[GIT PULL] Add IORING_REGISTER_CLONE_FILES support and tests

man/io_uring_clone_files.3

@@ -0,0 +1,135 @@
+.\" Copyright (C) 2026 Harshal Chavan <harshal24.chavan@gmail.com>
+.\"
+.\" SPDX-License-Identifier: LGPL-2.0-or-later
+.\"
+.TH io_uring_clone_files 3 "June 24, 2026" "liburing-2.12" "liburing Manual"
+.SH NAME
+io_uring_clone_files \- Clones registered files between rings
+.SH SYNOPSIS
+.nf
+.B #include <liburing.h>
+.PP
+.BI "int io_uring_clone_files(struct io_uring *" dst ","
+.BI "                         struct io_uring * " src ");"
+.PP
+.BI "int __io_uring_clone_files(struct io_uring *" dst ","
+.BI "                           struct io_uring * " src ","
+.BI "                           unsigned int " flags ");"
+.PP
+.BI "int io_uring_clone_files_offset(struct io_uring *" dst ","
+.BI "                                struct io_uring * " src ","
+.BI "                                unsigned int " dst_off ","
+.BI "                                unsigned int " src_off ","
+.BI "                                unsigned int " nr ","
+.BI "                                unsigned int " flags ");"
+.PP
+.BI "int __io_uring_clone_files_offset(struct io_uring *" dst ","
+.BI "                                  struct io_uring * " src ","
+.BI "                                  unsigned int " dst_off ","
+.BI "                                  unsigned int " src_off ","
+.BI "                                  unsigned int " nr ","
+.BI "                                  unsigned int " flags ");"
+.PP
+.fi
+.SH DESCRIPTION
+.PP
+The
+.BR io_uring_clone_files (3)
+function clones registered file descriptors from the ring indicated by
+.IR src
+to the ring indicated by
+.IR dst .
+Upon successful completion of this operation,
+.IR src
+and
+.IR dst
+will have the same set of registered files.
+
+The
+.IR dst
+ring must not have any files currently registered. If files are currently
+registered on the destination ring, they must be unregistered with
+.BR io_uring_unregister_files (3)
+first or pass the IORING_REGISTER_DST_REPLACE flag to replace the old files in 
+.IR dst
+ring.
+
+
+Not yet available in the kernel.
+
+The
+.BR io_uring_clone_files_offset (3)
+function also clones files from the
+.IR src
+ring to the
+.IR dst
+ring, however it supports cloning only a subset of the files, where
+.BR io_uring_clone_files (3)
+always clones all of them.
+.IR dst_off
+indicates at what offset cloning should start in the destination,
+.IR src_off
+indicates at what offset cloning should start in the source, and
+.IR nr
+indicates how many files to clone at the given offset. If both
+.IR dst_off ,
+.IR src_off ,
+and
+.IR nr
+are given as
+.B 0 ,
+then
+.BR io_uring_clone_files_offset (3)
+performs the same action as
+.BR io_uring_clone_files (3) .
+
+.IR flags
+may be set to the following values:
+.TP
+.B IORING_REGISTER_SRC_REGISTERED
+If the source ring is registered AND the calling thread is the one that
+originally registered its ring fd, then this flag may be set to lookup the
+registered index rather than use the normal file descriptor. If the normal
+file descriptor wasn't closed after registering it, there's no need to set
+this flag.
+.TP
+.B IORING_REGISTER_DST_REPLACE
+If set, cloning may happen for a destination ring that already has a file
+table assigned. In that case, existing nodes that overlap with the specified
+range will be released and replaced.
+.PP
+
+.SH NOTES
+A ring cannot safely clone its file table into itself. Attempting to use the
+same ring for both
+.IR src
+and
+.IR dst
+will fail.
+.SH RETURN VALUE
+On success
+.BR io_uring_clone_files (3)
+and
+.BR io_uring_clone_files_offset (3)
+return 0.
+On failure, they return
+.BR -errno ,
+specifically
+.TP
+.B -EBUSY
+The destination ring already has files registered, and
+.B IORING_REGISTER_DST_REPLACE
+wasn't set.
+.TP
+.B -EINVAL
+An attempt was made to clone a ring into itself, or an invalid flag/offset was specified.
+.TP
+.B -ENOMEM
+The kernel ran out of memory.
+.TP
+.B -ENXIO
+The source ring doesn't have any files registered.
+.SH SEE ALSO
+.BR io_uring_register (2),
+.BR io_uring_unregister_files (3),
+.BR io_uring_register_files (3)

src/include/liburing.h

@@ -279,6 +279,18 @@ int io_uring_clone_buffers(struct io_uring *dst, struct io_uring *src)
 	LIBURING_NOEXCEPT;
 int __io_uring_clone_buffers(struct io_uring *dst, struct io_uring *src,
 			     unsigned int flags) LIBURING_NOEXCEPT;
+int io_uring_clone_files_offset(struct io_uring *dst, struct io_uring *src,
+				  unsigned int dst_off, unsigned int src_off,
+				  unsigned int nr, unsigned int flags)
+	LIBURING_NOEXCEPT;
+int __io_uring_clone_files_offset(struct io_uring *dst, struct io_uring *src,
+				  unsigned int dst_off, unsigned int src_off,
+				  unsigned int nr, unsigned int flags)
+	LIBURING_NOEXCEPT;
+int io_uring_clone_files(struct io_uring *dst, struct io_uring *src)
+	LIBURING_NOEXCEPT;
+int __io_uring_clone_files(struct io_uring *dst, struct io_uring *src,
+			     unsigned int flags) LIBURING_NOEXCEPT;
 int io_uring_register_buffers(struct io_uring *ring, const struct iovec *iovecs,
 			      unsigned nr_iovecs) LIBURING_NOEXCEPT;
 int io_uring_register_buffers_tags(struct io_uring *ring,

src/include/liburing/io_uring.h

@@ -709,6 +709,9 @@ enum io_uring_register_op {
 	/* register bpf filtering programs */
 	IORING_REGISTER_BPF_FILTER		= 37,
 
+	/* clone file descriptors from another ring */
+	IORING_REGISTER_CLONE_FILES		= 38,
+
 	/* this goes last */
 	IORING_REGISTER_LAST,
 
@@ -840,6 +843,16 @@ struct io_uring_clone_buffers {
 	__u32	pad[3];
 };
 
+
+struct io_uring_clone_files {
+	__u32 src_fd;
+	__u32 flags;
+	__u32 src_off;
+	__u32 dst_off;
+	__u32 nr;
+	__u32 pad[3];
+};
+
 struct io_uring_buf {
 	__u64	addr;
 	__u32	len;

src/liburing-ffi.map

@@ -274,4 +274,8 @@ LIBURING_2.15 {
 		__io_uring_peek_cqe;
 		io_uring_register_zcrx_ctrl;
 		io_uring_register_query;
+    io_uring_clone_files;
+		__io_uring_clone_files;
+		io_uring_clone_files_offset;
+		__io_uring_clone_files_offset;
 } LIBURING_2.14;

src/liburing.map

@@ -145,4 +145,8 @@ LIBURING_2.15 {
 		io_uring_register_bpf_filter_task;
 		io_uring_register_zcrx_ctrl;
 		io_uring_register_query;
+    io_uring_clone_files;
+		__io_uring_clone_files;
+		io_uring_clone_files_offset;
+		__io_uring_clone_files_offset;
 } LIBURING_2.14;

src/register.c

@@ -443,6 +443,49 @@ int __io_uring_clone_buffers(struct io_uring *dst, struct io_uring *src,
 	return __io_uring_clone_buffers_offset(dst, src, 0, 0, 0, flags);
 }
 
+int __io_uring_clone_files_offset(struct io_uring *dst, struct io_uring *src,
+				    unsigned int dst_off, unsigned int src_off,
+				    unsigned int nr, unsigned int flags)
+{
+	struct io_uring_clone_files buf = {
+		.src_fd		= src->ring_fd,
+		.flags		= flags,
+		.src_off	= src_off,
+		.dst_off	= dst_off,
+		.nr		= nr,
+	};
+
+	if (flags & IORING_REGISTER_SRC_REGISTERED &&
+	    src->int_flags & INT_FLAG_REG_REG_RING) {
+		buf.src_fd = src->enter_ring_fd;
+	} else {
+		buf.src_fd = src->ring_fd;
+		buf.flags &= ~IORING_REGISTER_SRC_REGISTERED;
+	}
+
+	return do_register(dst, IORING_REGISTER_CLONE_FILES, &buf, 1);
+}
+
+int io_uring_clone_files_offset(struct io_uring *dst, struct io_uring *src,
+				  unsigned int dst_off, unsigned int src_off,
+				  unsigned int nr, unsigned int flags)
+{
+	return __io_uring_clone_files_offset(dst, src, dst_off, src_off, nr,
+						flags | IORING_REGISTER_SRC_REGISTERED);
+}
+
+int io_uring_clone_files(struct io_uring *dst, struct io_uring *src)
+{
+	return __io_uring_clone_files_offset(dst, src, 0, 0, 0, IORING_REGISTER_SRC_REGISTERED);
+}
+
+int __io_uring_clone_files(struct io_uring *dst, struct io_uring *src,
+			     unsigned int flags)
+{
+	return __io_uring_clone_files_offset(dst, src, 0, 0, 0, flags);
+}
+
+
 int io_uring_register_ifq(struct io_uring *ring,
 			  struct io_uring_zcrx_ifq_reg *reg)
 {

test/Makefile

@@ -84,6 +84,7 @@ test_srcs := \
 	cancel-race.c \
 	cbpf_filter.c \
 	ce593a6c480a.c \
+	clone-files.c \
 	close-opath.c \
 	conn-unreach.c \
 	connect.c \