On Tue, May 29, 2018 at 04:46:00PM +0200, Miklos Szeredi wrote:
> From: Vivek Goyal <[email protected]>
> 
> Metacopy dentry/inode is internal to overlay and is never exposed outside
> of it.  Exception is metacopy upper file used for fsync().  Modify d_real()
> to look for dentries/inode which have data, but also allow matching upper
> inode without data for the fsync case.
> 

Hi Miklos,

I am not able to see how in fsync() path d_real() gets called. If we
decide to do fsync() on upper metacopy, then opening upper will not
go through d_real(). And we never issue fsync() on lower.

So I am scratching my head while trying to understand the d_real() and
fsync() connection.

Thanks
Vivek

> Signed-off-by: Vivek Goyal <[email protected]>
> Reviewed-by: Amir Goldstein <[email protected]>
> Signed-off-by: Miklos Szeredi <[email protected]>
> ---
>  fs/overlayfs/super.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
> index e0326a686f45..6687d547ec6b 100644
> --- a/fs/overlayfs/super.c
> +++ b/fs/overlayfs/super.c
> @@ -101,10 +101,13 @@ static struct dentry *ovl_d_real(struct dentry *dentry,
>       }
>  
>       real = ovl_dentry_upper(dentry);
> -     if (real && (!inode || inode == d_inode(real)))
> +     if (real && (inode == d_inode(real)))
>               return real;
>  
> -     real = ovl_dentry_lower(dentry);
> +     if (real && !inode && ovl_has_upperdata(d_inode(dentry)))
> +             return real;
> +
> +     real = ovl_dentry_lowerdata(dentry);
>       if (!real)
>               goto bug;
>  
> -- 
> 2.14.3
> 
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