netdev - [PATCH net-next 1/3] net: devmem: support single IOV with sendmsg

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Message-ID: <20250520203044.2689904-1-stfomichev@gmail.com>
Date: Tue, 20 May 2025 13:30:42 -0700
From: Stanislav Fomichev <stfomichev@...il.com>
To: netdev@...r.kernel.org
Cc: davem@...emloft.net,
	edumazet@...gle.com,
	kuba@...nel.org,
	pabeni@...hat.com,
	viro@...iv.linux.org.uk,
	horms@...nel.org,
	andrew+netdev@...n.ch,
	shuah@...nel.org,
	sagi@...mberg.me,
	willemb@...gle.com,
	asml.silence@...il.com,
	almasrymina@...gle.com,
	stfomichev@...il.com,
	jdamato@...tly.com,
	kaiyuanz@...gle.com,
	linux-kernel@...r.kernel.org,
	linux-kselftest@...r.kernel.org
Subject: [PATCH net-next 1/3] net: devmem: support single IOV with sendmsg

sendmsg() with a single iov becomes ITER_UBUF, sendmsg() with multiple
iovs becomes ITER_IOVEC. iter_iov_len does not return correct
value for UBUF, so teach to treat UBUF differently.

Cc: Al Viro <viro@...iv.linux.org.uk>
Cc: Pavel Begunkov <asml.silence@...il.com>
Cc: Mina Almasry <almasrymina@...gle.com>
Fixes: bd61848900bf ("net: devmem: Implement TX path")
Signed-off-by: Stanislav Fomichev <stfomichev@...il.com>
---
 include/linux/uio.h | 8 +++++++-
 net/core/datagram.c | 3 ++-
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/include/linux/uio.h b/include/linux/uio.h
index 49ece9e1888f..393d0622cc28 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -99,7 +99,13 @@ static inline const struct iovec *iter_iov(const struct iov_iter *iter)
 }
 
 #define iter_iov_addr(iter)	(iter_iov(iter)->iov_base + (iter)->iov_offset)
-#define iter_iov_len(iter)	(iter_iov(iter)->iov_len - (iter)->iov_offset)
+
+static inline size_t iter_iov_len(const struct iov_iter *i)
+{
+	if (i->iter_type == ITER_UBUF)
+		return i->count;
+	return iter_iov(i)->iov_len - i->iov_offset;
+}
 
 static inline enum iter_type iov_iter_type(const struct iov_iter *i)
 {
diff --git a/net/core/datagram.c b/net/core/datagram.c
index 9ef5442536f5..c44f1d2b70a4 100644
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -706,7 +706,8 @@ zerocopy_fill_skb_from_devmem(struct sk_buff *skb, struct iov_iter *from,
 	 * iov_addrs are interpreted as an offset in bytes into the dma-buf to
 	 * send from. We do not support other iter types.
 	 */
-	if (iov_iter_type(from) != ITER_IOVEC)
+	if (iov_iter_type(from) != ITER_IOVEC &&
+	    iov_iter_type(from) != ITER_UBUF)
 		return -EFAULT;
 
 	while (length && iov_iter_count(from)) {
-- 
2.49.0