Re: [PATCH v3 2/3] btrfs: block-group: Refactor btrfs_read_block_groups()

[Qu WenRuo <wqu@suse.com>]

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On 2019/10/10 上午10:39, Qu Wenruo wrote:
> Refactor the work inside the loop of btrfs_read_block_groups() into one
> separate function, read_one_block_group().
> 
> This allows read_one_block_group to be reused for later BG_TREE feature.
> 
> The refactor does the following extra fix:
> - Use btrfs_fs_incompat() to replace open-coded feature check
> 
> Signed-off-by: Qu Wenruo <wqu@suse.com>
> Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
> Reviewed-by: Anand Jain <anand.jain@oracle.com>

Hi David,

Mind to add this patch to for-next branch?

Considering the recent changes to struct btrfs_block_group_cache, there
is some considerable conflicts.

It would be much easier to solve them sooner than later.
If needed I could send a newer version based on latest for-next branch.

Thanks,
Qu

> ---
>  fs/btrfs/block-group.c | 215 +++++++++++++++++++++--------------------
>  1 file changed, 108 insertions(+), 107 deletions(-)
> 
> diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
> index c906a2b6c2cf..0c5eef0610fa 100644
> --- a/fs/btrfs/block-group.c
> +++ b/fs/btrfs/block-group.c
> @@ -1687,6 +1687,109 @@ static int check_chunk_block_group_mappings(struct btrfs_fs_info *fs_info)
>  	return ret;
>  }
>  
> +static int read_one_block_group(struct btrfs_fs_info *info,
> +				struct btrfs_path *path,
> +				int need_clear)
> +{
> +	struct extent_buffer *leaf = path->nodes[0];
> +	struct btrfs_block_group_cache *cache;
> +	struct btrfs_space_info *space_info;
> +	struct btrfs_key key;
> +	int mixed = btrfs_fs_incompat(info, MIXED_GROUPS);
> +	int slot = path->slots[0];
> +	int ret;
> +
> +	btrfs_item_key_to_cpu(leaf, &key, slot);
> +	ASSERT(key.type == BTRFS_BLOCK_GROUP_ITEM_KEY);
> +
> +	cache = btrfs_create_block_group_cache(info, key.objectid,
> +					       key.offset);
> +	if (!cache)
> +		return -ENOMEM;
> +
> +	if (need_clear) {
> +		/*
> +		 * When we mount with old space cache, we need to
> +		 * set BTRFS_DC_CLEAR and set dirty flag.
> +		 *
> +		 * a) Setting 'BTRFS_DC_CLEAR' makes sure that we
> +		 *    truncate the old free space cache inode and
> +		 *    setup a new one.
> +		 * b) Setting 'dirty flag' makes sure that we flush
> +		 *    the new space cache info onto disk.
> +		 */
> +		if (btrfs_test_opt(info, SPACE_CACHE))
> +			cache->disk_cache_state = BTRFS_DC_CLEAR;
> +	}
> +	read_extent_buffer(leaf, &cache->item,
> +			   btrfs_item_ptr_offset(leaf, slot),
> +			   sizeof(cache->item));
> +	cache->flags = btrfs_block_group_flags(&cache->item);
> +	if (!mixed && ((cache->flags & BTRFS_BLOCK_GROUP_METADATA) &&
> +	    (cache->flags & BTRFS_BLOCK_GROUP_DATA))) {
> +			btrfs_err(info,
> +"bg %llu is a mixed block group but filesystem hasn't enabled mixed block groups",
> +				  cache->key.objectid);
> +			ret = -EINVAL;
> +			goto error;
> +	}
> +
> +	/*
> +	 * We need to exclude the super stripes now so that the space info has
> +	 * super bytes accounted for, otherwise we'll think we have more space
> +	 * than we actually do.
> +	 */
> +	ret = exclude_super_stripes(cache);
> +	if (ret) {
> +		/* We may have excluded something, so call this just in case. */
> +		btrfs_free_excluded_extents(cache);
> +		goto error;
> +	}
> +
> +	/*
> +	 * Check for two cases, either we are full, and therefore don't need
> +	 * to bother with the caching work since we won't find any space, or we
> +	 * are empty, and we can just add all the space in and be done with it.
> +	 * This saves us _a_lot_ of time, particularly in the full case.
> +	 */
> +	if (key.offset == btrfs_block_group_used(&cache->item)) {
> +		cache->last_byte_to_unpin = (u64)-1;
> +		cache->cached = BTRFS_CACHE_FINISHED;
> +		btrfs_free_excluded_extents(cache);
> +	} else if (btrfs_block_group_used(&cache->item) == 0) {
> +		cache->last_byte_to_unpin = (u64)-1;
> +		cache->cached = BTRFS_CACHE_FINISHED;
> +		add_new_free_space(cache, key.objectid,
> +				   key.objectid + key.offset);
> +		btrfs_free_excluded_extents(cache);
> +	}
> +	ret = btrfs_add_block_group_cache(info, cache);
> +	if (ret) {
> +		btrfs_remove_free_space_cache(cache);
> +		goto error;
> +	}
> +	trace_btrfs_add_block_group(info, cache, 0);
> +	btrfs_update_space_info(info, cache->flags, key.offset,
> +				btrfs_block_group_used(&cache->item),
> +				cache->bytes_super, &space_info);
> +
> +	cache->space_info = space_info;
> +
> +	link_block_group(cache);
> +
> +	set_avail_alloc_bits(info, cache->flags);
> +	if (btrfs_chunk_readonly(info, cache->key.objectid)) {
> +		inc_block_group_ro(cache, 1);
> +	} else if (btrfs_block_group_used(&cache->item) == 0) {
> +		ASSERT(list_empty(&cache->bg_list));
> +		btrfs_mark_bg_unused(cache);
> +	}
> +	return 0;
> +error:
> +	btrfs_put_block_group(cache);
> +	return ret;
> +}
> +
>  int btrfs_read_block_groups(struct btrfs_fs_info *info)
>  {
>  	struct btrfs_path *path;
> @@ -1694,15 +1797,8 @@ int btrfs_read_block_groups(struct btrfs_fs_info *info)
>  	struct btrfs_block_group_cache *cache;
>  	struct btrfs_space_info *space_info;
>  	struct btrfs_key key;
> -	struct btrfs_key found_key;
> -	struct extent_buffer *leaf;
>  	int need_clear = 0;
>  	u64 cache_gen;
> -	u64 feature;
> -	int mixed;
> -
> -	feature = btrfs_super_incompat_flags(info->super_copy);
> -	mixed = !!(feature & BTRFS_FEATURE_INCOMPAT_MIXED_GROUPS);
>  
>  	key.objectid = 0;
>  	key.offset = 0;
> @@ -1726,108 +1822,13 @@ int btrfs_read_block_groups(struct btrfs_fs_info *info)
>  		if (ret != 0)
>  			goto error;
>  
> -		leaf = path->nodes[0];
> -		btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
> -
> -		cache = btrfs_create_block_group_cache(info, found_key.objectid,
> -						       found_key.offset);
> -		if (!cache) {
> -			ret = -ENOMEM;
> -			goto error;
> -		}
> -
> -		if (need_clear) {
> -			/*
> -			 * When we mount with old space cache, we need to
> -			 * set BTRFS_DC_CLEAR and set dirty flag.
> -			 *
> -			 * a) Setting 'BTRFS_DC_CLEAR' makes sure that we
> -			 *    truncate the old free space cache inode and
> -			 *    setup a new one.
> -			 * b) Setting 'dirty flag' makes sure that we flush
> -			 *    the new space cache info onto disk.
> -			 */
> -			if (btrfs_test_opt(info, SPACE_CACHE))
> -				cache->disk_cache_state = BTRFS_DC_CLEAR;
> -		}
> -
> -		read_extent_buffer(leaf, &cache->item,
> -				   btrfs_item_ptr_offset(leaf, path->slots[0]),
> -				   sizeof(cache->item));
> -		cache->flags = btrfs_block_group_flags(&cache->item);
> -		if (!mixed &&
> -		    ((cache->flags & BTRFS_BLOCK_GROUP_METADATA) &&
> -		    (cache->flags & BTRFS_BLOCK_GROUP_DATA))) {
> -			btrfs_err(info,
> -"bg %llu is a mixed block group but filesystem hasn't enabled mixed block groups",
> -				  cache->key.objectid);
> -			ret = -EINVAL;
> -			btrfs_put_block_group(cache);
> +		btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
> +		ret = read_one_block_group(info, path, need_clear);
> +		if (ret < 0)
>  			goto error;
> -		}
> -
> -		key.objectid = found_key.objectid + found_key.offset;
> +		key.objectid += key.offset;
> +		key.offset = 0;
>  		btrfs_release_path(path);
> -
> -		/*
> -		 * We need to exclude the super stripes now so that the space
> -		 * info has super bytes accounted for, otherwise we'll think
> -		 * we have more space than we actually do.
> -		 */
> -		ret = exclude_super_stripes(cache);
> -		if (ret) {
> -			/*
> -			 * We may have excluded something, so call this just in
> -			 * case.
> -			 */
> -			btrfs_free_excluded_extents(cache);
> -			btrfs_put_block_group(cache);
> -			goto error;
> -		}
> -
> -		/*
> -		 * Check for two cases, either we are full, and therefore
> -		 * don't need to bother with the caching work since we won't
> -		 * find any space, or we are empty, and we can just add all
> -		 * the space in and be done with it.  This saves us _a_lot_ of
> -		 * time, particularly in the full case.
> -		 */
> -		if (found_key.offset == btrfs_block_group_used(&cache->item)) {
> -			cache->last_byte_to_unpin = (u64)-1;
> -			cache->cached = BTRFS_CACHE_FINISHED;
> -			btrfs_free_excluded_extents(cache);
> -		} else if (btrfs_block_group_used(&cache->item) == 0) {
> -			cache->last_byte_to_unpin = (u64)-1;
> -			cache->cached = BTRFS_CACHE_FINISHED;
> -			add_new_free_space(cache, found_key.objectid,
> -					   found_key.objectid +
> -					   found_key.offset);
> -			btrfs_free_excluded_extents(cache);
> -		}
> -
> -		ret = btrfs_add_block_group_cache(info, cache);
> -		if (ret) {
> -			btrfs_remove_free_space_cache(cache);
> -			btrfs_put_block_group(cache);
> -			goto error;
> -		}
> -
> -		trace_btrfs_add_block_group(info, cache, 0);
> -		btrfs_update_space_info(info, cache->flags, found_key.offset,
> -					btrfs_block_group_used(&cache->item),
> -					cache->bytes_super, &space_info);
> -
> -		cache->space_info = space_info;
> -
> -		link_block_group(cache);
> -
> -		set_avail_alloc_bits(info, cache->flags);
> -		if (btrfs_chunk_readonly(info, cache->key.objectid)) {
> -			inc_block_group_ro(cache, 1);
> -		} else if (btrfs_block_group_used(&cache->item) == 0) {
> -			ASSERT(list_empty(&cache->bg_list));
> -			btrfs_mark_bg_unused(cache);
> -		}
>  	}
>  
>  	list_for_each_entry_rcu(space_info, &info->space_info, list) {
> 


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