[net-next,v6,09/14] kcm: Use splice_eof() to flush

Commit Message

David Howells June 7, 2023, 6:19 p.m. UTC

Allow splice to undo the effects of MSG_MORE after prematurely ending a
splice/sendfile due to getting an EOF condition (->splice_read() returned
0) after splice had called sendmsg() with MSG_MORE set when the user didn't
set MSG_MORE.

Suggested-by: Linus Torvalds <[e-mail]>
Link: https://lore.kernel.org/r/CAHk-=wh=[e-mail]/
Signed-off-by: David Howells <[e-mail]>
cc: Tom Herbert <[e-mail]>
cc: Tom Herbert <[e-mail]>
cc: Cong Wang <[e-mail]>
cc: Jakub Kicinski <[e-mail]>
cc: Eric Dumazet <[e-mail]>
cc: "David S. Miller" <[e-mail]>
cc: Paolo Abeni <[e-mail]>
cc: Jens Axboe <[e-mail]>
cc: Matthew Wilcox <[e-mail]>
cc: [e-mail]
---

Notes:
    ver #6)
     - In kcm_splice_eof(), use skb_queue_empty_lockless().

 net/kcm/kcmsock.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

Patch

diff --git a/net/kcm/kcmsock.c b/net/kcm/kcmsock.c
index ba22af16b96d..7dee74430b59 100644
--- a/net/kcm/kcmsock.c
+++ b/net/kcm/kcmsock.c
@@ -968,6 +968,19 @@  static int kcm_sendmsg(struct socket *sock, struct msghdr *msg, size_t len)
 	return err;
 }
 
+static void kcm_splice_eof(struct socket *sock)
+{
+	struct sock *sk = sock->sk;
+	struct kcm_sock *kcm = kcm_sk(sk);
+
+	if (skb_queue_empty_lockless(&sk->sk_write_queue))
+		return;
+
+	lock_sock(sk);
+	kcm_write_msgs(kcm);
+	release_sock(sk);
+}
+
 static ssize_t kcm_sendpage(struct socket *sock, struct page *page,
 			    int offset, size_t size, int flags)
 
@@ -1773,6 +1786,7 @@  static const struct proto_ops kcm_dgram_ops = {
 	.sendmsg =	kcm_sendmsg,
 	.recvmsg =	kcm_recvmsg,
 	.mmap =		sock_no_mmap,
+	.splice_eof =	kcm_splice_eof,
 	.sendpage =	kcm_sendpage,
 };
 
@@ -1794,6 +1808,7 @@  static const struct proto_ops kcm_seqpacket_ops = {
 	.sendmsg =	kcm_sendmsg,
 	.recvmsg =	kcm_recvmsg,
 	.mmap =		sock_no_mmap,
+	.splice_eof =	kcm_splice_eof,
 	.sendpage =	kcm_sendpage,
 	.splice_read =	kcm_splice_read,
 };