io_uring: introduce attributes for read/write and PI support

Add the ability to pass additional attributes along with read/write.
Application can prepare attibute specific information and pass its
address using the SQE field:
	__u64	attr_ptr;

Along with setting a mask indicating attributes being passed:
	__u64	attr_type_mask;

Overall 64 attributes are allowed and currently one attribute
'IORING_RW_ATTR_FLAG_PI' is supported.

With PI attribute, userspace can pass following information:
- flags: integrity check flags IO_INTEGRITY_CHK_{GUARD/APPTAG/REFTAG}
- len: length of PI/metadata buffer
- addr: address of metadata buffer
- seed: seed value for reftag remapping
- app_tag: application defined 16b value

Process this information to prepare uio_meta_descriptor and pass it down
using kiocb->private.

PI attribute is supported only for direct IO.

Signed-off-by: Anuj Gupta <anuj20.g@samsung.com>
Signed-off-by: Kanchan Joshi <joshi.k@samsung.com>
Link: https://lore.kernel.org/r/20241128112240.8867-7-anuj20.g@samsung.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

include/uapi/linux/io_uring.h

@@ -98,6 +98,10 @@ struct io_uring_sqe {
 			__u64	addr3;
 			__u64	__pad2[1];
 		};
+		struct {
+			__u64	attr_ptr; /* pointer to attribute information */
+			__u64	attr_type_mask; /* bit mask of attributes */
+		};
 		__u64	optval;
 		/*
 		 * If the ring is initialized with IORING_SETUP_SQE128, then
@@ -107,6 +111,18 @@ struct io_uring_sqe {
 	};
 };
 
+/* sqe->attr_type_mask flags */
+#define IORING_RW_ATTR_FLAG_PI	(1U << 0)
+/* PI attribute information */
+struct io_uring_attr_pi {
+		__u16	flags;
+		__u16	app_tag;
+		__u32	len;
+		__u64	addr;
+		__u64	seed;
+		__u64	rsvd;
+};
+
 /*
  * If sqe->file_index is set to this for opcodes that instantiate a new
  * direct descriptor (like openat/openat2/accept), then io_uring will allocate