[PATCH 13/18] ovl: store lower path in ovl_inode

[Christian Brauner <brauner@kernel.org>]

From: Amir Goldstein <amir73il@gmail.com>

Create some ovl_i_* helpers to get real path from ovl inode. Instead of
just stashing struct inode for the lower layer we stash struct path for
the lower layer. The helpers allow to retrieve a struct path for the
relevant upper or lower layer. This will be used when retrieving
information based on struct inode when copying up inode attributes from
upper or lower inodes to ovl inodes and when checking permissions in
ovl_permission() in following patches. This is needed to support
idmapped base layers with overlay.

Cc: <linux-unionfs@vger.kernel.org>
Tested-by: Giuseppe Scrivano <gscrivan@redhat.com>
Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
---
 fs/overlayfs/inode.c     | 11 +++++---
 fs/overlayfs/overlayfs.h |  6 ++++
 fs/overlayfs/ovl_entry.h |  2 +-
 fs/overlayfs/super.c     |  5 ++--
 fs/overlayfs/util.c      | 61 ++++++++++++++++++++++++++++++++++------
 5 files changed, 69 insertions(+), 16 deletions(-)

diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index f18b02b9dd53..e28b7ed755b3 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -779,13 +779,16 @@ void ovl_inode_init(struct inode *inode, struct ovl_inode_params *oip,
 		    unsigned long ino, int fsid)
 {
 	struct inode *realinode;
+	struct ovl_inode *oi = OVL_I(inode);
 
 	if (oip->upperdentry)
-		OVL_I(inode)->__upperdentry = oip->upperdentry;
-	if (oip->lowerpath && oip->lowerpath->dentry)
-		OVL_I(inode)->lower = igrab(d_inode(oip->lowerpath->dentry));
+		oi->__upperdentry = oip->upperdentry;
+	if (oip->lowerpath && oip->lowerpath->dentry) {
+		oi->lowerpath.dentry = dget(oip->lowerpath->dentry);
+		oi->lowerpath.layer = oip->lowerpath->layer;
+	}
 	if (oip->lowerdata)
-		OVL_I(inode)->lowerdata = igrab(d_inode(oip->lowerdata));
+		oi->lowerdata = igrab(d_inode(oip->lowerdata));
 
 	realinode = ovl_inode_real(inode);
 	ovl_copyattr(realinode, inode);
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index 470c8b1912fe..c3f7e5602699 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -359,18 +359,24 @@ bool ovl_dentry_remote(struct dentry *dentry);
 void ovl_dentry_update_reval(struct dentry *dentry, struct dentry *upperdentry,
 			     unsigned int mask);
 bool ovl_dentry_weird(struct dentry *dentry);
+enum ovl_path_type ovl_i_path_type(struct inode *inode, bool is_dir,
+				   int numlower);
 enum ovl_path_type ovl_path_type(struct dentry *dentry);
 void ovl_path_upper(struct dentry *dentry, struct path *path);
 void ovl_path_lower(struct dentry *dentry, struct path *path);
 void ovl_path_lowerdata(struct dentry *dentry, struct path *path);
+enum ovl_path_type ovl_i_path_real(struct inode *inode, struct path *path);
 enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path);
 enum ovl_path_type ovl_path_realdata(struct dentry *dentry, struct path *path);
 struct dentry *ovl_dentry_upper(struct dentry *dentry);
 struct dentry *ovl_dentry_lower(struct dentry *dentry);
 struct dentry *ovl_dentry_lowerdata(struct dentry *dentry);
+const struct ovl_layer *ovl_i_layer_lower(struct inode *inode);
 const struct ovl_layer *ovl_layer_lower(struct dentry *dentry);
 struct dentry *ovl_dentry_real(struct dentry *dentry);
+struct dentry *ovl_i_dentry_real(struct inode *inode);
 struct dentry *ovl_i_dentry_upper(struct inode *inode);
+struct dentry *ovl_i_dentry_lower(struct inode *inode);
 struct inode *ovl_inode_upper(struct inode *inode);
 struct inode *ovl_inode_lower(struct inode *inode);
 struct inode *ovl_inode_lowerdata(struct inode *inode);
diff --git a/fs/overlayfs/ovl_entry.h b/fs/overlayfs/ovl_entry.h
index cf6aebcf893c..898b002a5c6f 100644
--- a/fs/overlayfs/ovl_entry.h
+++ b/fs/overlayfs/ovl_entry.h
@@ -134,7 +134,7 @@ struct ovl_inode {
 	unsigned long flags;
 	struct inode vfs_inode;
 	struct dentry *__upperdentry;
-	struct inode *lower;
+	struct ovl_path lowerpath;
 
 	/* synchronize copy up and more */
 	struct mutex lock;
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 1ed230c7baf1..9a656a24f7b1 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -184,7 +184,8 @@ static struct inode *ovl_alloc_inode(struct super_block *sb)
 	oi->version = 0;
 	oi->flags = 0;
 	oi->__upperdentry = NULL;
-	oi->lower = NULL;
+	oi->lowerpath.dentry = NULL;
+	oi->lowerpath.layer = NULL;
 	oi->lowerdata = NULL;
 	mutex_init(&oi->lock);
 
@@ -205,7 +206,7 @@ static void ovl_destroy_inode(struct inode *inode)
 	struct ovl_inode *oi = OVL_I(inode);
 
 	dput(oi->__upperdentry);
-	iput(oi->lower);
+	dput(oi->lowerpath.dentry);
 	if (S_ISDIR(inode->i_mode))
 		ovl_dir_cache_free(inode);
 	else
diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index 3065393d143e..7dd9901c9d17 100644
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -125,31 +125,37 @@ bool ovl_dentry_weird(struct dentry *dentry)
 				  DCACHE_OP_COMPARE);
 }
 
-enum ovl_path_type ovl_path_type(struct dentry *dentry)
+enum ovl_path_type ovl_i_path_type(struct inode *inode, bool is_dir,
+				   int numlower)
 {
-	struct ovl_entry *oe = dentry->d_fsdata;
 	enum ovl_path_type type = 0;
 
-	if (ovl_dentry_upper(dentry)) {
+	if (ovl_i_dentry_upper(inode)) {
 		type = __OVL_PATH_UPPER;
 
 		/*
 		 * Non-dir dentry can hold lower dentry of its copy up origin.
 		 */
-		if (oe->numlower) {
-			if (ovl_test_flag(OVL_CONST_INO, d_inode(dentry)))
+		if (numlower) {
+			if (ovl_test_flag(OVL_CONST_INO, inode))
 				type |= __OVL_PATH_ORIGIN;
-			if (d_is_dir(dentry) ||
-			    !ovl_has_upperdata(d_inode(dentry)))
+			if (is_dir || !ovl_has_upperdata(inode))
 				type |= __OVL_PATH_MERGE;
 		}
 	} else {
-		if (oe->numlower > 1)
+		if (numlower > 1)
 			type |= __OVL_PATH_MERGE;
 	}
 	return type;
 }
 
+enum ovl_path_type ovl_path_type(struct dentry *dentry)
+{
+	struct ovl_entry *oe = dentry->d_fsdata;
+
+	return ovl_i_path_type(d_inode(dentry), d_is_dir(dentry), oe->numlower);
+}
+
 void ovl_path_upper(struct dentry *dentry, struct path *path)
 {
 	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
@@ -250,6 +256,41 @@ struct dentry *ovl_i_dentry_upper(struct inode *inode)
 	return ovl_upperdentry_dereference(OVL_I(inode));
 }
 
+struct dentry *ovl_i_dentry_lower(struct inode *inode)
+{
+	return OVL_I(inode)->lowerpath.dentry;
+}
+
+struct dentry *ovl_i_dentry_real(struct inode *inode)
+{
+	return ovl_i_dentry_upper(inode) ?: ovl_i_dentry_lower(inode);
+}
+
+const struct ovl_layer *ovl_i_layer_lower(struct inode *inode)
+{
+	return OVL_I(inode)->lowerpath.layer;
+}
+
+enum ovl_path_type ovl_i_path_real(struct inode *inode, struct path *path)
+{
+	struct dentry *lowerdentry = ovl_i_dentry_lower(inode);
+	/* Will not set the __OVL_PATH_MERGE bit for merge lowers dir */
+	enum ovl_path_type type = ovl_i_path_type(inode, S_ISDIR(inode->i_mode),
+						  !!lowerdentry);
+
+	if (OVL_TYPE_UPPER(type)) {
+		path->dentry = ovl_i_dentry_upper(inode);
+		path->mnt = ovl_upper_mnt(OVL_FS(inode->i_sb));
+	} else if (lowerdentry) {
+		path->dentry = lowerdentry;
+		path->mnt = ovl_i_layer_lower(inode)->mnt;
+	} else {
+		*path = (struct path) { };
+	}
+
+	return type;
+}
+
 struct inode *ovl_inode_upper(struct inode *inode)
 {
 	struct dentry *upperdentry = ovl_i_dentry_upper(inode);
@@ -259,7 +300,9 @@ struct inode *ovl_inode_upper(struct inode *inode)
 
 struct inode *ovl_inode_lower(struct inode *inode)
 {
-	return OVL_I(inode)->lower;
+	struct dentry *lowerdentry = ovl_i_dentry_lower(inode);
+
+	return lowerdentry ? d_inode(lowerdentry) : NULL;
 }
 
 struct inode *ovl_inode_real(struct inode *inode)
-- 
2.32.0