ioctl: Rearrange members in nvme_ns_mgmt_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_ns_mgmt_args {
        int                        args_size;            /*     0     4 */
        int                        fd;                   /*     4     4 */
        __u32 *                    result;               /*     8     8 */
        __u32                      timeout;              /*    16     4 */
        __u32                      nsid;                 /*    20     4 */
        struct nvme_id_ns *        ns;                   /*    24     8 */
        enum nvme_ns_mgmt_sel      sel;                  /*    32     4 */
        __u8                       csi;                  /*    36     1 */

        /* size: 40, cachelines: 1, members: 8 */
        /* padding: 3 */
        /* last cacheline: 40 bytes */
} __attribute__((__aligned__(8)));

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

Author: dwsuse

src/nvme/ioctl.h

@@ -2693,23 +2693,23 @@ int nvme_format_nvm(struct nvme_format_nvm_args *args);
 /**
  * nvme_ns_mgmt_args - Arguments for NVMe Namespace Management command
  * @fd:		File descriptor of nvme device
- * @nsid:	Namespace identifier
- * @sel:	Type of management operation to perform
- * @ns:		Namespace identication descriptors
  * @result:	NVMe command result
  * @timeout:	Timeout in ms
+ * @nsid:	Namespace identifier
+ * @ns:		Namespace identication descriptors
+ * @sel:	Type of management operation to perform
  * @csi:	Command Set Identifier
  */
 struct nvme_ns_mgmt_args {
 	int args_size;
 	int fd;
-	__u32 nsid;
-	enum nvme_ns_mgmt_sel sel;
-	struct nvme_id_ns *ns;
 	__u32 *result;
 	__u32 timeout;
+	__u32 nsid;
+	struct nvme_id_ns *ns;
+	enum nvme_ns_mgmt_sel sel;
 	__u8 csi;
-};
+} __attribute__((packed, aligned(__alignof__(__u32*))));
 
 /**
  * nvme_ns_mgmt() -
@@ -2739,11 +2739,11 @@ static inline int nvme_ns_mgmt_create(int fd, struct nvme_id_ns *ns,
 	struct nvme_ns_mgmt_args args = {
 		.args_size = sizeof(args),
 		.fd = fd,
-		.nsid = NVME_NSID_NONE,
-		.sel = NVME_NS_MGMT_SEL_CREATE,
-		.ns = ns,
 		.result = nsid,
 		.timeout = timeout,
+		.nsid = NVME_NSID_NONE,
+		.ns = ns,
+		.sel = NVME_NS_MGMT_SEL_CREATE,
 		.csi = csi,
 	};
 
@@ -2767,11 +2767,11 @@ static inline int nvme_ns_mgmt_delete(int fd, __u32 nsid)
 	struct nvme_ns_mgmt_args args = {
 		.args_size = sizeof(args),
 		.fd = fd,
-		.nsid = nsid,
-		.sel = NVME_NS_MGMT_SEL_DELETE,
-		.ns = NULL,
 		.result = NULL,
 		.timeout = 0,
+		.nsid = nsid,
+		.ns = NULL,
+		.sel = NVME_NS_MGMT_SEL_DELETE,
 		.csi = 0,
 	};