Re: [PATCH 2/2] exportfs: fix 32-bit nfsd handling of 64-bit inode numbers

["J. Bruce Fields" <bfields@fieldses.org>]

On Fri, Oct 04, 2013 at 06:15:22PM -0400, J. Bruce Fields wrote:
> On Fri, Oct 04, 2013 at 06:12:16PM -0400, bfields wrote:
> > On Wed, Oct 02, 2013 at 05:28:14PM -0400, J. Bruce Fields wrote:
> > > @@ -268,6 +268,16 @@ static int get_name(const struct path *path, char *name, struct dentry *child)
> > >  	if (!dir->i_fop)
> > >  		goto out;
> > >  	/*
> > > +	 * inode->i_ino is unsigned long, kstat->ino is u64, so the
> > > +	 * former would be insufficient on 32-bit hosts when the
> > > +	 * filesystem supports 64-bit inode numbers.  So we need to
> > > +	 * actually call ->getattr, not just read i_ino:
> > > +	 */
> > > +	error = vfs_getattr_nosec(path, &stat);
> > 
> > Doh, "path" here is for the parent....  The following works better!
> 
> By the way, I'm testing this with:
> 
> 	- create a bunch of nested subdirectories, use
> 	  name_to_fhandle_at to get a handle for the bottom directory.
> 	- echo 2 >/proc/sys/vm/drop_caches
> 	- open_by_fhandle_at on the filehandle
> 
> But this only actually exercises the reconnect path on the first run
> after boot.  Is there something obvious I'm missing here?

Looking at the code....  OK, most of the work of drop_caches is done by
shrink_slab_node, which doesn't actually try to free every single thing
that it could free--in particular, it won't try to free anything if it
thinks there are less than shrinker->batch_size (1024 in the
super_block->s_shrink case) objects to free.

So for now I'm just nesting deeper (2048 subdirectories) to get a
reliable way to exercise reconnect_path.

--b.