[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>
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 8093e39..4fa2d75 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1171,7 +1171,6 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
bool zerocopy = false;
int err;
u32 rxhash;
- ssize_t n;
if (!(tun->dev->flags & IFF_UP))
return -EIO;
@@ -1181,8 +1180,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
return -EINVAL;
len -= sizeof(pi);
- n = copy_from_iter(&pi, sizeof(pi), from);
- if (n != sizeof(pi))
+ if (!copy_from_iter_full(&pi, sizeof(pi), from))
return -EFAULT;
}
@@ -1191,8 +1189,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
return -EINVAL;
len -= tun->vnet_hdr_sz;
- n = copy_from_iter(&gso, sizeof(gso), from);
- if (n != sizeof(gso))
+ if (!copy_from_iter_full(&gso, sizeof(gso), from))
return -EFAULT;
if ((gso.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) &&