Is vnode number also limit system-wide number of open file?

[ablacktshirt@gmail.com (Yubin Ruan)]

On Wed, May 31, 2017 at 08:34:09AM +0100, Okash Khawaja wrote:
> 
> 
> > On 31 May 2017, at 14:37, Yubin Ruan <ablacktshirt@gmail.com> wrote:
> > 
> > I notice that there is a 
> > 
> >    unsigned long        i_ino;
> > 
> > in definition of `struct inode' [1], which is the virtual filesystem inode.
> > Does that mean "inode number" and is it used for indexing in the system-wide
> > inode table? 
> > 
> > If that is the case, would that limit the number of open file in Linux?
> > 
> > I know there *is* such a limit, and superusers can adjust that by
> > /proc/sys/fs/file-max. Currently I cannot raise that to too high, otherwise
> > the system would crash, which I think is because I have limited memory. But,
> > the point is, if I have lots of memory in my machine (say hunderds of
> > Gigabytes), would the number of open file system-wide limited by the `i_ino'
> > above? Since its type is "unsigned long", I guess I can only open
> > 2^(sizeof(unsigned long)) file simultaneously? 
> 
> 2^(8*sizeof(unsigned long))
 
 good catch.

> Which is big. Is there some use case for very large number of files?

No, I just wonder whether this is the limit...

--
Yubin