fs, iov_iter: define meta io descriptor

Add flags to describe checks for integrity meta buffer. Also, introduce
a  new 'uio_meta' structure that upper layer can use to pass the
meta/integrity information.

Signed-off-by: Kanchan Joshi <[email protected]>
Signed-off-by: Anuj Gupta <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>

Author: Anuj Gupta

include/linux/uio.h

@@ -82,6 +82,15 @@ struct iov_iter {
 	};
 };
 
+typedef __u16 uio_meta_flags_t;
+
+struct uio_meta {
+	uio_meta_flags_t	flags;
+	u16			app_tag;
+	u64			seed;
+	struct iov_iter		iter;
+};
+
 static inline const struct iovec *iter_iov(const struct iov_iter *iter)
 {
 	if (iter->iter_type == ITER_UBUF)

include/uapi/linux/fs.h

@@ -40,6 +40,15 @@
 #define BLOCK_SIZE_BITS 10
 #define BLOCK_SIZE (1<<BLOCK_SIZE_BITS)
 
+/* flags for integrity meta */
+#define IO_INTEGRITY_CHK_GUARD		(1U << 0) /* enforce guard check */
+#define IO_INTEGRITY_CHK_REFTAG		(1U << 1) /* enforce ref check */
+#define IO_INTEGRITY_CHK_APPTAG		(1U << 2) /* enforce app check */
+
+#define IO_INTEGRITY_VALID_FLAGS (IO_INTEGRITY_CHK_GUARD | \
+				  IO_INTEGRITY_CHK_REFTAG | \
+				  IO_INTEGRITY_CHK_APPTAG)
+
 #define SEEK_SET	0	/* seek relative to beginning of file */
 #define SEEK_CUR	1	/* seek relative to current file position */
 #define SEEK_END	2	/* seek relative to end of file */