Updates md-moduleioctl-setarrayinfo.md

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Author: Gioh Kim

md-moduleioctl-getarrayinfo.md

@@ -0,0 +1,18 @@
+
+
+```
+Breakpoint 3, md_ioctl (bdev=0xffff880006174000, mode=393375, cmd=2152204561, arg=140731375340208)
+    at drivers/md/md.c:6691
+6691	{
+(gdb) p/x cmd
+$19 = 0x80480911
+......
+(gdb) n
+6697		if (!md_ioctl_valid(cmd))
+(gdb) n
+6732		mddev = bdev->bd_disk->private_data;
+(gdb) n
+(gdb) p mddev->gendisk->disk_name
+$26 = "md0", '\000' <repeats 28 times>
+
+```

md-moduleioctl-setarrayinfo.md

@@ -19,4 +19,77 @@ static int md_ioctl(struct block_device *bdev, fmode_t mode,
 ......
 	mddev = bdev->bd_disk->private_data;
 
-```
+```
+
+
+```
+	if (cmd == SET_ARRAY_INFO) {
+		mdu_array_info_t info;
+		if (!arg)
+			memset(&info, 0, sizeof(info));
+		else if (copy_from_user(&info, argp, sizeof(info))) {
+			err = -EFAULT;
+			goto unlock;
+		}
+```
+
+
+```
+(gdb) p info
+$36 = {major_version = 1, minor_version = 2, patch_version = 0, ctime = 0, level = 0, size = 0, 
+  nr_disks = 0, raid_disks = 0, md_minor = 0, not_persistent = 0, utime = 0, state = 0, 
+  active_disks = 0, working_disks = 0, failed_disks = 0, spare_disks = 0, layout = 0, 
+  chunk_size = 0}
+```
+
+
+				
+```
+		if (mddev->pers) {
+			err = update_array_info(mddev, &info);
+			if (err) {
+				printk(KERN_WARNING "md: couldn't update"
+				       " array info. %d\n", err);
+				goto unlock;
+			}
+			goto unlock;
+		}
+		if (!list_empty(&mddev->disks)) {
+			printk(KERN_WARNING
+			       "md: array %s already has disks!\n",
+			       mdname(mddev));
+			err = -EBUSY;
+			goto unlock;
+		}
+		if (mddev->raid_disks) {
+			printk(KERN_WARNING
+			       "md: array %s already initialised!\n",
+			       mdname(mddev));
+			err = -EBUSY;
+			goto unlock;
+		}
+```
+
+아직 생성이 안된 md 디스크이기때문에 mddev 객체에는 아무 정보도 없습니다.
+```
+(gdb) p mddev->pers
+$39 = (struct md_personality *) 0x0 <irq_stack_union>
+(gdb) p mddev->raid_disks
+$37 = 0
+(gdb) p mddev->disks
+$38 = {next = 0xffff880006832818, prev = 0xffff880006832818}
+```
+
+
+```
+		err = set_array_info(mddev, &info);
+		if (err) {
+			printk(KERN_WARNING "md: couldn't set"
+			       " array info. %d\n", err);
+			goto unlock;
+		}
+		goto unlock;
+	}
+```
+
+