[PATCH 02/18] xstat: Add a pair of system calls to make extended file stats available [ver #6]

[Jan Engelhardt]

On Sunday 2010-07-18 10:48, Christoph Hellwig wrote:

>Adding Uli to the Cc list to make sure this system call is useful
>for glibc / can be exported by it.  Otherwise it's rather pointless
>to add it.
>
>>  (6) BSD stat compatibility: Including more fields from the BSD stat such as
>>      creation time (st_btime) and inode generation number (st_gen) [Jeremy
>>      Allison, Bernd Schubert]
>
>How is this different from (1) and (4)?

(4), the inode generation number, need not be related to time.

>>  (8) Allow the filesystem to indicate what it can/cannot provide: A filesystem
>>      can now say it doesn't support a standard stat feature if that isn't
>>      available.
>
>What for?

Given xstat.otime=0, how would you determine whether the file is really 
tagged with a date of 1970, or whether it's just the fs which didnot 
store this kind of information.