tree 5432d8aeecc31c96696a19c56c0577d4499abdaa
parent c00d2c7e89880036f288a764599b2b8b87c0a364
author Al Viro <viro@zeniv.linux.org.uk> 1482375302 -0500
committer Al Viro <viro@zeniv.linux.org.uk> 1482465622 -0500

[iov_iter] fix iterate_all_kinds() on empty iterators

Problem similar to ones dealt with in "fold checks into iterate_and_advance()"
and followups, except that in this case we really want to do nothing when
asked for zero-length operation - unlike zero-length iterate_and_advance(),
zero-length iterate_all_kinds() has no side effects, and callers are simpler
that way.

That got exposed when copy_from_iter_full() had been used by tipc, which
builds an msghdr with zero payload and (now) feeds it to a primitive
based on iterate_all_kinds() instead of iterate_and_advance().

Reported-by: Jon Maloy <jon.maloy@ericsson.com>
Tested-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>