Re: Bug in 2.4.26 in mm/filemap.c when using RLIMIT_RSS

[Marcelo Tosatti <marcelo.tosatti@cyclades.com>]

On Fri, Jan 28, 2005 at 03:09:40PM +0000, Hugh Dickins wrote:
> On Thu, 27 Jan 2005, Marcelo Tosatti wrote:
> > On Thu, Jan 27, 2005 at 07:38:49AM +0100, Ake wrote:
> > > On Wed, Jan 26, 2005 at 12:49:04PM -0200, Marcelo Tosatti wrote:
> > > > 
> > > > --- a/mm/filemap.c.orig	2004-11-17 09:54:22.000000000 -0200
> > > > +++ b/mm/filemap.c	2005-01-26 15:21:10.614842296 -0200
> > > > @@ -2609,6 +2609,9 @@
> > > >  	error = -EIO;
> > > >  	rlim_rss = current->rlim ?  current->rlim[RLIMIT_RSS].rlim_cur :
> > > >  				LONG_MAX; /* default: see resource.h */
> > > > +
> > > > +	rlim_rss = (rlim_rss & PAGE_MASK) >> PAGE_SHIFT;
> > > > +
> > > >  	if ((vma->vm_mm->rss + (end - start)) > rlim_rss)
> > > >  		return error;
> 
> Isn't the right fix just to remove rlim_rss and this RLIMIT_RSS code
> from here?  It's pretty silly for madvise alone to be taking notice
> of it.  Presumably the code crept in by mistake from some tree which
> was using an RLIMIT_RSS patch on 2.4.

True. Will do it. 

> > > Since we don't use it i can't really test it, but a visual inspection is
> > > good enough in this simple case. And since this is the only place in 2.4
> > > that RLIMIT_RSS is used, the problem is solved.
> > > 
> > > BTW do you know if there is any plans for 2.6++ to actually use
> > > RLIMIT_RSS? I saw a hint in that direction in mm/thrash.c
> > > grab_swap_token but it is commented out and only skeleton code...
> > 
> > Nope, RLIMIT_RSS does not seem to be used at all in v2.6:
> > 
> > Its there for compatibility reasons, support for it might be added
> > in the future?
> 
> Rik had a patch implementing RLIMIT_RSS in 2.6-mm for a while.
> But I think there were a couple of problems with it, and no great
> demand for the feature, so Andrew dropped it until someone makes
> a better case for it.
> 
> Hugh