[iov_iter] new primitives - copy_from_iter_full() and friends

copy_from_iter_full(), copy_from_iter_full_nocache() and
csum_and_copy_from_iter_full() - counterparts of copy_from_iter()
et.al., advancing iterator only in case of successful full copy
and returning whether it had been successful or not.

Convert some obvious users.  *NOTE* - do not blindly assume that
something is a good candidate for those unless you are sure that
not advancing iov_iter in failure case is the right thing in
this case.  Anything that does short read/short write kind of
stuff (or is in a loop, etc.) is unlikely to be a good one.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 1 insertions, 2 deletions

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index c6f2d89c0e97..06e8b81b6253 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -1862,8 +1862,7 @@ static int get_indirect(struct vhost_virtqueue *vq,
                                i, count);
                         return -EINVAL;
                 }
-                if (unlikely(copy_from_iter(&desc, sizeof(desc), &from) !=
-                             sizeof(desc))) {
+                if (unlikely(!copy_from_iter_full(&desc, sizeof(desc), &from))) {
                         vq_err(vq, "Failed indirect descriptor: idx %d, %zx\n",
                                i, (size_t)vhost64_to_cpu(vq, indirect->addr) + i * sizeof desc);
                         return -EINVAL;