* fix(storage): use ceil division for EC shard slots in maxVolumeCount
* fix(topology): use ceil division for EC shard slots consistently
Applies the same ceiling-division formula used in store.go to the
four remaining master-side sites that computed volume-slots consumed
by EC shards with off-by-one approximations:
- disk.go ToDiskInfo / Disk.ToDiskInfo used (n+1)/d, which under-counts
slots for non-multiples of DataShardsCount, over-reporting
FreeVolumeCount.
- DiskUsageCounts.FreeSpace and NodeImpl.AvailableSpaceFor subtracted
n/d + 1, which over-counts slots at multiples of DataShardsCount,
under-reporting free space (and suppressing volume growth on nodes
that still had room).
All four now use (n + DataShardsCount - 1) / DataShardsCount, matching
store.go:393, store.go:810, and command_ec_decode.go:422.
* refactor(topology): extract ecShardSlots helper
Deduplicates the (n + DataShardsCount - 1) / DataShardsCount ceiling
expression now used by ToDiskInfo, DiskUsageCounts.FreeSpace,
Disk.ToDiskInfo, and AvailableSpaceFor. Addresses PR review feedback.
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Co-authored-by: Chris Lu <chris.lu@gmail.com>
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