android-mainline/ANDROID-vfs-add-d_canonical_path-for-stacked-filesystem-support.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Daniel Rosenberg <drosen@google.com>
Date: Thu, 11 Feb 2016 16:44:15 -0800
Subject: ANDROID: vfs: add d_canonical_path for stacked filesystem support

Inotify does not currently know when a filesystem
is acting as a wrapper around another fs. This means
that inotify watchers will miss any modifications to
the base file, as well as any made in a separate
stacked fs that points to the same file.
d_canonical_path solves this problem by allowing the fs
to map a dentry to a path in the lower fs. Inotify
can use it to find the appropriate place to watch to
be informed of all changes to a file.

Test: HiKey/X15 + Pie + android-mainline,
      and HiKey + AOSP Maser + android-mainline,
      directories under /sdcard created,
      output of mount is right,
      CTS test collecting device infor works

Bug: 70706497
Change-Id: I09563baffad1711a045e45c1bd0bd8713c2cc0b6
Signed-off-by: Daniel Rosenberg <drosen@google.com>
[adelva: Folded 34df4102216e ("ANDROID: fsnotify: Notify lower fs of open")
         into this patch]
Signed-off-by: Alistair Delva <adelva@google.com>
Signed-off-by: Yongqin Liu <yongqin.liu@linaro.org>
---
 fs/notify/inotify/inotify_user.c | 15 +++++++++++++--
 include/linux/dcache.h           |  1 +
 include/linux/fsnotify.h         |  7 +++++++
 3 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c
index 3e66e6c8f53a..bd16ec03b5fd 100644
--- a/fs/notify/inotify/inotify_user.c
+++ b/fs/notify/inotify/inotify_user.c
@@ -701,6 +701,8 @@ 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 10090f11ab95..d59a73cdb10e 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -147,6 +147,7 @@ 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 *);
 } ____cacheline_aligned;
 
 /*
diff --git a/include/linux/fsnotify.h b/include/linux/fsnotify.h
index a2d5d175d3c1..e018872b047c 100644
--- a/include/linux/fsnotify.h
+++ b/include/linux/fsnotify.h
@@ -262,6 +262,7 @@ 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;
 
@@ -270,6 +271,12 @@ static inline void fsnotify_open(struct file *file)
 	if (file->f_flags & __FMODE_EXEC)
 		mask |= FS_OPEN_EXEC;
 
+	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_path(inode, path, mask);
 }