Re: [PATCH] btrfs: fix bytes_may_use leak in move_existing_remap()

[Boris Burkov <boris@bur.io>]

On Mon, Mar 23, 2026 at 02:36:14PM +0000, Mark Harmstone wrote:
> If the call to btrfs_reserve_extent() in move_existing_remap() returns a
> smaller extent than we asked for, currently we're not undoing the
> bytes_may_use change that we made. Fix this by calling
> btrfs_space_info_update_bytes_may_use() again for the difference.
> 
> Signed-off-by: Mark Harmstone <mark@harmstone.com>
Reviewed-by: Boris Burkov <boris@bur.io>
> Fixes: bbea42dfb91f ("btrfs: move existing remaps before relocating block group")
> ---
>  fs/btrfs/relocation.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
> index 1c42c5180bddd5..3d1756b6116246 100644
> --- a/fs/btrfs/relocation.c
> +++ b/fs/btrfs/relocation.c
> @@ -4174,6 +4174,12 @@ static int move_existing_remap(struct btrfs_fs_info *fs_info,
>  		return ret;
>  	}
>  
> +	if (ins.offset < length) {
> +		spin_lock(&sinfo->lock);
> +		btrfs_space_info_update_bytes_may_use(sinfo, ins.offset - length);
> +		spin_unlock(&sinfo->lock);
> +	}
> +
>  	dest_addr = ins.objectid;
>  	dest_length = ins.offset;
>  
> -- 
> 2.52.0
>