Re: stat64 for over 2TB file returned invalid st_blocks

["Takashi Sato" <sho@bsd.tnes.nec.co.jp>]

Hi,

> On Dec 03, 2005  22:00 +0900, Takashi Sato wrote:
>> Andreas Dilger wrote:
>> >Actually, it should probably be "sector_t", because it isn't really
>> >possible to have a file with more blocks than the size of the block
>> >device.  This avoids memory overhead for small systems that have no
>> >need for it in a very highly-used struct.  It may be for some network
>> >filesystems that support gigantic non-sparse files they would need to
>> >enable CONFIG_LBD in order to get support for this.
>> 
>> I think sector_t is ok for local filesystem as you said.  However,
>> on NFS, there may be over 2TB file on server side, and inode.i_blocks
>> for over 2TB file will become invalid on client side in case CONFIG_LBD
>> is disabled.
> 
> I don't know the exact specs of NFS v2 and v3, but I doubt they can have
> single files larger than 2TB.  Even if they could then this is not a

I believe NFS v3 can handle over 2TB file. :-)

> very common situation and if someone is running in such an environment
> then they can easily enable CONFIG_LBD (or make e.g. CONFIG_NFS_V4 have
> a dependency to enable this if it is important enough).  What I'd rather
> avoid is needless growth of heavily-used structures for rather uncommon
> cases (at the current time at least, this can be re-examined later).

I agree above.

> It might also be possible to have a separate CONFIG_LSF (or whatever)
> that enables support for large single files, maybe enabled by default
> with CONFIG_LBD and also configurable separately for clients of network
> filesystems with large single files.  Someone who cares more about the
> proliferation of configuration options than I can decide whether it
> makes sense to keep these as separate options.

I don't think CONFIG_LBD should determine whether large single
files is enabled.  So, I agree your suggestion basically.
It would be nice if there was a suitable configuration option for it.
I will examine the implementation in detail.

-- Takashi Sato