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Commit 2e4aa2a5 authored by Daniel Rosenberg's avatar Daniel Rosenberg Committed by Amit Pundir
Browse files

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: default avatarDaniel Rosenberg <drosen@google.com>
parent 7a9d2174

fs/fuse/dev.c

+5 −0
Original line number Diff line number Diff line
@@ -13,6 +13,7 @@ 
#include <linux/poll.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>
@@ -1878,6 +1879,10 @@ static ssize_t fuse_dev_do_write(struct fuse_dev *fud, 
		cs->move_pages = 0;



	err = copy_out_args(cs, &req->out, nbytes);

	if (req->in.h.opcode == FUSE_CANONICAL_PATH) {

		req->out.h.error = kern_path((char *)req->out.args[0].value, 0,

							req->canonical_path);

	}

	fuse_copy_finish(cs);



	spin_lock(&fpq->lock);

fs/fuse/dir.c

+45 −0
Original line number Diff line number Diff line
@@ -262,6 +262,50 @@ static int fuse_dentry_revalidate(struct dentry *entry, unsigned int flags) 
	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;
@@ -284,6 +328,7 @@ 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,

};



int fuse_valid_type(int m)

fs/fuse/fuse_i.h

+3 −0
Original line number Diff line number Diff line
@@ -368,6 +368,9 @@ struct fuse_req { 
	/** Inode used in the request or NULL */

	struct inode *inode;



	/** Path used for completing d_canonical_path */

	struct path *canonical_path;



	/** AIO control block */

	struct fuse_io_priv *io;

include/uapi/linux/fuse.h

+1 −0
Original line number Diff line number Diff line
@@ -375,6 +375,7 @@ enum fuse_opcode { 
	FUSE_READDIRPLUS   = 44,

	FUSE_RENAME2       = 45,

	FUSE_LSEEK         = 46,

	FUSE_CANONICAL_PATH= 2016,



	/* CUSE specific operations */

	CUSE_INIT          = 4096,