Re: [PATCH v2 1/4] btrfs: store stripe size and chunk size in space-info struct.

[Josef Bacik <josef@toxicpanda.com>]

On Wed, Oct 27, 2021 at 01:14:38PM -0700, Stefan Roesch wrote:
> The stripe size and chunk size are stored in the btrfs_space_info
> structure. They are initialized at the start and are then used.
> 
> Two api's are added to get the current value and one to update
> the value.
> 
> These api's will be used to be able to expose the stripe_size
> as a sysfs setting.
> 
> Signed-off-by: Stefan Roesch <shr@fb.com>
> ---
>  fs/btrfs/space-info.c | 72 +++++++++++++++++++++++++++++++++++++++++++
>  fs/btrfs/space-info.h |  4 +++
>  fs/btrfs/volumes.c    | 28 ++++++-----------
>  3 files changed, 85 insertions(+), 19 deletions(-)
> 
> diff --git a/fs/btrfs/space-info.c b/fs/btrfs/space-info.c
> index 48d77f360a24..570acfebeae4 100644
> --- a/fs/btrfs/space-info.c
> +++ b/fs/btrfs/space-info.c
> @@ -181,6 +181,74 @@ void btrfs_clear_space_info_full(struct btrfs_fs_info *info)
>  		found->full = 0;
>  }
>  
> +/*
> + * Compute stripe size depending on block type for regular volumes.
> + */
> +static u64 compute_stripe_size_regular(struct btrfs_fs_info *info, u64 flags)
> +{
> +	ASSERT(flags & BTRFS_BLOCK_GROUP_TYPE_MASK);
> +
> +	if (flags & BTRFS_BLOCK_GROUP_DATA)
> +		return SZ_1G;
> +	else if (flags & BTRFS_BLOCK_GROUP_SYSTEM)
> +		return SZ_32M;
> +
> +	/* Handle BTRFS_BLOCK_GROUP_METADATA */
> +	if (info->fs_devices->total_rw_bytes > 50ULL * SZ_1G)
> +		return SZ_1G;
> +
> +	return SZ_256M;
> +}
> +
> +/*
> + * Compute stripe size for zoned volumes.
> + */
> +static u64 compute_stripe_size_zoned(struct btrfs_fs_info *info)
> +{
> +	return info->zone_size;
> +}
> +
> +/*
> + * Compute stripe size depending on volume type.
> + */
> +static u64 compute_stripe_size(struct btrfs_fs_info *info, u64 flags)
> +{
> +	if (btrfs_is_zoned(info))
> +		return compute_stripe_size_zoned(info);
> +
> +	return compute_stripe_size_regular(info, flags);
> +}
> +
> +/*
> + * Compute chunk size depending on block type and stripe size.
> + */
> +static u64 compute_chunk_size(u64 flags, u64 max_stripe_size)
> +{
> +	ASSERT(flags & BTRFS_BLOCK_GROUP_TYPE_MASK);
> +
> +	if (flags & BTRFS_BLOCK_GROUP_DATA)
> +		return BTRFS_MAX_DATA_CHUNK_SIZE;
> +	else if (flags & BTRFS_BLOCK_GROUP_METADATA)
> +		return max_stripe_size;
> +
> +	/* Handle BTRFS_BLOCK_GROUP_SYSTEM */
> +	return 2 * max_stripe_size;
> +}
> +
> +/*
> + * Update maximum stripe size and chunk size.
> + *
> + */
> +void btrfs_update_space_info_max_alloc_sizes(struct btrfs_space_info *space_info,
> +					     u64 flags, u64 max_stripe_size)
> +{
> +	spin_lock(&space_info->lock);
> +	space_info->max_stripe_size = max_stripe_size;
> +	space_info->max_chunk_size = compute_chunk_size(flags,
> +						space_info->max_stripe_size);
> +	spin_unlock(&space_info->lock);
> +}
> +
>  static int create_space_info(struct btrfs_fs_info *info, u64 flags)
>  {
>  
> @@ -203,6 +271,10 @@ static int create_space_info(struct btrfs_fs_info *info, u64 flags)
>  	INIT_LIST_HEAD(&space_info->priority_tickets);
>  	space_info->clamp = 1;
>  
> +	space_info->max_stripe_size = compute_stripe_size(info, flags);
> +	space_info->max_chunk_size = compute_chunk_size(flags,
> +						space_info->max_stripe_size);
> +
>  	ret = btrfs_sysfs_add_space_info_type(info, space_info);
>  	if (ret)
>  		return ret;
> diff --git a/fs/btrfs/space-info.h b/fs/btrfs/space-info.h
> index cb5056472e79..5ee3e381de38 100644
> --- a/fs/btrfs/space-info.h
> +++ b/fs/btrfs/space-info.h
> @@ -23,6 +23,8 @@ struct btrfs_space_info {
>  	u64 max_extent_size;	/* This will hold the maximum extent size of
>  				   the space info if we had an ENOSPC in the
>  				   allocator. */
> +	u64 max_chunk_size; /* maximum chunk size in bytes */
> +	u64 max_stripe_size; /* maximum stripe size in bytes */

max_chunk_size isn't user set-able, and can be calculated from the
max_stripe_size.  You may change the names based on my previous emails, but
whatever it ends up being you only need one of these stored, the other can be
inferred.  Thanks,

Josef