On Tue, Nov 28, 2017 at 08:40:47AM +0800, Qu Wenruo wrote:
>
>
> On 2017年11月28日 07:21, David Sterba wrote:
> > 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?
>
> Just a few lines under.
> >
> >> + 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;
> Here data DUP is also handled.
>
> So the problem is about the word "Only".
Yeah, it's confusing when comment does not match the code because it's
not clear what's the actual intention.
> Do I need to re-submit the whole patchset or just a separate patch to
> update the comment?
No, I'll update it myself as it is fairly trivial change.
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