[RFC -next 05/10] fs: Add splice_write_sd to file operations

Joe Damato
2025-03-19T00:15:45Z

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@fastly.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