The vfs takes care of updating ctime and mtime on ftruncate(), but on
truncate() it must be done by the module.

This patch can be tested with xfstests generic/313.

Link: http://lkml.kernel.org/r/9beb0913eea37288599e8e1b7cec8768fb52d1b8.1539316825.git.ernesto.mnd.fernandez@gmail.comSigned-off-by: Ernesto A. Fernández <ernesto.mnd.fernandez@gmail.com>
Reviewed-by: Vyacheslav Dubeyko <slava@dubeyko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>