KVM: Don't pre-reserve xarray entries when storing empty/NULL attributesgrafted

Skip the xarray reservation loop when clearing all memory attributes, as
storing NULL only erases the entry and never needs to allocate, so no
reservation (and no cleanup of a failed one) is required in that case.

Suggested-by: Sean Christopherson <seanjc@google.com>
Cc: David Ballesteros <davimaba.v@proton.me>
Signed-off-by: Zeng Chi <zengchi@kylinos.cn>
Link: https://patch.msgid.link/20260921102442.1232375-1-zeng_chi911@163.com
[sean: split to separate patch]
Signed-off-by: Sean Christopherson <seanjc@google.com>

1 files changed, 149 insertions, 0 deletions

diff --git a/io_uring/splice.c b/io_uring/splice.c
new file mode 100644
index 000000000..e81ebbb91
--- /dev/null
+++ b/io_uring/splice.c
@@ -0,0 +1,149 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/namei.h>
+#include <linux/io_uring.h>
+#include <linux/splice.h>
+
+#include <uapi/linux/io_uring.h>
+
+#include "filetable.h"
+#include "io_uring.h"
+#include "splice.h"
+
+struct io_splice {
+	struct file			*file_out;
+	loff_t				off_out;
+	loff_t				off_in;
+	u64				len;
+	int				splice_fd_in;
+	unsigned int			flags;
+	struct io_rsrc_node		*rsrc_node;
+};
+
+static int __io_splice_prep(struct io_kiocb *req,
+			    const struct io_uring_sqe *sqe)
+{
+	struct io_splice *sp = io_kiocb_to_cmd(req, struct io_splice);
+	unsigned int valid_flags = SPLICE_F_FD_IN_FIXED | SPLICE_F_ALL;
+
+	sp->len = READ_ONCE(sqe->len);
+	sp->flags = READ_ONCE(sqe->splice_flags);
+	if (unlikely(sp->flags & ~valid_flags))
+		return -EINVAL;
+	sp->splice_fd_in = READ_ONCE(sqe->splice_fd_in);
+	sp->rsrc_node = NULL;
+	req->flags |= REQ_F_FORCE_ASYNC;
+	return 0;
+}
+
+int io_tee_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+{
+	if (READ_ONCE(sqe->splice_off_in) || READ_ONCE(sqe->off))
+		return -EINVAL;
+	return __io_splice_prep(req, sqe);
+}
+
+void io_splice_cleanup(struct io_kiocb *req)
+{
+	struct io_splice *sp = io_kiocb_to_cmd(req, struct io_splice);
+
+	if (sp->rsrc_node)
+		io_put_rsrc_node(req->ctx, sp->rsrc_node);
+}
+
+static struct file *io_splice_get_file(struct io_kiocb *req,
+				       unsigned int issue_flags)
+{
+	struct io_splice *sp = io_kiocb_to_cmd(req, struct io_splice);
+	struct io_ring_ctx *ctx = req->ctx;
+	struct io_rsrc_node *node;
+	struct file *file = NULL;
+
+	if (!(sp->flags & SPLICE_F_FD_IN_FIXED))
+		return io_file_get_normal(req, sp->splice_fd_in);
+
+	io_ring_submit_lock(ctx, issue_flags);
+	node = io_rsrc_node_lookup(&ctx->file_table.data, sp->splice_fd_in);
+	if (node) {
+		node->refs++;
+		sp->rsrc_node = node;
+		file = io_slot_file(node);
+		req->flags |= REQ_F_NEED_CLEANUP;
+	}
+	io_ring_submit_unlock(ctx, issue_flags);
+	return file;
+}
+
+int io_tee(struct io_kiocb *req, unsigned int issue_flags)
+{
+	struct io_splice *sp = io_kiocb_to_cmd(req, struct io_splice);
+	struct file *out = sp->file_out;
+	unsigned int flags = sp->flags & ~SPLICE_F_FD_IN_FIXED;
+	struct file *in;
+	ssize_t ret = 0;
+
+	WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK);
+
+	in = io_splice_get_file(req, issue_flags);
+	if (!in) {
+		ret = -EBADF;
+		goto done;
+	}
+
+	if (sp->len)
+		ret = do_tee(in, out, sp->len, flags);
+
+	if (!(sp->flags & SPLICE_F_FD_IN_FIXED))
+		fput(in);
+done:
+	if (ret != sp->len)
+		req_set_fail(req);
+	io_req_set_res(req, ret, 0);
+	return IOU_COMPLETE;
+}
+
+int io_splice_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+{
+	struct io_splice *sp = io_kiocb_to_cmd(req, struct io_splice);
+
+	sp->off_in = READ_ONCE(sqe->splice_off_in);
+	sp->off_out = READ_ONCE(sqe->off);
+	return __io_splice_prep(req, sqe);
+}
+
+int io_splice(struct io_kiocb *req, unsigned int issue_flags)
+{
+	struct io_splice *sp = io_kiocb_to_cmd(req, struct io_splice);
+	struct file *out = sp->file_out;
+	unsigned int flags = sp->flags & ~SPLICE_F_FD_IN_FIXED;
+	loff_t *poff_in, *poff_out;
+	struct file *in;
+	ssize_t ret = 0;
+
+	WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK);
+
+	in = io_splice_get_file(req, issue_flags);
+	if (!in) {
+		ret = -EBADF;
+		goto done;
+	}
+
+	poff_in = (sp->off_in == -1) ? NULL : &sp->off_in;
+	poff_out = (sp->off_out == -1) ? NULL : &sp->off_out;
+
+	if (sp->len)
+		ret = do_splice(in, poff_in, out, poff_out, sp->len, flags);
+
+	if (!(sp->flags & SPLICE_F_FD_IN_FIXED))
+		fput(in);
+done:
+	if (ret != sp->len)
+		req_set_fail(req);
+	io_req_set_res(req, ret, 0);
+	return IOU_COMPLETE;
+}