Re: [patch 22/23] fs: check for statfs overflow

[Andreas Dilger <adilger@sun.com>]

On May 30, 2008  03:14 +0200, Nick Piggin wrote:
> On Thu, May 29, 2008 at 05:56:07PM -0600, Andreas Dilger wrote:
> > On May 28, 2008  11:02 +0200, Nick Piggin wrote:
> > > @@ -197,8 +197,8 @@ static int put_compat_statfs(struct comp
> > >  	if (sizeof ubuf->f_blocks == 4) {
> > > +		if ((kbuf->f_blocks | kbuf->f_bfree | kbuf->f_bavail |
> > > +		     kbuf->f_bsize | kbuf->f_frsize) & 0xffffffff00000000ULL)
> > >  			return -EOVERFLOW;
> > 
> > Hmm, doesn't this check break every filesystem > 16TB on 4kB PAGE_SIZE
> > nodes?  It would be better, IMHO, to scale down f_blocks, f_bfree, and
> > f_bavail and correspondingly scale up f_bsize to fit into the 32-bit
> > statfs structure.
> 
> Oh? Hmm, from my reading, such filesystems will already overflow f_blocks
> check which is already there. Jon's patch only adds checks for f_bsize
> and f_frsize.

Sorry, you are right - I meant that the whole f_blocks check is broken
for filesystems > 16TB.  Scaling f_bsize is easy, and prevents gratuitous
breakage of old applications for a few kB of accuracy.

Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.