Re: [PATCH] btrfs: change block group reclaim_mark to bool

On Wed, Jun 24, 2026 at 12:02:27PM +0800, Sun YangKai wrote:
> The reclaim_mark field in struct btrfs_block_group was a u64 that was
> incremented when marking block groups for reclaim during sweeping, but
> the actual counter value was never used - only the zero/non-zero state
> mattered for determining if a block group needed reclaim.
> 
> Convert it to a bool to properly reflect its usage and reduce memory
> footprint by 8 bytes. Update assignments to use true/false instead of
> increment and zero.
> 

LGTM, thanks.
Reviewed-by: Boris Burkov <[email protected]>

> Signed-off-by: Sun YangKai <[email protected]>
> ---
>  fs/btrfs/block-group.c | 2 +-
>  fs/btrfs/block-group.h | 7 ++++++-
>  fs/btrfs/space-info.c  | 2 +-
>  3 files changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
> index 9e937407d12a9..5829c806c4d48 100644
> --- a/fs/btrfs/block-group.c
> +++ b/fs/btrfs/block-group.c
> @@ -3923,7 +3923,7 @@ int btrfs_update_block_group(struct btrfs_trans_handle *trans,
>  		old_val += num_bytes;
>  		cache->used = old_val;
>  		cache->reserved -= num_bytes;
> -		cache->reclaim_mark = 0;
> +		cache->reclaim_mark = false;
>  		space_info->bytes_reserved -= num_bytes;
>  		space_info->bytes_used += num_bytes;
>  		space_info->disk_used += num_bytes * factor;
> diff --git a/fs/btrfs/block-group.h b/fs/btrfs/block-group.h
> index 790c2d467af57..942befdf75df7 100644
> --- a/fs/btrfs/block-group.h
> +++ b/fs/btrfs/block-group.h
> @@ -263,6 +263,12 @@ struct btrfs_block_group {
>  
>  	enum btrfs_block_group_size_class size_class:8;
>  
> +	/*
> +	 * Mark this blockgroup is not used for allocation
> +	 * between two reclaim sweeps.

nit: this grammar doesn't parse great to me. Maybe drop "Mark"?
or change it to "We identified this for reclaim on a previous pass, so
it stably needs reclaim across passes" or something like that.

> +	 */
> +	bool reclaim_mark;
> +
>  	/*
>  	 * Number of extents in this block group used for swap files.
>  	 * All accesses protected by the spinlock 'lock'.
> @@ -281,7 +287,6 @@ struct btrfs_block_group {
>  	struct list_head active_bg_list;
>  	struct work_struct zone_finish_work;
>  	struct extent_buffer *last_eb;
> -	u64 reclaim_mark;
>  };
>  
>  static inline u64 btrfs_block_group_end(const struct btrfs_block_group *block_group)
> diff --git a/fs/btrfs/space-info.c b/fs/btrfs/space-info.c
> index e6641597b321e..39a28e1bec8ad 100644
> --- a/fs/btrfs/space-info.c
> +++ b/fs/btrfs/space-info.c
> @@ -2156,7 +2156,7 @@ static bool do_reclaim_sweep(struct btrfs_space_info *space_info, int raid)
>  			will_reclaim = true;
>  			reclaim = true;
>  		}
> -		bg->reclaim_mark++;
> +		bg->reclaim_mark = true;
>  		spin_unlock(&bg->lock);
>  		if (reclaim)
>  			btrfs_mark_bg_to_reclaim(bg);
> -- 
> 2.54.0
>