Re: [PATCH v2 03/23] ovl: store layer index in ovl_layer

[Vivek Goyal <vgoyal@redhat.com>]

On Thu, Jan 04, 2018 at 06:39:58PM +0200, Amir Goldstein wrote:
> Store the fs root layer index inside ovl_layer struct, so we can
> get the root fs layer index from merge dir lower layer instead of
> find it with ovl_find_layer() helper.
> 
> Signed-off-by: Amir Goldstein <amir73il@gmail.com>
> ---
>  fs/overlayfs/namei.c     | 17 +----------------
>  fs/overlayfs/ovl_entry.h |  2 ++
>  fs/overlayfs/super.c     |  1 +
>  3 files changed, 4 insertions(+), 16 deletions(-)
> 
> diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
> index 71db9a966d88..a48ee02c4524 100644
> --- a/fs/overlayfs/namei.c
> +++ b/fs/overlayfs/namei.c
> @@ -572,18 +572,6 @@ int ovl_path_next(int idx, struct dentry *dentry, struct path *path)
>  	return (idx < oe->numlower) ? idx + 1 : -1;
>  }
>  
> -static int ovl_find_layer(struct ovl_fs *ofs, struct ovl_path *path)
> -{
> -	int i;
> -
> -	for (i = 0; i < ofs->numlower; i++) {
> -		if (ofs->lower_layers[i].mnt == path->layer->mnt)
> -			break;
> -	}
> -
> -	return i;
> -}
> -
>  /* Fix missing 'origin' xattr */
>  static int ovl_fix_origin(struct dentry *dentry, struct dentry *lower,
>  			  struct dentry *upper)
> @@ -733,11 +721,8 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
>  
>  		if (d.redirect && d.redirect[0] == '/' && poe != roe) {
>  			poe = roe;
> -
>  			/* Find the current layer on the root dentry */
> -			i = ovl_find_layer(ofs, &lower);
> -			if (WARN_ON(i == ofs->numlower))
> -				break;
> +			i = lower.layer->idx - 1;
>  		}
>  	}
>  
> diff --git a/fs/overlayfs/ovl_entry.h b/fs/overlayfs/ovl_entry.h
> index 9d0bc03bf6e4..608e48755070 100644
> --- a/fs/overlayfs/ovl_entry.h
> +++ b/fs/overlayfs/ovl_entry.h
> @@ -22,6 +22,8 @@ struct ovl_config {
>  struct ovl_layer {
>  	struct vfsmount *mnt;
>  	dev_t pseudo_dev;
> +	/* Index of this layer in fs root (upper == 0) */
> +	int idx;

Just curious. If we are stroing idx, then do we have to store ovl_layer
and every ovl_entry. Just idx can give us the position and we should
be able to then access mnt and pseudo_dev directly from
ofs->lower_layers[idx]. If yes, we can avoid storing vfsmount and 
pseudo_dev per dentry.

Vivek

>  };
>  
>  struct ovl_path {
> diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
> index 7e33c83c5a07..2b58620eedf0 100644
> --- a/fs/overlayfs/super.c
> +++ b/fs/overlayfs/super.c
> @@ -1111,6 +1111,7 @@ static int ovl_get_lower_layers(struct ovl_fs *ofs, struct path *stack,
>  
>  		ofs->lower_layers[ofs->numlower].mnt = mnt;
>  		ofs->lower_layers[ofs->numlower].pseudo_dev = dev;
> +		ofs->lower_layers[ofs->numlower].idx = i + 1;
>  		ofs->numlower++;
>  
>  		/* Check if all lower layers are on same sb */
> -- 
> 2.7.4
> 
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