Re: [PATCH v2 1/2] btrfs: Separate space_info create/update

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

On Wed, May 17, 2017 at 06:07:42PM +0300, Nikolay Borisov wrote:
> Currently the struct space_info creation code is intermixed in the
> udpate_space_info function. There are well-defined points at which the we
> actually want to create brand-new space_info structs (e.g. during mount of
> the filesystem as well as sometimes when adding/initialising new chunks). In
> such cases udpate_space_info is called with 0 as the bytes parameter. All of
> this makes for spaghetti code.
> 
> Fix it by factoring out the creation code in a separate create_space_info
> structure. This also allows to simplify the internals. Furthermore it will
> make the update_space_info function not fail, allowing to remove error
> handling in callers. This will come in a follow up patch.
> 
> This bears no functional changes
> 
> Signed-off-by: Nikolay Borisov <nborisov@suse.com>
> Reviewed-by: Jeff Mahoney <jeffm@suse.com>
> ---
>  fs/btrfs/extent-tree.c | 127 ++++++++++++++++++++++++-------------------------
>  1 file changed, 62 insertions(+), 65 deletions(-)
> 
> Change since v1: 
> 
>  Incorporated Jeff Mahoney's feedback and added his reviewed-by
> 
> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> index be5477676cc8..28848e45b018 100644
> --- a/fs/btrfs/extent-tree.c
> +++ b/fs/btrfs/extent-tree.c
> @@ -3914,15 +3914,58 @@ static const char *alloc_name(u64 flags)
>  	};
>  }
>  
> +static int create_space_info(struct btrfs_fs_info *info, u64 flags,
> +			     struct btrfs_space_info **new) {
> +
> +	struct btrfs_space_info *space_info;
> +	int i;
> +	int ret;
> +
> +	space_info = kzalloc(sizeof(*space_info), GFP_NOFS);
> +	if (!space_info)
> +		return -ENOMEM;
> +
> +	ret = percpu_counter_init(&space_info->total_bytes_pinned, 0, GFP_KERNEL);

over 80.

> +	if (ret) {
> +		kfree(space_info);
> +		return ret;
> +	}
> +
> +	for (i = 0; i < BTRFS_NR_RAID_TYPES; i++)
> +		INIT_LIST_HEAD(&space_info->block_groups[i]);
> +	init_rwsem(&space_info->groups_sem);
> +	spin_lock_init(&space_info->lock);
> +	space_info->flags = flags & BTRFS_BLOCK_GROUP_TYPE_MASK;
> +	space_info->force_alloc = CHUNK_ALLOC_NO_FORCE;
> +	init_waitqueue_head(&space_info->wait);
> +	INIT_LIST_HEAD(&space_info->ro_bgs);
> +	INIT_LIST_HEAD(&space_info->tickets);
> +	INIT_LIST_HEAD(&space_info->priority_tickets);
> +
> +	ret = kobject_init_and_add(&space_info->kobj, &space_info_ktype,
> +				    info->space_info_kobj, "%s",
> +				    alloc_name(space_info->flags));
> +	if (ret) {
> +		percpu_counter_destroy(&space_info->total_bytes_pinned);
> +		kfree(space_info);
> +		return ret;
> +	}
> +
> +	*new = space_info;
> +	list_add_rcu(&space_info->list, &info->space_info);
> +	if (flags & BTRFS_BLOCK_GROUP_DATA)
> +		info->data_sinfo = space_info;
> +
> +	return ret;
> +}
> +
>  static int update_space_info(struct btrfs_fs_info *info, u64 flags,
>  			     u64 total_bytes, u64 bytes_used,
>  			     u64 bytes_readonly,
>  			     struct btrfs_space_info **space_info)
>  {
>  	struct btrfs_space_info *found;
> -	int i;
>  	int factor;
> -	int ret;
>  
>  	if (flags & (BTRFS_BLOCK_GROUP_DUP | BTRFS_BLOCK_GROUP_RAID1 |
>  		     BTRFS_BLOCK_GROUP_RAID10))
> @@ -3946,53 +3989,6 @@ static int update_space_info(struct btrfs_fs_info *info, u64 flags,
>  		*space_info = found;
>  		return 0;
>  	}
> -	found = kzalloc(sizeof(*found), GFP_NOFS);
> -	if (!found)
> -		return -ENOMEM;
> -
> -	ret = percpu_counter_init(&found->total_bytes_pinned, 0, GFP_KERNEL);
> -	if (ret) {
> -		kfree(found);
> -		return ret;
> -	}
> -
> -	for (i = 0; i < BTRFS_NR_RAID_TYPES; i++)
> -		INIT_LIST_HEAD(&found->block_groups[i]);
> -	init_rwsem(&found->groups_sem);
> -	spin_lock_init(&found->lock);
> -	found->flags = flags & BTRFS_BLOCK_GROUP_TYPE_MASK;
> -	found->total_bytes = total_bytes;
> -	found->disk_total = total_bytes * factor;
> -	found->bytes_used = bytes_used;
> -	found->disk_used = bytes_used * factor;
> -	found->bytes_pinned = 0;
> -	found->bytes_reserved = 0;
> -	found->bytes_readonly = bytes_readonly;
> -	found->bytes_may_use = 0;
> -	found->full = 0;
> -	found->max_extent_size = 0;
> -	found->force_alloc = CHUNK_ALLOC_NO_FORCE;
> -	found->chunk_alloc = 0;
> -	found->flush = 0;
> -	init_waitqueue_head(&found->wait);
> -	INIT_LIST_HEAD(&found->ro_bgs);
> -	INIT_LIST_HEAD(&found->tickets);
> -	INIT_LIST_HEAD(&found->priority_tickets);
> -
> -	ret = kobject_init_and_add(&found->kobj, &space_info_ktype,
> -				    info->space_info_kobj, "%s",
> -				    alloc_name(found->flags));
> -	if (ret) {
> -		kfree(found);
> -		return ret;
> -	}
> -
> -	*space_info = found;
> -	list_add_rcu(&found->list, &info->space_info);
> -	if (flags & BTRFS_BLOCK_GROUP_DATA)
> -		info->data_sinfo = found;
> -
> -	return ret;
>  }
>  
>  static void set_avail_alloc_bits(struct btrfs_fs_info *fs_info, u64 flags)
> @@ -4495,10 +4491,9 @@ static int do_chunk_alloc(struct btrfs_trans_handle *trans,
>  
>  	space_info = __find_space_info(fs_info, flags);
>  	if (!space_info) {
> -		ret = update_space_info(fs_info, flags, 0, 0, 0, &space_info);
> +		ret = create_space_info(fs_info, flags, &space_info);
>  		BUG_ON(ret); /* -ENOMEM */

While we're here, can we drop the BUG_ON?  (a separate patch is fine)

>  	}
> -	BUG_ON(!space_info); /* Logic error */
>  
>  again:
>  	spin_lock(&space_info->lock);
> @@ -5763,7 +5758,7 @@ int btrfs_orphan_reserve_metadata(struct btrfs_trans_handle *trans,
>  	 */
>  	u64 num_bytes = btrfs_calc_trans_metadata_size(fs_info, 1);
>  
> -	trace_btrfs_space_reservation(fs_info, "orphan", btrfs_ino(inode), 
> +	trace_btrfs_space_reservation(fs_info, "orphan", btrfs_ino(inode),

whitespace?

>  			num_bytes, 1);
>  	return btrfs_block_rsv_migrate(src_rsv, dst_rsv, num_bytes, 1);
>  }
> @@ -10191,16 +10186,18 @@ int btrfs_make_block_group(struct btrfs_trans_handle *trans,
>  	}
>  #endif
>  	/*
> -	 * Call to ensure the corresponding space_info object is created and
> -	 * assigned to our block group, but don't update its counters just yet.
> -	 * We want our bg to be added to the rbtree with its ->space_info set.
> +	 * Ensure the corresponding space_info object is created and
> +	 * assigned to our block group. We want our bg to be added to the rbtree
> +	 * with its ->space_info set.
>  	 */
> -	ret = update_space_info(fs_info, cache->flags, 0, 0, 0,
> -				&cache->space_info);
> -	if (ret) {
> -		btrfs_remove_free_space_cache(cache);
> -		btrfs_put_block_group(cache);
> -		return ret;
> +	cache->space_info = __find_space_info(fs_info, cache->flags);
> +	if (!cache->space_info) {
> +		ret = create_space_info(fs_info, cache->flags, &cache->space_info);

over 80, please trim it.

Others look good.

Reviewed-by: Liu Bo <bo.li.liu@oracle.com>

Thanks,

-liubo

> +		if (ret) {
> +			btrfs_remove_free_space_cache(cache);
> +			btrfs_put_block_group(cache);
> +			return ret;
> +		}
>  	}
>  
>  	ret = btrfs_add_block_group_cache(fs_info, cache);
> @@ -10774,21 +10771,21 @@ int btrfs_init_space_info(struct btrfs_fs_info *fs_info)
>  		mixed = 1;
>  
>  	flags = BTRFS_BLOCK_GROUP_SYSTEM;
> -	ret = update_space_info(fs_info, flags, 0, 0, 0, &space_info);
> +	ret = create_space_info(fs_info, flags, &space_info);
>  	if (ret)
>  		goto out;
>  
>  	if (mixed) {
>  		flags = BTRFS_BLOCK_GROUP_METADATA | BTRFS_BLOCK_GROUP_DATA;
> -		ret = update_space_info(fs_info, flags, 0, 0, 0, &space_info);
> +		ret = create_space_info(fs_info, flags, &space_info);
>  	} else {
>  		flags = BTRFS_BLOCK_GROUP_METADATA;
> -		ret = update_space_info(fs_info, flags, 0, 0, 0, &space_info);
> +		ret = create_space_info(fs_info, flags, &space_info);
>  		if (ret)
>  			goto out;
>  
>  		flags = BTRFS_BLOCK_GROUP_DATA;
> -		ret = update_space_info(fs_info, flags, 0, 0, 0, &space_info);
> +		ret = create_space_info(fs_info, flags, &space_info);
>  	}
>  out:
>  	return ret;
> -- 
> 2.7.4
> 
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