Re: [PATCH v4 1/4] btrfs-progs: mkfs: Enhance minimal device size calculation to fix mkfs failure on small file

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

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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".

Do I need to re-submit the whole patchset or just a separate patch to
update the comment?

Thanks,
Qu

>> +	reserved += data_size;
>> +	return reserved;
>> +}
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