Re: [PATCH v13 13/28] ovl: Add helper ovl_dentry_lowerdata() to get lower data dentry

[Vivek Goyal <vgoyal@redhat.com>]

On Fri, Mar 30, 2018 at 09:01:12AM +0300, Amir Goldstein wrote:
> On Thu, Mar 29, 2018 at 10:38 PM, Vivek Goyal <vgoyal@redhat.com> wrote:
> > Now we have the notion of data dentry and metacopy dentry. ovl_dentry_lower()
> > will return lower dentry at idx 0, but it could be either data or metacopy
> 
> will return the upper most lower dentry. (idx 0 means upper).

I am explaining the behavior of current ovl_dentry_lower() helper here.
(And not of new helper).
> 
> > dentry. Now we support metacopy dentries in lower layers so it is possible
> > that lowerstack[0] is metacopy dentry while lowerstack[1] is actual data
> > dentry.
> >
> > So add an helper which returns lowest most dentry which is supposed to be
> > data dentry.
> >
> > Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
> Reviewed-by: Amir Goldstein <amir73il@gmail.com>
> 
> > ---
> >  fs/overlayfs/overlayfs.h |  1 +
> >  fs/overlayfs/util.c      | 14 ++++++++++++++
> >  2 files changed, 15 insertions(+)
> >
> > diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
> > index 4eb4b765887f..214d9f08c574 100644
> > --- a/fs/overlayfs/overlayfs.h
> > +++ b/fs/overlayfs/overlayfs.h
> > @@ -226,6 +226,7 @@ void ovl_path_lowerdata(struct dentry *dentry, struct path *path);
> >  enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path);
> >  struct dentry *ovl_dentry_upper(struct dentry *dentry);
> >  struct dentry *ovl_dentry_lower(struct dentry *dentry);
> > +struct dentry *ovl_dentry_lowerdata(struct dentry *dentry);
> >  struct dentry *ovl_dentry_real(struct dentry *dentry);
> >  struct dentry *ovl_i_dentry_upper(struct inode *inode);
> >  struct inode *ovl_inode_upper(struct inode *inode);
> > diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
> > index fd98329e820c..394674c4c820 100644
> > --- a/fs/overlayfs/util.c
> > +++ b/fs/overlayfs/util.c
> > @@ -186,6 +186,20 @@ struct dentry *ovl_dentry_lower(struct dentry *dentry)
> >         return oe->numlower ? oe->lowerstack[0].dentry : NULL;
> >  }
> >
> > +/*
> > + * ovl_dentry_lower() could return either a data dentry or metacopy dentry
> > + * dependig on what is stored in lowerstack[0]. At times we need to find
> > + * lower dentry which has data (and not metacopy dntry). This helper
> > + * returns the lower data dentry.
> > + */
> > +struct dentry *ovl_dentry_lowerdata(struct dentry *dentry)
> > +{
> > +       struct ovl_entry *oe = dentry->d_fsdata;
> > +       int idx = oe->numlower - 1;
> 
> Please stick with convention of layer->idx that idx 0 is upper.
> 
> > +
> > +       return idx >= 0 ? oe->lowerstack[idx].dentry : NULL;
> > +}
> > +
> >  struct dentry *ovl_dentry_real(struct dentry *dentry)
> >  {
> >         return ovl_dentry_upper(dentry) ?: ovl_dentry_lower(dentry);
> > --
> > 2.13.6
> >