On Wed, Nov 01, 2017 at 09:30:40AM +0800, Qu Wenruo wrote:
> +u64 btrfs_min_dev_size(u32 nodesize, int mixed, u64 meta_profile,
> + u64 data_profile)
> +{
> + u64 reserved = 0;
> + u64 meta_size;
> + u64 data_size;
> +
> + if (mixed)
> + return 2 * (BTRFS_MKFS_SYSTEM_GROUP_SIZE +
> + btrfs_min_global_blk_rsv_size(nodesize));
> +
> + /*
> + * minimal size calculation is complex due to several factors:
> + * 1) Temporary chunk resue
> + * If specified chunk profile is SINGLE, we can resue
> + * temporary chunks, no need to alloc new chunks.
> + *
> + * 2) Different minimal chunk size for different profile
> + * For initial sys chunk, chunk size is fixed to 4M.
> + * For single profile, minimal chunk size is 8M for all.
> + * For other profiles, minimal chunk and stripe size
> + * differs from 8M to 64M.
> + *
> + * To calculate it a little easier, here we assume we don't
> + * reuse any temporary chunk, and calculate the size all
> + * by ourselves.
> + *
> + * Temporary chunks sizes are always fixed:
> + * One initial sys chunk, one SINGLE meta, and one SINGLE data.
> + * The latter two are all 8M, accroding to @calc_size of
> + * btrfs_alloc_chunk().
> + */
> + reserved += BTRFS_MKFS_SYSTEM_GROUP_SIZE + SZ_8M * 2;
> +
> + /*
> + * For real chunks, we need to refer different sizes:
> + * For SINGLE, it's still fixed to 8M (@calc_size).
> + * For other profiles, refer to max(@min_stripe_size, @calc_size).
> + *
> + * And use the stripe size to calculate its physical used space.
> + */
> + if (meta_profile & BTRFS_BLOCK_GROUP_PROFILE_MASK)
> + meta_size = SZ_8M + SZ_32M;
> + else
> + meta_size = SZ_8M + SZ_8M;
> + /* Only metadata put 2 stripes into one disk */
'mkfs.btrfs -d dup' also works, so I think this should be handled here
the same way as metadata, right?
> + if (meta_profile & BTRFS_BLOCK_GROUP_DUP)
> + meta_size *= 2;
> + reserved += meta_size;
> +
> + if (data_profile & BTRFS_BLOCK_GROUP_PROFILE_MASK)
> + data_size = SZ_64M;
> + else
> + data_size = SZ_8M;
> + if (data_profile & BTRFS_BLOCK_GROUP_DUP)
> + data_size *= 2;
> + reserved += data_size;
> + return reserved;
> +}
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