[RFC -next 04/10] splice: Add SPLICE_F_ZC and attach ubuf
From: Joe Damato <hidden>
Date: 2025-03-19 00:15:43
Also in:
linux-api, linux-arch, linux-fsdevel, linux-kselftest, lkml
Subsystem:
filesystems (vfs and infrastructure), the rest · Maintainers:
Alexander Viro, Christian Brauner, Linus Torvalds
Add the SPLICE_F_ZC flag and when it is set, allocate a ubuf and attach it to generate zerocopy notifications. Signed-off-by: Joe Damato <redacted> --- fs/splice.c | 20 ++++++++++++++++++++ include/linux/splice.h | 3 ++- 2 files changed, 22 insertions(+), 1 deletion(-)
diff --git a/fs/splice.c b/fs/splice.c
index 1f27ce6d1c34..6dc60f47f84e 100644
--- a/fs/splice.c
+++ b/fs/splice.c@@ -875,6 +875,11 @@ static ssize_t splice_socket_generic(struct pipe_inode_info *pipe, if (out->f_flags & O_NONBLOCK) msg.msg_flags |= MSG_DONTWAIT; + if (unlikely(flags & SPLICE_F_ZC) && ubuf_info) { + msg.msg_flags = MSG_ZEROCOPY; + msg.msg_ubuf = ubuf_info; + } + iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, bvec, bc, len - remain); ret = sock_sendmsg(sock, &msg);
@@ -1223,12 +1228,27 @@ static ssize_t do_splice_direct_actor(struct file *in, loff_t *ppos, if (unlikely(out->f_flags & O_APPEND)) return -EINVAL; + if (unlikely(flags & SPLICE_F_ZC)) { + struct socket *sock = sock_from_file(out); + struct sock *sk = sock->sk; + struct ubuf_info *ubuf_info; + + ubuf_info = msg_zerocopy_realloc(sk, len, NULL); + if (!ubuf_info) + return -ENOMEM; + sd.ubuf_info = ubuf_info; + } + ret = splice_direct_to_actor(in, &sd, actor); if (ret > 0) *ppos = sd.pos; + if (unlikely(flags & SPLICE_F_ZC)) + refcount_dec(&sd.ubuf_info->refcnt); + return ret; } + /** * do_splice_direct - splices data directly between two files * @in: file to splice from
diff --git a/include/linux/splice.h b/include/linux/splice.h
index 7477df3916e2..a88588cf2754 100644
--- a/include/linux/splice.h
+++ b/include/linux/splice.h@@ -21,8 +21,9 @@ /* from/to, of course */ #define SPLICE_F_MORE (0x04) /* expect more data */ #define SPLICE_F_GIFT (0x08) /* pages passed in are a gift */ +#define SPLICE_F_ZC (0x10) /* generate zero copy notifications */ -#define SPLICE_F_ALL (SPLICE_F_MOVE|SPLICE_F_NONBLOCK|SPLICE_F_MORE|SPLICE_F_GIFT) +#define SPLICE_F_ALL (SPLICE_F_MOVE|SPLICE_F_NONBLOCK|SPLICE_F_MORE|SPLICE_F_GIFT|SPLICE_F_ZC) /* * Passed to the actors
--
2.43.0