[PATCH v5] io_uring/register: add IORING_REGISTER_CLONE_FILES opcode

[PATCH v5] io_uring/register: add IORING_REGISTER_CLONE_FILES opcode

[Harshal Chavan]

Currently, if an application wants to duplicate registered file
descriptors from one io_uring instance to another, it must manually
unregister and re-register them, incurring unnecessary overhead.

Add IORING_REGISTER_CLONE_FILES to allow direct cloning of the file
table from a source ring to a destination ring. This implementation
strictly mirrors the io_clone_buffers UAPI, supporting partial offsets
and the IORING_REGISTER_DST_REPLACE flag.

To ensure lock synchronization safety, destination nodes are strictly
allocated as new, private io_rsrc_nodes rather than sharing references
across rings.

Signed-off-by: Harshal Chavan <harshal24.chavan@gmail.com>

---
v5:
  - Added missing spacing in comment (Gabriel).
  - Removed ctx->user and mm_account checks (Gabriel).
  - Used !! for boolean conversion (Gabriel).
  - Moved mutex_unlock unconditionally above the out label (Gabriel).
  - liburing implementation and tests: https://github.com/axboe/liburing/pull/1606
v4:
  - Updated Signed-off-by to use real name and moved above the scissors line (Greg KH).
v3:
  - Rewrote the cloning loop to allocate private destination nodes via io_rsrc_node_alloc to fix non-atomic ref lock synchronization (Jens).
  - Maintained partial offset/copy support to mirror io_clone_buffers UAPI (Jens).
  - Gated the replacement free check on ctx->file_table.data.nr (Gabriel).
  - Prevented self-cloning by checking ctx == src_ctx (Gabriel).
  - Removed submitter_task check to allow cross-thread pooling setups (Gabriel).
v2:
  - Dropped unrelated whitespace formatting changes from v1
---
 include/uapi/linux/io_uring.h |  12 +++
 io_uring/register.c           |   6 ++
 io_uring/rsrc.c               | 145 ++++++++++++++++++++++++++++++++++
 io_uring/rsrc.h               |   1 +
 4 files changed, 164 insertions(+)

diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index 909fb7aea638..67fcc40f8dfc 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -723,6 +723,9 @@ 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,
 
@@ -854,6 +857,15 @@ 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;
diff --git a/io_uring/register.c b/io_uring/register.c
index dce5e2f9cf77..bbc8c506ea2d 100644
--- a/io_uring/register.c
+++ b/io_uring/register.c
@@ -924,6 +924,12 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
 			break;
 		ret = io_register_clone_buffers(ctx, arg);
 		break;
+	case IORING_REGISTER_CLONE_FILES:
+		ret = -EINVAL;
+		if (!arg || nr_args != 1)
+			break;
+		ret = io_register_clone_files(ctx, arg);
+		break;
 	case IORING_REGISTER_ZCRX_IFQ:
 		ret = -EINVAL;
 		if (!arg || nr_args != 1)
diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c
index 650303626be6..5ddd715e2a63 100644
--- a/io_uring/rsrc.c
+++ b/io_uring/rsrc.c
@@ -1303,6 +1303,151 @@ int io_register_clone_buffers(struct io_ring_ctx *ctx, void __user *arg)
 	return ret;
 }
 
+static int io_clone_file_node(struct io_ring_ctx *ctx,
+			      struct io_rsrc_node *src_node,
+			      int dst_index,
+			      struct io_file_table *new_table)
+{
+	struct io_rsrc_node *dst_node;
+	struct file *file;
+
+	dst_node = io_rsrc_node_alloc(ctx, IORING_RSRC_FILE);
+	if (!dst_node)
+		return -ENOMEM;
+
+	file = io_slot_file(src_node);
+	get_file(file);
+	io_fixed_file_set(dst_node, file);
+
+	new_table->data.nodes[dst_index] = dst_node;
+	io_file_bitmap_set(new_table, dst_index);
+
+	return 0;
+}
+
+static int io_clone_files(struct io_ring_ctx *ctx, struct io_ring_ctx *src_ctx,
+			  struct io_uring_clone_files *arg)
+{
+	struct io_file_table new_file_table;
+	unsigned int dst_nr = ctx->file_table.data.nr;
+	unsigned int src_nr = src_ctx->file_table.data.nr;
+	unsigned int new_nr, i;
+
+	lockdep_assert_held(&ctx->uring_lock);
+	lockdep_assert_held(&src_ctx->uring_lock);
+
+	if (dst_nr && !(arg->flags & IORING_REGISTER_DST_REPLACE))
+		return -EBUSY;
+
+	if (!src_nr)
+		return -ENXIO;
+
+	if (!arg->nr)
+		arg->nr = src_nr;
+	else if (arg->nr > src_nr)
+		return -EINVAL;
+
+	if (check_add_overflow(arg->src_off, arg->nr, &i) || i > src_nr)
+		return -EINVAL;
+	if (check_add_overflow(arg->dst_off, arg->nr, &i))
+		return -EINVAL;
+
+	new_nr = max(dst_nr, arg->dst_off + arg->nr);
+	if (new_nr > IORING_MAX_FIXED_FILES)
+		return -EINVAL;
+
+	memset(&new_file_table, 0, sizeof(new_file_table));
+	if (!io_alloc_file_tables(ctx, &new_file_table, new_nr))
+		return -ENOMEM;
+
+	/* Copy original nodes from before the cloned range */
+	for (i = 0; i < min(arg->dst_off, dst_nr); i++) {
+		struct io_rsrc_node *src_node = io_rsrc_node_lookup(&ctx->file_table.data, i);
+
+		if (!src_node)
+			continue;
+		if (io_clone_file_node(ctx, src_node, i, &new_file_table))
+			goto out;
+	}
+
+	/* Copy the actual cloned range from the source ring */
+	for (i = 0; i < arg->nr; i++) {
+		struct io_rsrc_node *src_node = io_rsrc_node_lookup(&src_ctx->file_table.data,
+				arg->src_off + i);
+
+		if (!src_node)
+			continue;
+		if (io_clone_file_node(ctx, src_node, arg->dst_off + i, &new_file_table))
+			goto out;
+	}
+
+	/* Copy original nodes from after the cloned range */
+	for (i = arg->dst_off + arg->nr; i < dst_nr; i++) {
+		struct io_rsrc_node *src_node = io_rsrc_node_lookup(&ctx->file_table.data, i);
+
+		if (!src_node)
+			continue;
+		if (io_clone_file_node(ctx, src_node, i, &new_file_table))
+			goto out;
+	}
+
+	/* free the old file table if there is any data present */
+	if (dst_nr)
+		io_free_file_tables(ctx, &ctx->file_table);
+
+	WARN_ON_ONCE(ctx->file_table.data.nr);
+	ctx->file_table = new_file_table;
+	io_file_table_set_alloc_range(ctx, 0, ctx->file_table.data.nr);
+	return 0;
+
+out:
+	/* Error Path: Safely destroy whatever we partially built */
+	io_free_file_tables(ctx, &new_file_table);
+	return -ENOMEM;
+}
+
+int io_register_clone_files(struct io_ring_ctx *ctx, void __user *arg)
+{
+	struct io_uring_clone_files clone_arg;
+	struct io_ring_ctx *src_ctx;
+	bool registered_src;
+	struct file *file;
+	int ret;
+
+	if (copy_from_user(&clone_arg, arg, sizeof(clone_arg)))
+		return -EFAULT;
+	if (clone_arg.flags &
+	    ~(IORING_REGISTER_SRC_REGISTERED | IORING_REGISTER_DST_REPLACE))
+		return -EINVAL;
+
+	if (memchr_inv(clone_arg.pad, 0, sizeof(clone_arg.pad)))
+		return -EINVAL;
+
+	registered_src = !!(clone_arg.flags & IORING_REGISTER_SRC_REGISTERED); 
+	file = io_uring_ctx_get_file(clone_arg.src_fd, registered_src);
+	if (IS_ERR(file))
+		return PTR_ERR(file);
+
+	src_ctx = file->private_data;
+	/* Same ring clone is not allowed */
+	if (src_ctx == ctx) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	mutex_unlock(&ctx->uring_lock);
+	lock_two_rings(ctx, src_ctx);
+
+	ret = io_clone_files(ctx, src_ctx, &clone_arg);
+
+	mutex_unlock(&src_ctx->uring_lock);
+
+out:
+	if (!registered_src)
+		fput(file);
+	return ret;
+}
+
 void io_vec_free(struct iou_vec *iv)
 {
 	if (!iv->iovec)
diff --git a/io_uring/rsrc.h b/io_uring/rsrc.h
index 44e3386f7c1c..32f5c47c46af 100644
--- a/io_uring/rsrc.h
+++ b/io_uring/rsrc.h
@@ -75,6 +75,7 @@ int io_prep_reg_iovec(struct io_kiocb *req, struct iou_vec *iv,
 			const struct iovec __user *uvec, size_t uvec_segs);
 
 int io_register_clone_buffers(struct io_ring_ctx *ctx, void __user *arg);
+int io_register_clone_files(struct io_ring_ctx *ctx, void __user *arg);
 int io_sqe_buffers_unregister(struct io_ring_ctx *ctx);
 int io_sqe_buffers_register(struct io_ring_ctx *ctx, void __user *arg,
 			    unsigned int nr_args, u64 __user *tags);
-- 
2.54.0

[PATCH v6] io_uring/register: add IORING_REGISTER_CLONE_FILES opcode

[Harshal Chavan]

Currently, if an application wants to duplicate registered file
descriptors from one io_uring instance to another, it must manually
unregister and re-register them, incurring unnecessary overhead.

Add IORING_REGISTER_CLONE_FILES to allow direct cloning of the file
table from a source ring to a destination ring. This implementation
strictly mirrors the io_clone_buffers UAPI, supporting partial offsets
and the IORING_REGISTER_DST_REPLACE flag.

To ensure lock synchronization safety, destination nodes are strictly
allocated as new, private io_rsrc_nodes rather than sharing references
across rings.

Signed-off-by: Harshal Chavan <harshal24.chavan@gmail.com>

---
Sorry for the noise on the previous email! I accidentally sent the patch 
before running checkpatch and missed a whitespace error. This v6 corrects it.

v6:
  - Fixed trailing whitespace checkpatch error.
v5:
  - Added missing spacing in comment (Gabriel).
  - Removed ctx->user and mm_account checks (Gabriel).
  - Used !! for boolean conversion (Gabriel).
  - Moved mutex_unlock unconditionally above the out label (Gabriel).
  - liburing implementation and tests: https://github.com/axboe/liburing/pull/1606
v4:
  - Updated Signed-off-by to use real name and moved above the scissors line (Greg KH).
v3:
  - Rewrote the cloning loop to allocate private destination nodes via io_rsrc_node_alloc to fix non-atomic ref lock synchronization (Jens).
  - Maintained partial offset/copy support to mirror io_clone_buffers UAPI (Jens).
  - Gated the replacement free check on ctx->file_table.data.nr (Gabriel).
  - Prevented self-cloning by checking ctx == src_ctx (Gabriel).
  - Removed submitter_task check to allow cross-thread pooling setups (Gabriel).
v2:
  - Dropped unrelated whitespace formatting changes from v1
---
 include/uapi/linux/io_uring.h |  12 +++
 io_uring/register.c           |   6 ++
 io_uring/rsrc.c               | 145 ++++++++++++++++++++++++++++++++++
 io_uring/rsrc.h               |   1 +
 4 files changed, 164 insertions(+)

diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index 909fb7aea638..67fcc40f8dfc 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -723,6 +723,9 @@ 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,
 
@@ -854,6 +857,15 @@ 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;
diff --git a/io_uring/register.c b/io_uring/register.c
index dce5e2f9cf77..bbc8c506ea2d 100644
--- a/io_uring/register.c
+++ b/io_uring/register.c
@@ -924,6 +924,12 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
 			break;
 		ret = io_register_clone_buffers(ctx, arg);
 		break;
+	case IORING_REGISTER_CLONE_FILES:
+		ret = -EINVAL;
+		if (!arg || nr_args != 1)
+			break;
+		ret = io_register_clone_files(ctx, arg);
+		break;
 	case IORING_REGISTER_ZCRX_IFQ:
 		ret = -EINVAL;
 		if (!arg || nr_args != 1)
diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c
index 650303626be6..1d58c256b3a5 100644
--- a/io_uring/rsrc.c
+++ b/io_uring/rsrc.c
@@ -1303,6 +1303,151 @@ int io_register_clone_buffers(struct io_ring_ctx *ctx, void __user *arg)
 	return ret;
 }
 
+static int io_clone_file_node(struct io_ring_ctx *ctx,
+			      struct io_rsrc_node *src_node,
+			      int dst_index,
+			      struct io_file_table *new_table)
+{
+	struct io_rsrc_node *dst_node;
+	struct file *file;
+
+	dst_node = io_rsrc_node_alloc(ctx, IORING_RSRC_FILE);
+	if (!dst_node)
+		return -ENOMEM;
+
+	file = io_slot_file(src_node);
+	get_file(file);
+	io_fixed_file_set(dst_node, file);
+
+	new_table->data.nodes[dst_index] = dst_node;
+	io_file_bitmap_set(new_table, dst_index);
+
+	return 0;
+}
+
+static int io_clone_files(struct io_ring_ctx *ctx, struct io_ring_ctx *src_ctx,
+			  struct io_uring_clone_files *arg)
+{
+	struct io_file_table new_file_table;
+	unsigned int dst_nr = ctx->file_table.data.nr;
+	unsigned int src_nr = src_ctx->file_table.data.nr;
+	unsigned int new_nr, i;
+
+	lockdep_assert_held(&ctx->uring_lock);
+	lockdep_assert_held(&src_ctx->uring_lock);
+
+	if (dst_nr && !(arg->flags & IORING_REGISTER_DST_REPLACE))
+		return -EBUSY;
+
+	if (!src_nr)
+		return -ENXIO;
+
+	if (!arg->nr)
+		arg->nr = src_nr;
+	else if (arg->nr > src_nr)
+		return -EINVAL;
+
+	if (check_add_overflow(arg->src_off, arg->nr, &i) || i > src_nr)
+		return -EINVAL;
+	if (check_add_overflow(arg->dst_off, arg->nr, &i))
+		return -EINVAL;
+
+	new_nr = max(dst_nr, arg->dst_off + arg->nr);
+	if (new_nr > IORING_MAX_FIXED_FILES)
+		return -EINVAL;
+
+	memset(&new_file_table, 0, sizeof(new_file_table));
+	if (!io_alloc_file_tables(ctx, &new_file_table, new_nr))
+		return -ENOMEM;
+
+	/* Copy original nodes from before the cloned range */
+	for (i = 0; i < min(arg->dst_off, dst_nr); i++) {
+		struct io_rsrc_node *src_node = io_rsrc_node_lookup(&ctx->file_table.data, i);
+
+		if (!src_node)
+			continue;
+		if (io_clone_file_node(ctx, src_node, i, &new_file_table))
+			goto out;
+	}
+
+	/* Copy the actual cloned range from the source ring */
+	for (i = 0; i < arg->nr; i++) {
+		struct io_rsrc_node *src_node = io_rsrc_node_lookup(&src_ctx->file_table.data,
+				arg->src_off + i);
+
+		if (!src_node)
+			continue;
+		if (io_clone_file_node(ctx, src_node, arg->dst_off + i, &new_file_table))
+			goto out;
+	}
+
+	/* Copy original nodes from after the cloned range */
+	for (i = arg->dst_off + arg->nr; i < dst_nr; i++) {
+		struct io_rsrc_node *src_node = io_rsrc_node_lookup(&ctx->file_table.data, i);
+
+		if (!src_node)
+			continue;
+		if (io_clone_file_node(ctx, src_node, i, &new_file_table))
+			goto out;
+	}
+
+	/* free the old file table if there is any data present */
+	if (dst_nr)
+		io_free_file_tables(ctx, &ctx->file_table);
+
+	WARN_ON_ONCE(ctx->file_table.data.nr);
+	ctx->file_table = new_file_table;
+	io_file_table_set_alloc_range(ctx, 0, ctx->file_table.data.nr);
+	return 0;
+
+out:
+	/* Error Path: Safely destroy whatever we partially built */
+	io_free_file_tables(ctx, &new_file_table);
+	return -ENOMEM;
+}
+
+int io_register_clone_files(struct io_ring_ctx *ctx, void __user *arg)
+{
+	struct io_uring_clone_files clone_arg;
+	struct io_ring_ctx *src_ctx;
+	bool registered_src;
+	struct file *file;
+	int ret;
+
+	if (copy_from_user(&clone_arg, arg, sizeof(clone_arg)))
+		return -EFAULT;
+	if (clone_arg.flags &
+	    ~(IORING_REGISTER_SRC_REGISTERED | IORING_REGISTER_DST_REPLACE))
+		return -EINVAL;
+
+	if (memchr_inv(clone_arg.pad, 0, sizeof(clone_arg.pad)))
+		return -EINVAL;
+
+	registered_src = !!(clone_arg.flags & IORING_REGISTER_SRC_REGISTERED);
+	file = io_uring_ctx_get_file(clone_arg.src_fd, registered_src);
+	if (IS_ERR(file))
+		return PTR_ERR(file);
+
+	src_ctx = file->private_data;
+	/* Same ring clone is not allowed */
+	if (src_ctx == ctx) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	mutex_unlock(&ctx->uring_lock);
+	lock_two_rings(ctx, src_ctx);
+
+	ret = io_clone_files(ctx, src_ctx, &clone_arg);
+
+	mutex_unlock(&src_ctx->uring_lock);
+
+out:
+	if (!registered_src)
+		fput(file);
+	return ret;
+}
+
 void io_vec_free(struct iou_vec *iv)
 {
 	if (!iv->iovec)
diff --git a/io_uring/rsrc.h b/io_uring/rsrc.h
index 44e3386f7c1c..32f5c47c46af 100644
--- a/io_uring/rsrc.h
+++ b/io_uring/rsrc.h
@@ -75,6 +75,7 @@ int io_prep_reg_iovec(struct io_kiocb *req, struct iou_vec *iv,
 			const struct iovec __user *uvec, size_t uvec_segs);
 
 int io_register_clone_buffers(struct io_ring_ctx *ctx, void __user *arg);
+int io_register_clone_files(struct io_ring_ctx *ctx, void __user *arg);
 int io_sqe_buffers_unregister(struct io_ring_ctx *ctx);
 int io_sqe_buffers_register(struct io_ring_ctx *ctx, void __user *arg,
 			    unsigned int nr_args, u64 __user *tags);
-- 
2.54.0

Re: [PATCH v6] io_uring/register: add IORING_REGISTER_CLONE_FILES opcode

[Gabriel Krisman Bertazi]

Harshal Chavan <harshal24.chavan@gmail.com> writes:

> Currently, if an application wants to duplicate registered file
> descriptors from one io_uring instance to another, it must manually
> unregister and re-register them, incurring unnecessary overhead.
>
> Add IORING_REGISTER_CLONE_FILES to allow direct cloning of the file
> table from a source ring to a destination ring. This implementation
> strictly mirrors the io_clone_buffers UAPI, supporting partial offsets
> and the IORING_REGISTER_DST_REPLACE flag.
>
> To ensure lock synchronization safety, destination nodes are strictly
> allocated as new, private io_rsrc_nodes rather than sharing references
> across rings.
>
> Signed-off-by: Harshal Chavan <harshal24.chavan@gmail.com>
>
> ---
> Sorry for the noise on the previous email! I accidentally sent the patch 
> before running checkpatch and missed a whitespace error. This v6 corrects it.
>
> v6:
>   - Fixed trailing whitespace checkpatch error.
> v5:
>   - Added missing spacing in comment (Gabriel).
>   - Removed ctx->user and mm_account checks (Gabriel).
>   - Used !! for boolean conversion (Gabriel).
>   - Moved mutex_unlock unconditionally above the out label (Gabriel).
>   - liburing implementation and tests: https://github.com/axboe/liburing/pull/1606
> v4:
>   - Updated Signed-off-by to use real name and moved above the scissors line (Greg KH).
> v3:
>   - Rewrote the cloning loop to allocate private destination nodes via io_rsrc_node_alloc to fix non-atomic ref lock synchronization (Jens).
>   - Maintained partial offset/copy support to mirror io_clone_buffers UAPI (Jens).
>   - Gated the replacement free check on ctx->file_table.data.nr (Gabriel).
>   - Prevented self-cloning by checking ctx == src_ctx (Gabriel).
>   - Removed submitter_task check to allow cross-thread pooling setups (Gabriel).
> v2:
>   - Dropped unrelated whitespace formatting changes from v1

> +static int io_clone_file_node(struct io_ring_ctx *ctx,
> +			      struct io_rsrc_node *src_node,
> +			      int dst_index,
> +			      struct io_file_table *new_table)
> +{
> +	struct io_rsrc_node *dst_node;
> +	struct file *file;
> +
> +	dst_node = io_rsrc_node_alloc(ctx, IORING_RSRC_FILE);
> +	if (!dst_node)
> +		return -ENOMEM;
> +
> +	file = io_slot_file(src_node);
> +	get_file(file);
> +	io_fixed_file_set(dst_node, file);

don't you need to copy the src_node->tag here as well?

I didn't get a chance to run it yet, sorry.  I'd suggest you wait for
Jens feedback before pushing the v7 too, so you don't need to keep
iterating drop by drop :)

> +
> +	new_table->data.nodes[dst_index] = dst_node;
> +	io_file_bitmap_set(new_table, dst_index);
> +
> +	return 0;
> +}
> +
> +static int io_clone_files(struct io_ring_ctx *ctx, struct io_ring_ctx *src_ctx,
> +			  struct io_uring_clone_files *arg)
> +{
> +	struct io_file_table new_file_table;
> +	unsigned int dst_nr = ctx->file_table.data.nr;
> +	unsigned int src_nr = src_ctx->file_table.data.nr;
> +	unsigned int new_nr, i;
> +
> +	lockdep_assert_held(&ctx->uring_lock);
> +	lockdep_assert_held(&src_ctx->uring_lock);
> +
> +	if (dst_nr && !(arg->flags & IORING_REGISTER_DST_REPLACE))
> +		return -EBUSY;
> +
> +	if (!src_nr)
> +		return -ENXIO;
> +
> +	if (!arg->nr)
> +		arg->nr = src_nr;
> +	else if (arg->nr > src_nr)
> +		return -EINVAL;
> +
> +	if (check_add_overflow(arg->src_off, arg->nr, &i) || i > src_nr)
> +		return -EINVAL;
> +	if (check_add_overflow(arg->dst_off, arg->nr, &i))
> +		return -EINVAL;
> +
> +	new_nr = max(dst_nr, arg->dst_off + arg->nr);
> +	if (new_nr > IORING_MAX_FIXED_FILES)
> +		return -EINVAL;
> +
> +	memset(&new_file_table, 0, sizeof(new_file_table));
> +	if (!io_alloc_file_tables(ctx, &new_file_table, new_nr))
> +		return -ENOMEM;
> +
> +	/* Copy original nodes from before the cloned range */
> +	for (i = 0; i < min(arg->dst_off, dst_nr); i++) {
> +		struct io_rsrc_node *src_node = io_rsrc_node_lookup(&ctx->file_table.data, i);
> +
> +		if (!src_node)
> +			continue;
> +		if (io_clone_file_node(ctx, src_node, i, &new_file_table))
> +			goto out;
> +	}
> +
> +	/* Copy the actual cloned range from the source ring */
> +	for (i = 0; i < arg->nr; i++) {
> +		struct io_rsrc_node *src_node = io_rsrc_node_lookup(&src_ctx->file_table.data,
> +				arg->src_off + i);
> +
> +		if (!src_node)
> +			continue;
> +		if (io_clone_file_node(ctx, src_node, arg->dst_off + i, &new_file_table))
> +			goto out;
> +	}
> +
> +	/* Copy original nodes from after the cloned range */
> +	for (i = arg->dst_off + arg->nr; i < dst_nr; i++) {
> +		struct io_rsrc_node *src_node = io_rsrc_node_lookup(&ctx->file_table.data, i);
> +
> +		if (!src_node)
> +			continue;
> +		if (io_clone_file_node(ctx, src_node, i, &new_file_table))
> +			goto out;
> +	}
> +
> +	/* free the old file table if there is any data present */
> +	if (dst_nr)
> +		io_free_file_tables(ctx, &ctx->file_table);
> +
> +	WARN_ON_ONCE(ctx->file_table.data.nr);
> +	ctx->file_table = new_file_table;
> +	io_file_table_set_alloc_range(ctx, 0, ctx->file_table.data.nr);
> +	return 0;
> +
> +out:
> +	/* Error Path: Safely destroy whatever we partially built */
> +	io_free_file_tables(ctx, &new_file_table);
> +	return -ENOMEM;
> +}
> +
> +int io_register_clone_files(struct io_ring_ctx *ctx, void __user *arg)
> +{
> +	struct io_uring_clone_files clone_arg;
> +	struct io_ring_ctx *src_ctx;
> +	bool registered_src;
> +	struct file *file;
> +	int ret;
> +
> +	if (copy_from_user(&clone_arg, arg, sizeof(clone_arg)))
> +		return -EFAULT;
> +	if (clone_arg.flags &
> +	    ~(IORING_REGISTER_SRC_REGISTERED | IORING_REGISTER_DST_REPLACE))
> +		return -EINVAL;
> +
> +	if (memchr_inv(clone_arg.pad, 0, sizeof(clone_arg.pad)))
> +		return -EINVAL;
> +
> +	registered_src = !!(clone_arg.flags & IORING_REGISTER_SRC_REGISTERED);
> +	file = io_uring_ctx_get_file(clone_arg.src_fd, registered_src);
> +	if (IS_ERR(file))
> +		return PTR_ERR(file);
> +
> +	src_ctx = file->private_data;
> +	/* Same ring clone is not allowed */
> +	if (src_ctx == ctx) {
> +		ret = -EINVAL;
> +		goto out;
> +	}
> +
> +	mutex_unlock(&ctx->uring_lock);
> +	lock_two_rings(ctx, src_ctx);
> +
> +	ret = io_clone_files(ctx, src_ctx, &clone_arg);
> +
> +	mutex_unlock(&src_ctx->uring_lock);
> +
> +out:
> +	if (!registered_src)
> +		fput(file);
> +	return ret;
> +}
> +
>  void io_vec_free(struct iou_vec *iv)
>  {
>  	if (!iv->iovec)
> diff --git a/io_uring/rsrc.h b/io_uring/rsrc.h
> index 44e3386f7c1c..32f5c47c46af 100644
> --- a/io_uring/rsrc.h
> +++ b/io_uring/rsrc.h
> @@ -75,6 +75,7 @@ int io_prep_reg_iovec(struct io_kiocb *req, struct iou_vec *iv,
>  			const struct iovec __user *uvec, size_t uvec_segs);
>  
>  int io_register_clone_buffers(struct io_ring_ctx *ctx, void __user *arg);
> +int io_register_clone_files(struct io_ring_ctx *ctx, void __user *arg);
>  int io_sqe_buffers_unregister(struct io_ring_ctx *ctx);
>  int io_sqe_buffers_register(struct io_ring_ctx *ctx, void __user *arg,
>  			    unsigned int nr_args, u64 __user *tags);
> -- 
> 2.54.0
>

-- 
Gabriel Krisman Bertazi

Re: [PATCH v6] io_uring/register: add IORING_REGISTER_CLONE_FILES opcode

[Harshal Chavan]

>> +     file = io_slot_file(src_node);
>> +     get_file(file);
>> +     io_fixed_file_set(dst_node, file);

> don't you need to copy the src_node->tag here as well?

Yes, sorry for the silly mistakes, thanks for catching this!

> I didn't get a chance to run it yet, sorry.  I'd suggest you wait for
> Jens feedback before pushing the v7 too, so you don't need to keep
> iterating drop by drop :)

Okay, Yes I will wait for feedback from Jens and send the changes together
Thanks for the review.

Regards,
Harshal Chavan

On Fri, Jun 26, 2026 at 2:03 AM Gabriel Krisman Bertazi <krisman@suse.de> wrote:
>
> Harshal Chavan <harshal24.chavan@gmail.com> writes:
>
> > Currently, if an application wants to duplicate registered file
> > descriptors from one io_uring instance to another, it must manually
> > unregister and re-register them, incurring unnecessary overhead.
> >
> > Add IORING_REGISTER_CLONE_FILES to allow direct cloning of the file
> > table from a source ring to a destination ring. This implementation
> > strictly mirrors the io_clone_buffers UAPI, supporting partial offsets
> > and the IORING_REGISTER_DST_REPLACE flag.
> >
> > To ensure lock synchronization safety, destination nodes are strictly
> > allocated as new, private io_rsrc_nodes rather than sharing references
> > across rings.
> >
> > Signed-off-by: Harshal Chavan <harshal24.chavan@gmail.com>
> >
> > ---
> > Sorry for the noise on the previous email! I accidentally sent the patch
> > before running checkpatch and missed a whitespace error. This v6 corrects it.
> >
> > v6:
> >   - Fixed trailing whitespace checkpatch error.
> > v5:
> >   - Added missing spacing in comment (Gabriel).
> >   - Removed ctx->user and mm_account checks (Gabriel).
> >   - Used !! for boolean conversion (Gabriel).
> >   - Moved mutex_unlock unconditionally above the out label (Gabriel).
> >   - liburing implementation and tests: https://github.com/axboe/liburing/pull/1606
> > v4:
> >   - Updated Signed-off-by to use real name and moved above the scissors line (Greg KH).
> > v3:
> >   - Rewrote the cloning loop to allocate private destination nodes via io_rsrc_node_alloc to fix non-atomic ref lock synchronization (Jens).
> >   - Maintained partial offset/copy support to mirror io_clone_buffers UAPI (Jens).
> >   - Gated the replacement free check on ctx->file_table.data.nr (Gabriel).
> >   - Prevented self-cloning by checking ctx == src_ctx (Gabriel).
> >   - Removed submitter_task check to allow cross-thread pooling setups (Gabriel).
> > v2:
> >   - Dropped unrelated whitespace formatting changes from v1
>
> > +static int io_clone_file_node(struct io_ring_ctx *ctx,
> > +                           struct io_rsrc_node *src_node,
> > +                           int dst_index,
> > +                           struct io_file_table *new_table)
> > +{
> > +     struct io_rsrc_node *dst_node;
> > +     struct file *file;
> > +
> > +     dst_node = io_rsrc_node_alloc(ctx, IORING_RSRC_FILE);
> > +     if (!dst_node)
> > +             return -ENOMEM;
> > +
> > +     file = io_slot_file(src_node);
> > +     get_file(file);
> > +     io_fixed_file_set(dst_node, file);
>
> don't you need to copy the src_node->tag here as well?
>
> I didn't get a chance to run it yet, sorry.  I'd suggest you wait for
> Jens feedback before pushing the v7 too, so you don't need to keep
> iterating drop by drop :)
>
> > +
> > +     new_table->data.nodes[dst_index] = dst_node;
> > +     io_file_bitmap_set(new_table, dst_index);
> > +
> > +     return 0;
> > +}
> > +
> > +static int io_clone_files(struct io_ring_ctx *ctx, struct io_ring_ctx *src_ctx,
> > +                       struct io_uring_clone_files *arg)
> > +{
> > +     struct io_file_table new_file_table;
> > +     unsigned int dst_nr = ctx->file_table.data.nr;
> > +     unsigned int src_nr = src_ctx->file_table.data.nr;
> > +     unsigned int new_nr, i;
> > +
> > +     lockdep_assert_held(&ctx->uring_lock);
> > +     lockdep_assert_held(&src_ctx->uring_lock);
> > +
> > +     if (dst_nr && !(arg->flags & IORING_REGISTER_DST_REPLACE))
> > +             return -EBUSY;
> > +
> > +     if (!src_nr)
> > +             return -ENXIO;
> > +
> > +     if (!arg->nr)
> > +             arg->nr = src_nr;
> > +     else if (arg->nr > src_nr)
> > +             return -EINVAL;
> > +
> > +     if (check_add_overflow(arg->src_off, arg->nr, &i) || i > src_nr)
> > +             return -EINVAL;
> > +     if (check_add_overflow(arg->dst_off, arg->nr, &i))
> > +             return -EINVAL;
> > +
> > +     new_nr = max(dst_nr, arg->dst_off + arg->nr);
> > +     if (new_nr > IORING_MAX_FIXED_FILES)
> > +             return -EINVAL;
> > +
> > +     memset(&new_file_table, 0, sizeof(new_file_table));
> > +     if (!io_alloc_file_tables(ctx, &new_file_table, new_nr))
> > +             return -ENOMEM;
> > +
> > +     /* Copy original nodes from before the cloned range */
> > +     for (i = 0; i < min(arg->dst_off, dst_nr); i++) {
> > +             struct io_rsrc_node *src_node = io_rsrc_node_lookup(&ctx->file_table.data, i);
> > +
> > +             if (!src_node)
> > +                     continue;
> > +             if (io_clone_file_node(ctx, src_node, i, &new_file_table))
> > +                     goto out;
> > +     }
> > +
> > +     /* Copy the actual cloned range from the source ring */
> > +     for (i = 0; i < arg->nr; i++) {
> > +             struct io_rsrc_node *src_node = io_rsrc_node_lookup(&src_ctx->file_table.data,
> > +                             arg->src_off + i);
> > +
> > +             if (!src_node)
> > +                     continue;
> > +             if (io_clone_file_node(ctx, src_node, arg->dst_off + i, &new_file_table))
> > +                     goto out;
> > +     }
> > +
> > +     /* Copy original nodes from after the cloned range */
> > +     for (i = arg->dst_off + arg->nr; i < dst_nr; i++) {
> > +             struct io_rsrc_node *src_node = io_rsrc_node_lookup(&ctx->file_table.data, i);
> > +
> > +             if (!src_node)
> > +                     continue;
> > +             if (io_clone_file_node(ctx, src_node, i, &new_file_table))
> > +                     goto out;
> > +     }
> > +
> > +     /* free the old file table if there is any data present */
> > +     if (dst_nr)
> > +             io_free_file_tables(ctx, &ctx->file_table);
> > +
> > +     WARN_ON_ONCE(ctx->file_table.data.nr);
> > +     ctx->file_table = new_file_table;
> > +     io_file_table_set_alloc_range(ctx, 0, ctx->file_table.data.nr);
> > +     return 0;
> > +
> > +out:
> > +     /* Error Path: Safely destroy whatever we partially built */
> > +     io_free_file_tables(ctx, &new_file_table);
> > +     return -ENOMEM;
> > +}
> > +
> > +int io_register_clone_files(struct io_ring_ctx *ctx, void __user *arg)
> > +{
> > +     struct io_uring_clone_files clone_arg;
> > +     struct io_ring_ctx *src_ctx;
> > +     bool registered_src;
> > +     struct file *file;
> > +     int ret;
> > +
> > +     if (copy_from_user(&clone_arg, arg, sizeof(clone_arg)))
> > +             return -EFAULT;
> > +     if (clone_arg.flags &
> > +         ~(IORING_REGISTER_SRC_REGISTERED | IORING_REGISTER_DST_REPLACE))
> > +             return -EINVAL;
> > +
> > +     if (memchr_inv(clone_arg.pad, 0, sizeof(clone_arg.pad)))
> > +             return -EINVAL;
> > +
> > +     registered_src = !!(clone_arg.flags & IORING_REGISTER_SRC_REGISTERED);
> > +     file = io_uring_ctx_get_file(clone_arg.src_fd, registered_src);
> > +     if (IS_ERR(file))
> > +             return PTR_ERR(file);
> > +
> > +     src_ctx = file->private_data;
> > +     /* Same ring clone is not allowed */
> > +     if (src_ctx == ctx) {
> > +             ret = -EINVAL;
> > +             goto out;
> > +     }
> > +
> > +     mutex_unlock(&ctx->uring_lock);
> > +     lock_two_rings(ctx, src_ctx);
> > +
> > +     ret = io_clone_files(ctx, src_ctx, &clone_arg);
> > +
> > +     mutex_unlock(&src_ctx->uring_lock);
> > +
> > +out:
> > +     if (!registered_src)
> > +             fput(file);
> > +     return ret;
> > +}
> > +
> >  void io_vec_free(struct iou_vec *iv)
> >  {
> >       if (!iv->iovec)
> > diff --git a/io_uring/rsrc.h b/io_uring/rsrc.h
> > index 44e3386f7c1c..32f5c47c46af 100644
> > --- a/io_uring/rsrc.h
> > +++ b/io_uring/rsrc.h
> > @@ -75,6 +75,7 @@ int io_prep_reg_iovec(struct io_kiocb *req, struct iou_vec *iv,
> >                       const struct iovec __user *uvec, size_t uvec_segs);
> >
> >  int io_register_clone_buffers(struct io_ring_ctx *ctx, void __user *arg);
> > +int io_register_clone_files(struct io_ring_ctx *ctx, void __user *arg);
> >  int io_sqe_buffers_unregister(struct io_ring_ctx *ctx);
> >  int io_sqe_buffers_register(struct io_ring_ctx *ctx, void __user *arg,
> >                           unsigned int nr_args, u64 __user *tags);
> > --
> > 2.54.0
> >
>
> --
> Gabriel Krisman Bertazi