Re: [PATCH] nilfs2: fix oops due to a bad aops initialization

[Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>]

On Wed, 30 Mar 2011 13:07:46 +0200, Jens Axboe <jaxboe@fusionio.com> wrote:
> On 2011-03-30 06:25, Ryusuke Konishi wrote:
> > diff --git a/fs/nilfs2/page.c b/fs/nilfs2/page.c
> > index 4d2a1ee..9d2dc6b 100644
> > --- a/fs/nilfs2/page.c
> > +++ b/fs/nilfs2/page.c
> > @@ -495,12 +495,14 @@ unsigned nilfs_page_count_clean_buffers(struct page *page,
> >  void nilfs_mapping_init(struct address_space *mapping,
> >  			struct backing_dev_info *bdi)
> >  {
> > +	static const struct address_space_operations empty_aops;
> > +
> >  	mapping->host = NULL;
> >  	mapping->flags = 0;
> >  	mapping_set_gfp_mask(mapping, GFP_NOFS);
> >  	mapping->assoc_mapping = NULL;
> >  	mapping->backing_dev_info = bdi;
> > -	mapping->a_ops = NULL;
> > +	mapping->a_ops = &empty_aops;
> >  }
> 
> Hmm wait, inode init should set the mapping aops to an empty type
> already. Does the OOPS go away if you just remove the mapping->a_ops =
> NULL assignment?
> 
> -- 
> Jens Axboe

Nilfs has two mappings in each inode, one for data pages and another
for btree nodes.  The aops initialization is neede for the latter one.

Ryusuke Konishi