[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>

7 files changed, 8 insertions, 15 deletions

diff --git a/drivers/bluetooth/hci_vhci.c b/drivers/bluetooth/hci_vhci.c
index c4a75a18dcae..233e850fdac7 100644
--- a/drivers/bluetooth/hci_vhci.c
+++ b/drivers/bluetooth/hci_vhci.c
@@ -181,7 +181,7 @@ static inline ssize_t vhci_get_user(struct vhci_data *data,
 	if (!skb)
 		return -ENOMEM;
 
-	if (copy_from_iter(skb_put(skb, len), len, from) != len) {
+	if (!copy_from_iter_full(skb_put(skb, len), len, from)) {
 		kfree_skb(skb);
 		return -EFAULT;
 	}
diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index 070e3290aa6e..19d81ca3fb49 100644
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -673,7 +673,6 @@ static ssize_t macvtap_get_user(struct macvtap_queue *q, struct msghdr *m,
 	int depth;
 	bool zerocopy = false;
 	size_t linear;
-	ssize_t n;
 
 	if (q->flags & IFF_VNET_HDR) {
 		vnet_hdr_len = q->vnet_hdr_sz;
@@ -684,8 +683,7 @@ static ssize_t macvtap_get_user(struct macvtap_queue *q, struct msghdr *m,
 		len -= vnet_hdr_len;
 
 		err = -EFAULT;
-		n = copy_from_iter(&vnet_hdr, sizeof(vnet_hdr), from);
-		if (n != sizeof(vnet_hdr))
+		if (!copy_from_iter_full(&vnet_hdr, sizeof(vnet_hdr), from))
 			goto err;
 		iov_iter_advance(from, vnet_hdr_len - sizeof(vnet_hdr));
 		if ((vnet_hdr.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) &&
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 8093e39ae263..4fa2d756548a 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) &&
diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
index 17989b72cdae..0bfd1e25b431 100644
--- a/drivers/usb/gadget/function/f_fs.c
+++ b/drivers/usb/gadget/function/f_fs.c
@@ -949,7 +949,7 @@ static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data)
 			goto error_mutex;
 		}
 		if (!io_data->read &&
-		    copy_from_iter(data, data_len, &io_data->data) != data_len) {
+		    !copy_from_iter_full(data, data_len, &io_data->data)) {
 			ret = -EFAULT;
 			goto error_mutex;
 		}
diff --git a/drivers/usb/gadget/legacy/inode.c b/drivers/usb/gadget/legacy/inode.c
index bd82dd12deff..10b2576f8b6a 100644
--- a/drivers/usb/gadget/legacy/inode.c
+++ b/drivers/usb/gadget/legacy/inode.c
@@ -667,7 +667,7 @@ ep_write_iter(struct kiocb *iocb, struct iov_iter *from)
 		return -ENOMEM;
 	}
 
-	if (unlikely(copy_from_iter(buf, len, from) != len)) {
+	if (unlikely(!copy_from_iter_full(buf, len, from))) {
 		value = -EFAULT;
 		goto out;
 	}
diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
index 6e29d053843d..b296985fda0d 100644
--- a/drivers/vhost/scsi.c
+++ b/drivers/vhost/scsi.c
@@ -922,8 +922,7 @@ vhost_scsi_handle_vq(struct vhost_scsi *vs, struct vhost_virtqueue *vq)
 		 */
 		iov_iter_init(&out_iter, WRITE, vq->iov, out, out_size);
 
-		ret = copy_from_iter(req, req_size, &out_iter);
-		if (unlikely(ret != req_size)) {
+		if (unlikely(!copy_from_iter_full(req, req_size, &out_iter))) {
 			vq_err(vq, "Faulted on copy_from_iter\n");
 			vhost_scsi_send_bad_target(vs, vq, head, out);
 			continue;
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;