On Thu, Jan 4, 2018 at 6:20 PM, Amir Goldstein <amir73il@xxxxxxxxx> wrote:
> We only need to encode origin if there is a chance that the same object was
> encoded pre copy up and then we need to stay consistent with the same
> encoding also after copy up.
>
> In case a non-pure upper is not indexed, then it was copied up before NFS
> export support was enabled. In that case, we don't need to worry about
> staying consistent with pre copy up encoding and we encode an upper file
> handle.
>
> This mitigates the problem that with no index, we cannot find an upper
> inode from origin inode, so we cannot decode a non-indexed upper from
> origin file handle.
>
> Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
> ---
> fs/overlayfs/export.c | 28 +++++++++++++++++++++++-----
> 1 file changed, 23 insertions(+), 5 deletions(-)
>
> diff --git a/fs/overlayfs/export.c b/fs/overlayfs/export.c
> index 48ae02f3acb8..919d43aaa387 100644
> --- a/fs/overlayfs/export.c
> +++ b/fs/overlayfs/export.c
> @@ -19,6 +19,28 @@
> #include <linux/ratelimit.h>
> #include "overlayfs.h"
>
> +/*
> + * We only need to encode origin if there is a chance that the same object was
> + * encoded pre copy up and then we need to stay consistent with the same
> + * encoding also after copy up. If non-pure upper is not indexed, then it was
> + * copied up before NFS export was enabled. In that case we don't need to worry
> + * about staying consistent with pre copy up encoding and we encode an upper
> + * file handle.
> + */
> +static bool ovl_should_encode_origin(struct dentry *dentry)
> +{
> + /* Root dentry was born upper */
> + if (dentry == dentry->d_sb->s_root)
> + return false;
Root can be lower, no (when there's no upper layer at all)? The
comment is confusing at best.
> +
> + /* Decoding a non-indexed upper from origin is not implemented */
> + if (ovl_dentry_upper(dentry) &&
> + !ovl_test_flag(OVL_INDEX, d_inode(dentry)))
> + return false;
> +
> + return true;
> +}
> +
> int ovl_d_to_fh(struct dentry *dentry, char *buf, int buflen)
> {
> struct dentry *upper = ovl_dentry_upper(dentry);
> @@ -26,11 +48,7 @@ int ovl_d_to_fh(struct dentry *dentry, char *buf, int buflen)
> struct ovl_fh *fh = NULL;
> int err;
>
> - /*
> - * Overlay root dir inode is encoded as an upper file handle upper,
> - * because root dir dentry is born upper and not indexed.
> - */
> - if (dentry == dentry->d_sb->s_root)
> + if (!ovl_should_encode_origin(dentry))
> origin = NULL;
>
> err = -EACCES;
> --
> 2.7.4
>
