Extended file stat: Splitting file- and fs-specific info?

[Andreas Dilger]

On 2012-05-10, at 11:10 AM, Roland McGrath wrote:
> POSIX specifies st_blksize thusly: "A file system-specific preferred
> I/O block size for this object. In some file system types, this may
> vary from file to file."
> 
> Since there is only one available to POSIX applications, it should map
> to the one that's described as "preferred IO size for general usage".

Sure, but statxat() isn't a POSIX API.

While I agree with the idea that there should be enough information about the underlying layout for applications to be able to submit good IO, it doesn't help if we have a bunch of extra fields that have vague meanings. 

They will get filled in by the filesystem in a haphazard way, and will not be used by application developers that don't understand what they mean.

Cheers, Andreas