ceph: allow object copies across different filesystems in the same cluster

OSDs are able to perform object copies across different pools.  Thus,
there's no need to prevent copy_file_range from doing remote copies if the
source and destination superblocks are different.  Only return -EXDEV if
they have different fsid (the cluster ID).
Signed-off-by: Luis Henriques <lhenriques@suse.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

fs/ceph/file.c

@@ -1922,6 +1922,7 @@ static ssize_t __ceph_copy_file_range(struct file *src_file, loff_t src_off,
 	struct ceph_inode_info *src_ci = ceph_inode(src_inode);
 	struct ceph_inode_info *dst_ci = ceph_inode(dst_inode);
 	struct ceph_cap_flush *prealloc_cf;
+	struct ceph_fs_client *src_fsc = ceph_inode_to_client(src_inode);
 	struct ceph_object_locator src_oloc, dst_oloc;
 	struct ceph_object_id src_oid, dst_oid;
 	loff_t endoff = 0, size;
@@ -1931,8 +1932,16 @@ static ssize_t __ceph_copy_file_range(struct file *src_file, loff_t src_off,
 	int src_got = 0, dst_got = 0, err, dirty;
 	bool do_final_copy = false;
 
-	if (src_inode->i_sb != dst_inode->i_sb)
-		return -EXDEV;
+	if (src_inode->i_sb != dst_inode->i_sb) {
+		struct ceph_fs_client *dst_fsc = ceph_inode_to_client(dst_inode);
+
+		if (ceph_fsid_compare(&src_fsc->client->fsid,
+				      &dst_fsc->client->fsid)) {
+			dout("Copying files across clusters: src: %pU dst: %pU\n",
+			     &src_fsc->client->fsid, &dst_fsc->client->fsid);
+			return -EXDEV;
+		}
+	}
 	if (ceph_snap(dst_inode) != CEPH_NOSNAP)
 		return -EROFS;
 
@@ -1944,7 +1953,7 @@ static ssize_t __ceph_copy_file_range(struct file *src_file, loff_t src_off,
 	 * efficient).
 	 */
 
-	if (ceph_test_mount_opt(ceph_inode_to_client(src_inode), NOCOPYFROM))
+	if (ceph_test_mount_opt(src_fsc, NOCOPYFROM))
 		return -EOPNOTSUPP;
 
 	if ((src_ci->i_layout.stripe_unit != dst_ci->i_layout.stripe_unit) ||
@@ -2059,7 +2068,7 @@ static ssize_t __ceph_copy_file_range(struct file *src_file, loff_t src_off,
 				dst_ci->i_vino.ino, dst_objnum);
 		/* Do an object remote copy */
 		err = ceph_osdc_copy_from(
-			&ceph_inode_to_client(src_inode)->client->osdc,
+			&src_fsc->client->osdc,
 			src_ci->i_vino.snap, 0,
 			&src_oid, &src_oloc,
 			CEPH_OSD_OP_FLAG_FADVISE_SEQUENTIAL |