Re: [Bug-tar] Detection of sparse files is broken on btrfs

[Joerg Schilling]

Paul Eggert <address@hidden> wrote:

> POSIX does not require that st_nblocks remain constant across any system 
> call. It doesn't even require that it remain constant if you merely call 
> stat twice on the same file, without doing anything else in between. So 
> I agree with you that it's irrelevant whether fsync or sync is called in 
> the interim. Where we disagree is that I don't think st_nblocks must 
> remain constant when a file is not modified. No such requirement is in 
> POSIX.

POSIX dos not document that the value of st_nblocks may vary while the content 
and the size of the file remains constant.

If POSIX would allow such unexpected behavior, this would have been documented.



Jörg

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