backup: improve write meta logic

[huanghaoyuanhhy]

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[huanghaoyuanhhy]

/kind improvement

[santiago-wjq]

PR Review: backup: improve write meta logic

Summary

This PR refactors the writeMeta function in core/backup/task.go, replacing repetitive meta build/write code blocks with a loop-based approach.

Changes Analysis

Before (~47 lines): 5 nearly identical code blocks for each meta type
After (~20 lines): Single loop iterating over a slice of meta entries

Pros ✅

1. Reduces code duplication - Eliminates 5 repetitive code blocks
2. Easier to maintain - Adding a new meta type only requires adding one line to the slice
3. Consistent error handling - All meta types use the same error format pattern

Suggestions ⚠️

1. Naming: The struct name metaTypes is slightly misleading since it represents a single meta entry, not multiple types. Consider renaming to metaEntry or metaWriter:

   type metaEntry struct {
       Type mpath.MetaType
       Fn   func() ([]byte, error)
   }

2. Logger inconsistency: The function starts with t.logger.Info("start write meta") but ends with log.Info("finish write meta"). Consider using t.logger consistently for both.

Overall

Good refactoring that follows the DRY principle. The logic is correct and functionality remains unchanged. 👍