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switch memcpy_to_msg() and skb_copy{,_and_csum}_datagram_msg() to pri…
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…mitives

... 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 <[email protected]>
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Al Viro committed Dec 9, 2014
1 parent 1783639 commit e5a4b0b
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Showing 3 changed files with 28 additions and 54 deletions.
12 changes: 5 additions & 7 deletions drivers/target/iscsi/iscsi_target_util.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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);
Expand Down
16 changes: 4 additions & 12 deletions include/linux/skbuff.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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);
Expand Down Expand Up @@ -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 {
Expand Down
54 changes: 19 additions & 35 deletions net/core/datagram.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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;
}

Expand All @@ -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;
Expand All @@ -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;
Expand Down Expand Up @@ -744,57 +737,48 @@ __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;

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:
return -EINVAL;
fault:
return -EFAULT;
}
EXPORT_SYMBOL(skb_copy_and_csum_datagram_iovec);
EXPORT_SYMBOL(skb_copy_and_csum_datagram_msg);

/**
* datagram_poll - generic datagram poll
Expand Down

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