ANDROID: fuse: Add support for d_canonical_path
Allows FUSE to report to inotify that it is acting
as a layered filesystem. The userspace component
returns a string representing the location of the
underlying file. If the string cannot be resolved
into a path, the top level path is returned instead.
bug: 23904372
Change-Id: Iabdca0bbedfbff59e9c820c58636a68ef9683d9f
Signed-off-by: Daniel Rosenberg <drosen@google.com>
diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index 096f799..340a618 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -262,6 +262,50 @@
goto out;
}
+/*
+ * Get the canonical path. Since we must translate to a path, this must be done
+ * in the context of the userspace daemon, however, the userspace daemon cannot
+ * look up paths on its own. Instead, we handle the lookup as a special case
+ * inside of the write request.
+ */
+static void fuse_dentry_canonical_path(const struct path *path, struct path *canonical_path) {
+ struct inode *inode = path->dentry->d_inode;
+ struct fuse_conn *fc = get_fuse_conn(inode);
+ struct fuse_req *req;
+ int err;
+ char *path_name;
+
+ req = fuse_get_req(fc, 1);
+ err = PTR_ERR(req);
+ if (IS_ERR(req))
+ goto default_path;
+
+ path_name = (char*)__get_free_page(GFP_KERNEL);
+ if (!path_name) {
+ fuse_put_request(fc, req);
+ goto default_path;
+ }
+
+ req->in.h.opcode = FUSE_CANONICAL_PATH;
+ req->in.h.nodeid = get_node_id(inode);
+ req->in.numargs = 0;
+ req->out.numargs = 1;
+ req->out.args[0].size = PATH_MAX;
+ req->out.args[0].value = path_name;
+ req->canonical_path = canonical_path;
+ req->out.argvar = 1;
+ fuse_request_send(fc, req);
+ err = req->out.h.error;
+ fuse_put_request(fc, req);
+ free_page((unsigned long)path_name);
+ if (!err)
+ return;
+default_path:
+ canonical_path->dentry = path->dentry;
+ canonical_path->mnt = path->mnt;
+ path_get(canonical_path);
+}
+
static int invalid_nodeid(u64 nodeid)
{
return !nodeid || nodeid == FUSE_ROOT_ID;
@@ -284,11 +328,13 @@
.d_revalidate = fuse_dentry_revalidate,
.d_init = fuse_dentry_init,
.d_release = fuse_dentry_release,
+ .d_canonical_path = fuse_dentry_canonical_path,
};
const struct dentry_operations fuse_root_dentry_operations = {
.d_init = fuse_dentry_init,
.d_release = fuse_dentry_release,
+ .d_canonical_path = fuse_dentry_canonical_path,
};
int fuse_valid_type(int m)