vfs: fix file length after fallocate & copyfilerange

[SandyXSD]

fix #4399

[codecov]

Codecov Report

Attention: Patch coverage is 58.33333% with 30 lines in your changes are missing coverage. Please review.

Project coverage is 56.03%. Comparing base (bf669aa) to head (871bd43).

Files	Patch %	Lines
pkg/meta/sql.go	35.71%	7 Missing and 2 partials ⚠️
pkg/meta/tkv.go	35.71%	7 Missing and 2 partials ⚠️
pkg/meta/redis.go	57.14%	4 Missing and 2 partials ⚠️
pkg/vfs/vfs.go	79.31%	4 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4427      +/-   ##
==========================================
+ Coverage   55.99%   56.03%   +0.04%     
==========================================
  Files         154      154              
  Lines       40093    40134      +41     
==========================================
+ Hits        22449    22491      +42     
+ Misses      15136    15127       -9     
- Partials     2508     2516       +8     

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