	.owner		= THIS_MODULE,
 	.name		= "btrfs",
 	.get_sb		= btrfs_get_sb,
-	.kill_sb	= kill_block_super,
+	.kill_sb	= kill_anon_super,
 	.fs_flags	= FS_REQUIRES_DEV,
 };
 
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 9826942..57746c1 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -738,9 +738,8 @@
 				   chunk_root->node->start);
 	btrfs_set_super_chunk_root_level(&root->fs_info->super_copy,
 					 btrfs_header_level(chunk_root->node));
-	write_extent_buffer(root->fs_info->sb_buffer,
-			    &root->fs_info->super_copy, 0,
-			    sizeof(root->fs_info->super_copy));
+	memcpy(&root->fs_info->super_for_commit, &root->fs_info->super_copy,
+	       sizeof(root->fs_info->super_copy));
 
 	btrfs_copy_pinned(root, pinned_copy);
 
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index b381875..55da5f0 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -45,6 +45,16 @@
 static DEFINE_MUTEX(uuid_mutex);
 static LIST_HEAD(fs_uuids);
 
+void btrfs_lock_volumes(void)
+{
+	mutex_lock(&uuid_mutex);
+}
+
+void btrfs_unlock_volumes(void)
+{
+	mutex_unlock(&uuid_mutex);
+}
+
 int btrfs_cleanup_fs_uuids(void)
 {
 	struct btrfs_fs_devices *fs_devices;
@@ -193,12 +203,14 @@
 			ret = PTR_ERR(bdev);
 			goto fail;
 		}
+		set_blocksize(bdev, 4096);
 		if (device->devid == fs_devices->latest_devid)
 			fs_devices->latest_bdev = bdev;
 		if (device->devid == fs_devices->lowest_devid) {
 			fs_devices->lowest_bdev = bdev;
 		}
 		device->bdev = bdev;
+
 	}
 	mutex_unlock(&uuid_mutex);
 	return 0;
@@ -393,6 +405,9 @@
 	struct btrfs_path *path;
 	struct btrfs_root *root = device->dev_root;
 	struct btrfs_key key;
+	struct btrfs_key found_key;
+	struct extent_buffer *leaf = NULL;
+	struct btrfs_dev_extent *extent = NULL;
 
 	path = btrfs_alloc_path();
 	if (!path)
@@ -403,8 +418,25 @@
 	key.type = BTRFS_DEV_EXTENT_KEY;
 
 	ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
+	if (ret > 0) {
+		ret = btrfs_previous_item(root, path, key.objectid,
+					  BTRFS_DEV_EXTENT_KEY);
+		BUG_ON(ret);
+		leaf = path->nodes[0];
+		btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
+		extent = btrfs_item_ptr(leaf, path->slots[0],
+					struct btrfs_dev_extent);
+		BUG_ON(found_key.offset > start || found_key.offset +
+		       btrfs_dev_extent_length(leaf, extent) < start);
+		ret = 0;
+	} else if (ret == 0) {
+		leaf = path->nodes[0];
+		extent = btrfs_item_ptr(leaf, path->slots[0],
+					struct btrfs_dev_extent);
+	}
 	BUG_ON(ret);
 
+	device->bytes_used -= btrfs_dev_extent_length(leaf, extent);
 	ret = btrfs_del_item(trans, root, path);
 	BUG_ON(ret);
 
@@ -593,6 +625,170 @@
 	return ret;
 }
 
+static int btrfs_rm_dev_item(struct btrfs_root *root,
+			     struct btrfs_device *device)
+{
+	int ret;
+	struct btrfs_path *path;
+	struct block_device *bdev = device->bdev;
+	struct btrfs_device *next_dev;
+	struct btrfs_key key;
+	u64 total_bytes;
+	struct btrfs_fs_devices *fs_devices;
+	struct btrfs_trans_handle *trans;
+
+	root = root->fs_info->chunk_root;
+
+	path = btrfs_alloc_path();
+	if (!path)
+		return -ENOMEM;
+
+	trans = btrfs_start_transaction(root, 1);
+	key.objectid = BTRFS_DEV_ITEMS_OBJECTID;
+	key.type = BTRFS_DEV_ITEM_KEY;
+	key.offset = device->devid;
+
+	ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
+	if (ret < 0)
+		goto out;
+
+	if (ret > 0) {
+		ret = -ENOENT;
+		goto out;
+	}
+
+	ret = btrfs_del_item(trans, root, path);
+	if (ret)
+		goto out;
+
+	/*
+	 * at this point, the device is zero sized.  We want to
+	 * remove it from the devices list and zero out the old super
+	 */
+	list_del_init(&device->dev_list);
+	list_del_init(&device->dev_alloc_list);
+	fs_devices = root->fs_info->fs_devices;
+
+	next_dev = list_entry(fs_devices->devices.next, struct btrfs_device,
+			      dev_list);
+	if (bdev == fs_devices->lowest_bdev)
+		fs_devices->lowest_bdev = next_dev->bdev;
+	if (bdev == root->fs_info->sb->s_bdev)
+		root->fs_info->sb->s_bdev = next_dev->bdev;
+	if (bdev == fs_devices->latest_bdev)
+		fs_devices->latest_bdev = next_dev->bdev;
+
+	total_bytes = btrfs_super_total_bytes(&root->fs_info->super_copy);
+	btrfs_set_super_total_bytes(&root->fs_info->super_copy,
+				    total_bytes - device->total_bytes);
+
+	total_bytes = btrfs_super_num_devices(&root->fs_info->super_copy);
+	btrfs_set_super_num_devices(&root->fs_info->super_copy,
+				    total_bytes - 1);
+out:
+	btrfs_free_path(path);
+	btrfs_commit_transaction(trans, root);
+	return ret;
+}
+
+int btrfs_rm_device(struct btrfs_root *root, char *device_path)
+{
+	struct btrfs_device *device;
+	struct block_device *bdev;
+	struct buffer_head *bh;
+	struct btrfs_super_block *disk_super;
+	u64 all_avail;
+	u64 devid;
+	int ret = 0;
+
+	mutex_lock(&root->fs_info->fs_mutex);
+	mutex_lock(&uuid_mutex);
+
+	all_avail = root->fs_info->avail_data_alloc_bits |
+		root->fs_info->avail_system_alloc_bits |
+		root->fs_info->avail_metadata_alloc_bits;
+
+	if ((all_avail & BTRFS_BLOCK_GROUP_RAID10) &&
+	    root->fs_info->fs_devices->num_devices <= 4) {
+		printk("btrfs: unable to go below four devices on raid10\n");
+		ret = -EINVAL;
+		goto out;
+	}
+
+	if ((all_avail & BTRFS_BLOCK_GROUP_RAID1) &&
+	    root->fs_info->fs_devices->num_devices <= 2) {
+		printk("btrfs: unable to go below two devices on raid1\n");
+		ret = -EINVAL;
+		goto out;
+	}
+
+	bdev = open_bdev_excl(device_path, 0, root->fs_info->bdev_holder);
+	if (IS_ERR(bdev)) {
+		ret = PTR_ERR(bdev);
+		goto out;
+	}
+
+	bh = __bread(bdev, BTRFS_SUPER_INFO_OFFSET / 4096, 4096);
+	if (!bh) {
+		ret = -EIO;
+		goto error_close;
+	}
+	disk_super = (struct btrfs_super_block *)bh->b_data;
+	if (strncmp((char *)(&disk_super->magic), BTRFS_MAGIC,
+	    sizeof(disk_super->magic))) {
+		ret = -ENOENT;
+		goto error_brelse;
+	}
+	if (memcmp(disk_super->fsid, root->fs_info->fsid, BTRFS_FSID_SIZE)) {
+		ret = -ENOENT;
+		goto error_brelse;
+	}
+	devid = le64_to_cpu(disk_super->dev_item.devid);
+	device = btrfs_find_device(root, devid, NULL);
+	if (!device) {
+		ret = -ENOENT;
+		goto error_brelse;
+	}
+
+	root->fs_info->fs_devices->num_devices--;
+
+	ret = btrfs_shrink_device(device, 0);
+	if (ret)
+		goto error_brelse;
+
+
+	ret = btrfs_rm_dev_item(root->fs_info->chunk_root, device);
+	if (ret)
+		goto error_brelse;
+
+	/* make sure this device isn't detected as part of the FS anymore */
+	memset(&disk_super->magic, 0, sizeof(disk_super->magic));
+	set_buffer_dirty(bh);
+	sync_dirty_buffer(bh);
+
+	brelse(bh);
+
+	/* one close for the device struct or super_block */
+	close_bdev_excl(device->bdev);
+
+	/* one close for us */
+	close_bdev_excl(device->bdev);
+
+	kfree(device->name);
+	kfree(device);
+	ret = 0;
+	goto out;
+
+error_brelse:
+	brelse(bh);
+error_close:
+	close_bdev_excl(bdev);
+out:
+	mutex_unlock(&uuid_mutex);
+	mutex_unlock(&root->fs_info->fs_mutex);
+	return ret;
+}
+
 int btrfs_init_new_device(struct btrfs_root *root, char *device_path)
 {
 	struct btrfs_trans_handle *trans;
@@ -831,13 +1027,17 @@
 	em = lookup_extent_mapping(em_tree, chunk_offset, 1);
 	spin_unlock(&em_tree->lock);
 
-	BUG_ON(em->start > chunk_offset || em->start + em->len < chunk_offset);
+	BUG_ON(em->start > chunk_offset ||
+	       em->start + em->len < chunk_offset);
 	map = (struct map_lookup *)em->bdev;
 
 	for (i = 0; i < map->num_stripes; i++) {
 		ret = btrfs_free_dev_extent(trans, map->stripes[i].dev,
 					    map->stripes[i].physical);
 		BUG_ON(ret);
+
+		ret = btrfs_update_device(trans, map->stripes[i].dev);
+		BUG_ON(ret);
 	}
 	ret = btrfs_free_chunk(trans, root, chunk_tree, chunk_objectid,
 			       chunk_offset);
@@ -847,11 +1047,8 @@
 	if (map->type & BTRFS_BLOCK_GROUP_SYSTEM) {
 		ret = btrfs_del_sys_chunk(root, chunk_objectid, chunk_offset);
 		BUG_ON(ret);
-		goto out;
 	}
 
-
-
 	spin_lock(&em_tree->lock);
 	remove_extent_mapping(em_tree, em);
 	kfree(map);
@@ -861,7 +1058,6 @@
 	free_extent_map(em);
 	spin_unlock(&em_tree->lock);
 
-out:
 	/* once for us */
 	free_extent_map(em);
 
@@ -1449,7 +1645,7 @@
 		return 0;
 
 	if (!em) {
-		printk("unable to find logical %Lu\n", logical);
+		printk("unable to find logical %Lu len %Lu\n", logical, *length);
 		BUG();
 	}
 
@@ -1712,6 +1908,7 @@
 
 	logical = key->offset;
 	length = btrfs_chunk_length(leaf, chunk);
+
 	spin_lock(&map_tree->map_tree.lock);
 	em = lookup_extent_mapping(&map_tree->map_tree, logical, 1);
 	spin_unlock(&map_tree->map_tree.lock);
@@ -1845,7 +2042,7 @@
 int btrfs_read_sys_array(struct btrfs_root *root)
 {
 	struct btrfs_super_block *super_copy = &root->fs_info->super_copy;
-	struct extent_buffer *sb = root->fs_info->sb_buffer;
+	struct extent_buffer *sb;
 	struct btrfs_disk_key *disk_key;
 	struct btrfs_chunk *chunk;
 	u8 *ptr;
@@ -1857,6 +2054,12 @@
 	u32 cur;
 	struct btrfs_key key;
 
+	sb = btrfs_find_create_tree_block(root, BTRFS_SUPER_INFO_OFFSET,
+					  BTRFS_SUPER_INFO_SIZE);
+	if (!sb)
+		return -ENOMEM;
+	btrfs_set_buffer_uptodate(sb);
+	write_extent_buffer(sb, super_copy, 0, BTRFS_SUPER_INFO_SIZE);
 	array_size = btrfs_super_sys_array_size(super_copy);
 
 	ptr = super_copy->sys_chunk_array;
@@ -1867,8 +2070,7 @@
 		disk_key = (struct btrfs_disk_key *)ptr;
 		btrfs_disk_key_to_cpu(&key, disk_key);
 
-		len = sizeof(*disk_key);
-		ptr += len;
+		len = sizeof(*disk_key); ptr += len;
 		sb_ptr += len;
 		cur += len;
 
@@ -1887,6 +2089,7 @@
 		sb_ptr += len;
 		cur += len;
 	}
+	free_extent_buffer(sb);
 	return ret;
 }
 
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index a9663e92..0f94a69 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -125,6 +125,7 @@
 int btrfs_add_device(struct btrfs_trans_handle *trans,
 		     struct btrfs_root *root,
 		     struct btrfs_device *device);
+int btrfs_rm_device(struct btrfs_root *root, char *device_path);
 int btrfs_cleanup_fs_uuids(void);
 int btrfs_num_copies(struct btrfs_mapping_tree *map_tree, u64 logical, u64 len);
 int btrfs_unplug_page(struct btrfs_mapping_tree *map_tree,
@@ -136,4 +137,6 @@
 int btrfs_shrink_device(struct btrfs_device *device, u64 new_size);
 int btrfs_init_new_device(struct btrfs_root *root, char *path);
 int btrfs_balance(struct btrfs_root *dev_root);
+void btrfs_unlock_volumes(void);
+void btrfs_lock_volumes(void);
 #endif