blkdev_get_by_dev — open a block device by device number
| struct block_device * blkdev_get_by_dev ( | dev_t dev, | 
| fmode_t mode, | |
| void * holder ); | 
devdevice number of block device to open
modeFMODE_* mask
holderexclusive holder identifier
   Open the blockdevice described by device number dev.  mode and
   holder are identical to blkdev_get.
   
Use it ONLY if you really do not have anything better - i.e. when you are behind a truly sucky interface and all you are given is a device number. _Never_ to be used for internal purposes. If you ever need it - reconsider your API.
On success, the returned block_device has reference count of one.