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, 53 insertions, 0 deletions

diff --git a/io_uring/rw.h b/io_uring/rw.h
new file mode 100644
index 000000000..1179506f9
--- /dev/null
+++ b/io_uring/rw.h
@@ -0,0 +1,53 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/io_uring_types.h>
+#include <linux/pagemap.h>
+#include <linux/uio.h>
+
+struct io_meta_state {
+	u32			seed;
+	struct iov_iter_state	iter_meta;
+};
+
+struct io_async_rw {
+	struct iou_vec			vec;
+	size_t				bytes_done;
+
+	struct_group(clear,
+		struct iov_iter			iter;
+		struct iov_iter_state		iter_state;
+		struct iovec			fast_iov;
+		unsigned			buf_group;
+
+		/*
+		 * wpq is for buffered io, while meta fields are used with
+		 * direct io
+		 */
+		union {
+			struct wait_page_queue		wpq;
+			struct {
+				struct uio_meta			meta;
+				struct io_meta_state		meta_state;
+			};
+		};
+	);
+};
+
+int io_prep_read_fixed(struct io_kiocb *req, const struct io_uring_sqe *sqe);
+int io_prep_write_fixed(struct io_kiocb *req, const struct io_uring_sqe *sqe);
+int io_prep_readv_fixed(struct io_kiocb *req, const struct io_uring_sqe *sqe);
+int io_prep_writev_fixed(struct io_kiocb *req, const struct io_uring_sqe *sqe);
+int io_prep_readv(struct io_kiocb *req, const struct io_uring_sqe *sqe);
+int io_prep_writev(struct io_kiocb *req, const struct io_uring_sqe *sqe);
+int io_prep_read(struct io_kiocb *req, const struct io_uring_sqe *sqe);
+int io_prep_write(struct io_kiocb *req, const struct io_uring_sqe *sqe);
+int io_read(struct io_kiocb *req, unsigned int issue_flags);
+int io_write(struct io_kiocb *req, unsigned int issue_flags);
+int io_read_fixed(struct io_kiocb *req, unsigned int issue_flags);
+int io_write_fixed(struct io_kiocb *req, unsigned int issue_flags);
+void io_readv_writev_cleanup(struct io_kiocb *req);
+void io_rw_fail(struct io_kiocb *req);
+void io_req_rw_complete(struct io_tw_req tw_req, io_tw_token_t tw);
+int io_read_mshot_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe);
+int io_read_mshot(struct io_kiocb *req, unsigned int issue_flags);
+void io_rw_cache_free(const void *entry);