Re: [PATCH] btrfs progs: fix extra metadata chunk allocation in --mixed case

[liubo <liubo2009@cn.fujitsu.com>]

On 05/05/2011 10:16 PM, Arne Jansen wrote:
> When creating a mixed fs with mkfs, an extra metadata chunk got allocated.
> This is because btrfs_reserve_extent calls do_chunk_alloc for METADATA,
> which in turn wasn't able to find the proper space_info, as __find_space_info
> did a hard compare of the flags. It is now sufficient for the space_info to
> include the proper flag. This reflects the change done to the kernel code
> to support mixed chunks.
> Also for a subsequent chunk allocation (which should not be hit in the mkfs
> case), the chunk is now created with the flags from the space_info instead
> of the requested flags. A better solution would be to pull the full changeset
> for the mixed case from the kernel into the user mode (or, even better, share
> the code)
> 
> The additional chunk probably confused block_rsv calculation, which in turn
> led to severeal ENOSPC Oopses.
> 

Good catch!

Reviewed-by: Liu Bo <liubo2009@cn.fujitsu.com>

> Signed-off-by: Arne Jansen <sensille@gmx.net>
> ---
>  extent-tree.c |    7 ++++---
>  1 files changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/extent-tree.c b/extent-tree.c
> index b2f9bb2..c6c77c6 100644
> --- a/extent-tree.c
> +++ b/extent-tree.c
> @@ -1735,7 +1735,7 @@ static struct btrfs_space_info *__find_space_info(struct btrfs_fs_info *info,
>  	struct btrfs_space_info *found;
>  	list_for_each(cur, head) {
>  		found = list_entry(cur, struct btrfs_space_info, list);
> -		if (found->flags == flags)
> +		if (found->flags & flags)
>  			return found;
>  	}
>  	return NULL;
> @@ -1812,7 +1812,8 @@ static int do_chunk_alloc(struct btrfs_trans_handle *trans,
>  	    thresh)
>  		return 0;
>  
> -	ret = btrfs_alloc_chunk(trans, extent_root, &start, &num_bytes, flags);
> +	ret = btrfs_alloc_chunk(trans, extent_root, &start, &num_bytes,
> +	                        space_info->flags);
>  	if (ret == -ENOSPC) {
>  		space_info->full = 1;
>  		return 0;
> @@ -1820,7 +1821,7 @@ static int do_chunk_alloc(struct btrfs_trans_handle *trans,
>  
>  	BUG_ON(ret);
>  
> -	ret = btrfs_make_block_group(trans, extent_root, 0, flags,
> +	ret = btrfs_make_block_group(trans, extent_root, 0, space_info->flags,
>  		     BTRFS_FIRST_CHUNK_TREE_OBJECTID, start, num_bytes);
>  	BUG_ON(ret);
>  	return 0;