Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit eb9e939d authored by Daniel Rosenberg's avatar Daniel Rosenberg Committed by Alistair Strachan
Browse files

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.

Bug: 70706497
Bug: 120446149
Change-Id: I09563baffad1711a045e45c1bd0bd8713c2cc0b6
Signed-off-by: default avatarDaniel Rosenberg <drosen@google.com>
[astrachan: Folded 34df4102216e ("ANDROID: fsnotify: Notify lower fs of
            open") into this patch]
Signed-off-by: default avatarAlistair Strachan <astrachan@google.com>
parent e81cea2a

fs/notify/inotify/inotify_user.c

+13 −2
Original line number Diff line number Diff line
@@ -699,6 +699,8 @@ 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;
@@ -742,13 +744,22 @@ 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;

include/linux/dcache.h

+1 −0
Original line number Diff line number Diff line
@@ -146,6 +146,7 @@ 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;



/*

include/linux/fsnotify.h

+7 −0
Original line number Diff line number Diff line
@@ -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);

}