switch memcpy_to_msg() and skb_copy{,_and_csum}_datagram_msg() to primitives

... making both non-draining.  That means that tcp_recvmsg() becomes
non-draining.  And _that_ would break iscsit_do_rx_data() unless we
	a) make sure tcp_recvmsg() is uniformly non-draining (it is)
	b) make sure it copes with arbitrary (including shifted)
iov_iter (it does, all it uses is iov_iter primitives)
	c) make iscsit_do_rx_data() initialize ->msg_iter only once.

Fortunately, (c) is doable with minimal work and we are rid of one
the two places where kernel send/recvmsg users would be unhappy with
non-draining behaviour.

Actually, that makes all but one of ->recvmsg() instances iov_iter-clean.
The exception is skcipher_recvmsg() and it also isn't hard to convert
to primitives (iov_iter_get_pages() is needed there).  That'll wait
a bit - there's some interplay with ->sendmsg() path for that one.

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

diff --git a/drivers/target/iscsi/iscsi_target_util.c b/drivers/target/iscsi/iscsi_target_util.c
index ce87ce9..7c6a95b 100644 (file)
--- a/drivers/target/iscsi/iscsi_target_util.c
+++ b/drivers/target/iscsi/iscsi_target_util.c
@@ -1326,21 +1326,19 @@ static int iscsit_do_rx_data(
        struct iscsi_conn *conn,
        struct iscsi_data_count *count)
 {
-       int data = count->data_length, rx_loop = 0, total_rx = 0, iov_len;
-       struct kvec *iov_p;
+       int data = count->data_length, rx_loop = 0, total_rx = 0;
        struct msghdr msg;
 
        if (!conn || !conn->sock || !conn->conn_ops)
                return -1;
 
        memset(&msg, 0, sizeof(struct msghdr));
-
-       iov_p = count->iov;
-       iov_len = count->iov_count;
+       iov_iter_kvec(&msg.msg_iter, READ | ITER_KVEC,
+                     count->iov, count->iov_count, data);
 
        while (total_rx < data) {
-               rx_loop = kernel_recvmsg(conn->sock, &msg, iov_p, iov_len,
-                                       (data - total_rx), MSG_WAITALL);
+               rx_loop = sock_recvmsg(conn->sock, &msg,
+                                     (data - total_rx), MSG_WAITALL);
                if (rx_loop <= 0) {
                        pr_debug("rx_loop: %d total_rx: %d\n",
                                rx_loop, total_rx);

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 52cf1bd..4902f2d 100644 (file)
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -2651,17 +2651,10 @@ int skb_copy_datagram_iter(const struct sk_buff *from, int offset,
 static inline int skb_copy_datagram_msg(const struct sk_buff *from, int offset,
                                        struct msghdr *msg, int size)
 {
-       /* XXX: stripping const */
-       return skb_copy_datagram_iovec(from, offset, (struct iovec *)msg->msg_iter.iov, size);
-}
-int skb_copy_and_csum_datagram_iovec(struct sk_buff *skb, int hlen,
-                                    struct iovec *iov);
-static inline int skb_copy_and_csum_datagram_msg(struct sk_buff *skb, int hlen,
-                           struct msghdr *msg)
-{
-       /* XXX: stripping const */
-       return skb_copy_and_csum_datagram_iovec(skb, hlen, (struct iovec *)msg->msg_iter.iov);
+       return skb_copy_datagram_iter(from, offset, &msg->msg_iter, size);
 }
+int skb_copy_and_csum_datagram_msg(struct sk_buff *skb, int hlen,
+                                  struct msghdr *msg);
 int skb_copy_datagram_from_iter(struct sk_buff *skb, int offset,
                                 struct iov_iter *from, int len);
 int zerocopy_sg_from_iter(struct sk_buff *skb, struct iov_iter *frm);
@@ -2697,8 +2690,7 @@ static inline int memcpy_from_msg(void *data, struct msghdr *msg, int len)
 
 static inline int memcpy_to_msg(struct msghdr *msg, void *data, int len)
 {
-       /* XXX: stripping const */
-       return memcpy_toiovec((struct iovec *)msg->msg_iter.iov, data, len);
+       return copy_to_iter(data, len, &msg->msg_iter) == len ? 0 : -EFAULT;
 }
 
 struct skb_checksum_ops {

diff --git a/net/core/datagram.c b/net/core/datagram.c
index b6e303b..41075ed 100644 (file)
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -615,27 +615,25 @@ int zerocopy_sg_from_iter(struct sk_buff *skb, struct iov_iter *from)
 EXPORT_SYMBOL(zerocopy_sg_from_iter);
 
 static int skb_copy_and_csum_datagram(const struct sk_buff *skb, int offset,
-                                     u8 __user *to, int len,
+                                     struct iov_iter *to, int len,
                                      __wsum *csump)
 {
        int start = skb_headlen(skb);
        int i, copy = start - offset;
        struct sk_buff *frag_iter;
        int pos = 0;
+       int n;
 
        /* Copy header. */
        if (copy > 0) {
-               int err = 0;
                if (copy > len)
                        copy = len;
-               *csump = csum_and_copy_to_user(skb->data + offset, to, copy,
-                                              *csump, &err);
-               if (err)
+               n = csum_and_copy_to_iter(skb->data + offset, copy, csump, to);
+               if (n != copy)
                        goto fault;
                if ((len -= copy) == 0)
                        return 0;
                offset += copy;
-               to += copy;
                pos = copy;
        }
 
@@ -647,26 +645,22 @@ static int skb_copy_and_csum_datagram(const struct sk_buff *skb, int offset,
 
                end = start + skb_frag_size(frag);
                if ((copy = end - offset) > 0) {
-                       __wsum csum2;
-                       int err = 0;
-                       u8  *vaddr;
+                       __wsum csum2 = 0;
                        struct page *page = skb_frag_page(frag);
+                       u8  *vaddr = kmap(page);
 
                        if (copy > len)
                                copy = len;
-                       vaddr = kmap(page);
-                       csum2 = csum_and_copy_to_user(vaddr +
-                                                       frag->page_offset +
-                                                       offset - start,
-                                                     to, copy, 0, &err);
+                       n = csum_and_copy_to_iter(vaddr + frag->page_offset +
+                                                 offset - start, copy,
+                                                 &csum2, to);
                        kunmap(page);
-                       if (err)
+                       if (n != copy)
                                goto fault;
                        *csump = csum_block_add(*csump, csum2, pos);
                        if (!(len -= copy))
                                return 0;
                        offset += copy;
-                       to += copy;
                        pos += copy;
                }
                start = end;
@@ -691,7 +685,6 @@ static int skb_copy_and_csum_datagram(const struct sk_buff *skb, int offset,
                        if ((len -= copy) == 0)
                                return 0;
                        offset += copy;
-                       to += copy;
                        pos += copy;
                }
                start = end;
@@ -744,20 +737,19 @@ __sum16 __skb_checksum_complete(struct sk_buff *skb)
 EXPORT_SYMBOL(__skb_checksum_complete);
 
 /**
- *     skb_copy_and_csum_datagram_iovec - Copy and checksum skb to user iovec.
+ *     skb_copy_and_csum_datagram_msg - Copy and checksum skb to user iovec.
  *     @skb: skbuff
  *     @hlen: hardware length
- *     @iov: io vector
+ *     @msg: destination
  *
  *     Caller _must_ check that skb will fit to this iovec.
  *
  *     Returns: 0       - success.
  *              -EINVAL - checksum failure.
- *              -EFAULT - fault during copy. Beware, in this case iovec
- *                        can be modified!
+ *              -EFAULT - fault during copy.
  */
-int skb_copy_and_csum_datagram_iovec(struct sk_buff *skb,
-                                    int hlen, struct iovec *iov)
+int skb_copy_and_csum_datagram_msg(struct sk_buff *skb,
+                                  int hlen, struct msghdr *msg)
 {
        __wsum csum;
        int chunk = skb->len - hlen;
@@ -765,28 +757,20 @@ int skb_copy_and_csum_datagram_iovec(struct sk_buff *skb,
        if (!chunk)
                return 0;
 
-       /* Skip filled elements.
-        * Pretty silly, look at memcpy_toiovec, though 8)
-        */
-       while (!iov->iov_len)
-               iov++;
-
-       if (iov->iov_len < chunk) {
+       if (iov_iter_count(&msg->msg_iter) < chunk) {
                if (__skb_checksum_complete(skb))
                        goto csum_error;
-               if (skb_copy_datagram_iovec(skb, hlen, iov, chunk))
+               if (skb_copy_datagram_msg(skb, hlen, msg, chunk))
                        goto fault;
        } else {
                csum = csum_partial(skb->data, hlen, skb->csum);
-               if (skb_copy_and_csum_datagram(skb, hlen, iov->iov_base,
+               if (skb_copy_and_csum_datagram(skb, hlen, &msg->msg_iter,
                                               chunk, &csum))
                        goto fault;
                if (csum_fold(csum))
                        goto csum_error;
                if (unlikely(skb->ip_summed == CHECKSUM_COMPLETE))
                        netdev_rx_csum_fault(skb->dev);
-               iov->iov_len -= chunk;
-               iov->iov_base += chunk;
        }
        return 0;
 csum_error:
@@ -794,7 +778,7 @@ csum_error:
 fault:
        return -EFAULT;
 }
-EXPORT_SYMBOL(skb_copy_and_csum_datagram_iovec);
+EXPORT_SYMBOL(skb_copy_and_csum_datagram_msg);
 
 /**
  *     datagram_poll - generic datagram poll