Re: [PATCH v3 21/22] btrfs-progs: convert: Strictly avoid meta or system chunk allocation

[Liu Bo <bo.li.liu@oracle.com>]

On Fri, Jan 29, 2016 at 01:03:31PM +0800, Qu Wenruo wrote:
> Before this patch, btrfs-convert only rely on large enough initial
> system/metadata chunk size to ensure no newer system/meta chunk will be
> created.
> 
> But that's not safe enough. So add two new members in fs_info,
> avoid_sys/meta_chunk_alloc flags to prevent any newer system or meta
> chunks to be created before init_btrfs_v2().
> 
> Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
> Signed-off-by: David Sterba <dsterba@suse.com>
> ---
>  btrfs-convert.c |  9 +++++++++
>  ctree.h         |  3 +++
>  extent-tree.c   | 10 ++++++++++
>  3 files changed, 22 insertions(+)
> 
> diff --git a/btrfs-convert.c b/btrfs-convert.c
> index efa3b02..333f413 100644
> --- a/btrfs-convert.c
> +++ b/btrfs-convert.c
> @@ -2322,6 +2322,13 @@ static int init_btrfs_v2(struct btrfs_mkfs_config *cfg, struct btrfs_root *root,
>  	struct btrfs_fs_info *fs_info = root->fs_info;
>  	int ret;
>  
> +	/*
> +	 * Don't alloc any metadata/system chunk, as we don't want
> +	 * any meta/sys chunk allcated before all data chunks are inserted.
> +	 * Or we screw up the chunk layout just like the old implement.
> +	 */

I don't get this, with this patch set, we can allocate data from DATA chunk,
allocate metadata from METADATA chunk, but then we're not allowed to allocate new chunks?

Thanks,

-liubo
> +	fs_info->avoid_sys_chunk_alloc = 1;
> +	fs_info->avoid_meta_chunk_alloc = 1;
>  	trans = btrfs_start_transaction(root, 1);
>  	BUG_ON(!trans);
>  	ret = btrfs_fix_block_accounting(trans, root);
> @@ -2359,6 +2366,8 @@ static int init_btrfs_v2(struct btrfs_mkfs_config *cfg, struct btrfs_root *root,
>  		goto err;
>  
>  	ret = btrfs_commit_transaction(trans, root);
> +	fs_info->avoid_sys_chunk_alloc = 0;
> +	fs_info->avoid_meta_chunk_alloc = 0;
>  err:
>  	return ret;
>  }
> diff --git a/ctree.h b/ctree.h
> index 1443746..187bd27 100644
> --- a/ctree.h
> +++ b/ctree.h
> @@ -1030,6 +1030,9 @@ struct btrfs_fs_info {
>  	unsigned int quota_enabled:1;
>  	unsigned int suppress_check_block_errors:1;
>  	unsigned int ignore_fsid_mismatch:1;
> +	unsigned int avoid_meta_chunk_alloc:1;
> +	unsigned int avoid_sys_chunk_alloc:1;
> +
>  
>  	int (*free_extent_hook)(struct btrfs_trans_handle *trans,
>  				struct btrfs_root *root,
> diff --git a/extent-tree.c b/extent-tree.c
> index 93b1945..e7c61b1 100644
> --- a/extent-tree.c
> +++ b/extent-tree.c
> @@ -1904,6 +1904,16 @@ static int do_chunk_alloc(struct btrfs_trans_handle *trans,
>  	    thresh)
>  		return 0;
>  
> +	/*
> +	 * Avoid allocating given chunk type
> +	 */
> +	if (extent_root->fs_info->avoid_meta_chunk_alloc &&
> +	    (flags & BTRFS_BLOCK_GROUP_METADATA))
> +		return 0;
> +	if (extent_root->fs_info->avoid_sys_chunk_alloc &&
> +	    (flags & BTRFS_BLOCK_GROUP_SYSTEM))
> +		return 0;
> +
>  	ret = btrfs_alloc_chunk(trans, extent_root, &start, &num_bytes,
>  	                        space_info->flags);
>  	if (ret == -ENOSPC) {
> -- 
> 2.7.0
> 
> 
> 
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