Re: BIG files & file systems

[Hans Reiser <reiser@namesys.com>]

Nikita Danilov wrote:

>Trond Myklebust writes:
> > >>>>> " " == Nikita Danilov <Nikita@Namesys.COM> writes:
> > 
> >      > But there still is a problem with applications (if any) calling
> >      > seekdir/telldir directly...
> > 
> > Agreed. Note however that the semantics for seekdir/telldir as
> > specified by SUSv2 are much weaker than those in our current
> > getdents()+lseek().
> > 
> > >From the Opengroup documentation for seekdir, it states that:
> > 
> >   On systems that conform to the Single UNIX Specification, Version 2,
> >   a subsequent call to readdir() may not be at the desired position if
> >   the value of loc was not obtained from an earlier call to telldir(),
> >   or if a call to rewinddir() occurred between the call to telldir()
> >   and the call to seekdir().
> > 
> > IOW assigning a unique offset to each and every entry in the directory
> > is overkill (unless the user is calling telldir() for all those
> > entries).
>
Forgive the really dumb question, but does this mean we can just store 
the last entry returned to readdir in the directory metadata, and 
completely ignore the value of loc?

>
>Are you implying some kind of ->telldir() file operation that notifies
>file-system that user has intention to later restart readdir from the
>"current" position and changing glibc to call sys_telldir/sys_seekdir in
>stead of lseek? This will allow file-systems like reiser4 that cannot
>restart readdir from 32bitsful of data to, at least, allocate something
>in kernel on call to ->telldir() and free in ->release().
>
> > 
> > Cheers,
> >   Trond
>
>Nikita.
>
>
>  
>


-- 
Hans