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

Commit fa199896 authored by Daniel Rosenberg's avatar Daniel Rosenberg Committed by Alessio Balsini
Browse files

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: default avatarDaniel Rosenberg <drosen@google.com>
Signed-off-by: default avatarAlessio Balsini <balsini@google.com>
parent 54b41388

fs/fuse/dev.c

+9 −0
Original line number Diff line number Diff line
@@ -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 @@ ssize_t fuse_simple_request(struct fuse_conn *fc, struct fuse_args *args) 
	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 @@ static ssize_t fuse_dev_do_write(struct fuse_dev *fud, 
	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)

fs/fuse/dir.c

+39 −0
Original line number Diff line number Diff line
@@ -281,10 +281,49 @@ static void fuse_dentry_release(struct dentry *dentry) 
	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 = {

fs/fuse/fuse_i.h

+6 −0
Original line number Diff line number Diff line
@@ -213,6 +213,9 @@ struct fuse_out { 


	/** 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 @@ struct fuse_args { 
		unsigned argvar:1;

		unsigned numargs;

		struct fuse_arg args[2];



		/* Path used for completing d_canonical_path */

		struct path *canonical_path;

	} out;

};

include/uapi/linux/fuse.h

+1 −0
Original line number Diff line number Diff line
@@ -383,6 +383,7 @@ enum fuse_opcode { 
	FUSE_READDIRPLUS   = 44,

	FUSE_RENAME2       = 45,

	FUSE_LSEEK         = 46,

	FUSE_CANONICAL_PATH= 2016,



	/* CUSE specific operations */

	CUSE_INIT          = 4096,