diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
index 13edbc959bac..4607577df484 100644
--- a/fs/btrfs/block-group.c
+++ b/fs/btrfs/block-group.c
@@ -1852,7 +1852,7 @@ static int read_one_block_group(struct btrfs_fs_info *info,
 			goto error;
 	}
 
-	ret = btrfs_load_block_group_zone_info(cache);
+	ret = btrfs_load_block_group_zone_info(cache, false);
 	if (ret) {
 		btrfs_err(info, "zoned: failed to load zone info of bg %llu",
 			  cache->start);
@@ -2147,7 +2147,7 @@ int btrfs_make_block_group(struct btrfs_trans_handle *trans, u64 bytes_used,
 	if (btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE))
 		cache->needs_free_space = 1;
 
-	ret = btrfs_load_block_group_zone_info(cache);
+	ret = btrfs_load_block_group_zone_info(cache, true);
 	if (ret) {
 		btrfs_put_block_group(cache);
 		return ret;
diff --git a/fs/btrfs/zoned.c b/fs/btrfs/zoned.c
index 78be99b3c090..e8e7bca81a30 100644
--- a/fs/btrfs/zoned.c
+++ b/fs/btrfs/zoned.c
@@ -930,7 +930,68 @@ int btrfs_ensure_empty_zones(struct btrfs_device *device, u64 start, u64 size)
 	return 0;
 }
 
-int btrfs_load_block_group_zone_info(struct btrfs_block_group *cache)
+/*
+ * Calculate an allocation pointer from the extent allocation information
+ * for a block group consist of conventional zones. It is pointed to the
+ * end of the last allocated extent in the block group as an allocation
+ * offset.
+ */
+static int calculate_alloc_pointer(struct btrfs_block_group *cache,
+				   u64 *offset_ret)
+{
+	struct btrfs_fs_info *fs_info = cache->fs_info;
+	struct btrfs_root *root = fs_info->extent_root;
+	struct btrfs_path *path;
+	struct btrfs_key key;
+	struct btrfs_key found_key;
+	int ret;
+	u64 length;
+
+	path = btrfs_alloc_path();
+	if (!path)
+		return -ENOMEM;
+
+	key.objectid = cache->start + cache->length;
+	key.type = 0;
+	key.offset = 0;
+
+	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+	/* We should not find the exact match */
+	if (!ret)
+		ret = -EUCLEAN;
+	if (ret < 0)
+		goto out;
+
+	ret = btrfs_previous_extent_item(root, path, cache->start);
+	if (ret) {
+		if (ret == 1) {
+			ret = 0;
+			*offset_ret = 0;
+		}
+		goto out;
+	}
+
+	btrfs_item_key_to_cpu(path->nodes[0], &found_key, path->slots[0]);
+
+	if (found_key.type == BTRFS_EXTENT_ITEM_KEY)
+		length = found_key.offset;
+	else
+		length = fs_info->nodesize;
+
+	if (!(found_key.objectid >= cache->start &&
+	       found_key.objectid + length <= cache->start + cache->length)) {
+		ret = -EUCLEAN;
+		goto out;
+	}
+	*offset_ret = found_key.objectid + length - cache->start;
+	ret = 0;
+
+out:
+	btrfs_free_path(path);
+	return ret;
+}
+
+int btrfs_load_block_group_zone_info(struct btrfs_block_group *cache, bool new)
 {
 	struct btrfs_fs_info *fs_info = cache->fs_info;
 	struct extent_map_tree *em_tree = &fs_info->mapping_tree;
@@ -944,6 +1005,7 @@ int btrfs_load_block_group_zone_info(struct btrfs_block_group *cache)
 	int i;
 	unsigned int nofs_flag;
 	u64 *alloc_offsets = NULL;
+	u64 last_alloc = 0;
 	u32 num_sequential = 0, num_conventional = 0;
 
 	if (!btrfs_is_zoned(fs_info))
@@ -1042,11 +1104,30 @@ int btrfs_load_block_group_zone_info(struct btrfs_block_group *cache)
 
 	if (num_conventional > 0) {
 		/*
-		 * Since conventional zones do not have a write pointer, we
-		 * cannot determine alloc_offset from the pointer
+		 * Avoid calling calculate_alloc_pointer() for new BG. It
+		 * is no use for new BG. It must be always 0.
+		 *
+		 * Also, we have a lock chain of extent buffer lock ->
+		 * chunk mutex.  For new BG, this function is called from
+		 * btrfs_make_block_group() which is already taking the
+		 * chunk mutex. Thus, we cannot call
+		 * calculate_alloc_pointer() which takes extent buffer
+		 * locks to avoid deadlock.
 		 */
-		ret = -EINVAL;
-		goto out;
+		if (new) {
+			cache->alloc_offset = 0;
+			goto out;
+		}
+		ret = calculate_alloc_pointer(cache, &last_alloc);
+		if (ret || map->num_stripes == num_conventional) {
+			if (!ret)
+				cache->alloc_offset = last_alloc;
+			else
+				btrfs_err(fs_info,
+			"zoned: failed to determine allocation offset of bg %llu",
+					  cache->start);
+			goto out;
+		}
 	}
 
 	switch (map->type & BTRFS_BLOCK_GROUP_PROFILE_MASK) {
@@ -1068,6 +1149,14 @@ int btrfs_load_block_group_zone_info(struct btrfs_block_group *cache)
 	}
 
 out:
+	/* An extent is allocated after the write pointer */
+	if (num_conventional && last_alloc > cache->alloc_offset) {
+		btrfs_err(fs_info,
+			  "zoned: got wrong write pointer in BG %llu: %llu > %llu",
+			  logical, last_alloc, cache->alloc_offset);
+		ret = -EIO;
+	}
+
 	kfree(alloc_offsets);
 	free_extent_map(em);
 
diff --git a/fs/btrfs/zoned.h b/fs/btrfs/zoned.h
index 491b98c97f48..b53403ba0b10 100644
--- a/fs/btrfs/zoned.h
+++ b/fs/btrfs/zoned.h
@@ -41,7 +41,7 @@ u64 btrfs_find_allocatable_zones(struct btrfs_device *device, u64 hole_start,
 int btrfs_reset_device_zone(struct btrfs_device *device, u64 physical,
 			    u64 length, u64 *bytes);
 int btrfs_ensure_empty_zones(struct btrfs_device *device, u64 start, u64 size);
-int btrfs_load_block_group_zone_info(struct btrfs_block_group *cache);
+int btrfs_load_block_group_zone_info(struct btrfs_block_group *cache, bool new);
 #else /* CONFIG_BLK_DEV_ZONED */
 static inline int btrfs_get_dev_zone(struct btrfs_device *device, u64 pos,
 				     struct blk_zone *zone)
@@ -119,7 +119,7 @@ static inline int btrfs_ensure_empty_zones(struct btrfs_device *device,
 }
 
 static inline int btrfs_load_block_group_zone_info(
-	struct btrfs_block_group *cache)
+	struct btrfs_block_group *cache, bool new)
 {
 	return 0;
 }
