From: NeilBrown It is possibly (and occasionally useful) to have a raid1 without persistent superblocks. The code in add_new_disk for adding a device to such an array always tries to read a superblock. This will obviously fail. So do the appropriate test and call md_import_device with appropriate args. Signed-off-by: Neil Brown Signed-off-by: Andrew Morton --- drivers/md/md.c | 7 +++++-- 1 files changed, 5 insertions(+), 2 deletions(-) diff -puN drivers/md/md.c~md-allow-hot-adding-devices-to-arrays-with-non-persistant-superblocks drivers/md/md.c --- devel/drivers/md/md.c~md-allow-hot-adding-devices-to-arrays-with-non-persistant-superblocks 2005-08-21 22:36:01.000000000 -0700 +++ devel-akpm/drivers/md/md.c 2005-08-21 22:36:01.000000000 -0700 @@ -2225,8 +2225,11 @@ static int add_new_disk(mddev_t * mddev, mdname(mddev)); return -EINVAL; } - rdev = md_import_device(dev, mddev->major_version, - mddev->minor_version); + if (mddev->persistent) + rdev = md_import_device(dev, mddev->major_version, + mddev->minor_version); + else + rdev = md_import_device(dev, -1, -1); if (IS_ERR(rdev)) { printk(KERN_WARNING "md: md_import_device returned %ld\n", _