ioctl: Rearrange members in nvme_format_nvm_args

Avoid any holes in the struct by rearranging the members. Also add the
attribute packed to struct definition to reduce ABI breakage.

struct nvme_format_nvm_args {
        int                        args_size;            /*     0     4 */
        int                        fd;                   /*     4     4 */
        __u32 *                    result;               /*     8     8 */
        __u32                      timeout;              /*    16     4 */
        __u32                      nsid;                 /*    20     4 */
        enum nvme_cmd_format_mset  mset;                 /*    24     4 */
        enum nvme_cmd_format_pi    pi;                   /*    28     4 */
        enum nvme_cmd_format_pil   pil;                  /*    32     4 */
        enum nvme_cmd_format_ses   ses;                  /*    36     4 */
        __u8                       lbaf;                 /*    40     1 */

        /* size: 48, cachelines: 1, members: 10 */
        /* padding: 7 */
        /* last cacheline: 48 bytes */
} __attribute__((__aligned__(8)));

Signed-off-by: Daniel Wagner <[email protected]>

Author: dwsuse

src/nvme/ioctl.h

@@ -2653,28 +2653,28 @@ int nvme_get_features_iocs_profile(int fd, enum nvme_get_features_sel sel,
 /**
  * nvme_format_nvm_args - Arguments for the Format Nvme Namespace command
  * @fd:		File descriptor of nvme device
+ * @result:	The command completion result from CQE dword0
+ * @timeout:	Set to override default timeout to this value in milliseconds;
+ *		useful for long running formats. 0 will use system default.
  * @nsid:	Namespace ID to format
- * @lbaf:	Logical block address format
  * @mset:	Metadata settings (extended or separated), true if extended
  * @pi:		Protection information type
  * @pil:	Protection information location (beginning or end), true if end
  * @ses:	Secure erase settings
- * @timeout:	Set to override default timeout to this value in milliseconds;
- * 		useful for long running formats. 0 will use system default.
- * @result:	The command completion result from CQE dword0
+ * @lbaf:	Logical block address format
  */
 struct nvme_format_nvm_args {
 	int args_size;
 	int fd;
+	__u32 *result;
+	__u32 timeout;
 	__u32 nsid;
-	__u8 lbaf;
 	enum nvme_cmd_format_mset mset;
 	enum nvme_cmd_format_pi pi;
 	enum nvme_cmd_format_pil pil;
 	enum nvme_cmd_format_ses ses;
-	__u32 timeout;
-	__u32 *result;
-};
+	__u8 lbaf;
+} __attribute__((packed, aligned(__alignof__(__u32*))));
 
 /**
  * nvme_format_nvm() - Format nvme namespace(s)