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
Bug: 171780975
Test: Pixel 4.19
Change-Id: Iabdca0bbedfbff59e9c820c58636a68ef9683d9f
Signed-off-by: Daniel Rosenberg <drosen@google.com>
Signed-off-by: Alessio Balsini <balsini@google.com>
diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 1ff5a6b..9861204 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -14,6 +14,7 @@
#include <linux/sched/signal.h>
#include <linux/uio.h>
#include <linux/miscdevice.h>
+#include <linux/namei.h>
#include <linux/pagemap.h>
#include <linux/file.h>
#include <linux/slab.h>
@@ -573,6 +574,7 @@
req->out.numargs = args->out.numargs;
memcpy(req->out.args, args->out.args,
args->out.numargs * sizeof(struct fuse_arg));
+ req->out.canonical_path = args->out.canonical_path;
fuse_request_send(fc, req);
ret = req->out.h.error;
if (!ret && args->out.argvar) {
@@ -1932,6 +1934,13 @@
err = copy_out_args(cs, &req->out, nbytes);
fuse_copy_finish(cs);
+ if (!err && req->in.h.opcode == FUSE_CANONICAL_PATH) {
+ char *path = (char *)req->out.args[0].value;
+
+ path[req->out.args[0].size - 1] = 0;
+ req->out.h.error = kern_path(path, 0, req->out.canonical_path);
+ }
+
spin_lock(&fpq->lock);
clear_bit(FR_LOCKED, &req->flags);
if (!fpq->connected)
diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index 6244345..90bd6c0 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -281,10 +281,49 @@
kfree_rcu(fd, rcu);
}
+/*
+ * 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 = d_inode(path->dentry);
+ struct fuse_conn *fc = get_fuse_conn(inode);
+ FUSE_ARGS(args);
+ char *path_name;
+ int err;
+
+ path_name = (char *)__get_free_page(GFP_KERNEL);
+ if (!path_name)
+ goto default_path;
+
+ args.in.h.opcode = FUSE_CANONICAL_PATH;
+ args.in.h.nodeid = get_node_id(inode);
+ args.in.numargs = 0;
+ args.out.numargs = 1;
+ args.out.args[0].size = PATH_MAX;
+ args.out.args[0].value = path_name;
+ args.out.argvar = 1;
+ args.out.canonical_path = canonical_path;
+
+ err = fuse_simple_request(fc, &args);
+ free_page((unsigned long)path_name);
+ if (err > 0)
+ return;
+default_path:
+ canonical_path->dentry = path->dentry;
+ canonical_path->mnt = path->mnt;
+ path_get(canonical_path);
+}
+
const struct dentry_operations fuse_dentry_operations = {
.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 = {
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index dbfc35e..123f878 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -213,6 +213,9 @@
/** Array of arguments */
struct fuse_arg args[2];
+
+ /* Path used for completing d_canonical_path */
+ struct path *canonical_path;
};
/** FUSE page descriptor */
@@ -235,6 +238,9 @@
unsigned argvar:1;
unsigned numargs;
struct fuse_arg args[2];
+
+ /* Path used for completing d_canonical_path */
+ struct path *canonical_path;
} out;
};
diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h
index 2170e58..24af4ed 100644
--- a/include/uapi/linux/fuse.h
+++ b/include/uapi/linux/fuse.h
@@ -383,6 +383,7 @@
FUSE_READDIRPLUS = 44,
FUSE_RENAME2 = 45,
FUSE_LSEEK = 46,
+ FUSE_CANONICAL_PATH= 2016,
/* CUSE specific operations */
CUSE_INIT = 4096,