From f9cb1a06e3d4059b6c43c5e0fb0e7a6d7d6c3fec Mon Sep 17 00:00:00 2001
From: Tao Huang <huangtao@rock-chips.com>
Date: Thu, 24 Sep 2020 19:52:02 +0800
Subject: [PATCH] Revert "Revert "ANDROID: vfs: add d_canonical_path for
 stacked filesystem support""

This reverts commit fc411cf98a0068d351c2e31331dd574076980ccc.

For sdcardfs.

Signed-off-by: Tao Huang <huangtao@rock-chips.com>
Change-Id: I56fd2ee1acda8664548055c4b9ce14a3cb3233ce
---
 fs/notify/inotify/inotify_user.c | 15 +++++++++++++--
 include/linux/dcache.h           |  2 +-
 include/linux/fsnotify.h         |  7 +++++++
 3 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c
index fcfc9087be7e..a415ffa73a6d 100644
--- a/fs/notify/inotify/inotify_user.c
+++ b/fs/notify/inotify/inotify_user.c
@@ -702,6 +702,8 @@ SYSCALL_DEFINE3(inotify_add_watch, int, fd, const char __user *, pathname,
 	struct fsnotify_group *group;
 	struct inode *inode;
 	struct path path;
+	struct path alteredpath;
+	struct path *canonical_path = &path;
 	struct fd f;
 	int ret;
 	unsigned flags = 0;
@@ -747,13 +749,22 @@ SYSCALL_DEFINE3(inotify_add_watch, int, fd, const char __user *, pathname,
 	if (ret)
 		goto fput_and_out;
 
+	/* support stacked filesystems */
+	if(path.dentry && path.dentry->d_op) {
+		if (path.dentry->d_op->d_canonical_path) {
+			path.dentry->d_op->d_canonical_path(&path, &alteredpath);
+			canonical_path = &alteredpath;
+			path_put(&path);
+		}
+	}
+
 	/* inode held in place by reference to path; group by fget on fd */
-	inode = path.dentry->d_inode;
+	inode = canonical_path->dentry->d_inode;
 	group = f.file->private_data;
 
 	/* create/update an inode mark */
 	ret = inotify_update_watch(group, inode, mask);
-	path_put(&path);
+	path_put(canonical_path);
 fput_and_out:
 	fdput(f);
 	return ret;
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 1c6bb25a8501..45b20e0d6f77 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -150,7 +150,7 @@ struct dentry_operations {
 	struct vfsmount *(*d_automount)(struct path *);
 	int (*d_manage)(const struct path *, bool);
 	struct dentry *(*d_real)(struct dentry *, const struct inode *);
-
+	void (*d_canonical_path)(const struct path *, struct path *);
 	ANDROID_KABI_RESERVE(1);
 	ANDROID_KABI_RESERVE(2);
 	ANDROID_KABI_RESERVE(3);
diff --git a/include/linux/fsnotify.h b/include/linux/fsnotify.h
index fd1ce10553bf..61b72519f2f2 100644
--- a/include/linux/fsnotify.h
+++ b/include/linux/fsnotify.h
@@ -210,12 +210,19 @@ static inline void fsnotify_modify(struct file *file)
 static inline void fsnotify_open(struct file *file)
 {
 	const struct path *path = &file->f_path;
+	struct path lower_path;
 	struct inode *inode = file_inode(file);
 	__u32 mask = FS_OPEN;
 
 	if (S_ISDIR(inode->i_mode))
 		mask |= FS_ISDIR;
 
+	if (path->dentry->d_op && path->dentry->d_op->d_canonical_path) {
+		path->dentry->d_op->d_canonical_path(path, &lower_path);
+		fsnotify_parent(&lower_path, NULL, mask);
+		fsnotify(lower_path.dentry->d_inode, mask, &lower_path, FSNOTIFY_EVENT_PATH, NULL, 0);
+		path_put(&lower_path);
+	}
 	fsnotify_parent(path, NULL, mask);
 	fsnotify(inode, mask, path, FSNOTIFY_EVENT_PATH, NULL, 0);
 }