ioctl-RUN_ARRAY

RUN_ARRAY는 드디어 md 디스크를 생성하는 명령입니다. do_md_run함수가 처리합니다.

static int md_ioctl(struct block_device *bdev, fmode_t mode,
            unsigned int cmd, unsigned long arg)
{
......
    case RUN_ARRAY:
        err = do_md_run(mddev);
        goto unlock;

do_md_run

• call md_run()
• set disk size at mddev->gendisk
• revalidate_disk
  • md_alloc(): gendisk->fops = md_fops
  • disk->fops->revalidate_disk = md_revalidate
  • check_disk_size_change(): print message "md100: detected capacity change from 0 to 104726528"
• throw uevent KBOJ_CHANGE for user-level event handler

md_run

do_md_run에서 첫번째로 호출하는 함수는 md_run입니다. md_run은 다음과 같은 일을 합니다.

• mddev->disks 리스트에 아무런 장치가 없으면 -EINVAL 반환
• mddev->pers, mddev->sysfs_active 값이 0이 아니면 새로 생성되는 디스크가 아니므로 -EBUSY 반환
• analyze_sbs 호출: mddev에 연결된 md_rdev 디스크들의 슈퍼블럭을 읽어서 정상적인 슈퍼블럭인지 확인
• pers = &raid1_personality
• pers->run = run() in raid1.c
  • setup_conf() creates conf object
    • conf->mirrors[0].rdev: pointer to md_rdev of /dev/vda
    • conf->mirrors[1].rdev: pointer to md_rdev of /dev/vdb
    • conf->mirrors[2,3]: for replacement, in case when vda or vdb is faulty
    • conf object keeps information of raid-disks
  • "md/raid1:md100: active with 2 out of 2 mirrors\n"
    • md100: device file name
    • 2 out of: mddev->raid_disks - mddev->degraded, if all devices are clean
    • 2 mirrors: mddev->raid_disks, the number of all raid-disks
  • mddev->thread = conf->thread: md100_raid1 thread
    • run raid1d() function
      • call md_check_recovery(): check MD_RECOVERY_NEEDED bit and do recovery or resync
    • this thread is not started yet, will start after md_run() is finished
      • see do_md_run(): md_wakeup_thread(mddev->thread)
    • We will look into what raid1d() does in later chapter
  • mddev->private = conf
• mddev->in_sync = 1
• mddev->pers = pers;
• mddev->ready = 1
• set MD_RECOVORY_NEEDED bit at mddev->recovery
  • comment in md.h: NEEDED: we might need to start a resync/recover
  • After creating md, md100_raid1 thread will start resync

struct md_personality

md_run:

• mddev->level = 1

    pers = find_pers(mddev->level, mddev->clevel);

raid1.c:

• raid1.ko is a module to support RAID-1
• If that module does not exist or is not loaded, find_pers would fails and md module results "md: personality for level %d is not loaded!" error.

static struct md_personality raid1_personality =
{
    .name        = "raid1",
    .level        = 1,
    .owner        = THIS_MODULE,
    .make_request    = make_request,
    .run        = run,
    .free        = raid1_free,
    .status        = status,
    .error_handler    = error,
    .hot_add_disk    = raid1_add_disk,
    .hot_remove_disk= raid1_remove_disk,
    .spare_active    = raid1_spare_active,
    .sync_request    = sync_request,
    .resize        = raid1_resize,
    .size        = raid1_size,
    .check_reshape    = raid1_reshape,
    .quiesce    = raid1_quiesce,
    .takeover    = raid1_takeover,
    .congested    = raid1_congested,
};

static int __init raid_init(void)
{
    return register_md_personality(&raid1_personality);
}