From: Paul Clements This fixes errors with utilities (such as LVM's vgscan) that try to scan all devices. Previously this would generate read errors when uninitialized nbd devices were scanned: # vgscan Reading all physical volumes. This may take a while... /dev/nbd0: read failed after 0 of 1024 at 0: Input/output error /dev/nbd0: read failed after 0 of 1024 at 509804544: Input/output error /dev/nbd0: read failed after 0 of 2048 at 0: Input/output error /dev/nbd1: read failed after 0 of 1024 at 509804544: Input/output error /dev/nbd1: read failed after 0 of 2048 at 0: Input/output error From now on, uninitialized nbd devices will have size zero, which prevents these errors. Signed-off-by: Paul Clements Signed-off-by: Andrew Morton --- drivers/block/nbd.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff -puN drivers/block/nbd.c~nbd-set-uninitialized-devices-to-size-0 drivers/block/nbd.c --- a/drivers/block/nbd.c~nbd-set-uninitialized-devices-to-size-0 +++ a/drivers/block/nbd.c @@ -581,6 +581,9 @@ static int nbd_ioctl(struct inode *inode printk(KERN_WARNING "%s: queue cleared\n", lo->disk->disk_name); if (file) fput(file); + lo->bytesize = 0; + inode->i_bdev->bd_inode->i_size = 0; + set_capacity(lo->disk, 0); return lo->harderror; case NBD_CLEAR_QUE: /* @@ -658,14 +661,14 @@ static int __init nbd_init(void) mutex_init(&nbd_dev[i].tx_lock); init_waitqueue_head(&nbd_dev[i].active_wq); nbd_dev[i].blksize = 1024; - nbd_dev[i].bytesize = 0x7ffffc00ULL << 10; /* 2TB */ + nbd_dev[i].bytesize = 0; disk->major = NBD_MAJOR; disk->first_minor = i; disk->fops = &nbd_fops; disk->private_data = &nbd_dev[i]; disk->flags |= GENHD_FL_SUPPRESS_PARTITION_INFO; sprintf(disk->disk_name, "nbd%d", i); - set_capacity(disk, 0x7ffffc00ULL << 1); /* 2 TB */ + set_capacity(disk, 0); add_disk(disk); } _