moves it over to the old name. The new file may be on a different
filesystem, so both st_dev and st_ino of the file may change.
-Any open files referring to this inode will access the old data and
-metadata. Similarly any file locks obtained before copy_up will not
-apply to the copied up file.
+Any open files referring to this inode will access the old data.
-On a file opened with O_RDONLY fchmod(2), fchown(2), futimesat(2) and
-fsetxattr(2) will fail with EROFS.
+Any file locks (and leases) obtained before copy_up will not apply
+to the copied up file.
If a file with multiple hard links is copied up, then this will
"break" the link. Changes will not be propagated to other names