Re: [PATCH] ramfs: pretend dirent sizes

[Jan Blunck <j.blunck@tu-harburg.de>]

Chris Wedgwood wrote:
> 
> Hos does that work if offset >= m?
> 

Eerrh, did you actually read my patch? The i_size of a directory is 
increased by SIMPLE_BOGO_DIRENT_SIZE for every entry in the directory.

 >>So you can seek to m*<stack-depth>+<offset> to access an offset into
 >>> >something at depth m?
 >>> >
 >>
 >> Yes.

I got that one wrong! You can seek to the "sum of i_sizes (of the m 
directories) + offset" to access offset in the m'th directory/stack-depth.

> 
> lseek talks about bytes --- yes, it means for files specifically but I
> still don't see why we need to define more counter-intuitive semantics
> for directories when we don't need them.

It is counter-intuitive to have a value which is information less, like 
in the zero case.

> 
> Also, how is lseek + readdir supposed to work in general?

This is how libc is reading directories (at least on arch s390x):

getdents() != 0
lseek() to d_off of last dirent
getdents() != 0
lseek() to d_off of last dirent
getdents() == 0
return

Therefore I really need values that make sense for d_off. Therefore I 
really need values that make (some kind of) sense for i_size.

Jan