Re: [RFC PATCH v3.1 3/6] btrfs: qgroup: Return actually freed bytes for qgroup release or free data

[David Sterba <dsterba@suse.cz>]

On Fri, May 12, 2017 at 11:30:43AM +0800, Qu Wenruo wrote:
> btrfs_qgroup_release/free_data() only returns 0 or minus error
> number(ENOMEM is the only possible error).

"btrfs_qgroup_release/free_data() only returns 0 or a negative error
number (ENOMEM is the only possible error)."

> This is normally good enough, but sometimes we need the accurate byte
> number it freed/released.
> 
> Change it to return actually released/freed bytenr number instead of 0
> for success.
> And slightly modify related extent_changeset structure, since in btrfs
> one none-hole data extent won't be larger than 128M, so "unsigned int"
      ^^^^^^^^^
      NO_HOLES or no-hole

> is large enough for the use case.
> 
> Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
> ---
>  fs/btrfs/extent-tree.c | 2 +-
>  fs/btrfs/extent_io.h   | 2 +-
>  fs/btrfs/qgroup.c      | 1 +
>  3 files changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> index e390451c72e6..4f62696131a6 100644
> --- a/fs/btrfs/extent-tree.c
> +++ b/fs/btrfs/extent-tree.c
> @@ -4298,7 +4298,7 @@ int btrfs_check_data_free_space(struct inode *inode, u64 start, u64 len)
>  
>  	/* Use new btrfs_qgroup_reserve_data to reserve precious data space. */
>  	ret = btrfs_qgroup_reserve_data(inode, start, len);
> -	if (ret)
> +	if (ret < 0)
>  		btrfs_free_reserved_data_space_noquota(inode, start, len);
>  	return ret;
>  }
> diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
> index 1eafa2f0ede3..cc1b08fa9fe7 100644
> --- a/fs/btrfs/extent_io.h
> +++ b/fs/btrfs/extent_io.h
> @@ -205,7 +205,7 @@ struct extent_buffer {
>   */
>  struct extent_changeset {
>  	/* How many bytes are set/cleared in this operation */
> -	u64 bytes_changed;
> +	unsigned int bytes_changed;

The alignment constraints will insert 4 bytes anyway, so we don't save
any space, but unsigned int is fine here, as we're not going to utilize u64.

>  	/* Changed ranges */
>  	struct ulist range_changed;
> diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
> index 9f01c25469f7..ad2e99491395 100644
> --- a/fs/btrfs/qgroup.c
> +++ b/fs/btrfs/qgroup.c
> @@ -2886,6 +2886,7 @@ static int __btrfs_qgroup_release_data(struct inode *inode, u64 start, u64 len,
>  		btrfs_qgroup_free_refroot(BTRFS_I(inode)->root->fs_info,
>  				BTRFS_I(inode)->root->objectid,
>  				changeset.bytes_changed);
> +	ret = changeset.bytes_changed;
>  out:
>  	ulist_release(&changeset.range_changed);
>  	return ret;
> -- 
> 2.12.2
> 
> 
> 
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