Re: [PATCH V3] fs: allow for more than 2^31 files

Robin Holt
2010-10-01T04:34:29Z

On Thu, Sep 30, 2010 at 10:45:45PM +0200, Eric Dumazet wrote:
> Le jeudi 30 septembre 2010 à 15:26 -0500, Robin Holt a écrit :
> > On Tue, Sep 28, 2010 at 05:46:51AM +0200, Eric Dumazet wrote:
> > > Le lundi 27 septembre 2010 à 15:36 -0700, David Miller a écrit :
> > ...
> >
> > > Fix is to let /proc/sys/fs/file-nr & /proc/sys/fs/file-max use long
> > > integers, and change af_unix to use an atomic_long_t instead of
> > > atomic_t.
> > >
> > > get_max_files() is changed to return an unsigned long.
> >
> > I _THINK_ we actually want get_max_files to return a long and have
> > the files_stat_struct definitions be longs. If we do not have it that
> > way, we could theoretically open enough files on a single cpu to make
> > get_nr_files return a negative without overflowing max_files. That,
> > of course, would require an insane amount of memory, but I think it is
> > technically more correct.
> >
>
> Number of opened file is technically a positive (or null) value, I have
> no idea why you want it being signed.
>
> >
> > > --- a/kernel/sysctl.c
> > > +++ b/kernel/sysctl.c
> > > @@ -1352,16 +1352,16 @@ static struct ctl_table fs_table[] = {
> > > {
> > > .procname = "file-nr",
> > > .data = &files_stat,
> > > - .maxlen = 3*sizeof(int),
> > > + .maxlen = sizeof(files_stat),
> > > .mode = 0444,
> > > - .proc_handler = proc_nr_files,
> > > + .proc_handler = proc_doulongvec_minmax,
> >
> > With this change, don't we lose the current nr_files value? I think
> > you need proc_nr_files to stay as it was. If you disagree, we should
> > probably eliminate the definitions for proc_nr_files as I don't believe
> > they are used anywhere else.
> >
>
> I have no idea why you think I changed something. I only made the value
> use 64bit on 64bit arches, so that we are not anymore limited to 2^31
> files.

The proc_handler used to be proc_nr_files() which would call
get_nr_files() and deposit the result in files_stat.nr_files then cascade
to proc_dointvec() which would dump the 3 values. Now it will dump the
three values, but not update the middle (nr_files) value first.

Robin