[PATCH 1/3] ovl: refactor lowerstack related functions

[Chengguang Xu <cgxu519@xxxxxxx>]

Introduce __ovl_path_lower() to handle lowerstack related things
and refactor ovl_dentry_lower()/ovl_layer_lower() based on it.

Signed-off-by: Chengguang Xu <cgxu519@xxxxxxx>
---
 fs/overlayfs/overlayfs.h |  1 +
 fs/overlayfs/util.c      | 35 +++++++++++++++++++++++++++++++----
 2 files changed, 32 insertions(+), 4 deletions(-)

diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index e0b7de7..abb5cf4 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -215,6 +215,7 @@ static inline struct dentry *ovl_do_tmpfile(struct dentry *dentry, umode_t mode)
 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 vfsmount *ovl_mnt_lower(struct dentry *dentry);
 struct ovl_layer *ovl_layer_lower(struct dentry *dentry);
 struct dentry *ovl_dentry_real(struct dentry *dentry);
 struct dentry *ovl_i_dentry_upper(struct inode *inode);
diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index 6f10780..a3459e6 100644
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -157,8 +157,8 @@ void ovl_path_lower(struct dentry *dentry, struct path *path)
 	struct ovl_entry *oe = dentry->d_fsdata;
 
 	if (oe->numlower) {
-		path->mnt = oe->lowerstack[0].layer->mnt;
-		path->dentry = oe->lowerstack[0].dentry;
+		path->mnt = ovl_mnt_lower(dentry);
+		path->dentry = ovl_dentry_lower(dentry);
 	} else {
 		*path = (struct path) { };
 	}
@@ -181,18 +181,45 @@ struct dentry *ovl_dentry_upper(struct dentry *dentry)
 	return ovl_upperdentry_dereference(OVL_I(d_inode(dentry)));
 }
 
+struct ovl_path *__ovl_path_lower(struct ovl_entry *oe, int layer)
+{
+	if (layer > oe->numlower)
+		return NULL;
+
+	return &oe->lowerstack[layer - 1];
+}
+
+struct vfsmount *ovl_mnt_lower(struct dentry *dentry)
+{
+	struct ovl_entry *oe = dentry->d_fsdata;
+	struct ovl_path *path = __ovl_path_lower(oe, 1);
+
+	if (path)
+		return path->layer->mnt;
+	else
+		return NULL;
+}
+
 struct dentry *ovl_dentry_lower(struct dentry *dentry)
 {
 	struct ovl_entry *oe = dentry->d_fsdata;
+	struct ovl_path *path = __ovl_path_lower(oe, 1);
 
-	return oe->numlower ? oe->lowerstack[0].dentry : NULL;
+	if (path)
+		return path->dentry;
+	else
+		return NULL;
 }
 
 struct ovl_layer *ovl_layer_lower(struct dentry *dentry)
 {
 	struct ovl_entry *oe = dentry->d_fsdata;
+	struct ovl_path *path = __ovl_path_lower(oe, 1);
 
-	return oe->numlower ? oe->lowerstack[0].layer : NULL;
+	if (path)
+		return path->layer;
+	else
+		return NULL;
 }
 
 struct dentry *ovl_dentry_real(struct dentry *dentry)
-- 
1.8.3.1

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