[PATCH] FUSE: add access call

Add a new access call, which will only be called if ->permission is invoked
from sys_access().  In all other cases permission checking is delayed until
the actual filesystem operation.
Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/fuse/dir.c

@@ -461,6 +461,38 @@ static int fuse_revalidate(struct dentry *entry)
 	return fuse_do_getattr(inode);
 }
 
+static int fuse_access(struct inode *inode, int mask)
+{
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	struct fuse_req *req;
+	struct fuse_access_in inarg;
+	int err;
+
+	if (fc->no_access)
+		return 0;
+
+	req = fuse_get_request(fc);
+	if (!req)
+		return -EINTR;
+
+	memset(&inarg, 0, sizeof(inarg));
+	inarg.mask = mask;
+	req->in.h.opcode = FUSE_ACCESS;
+	req->in.h.nodeid = get_node_id(inode);
+	req->inode = inode;
+	req->in.numargs = 1;
+	req->in.args[0].size = sizeof(inarg);
+	req->in.args[0].value = &inarg;
+	request_send(fc, req);
+	err = req->out.h.error;
+	fuse_put_request(fc, req);
+	if (err == -ENOSYS) {
+		fc->no_access = 1;
+		err = 0;
+	}
+	return err;
+}
+
 static int fuse_permission(struct inode *inode, int mask, struct nameidata *nd)
 {
 	struct fuse_conn *fc = get_fuse_conn(inode);
@@ -493,6 +525,9 @@ static int fuse_permission(struct inode *inode, int mask, struct nameidata *nd)
 		int mode = inode->i_mode;
 		if ((mask & MAY_EXEC) && !S_ISDIR(mode) && !(mode & S_IXUGO))
 			return -EACCES;
+
+		if (nd && (nd->flags & LOOKUP_ACCESS))
+			return fuse_access(inode, mask);
 		return 0;
 	}
 }

fs/fuse/fuse_i.h

@@ -266,6 +266,9 @@ struct fuse_conn {
 	/** Is removexattr not implemented by fs? */
 	unsigned no_removexattr : 1;
 
+	/** Is access not implemented by fs? */
+	unsigned no_access : 1;
+
 	/** Backing dev info */
 	struct backing_dev_info bdi;
 };

include/linux/fuse.h

@@ -99,7 +99,8 @@ enum fuse_opcode {
 	FUSE_OPENDIR       = 27,
 	FUSE_READDIR       = 28,
 	FUSE_RELEASEDIR    = 29,
-	FUSE_FSYNCDIR      = 30
+	FUSE_FSYNCDIR      = 30,
+	FUSE_ACCESS        = 34
 };
 
 /* Conservative buffer size for the client */
@@ -222,6 +223,11 @@ struct fuse_getxattr_out {
 	__u32	padding;
 };
 
+struct fuse_access_in {
+	__u32	mask;
+	__u32	padding;
+};
+
 struct fuse_init_in_out {
 	__u32	major;
 	__u32	minor;