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SubjectRe: [PATCH 16/28] ovl: Do not expose metacopy only dentry from d_real()
On Tue, May 29, 2018 at 04:46:00PM +0200, Miklos Szeredi wrote:
> From: Vivek Goyal <vgoyal@redhat.com>
>
> 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 <vgoyal@redhat.com>
> Reviewed-by: Amir Goldstein <amir73il@gmail.com>
> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
> ---
> 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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