Re: [PATCH] btrfs: trace: Add trace points for unused block groups

[David Sterba <dsterba@suse.cz>]

On Thu, Apr 26, 2018 at 05:17:20PM +0800, Qu Wenruo wrote:
> This patch will add the following trace events:
> 1) btrfs_remove_block_group
>    For btrfs_remove_block_group() function.
>    Triggered when a block group is really removed.
> 
> 2) btrfs_add_unused_block_group
>    Triggered which block group is added to unused_bgs list.
> 
> 3) btrfs_skip_unused_block_group
>    Triggered which unused block group is not deleted.
> 
> These trace events is pretty handy to debug case related to block group
> auto remove.

Sounds useful.

> Signed-off-by: Qu Wenruo <wqu@suse.com>

> +DECLARE_EVENT_CLASS(btrfs__block_group,
> +	TP_PROTO(const struct btrfs_block_group_cache *bg_cache),
> +
> +	TP_ARGS(bg_cache),
> +
> +	TP_STRUCT__entry_btrfs(
> +		__field(	u64,	bytenr		)
> +		__field(	u64,	flags		)
> +		__field(	u64,	len		)
> +		__field(	u64,	used		)
> +	),
> +
> +	TP_fast_assign_btrfs(bg_cache->fs_info,
> +		__entry->bytenr = bg_cache->key.objectid,
> +		__entry->len	= bg_cache->key.offset,
> +		__entry->flags	= bg_cache->flags;
> +		__entry->used	= btrfs_block_group_used(&bg_cache->item);
> +	),
> +
> +	TP_printk_btrfs("bg bytenr=%llu len=%llu used=%llu flags=%llu(%s)",
> +		__entry->bytenr, __entry->len, __entry->used, __entry->flags,
> +		__print_flags(__entry->flags, "|", BTRFS_GROUP_FLAGS))

I've reorered the fields so they're sorted the same way in all 3
sections, as defined in the printk (bytenr, len, used, flags).

Reviewed-by: David Sterba <dsterba@suse.com>