linux-kernel - [RFC -next 05/10] fs: Add splice_write

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Message-ID: <20250319001521.53249-6-jdamato@fastly.com>
Date: Wed, 19 Mar 2025 00:15:16 +0000
From: Joe Damato <jdamato@...tly.com>
To: netdev@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
	asml.silence@...il.com,
	linux-fsdevel@...r.kernel.org,
	edumazet@...gle.com,
	pabeni@...hat.com,
	horms@...nel.org,
	linux-api@...r.kernel.org,
	linux-arch@...r.kernel.org,
	viro@...iv.linux.org.uk,
	jack@...e.cz,
	kuba@...nel.org,
	shuah@...nel.org,
	sdf@...ichev.me,
	mingo@...hat.com,
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	brauner@...nel.org,
	akpm@...ux-foundation.org,
	tglx@...utronix.de,
	jolsa@...nel.org,
	linux-kselftest@...r.kernel.org,
	Joe Damato <jdamato@...tly.com>
Subject: [RFC -next 05/10] fs: Add splice_write_sd to file operations

Introduce splice_write_sd to file operations and export a new helper for
sockets splice_to_socket_sd to pass through the splice_desc context
allowing the allocated ubuf to be attached.

Signed-off-by: Joe Damato <jdamato@...tly.com>
---
 fs/splice.c            | 22 ++++++++++++++++++----
 include/linux/fs.h     |  2 ++
 include/linux/splice.h |  2 ++
 net/socket.c           |  1 +
 4 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/fs/splice.c b/fs/splice.c
index 6dc60f47f84e..d08fa2a6d930 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -935,6 +935,16 @@ ssize_t splice_to_socket(struct pipe_inode_info *pipe, struct file *out,
 {
 	return splice_socket_generic(pipe, out, ppos, len, flags, NULL);
 }
+
+ssize_t splice_to_socket_sd(struct pipe_inode_info *pipe,
+			    struct file *out, struct splice_desc *sd)
+{
+	ssize_t ret;
+
+	ret = splice_socket_generic(pipe, out, sd->opos, sd->total_len,
+				    sd->flags, sd->ubuf_info);
+	return ret;
+}
 #endif
 
 static int warn_unsupported(struct file *file, const char *op)
@@ -959,10 +969,14 @@ static ssize_t do_splice_from(struct pipe_inode_info *pipe, struct file *out,
 static ssize_t do_splice_from_sd(struct pipe_inode_info *pipe, struct file *out,
 				 struct splice_desc *sd)
 {
-	if (unlikely(!out->f_op->splice_write))
-		return warn_unsupported(out, "write");
-	return out->f_op->splice_write(pipe, out, sd->opos, sd->total_len,
-				       sd->flags);
+	if (likely(!(sd->flags & SPLICE_F_ZC))) {
+		if (unlikely(!out->f_op->splice_write))
+			return warn_unsupported(out, "write");
+		return out->f_op->splice_write(pipe, out, sd->opos,
+					       sd->total_len, sd->flags);
+	} else {
+		return out->f_op->splice_write_sd(pipe, out, sd);
+	}
 }
 
 /*
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 7e29433c5ecc..843e8b8a1d4d 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2065,6 +2065,7 @@ struct dir_context {
 struct iov_iter;
 struct io_uring_cmd;
 struct offset_ctx;
+struct splice_desc;
 
 typedef unsigned int __bitwise fop_flags_t;
 
@@ -2093,6 +2094,7 @@ struct file_operations {
 	int (*check_flags)(int);
 	int (*flock) (struct file *, int, struct file_lock *);
 	ssize_t (*splice_write)(struct pipe_inode_info *, struct file *, loff_t *, size_t, unsigned int);
+	ssize_t (*splice_write_sd)(struct pipe_inode_info *, struct file *, struct splice_desc *);
 	ssize_t (*splice_read)(struct file *, loff_t *, struct pipe_inode_info *, size_t, unsigned int);
 	void (*splice_eof)(struct file *file);
 	int (*setlease)(struct file *, int, struct file_lease **, void **);
diff --git a/include/linux/splice.h b/include/linux/splice.h
index a88588cf2754..356b8cae4818 100644
--- a/include/linux/splice.h
+++ b/include/linux/splice.h
@@ -100,6 +100,8 @@ static inline long splice_copy_file_range(struct file *in, loff_t pos_in,
 
 ssize_t do_tee(struct file *in, struct file *out, size_t len,
 	       unsigned int flags);
+ssize_t splice_to_socket_sd(struct pipe_inode_info *pipe, struct file *out,
+			    struct splice_desc *sd);
 ssize_t splice_to_socket(struct pipe_inode_info *pipe, struct file *out,
 			 loff_t *ppos, size_t len, unsigned int flags);
 
diff --git a/net/socket.c b/net/socket.c
index 9a117248f18f..4baf26a36477 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -165,6 +165,7 @@ static const struct file_operations socket_file_ops = {
 	.release =	sock_close,
 	.fasync =	sock_fasync,
 	.splice_write = splice_to_socket,
+	.splice_write_sd = splice_to_socket_sd,
 	.splice_read =	sock_splice_read,
 	.splice_eof =	sock_splice_eof,
 	.show_fdinfo =	sock_show_fdinfo,
-- 
2.43.0