ceph: fix uid/gid on resent mds requests

MDS requests can be rebuilt and resent in non-process context, but were
filling in uid/gid from current_fsuid/gid. Put that information in the
request struct on request setup.

This fixes incorrect (and root) uid/gid getting set for requests that
are forwarded between MDSs, usually due to metadata migrations.

Signed-off-by: Sage Weil <[e-mail]>

fs/ceph/mds_client.c

···
 	ceph_mdsc_get_request(req);
 	__insert_request(mdsc, req);
 
+	req->r_uid = current_fsuid();
+	req->r_gid = current_fsgid();
+
 	if (dir) {
 		struct ceph_inode_info *ci = ceph_inode(dir);
 
···
 
 	head->mdsmap_epoch = cpu_to_le32(mdsc->mdsmap->m_epoch);
 	head->op = cpu_to_le32(req->r_op);
-	head->caller_uid = cpu_to_le32(current_fsuid());
-	head->caller_gid = cpu_to_le32(current_fsgid());
+	head->caller_uid = cpu_to_le32(req->r_uid);
+	head->caller_gid = cpu_to_le32(req->r_gid);
 	head->args = req->r_args;
 
 	ceph_encode_filepath(&p, end, ino1, path1);

fs/ceph/mds_client.h

···
 
 	union ceph_mds_request_args r_args;
 	int r_fmode;        /* file mode, if expecting cap */
+	uid_t r_uid;
+	gid_t r_gid;
 
 	/* for choosing which mds to send this request to */
 	int r_direct_mode;